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INTRODUCTION EXCELLENCE IN ORTHODONTICS 2012

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Chapter

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Introduction David Birnie and Nigel Harradine Firstly, a formal written welcome to the course. This is the twenty-sixth year of Excellence in Orthodontics courses and, as always, we hope you find the course relevant, stimulating and enjoyable. It is perhaps with some surprise (and a small inner glow) that we realise that over quarter of a century has passed by since the first course was held in York in April 1987 and we have held an annual course at this time of the year every year since then. The course moved to the Royal Society of Medicine in 1989, the Royal College of Physicians in 2003 and the Royal College of Obstetricians and Gynaecologists in 2006. Excellence in Orthodontics courses have also been held in Australia, Germany, Hong Kong SAR China, Ireland, Jordan, Italy, Malaysia, The Netherlands, Norway, Saudi Arabia, Scotland, Sweden, South Africa and Switzerland.

excellenceinorthodontics.com Excellence in Orthodontics established its own website in 2001 – http://www.excellenceinorthodontics.com The purpose of the website is to make it easier to:

• • •

access information about current and future Excellence in Orthodontics courses improve course administration make it easier to contact o David Birnie or Nigel Harradine o the course administrator

We are now in our tenth year of running the website, hosted by the Faculty of Health Informatics at The Royal College of Surgeons of Edinburgh. It has made the administration of the course very much easier but as always, criticisms and suggestions for improvement are enormously appreciated. The website was totally redesigned for 2007 and we hope is it clearer and easier to use.

Lecture Course Title It is useful to say a word about our chosen title for these courses - Excellence in Orthodontics. This is not a claim that everything we do is perfection or the only way to do something. Nor does it imply that an occlusally perfect result is the only acceptable goal in every case - although in most cases we should be striving for an excellent occlusion. It is rather a declaration of intent or an attitude of mind. It is a commitment to do the best for each individual patient in the light of current knowledge and technique. We certainly believe that if a job is worth

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INTRODUCTION EXCELLENCE IN ORTHODONTICS 2012

doing - which orthodontic treatment certainly is - it is worth doing as excellently as possible and this requires continual, honest and thoughtful appraisal of the literature, and of the clinical efforts of ourselves and others.

In 2001, we dropped the words ‘Straight-Wire Appliance’ from the course title. The Straight-Wire Appliance was the first of the fully pre-adjusted edgewise appliances and has significantly changed the face of orthodontics.

However, with the universal adoption of pre-adjusted appliances of various types, the strength and development of self-ligating appliances and the evolution of digital orthodontics, the course has inevitably broadened from its original aims and now encompasses many aspects of contemporary, high technology orthodontics. In future our courses will continue to appear under the Excellence in Orthodontics title suffixed by the year in which the course is given.

Style

The style of the course involves approximate alternation of presenters to provide variety and presentations are scheduled for shorter rather than marathon lengths, with time allocated for the all-important discussion. The talks are the result of many happy weekend hours of joint planning and discussion between the presenters and are intended to be highly integrated with an absolute minimum of duplication. The clinical material is chosen to make specific points and cases are not chosen because they happened to go well - indeed some are included precisely because they gave us problems which were only partially overcome. Mistakes and imperfections frequently make better educational illustrations than exceptionally smooth and rapid successes! Some cases are shown in great detail and others are just dipped into to show a single point. This policy is intended to reduce what used to be known as supratentorial Kodachrome overload and make the best use of the time.

Aims The principal intentions of the course are twofold. Firstly, to scrutinise treatment goals to establish a clearer view of where exactly we should be heading with our treatment plans. A substantial part of the orthodontic literature is aimed at clarifying these goals, reflecting the need to continually examine this issue. Secondly, to provide a detailed and searching look at contemporary orthodontics in its many varieties, at how we prefer to practice it and at how well contemporary orthodontics does or does not match up to our requirements in getting us quickly and reliably to our chosen goals.

The fundamental goal of any enterprise is to create and deliver the most value from the customer’s perspective while consuming the fewest resources. Value is defined by the customer; in healthcare, the customer is the patient (although the interposition of various agencies between the provider and the patient sometimes obscures the link). The service given to the patient is usually seen as a combination of quality (doing the right thing, to the right patient, at the right time, first time), cost, morale (patient experience), delivery time and safety – often referred to as QCMDS. It is also important to consider these aspects from a staff point of view.

No course can be all things to all people and any audience will have varying experience and particular interests.

We aim this course at people who already have a good working knowledge of pre-adjusted edgewise appliance techniques, are keen to learn about cutting edge orthodontic concepts and who wish to think closely about both the overall strategy and the detailed practical tactics of treatment with these appliances.

Course Manual and e-Version The Course Manual was introduced in 1991 and has grown in both size and sophistication since then. It is now printed in colour (since 2003) and in 2002 was also provided on a CD as an Adobe Systems Portable Document Format (pdf) file, a feature is now a standard part of Excellence in Orthodontics Lecture Courses. The e-Version may move to a memory stick in the near future but at the time of writing, we do not know if it will remain on a CD or whether we will use a memory stick – hence the slightly cumbersome name! The production of the Course Manual is now a very complex affair and if you spot any errors or problems, please let us know through the website.

When choosing the topics and detailed content of these courses, we focus on those aspects which seem most relevant to clinicians at the current time. Introduction of new material therefore happens continually as clinical

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experience and research findings evolve in orthodontics. Discarding of material which still seems valid and useful but less at the forefront of current thought is more problematic, given the time constraints of a two day course.

Perhaps inevitably, we find that topics from past courses which we exclude as being slightly 'old hat' or less of a current burning issue are the subject of questions and suggestions in our questionnaire that we include them in future courses. We always receive suggestions in the questionnaire for additional topics to be included, but rarely for a current topic to be excluded. One of the roles of this manual is therefore to help overcome this dilemma and make available to course delegates our thoughts and suggested references on related topics that will not be included in the lectures in any detail, but are considered potentially useful to at least some of the course participants. So, although the manual usually follows the sequence and content of the talks, it also includes additional topics and details and we hope this does not prove a distraction to those following the lectures in the manual. These additional chapters are usually not significantly updated each year but are included because it is felt that they are important subjects and may be of interest to participants.

This year we have taken further steps to limit the size of the printed version. The feedback has consistently indicated that a printed version of the manual is popular, but it has steadily grown to a challenging size. We have pruned the references to exclude some worthy but older papers and we have removed some chapters to be available only on the USB stick. We feel this will help to keep the printed version portable whilst not removing material of continued usefulness.

A prime function of the manual is to lessen the need to take notes in order to recall the salient points of the talks.

Reading the manual after the course should help you to recall the pictures on the screens as well as, of course, the structure of the talks. In particular, you can rest assured that all references that appear on the screen are to the best of our ability included in the manual, so frantic scribbling won't be needed! However, a few blank pages appear at the end of each chapter for your personal notes.

Evidence-based clinical practice We continue to feel strongly that our opinion on important issues is less valuable than the actual current evidence in the literature, so a critical scrutiny of the relevant papers underpins our clinical practice and recommendations.

A look at the relevant literature is therefore an important feature of the course. This approach fits comfortably with a growing emphasis throughout all medical and dental specialties on evidence-based clinical practice. This scrutiny of the literature is complemented by extensive clinical illustration, concentrating on difficult and problem cases since these are the most informative. In the past few years we have substantially reduced the references in the manual in order to counter the tendency for the list to grow perpetually and become less user-friendly. The references that remain are particularly recommended as being of lasting quality or very recent additions to the evidence on a topic.

The hierarchy of the clinical relevance of evidence-based medicine is shown in Figure 1.1; it is worth considering whether it is necessarily appropriate for all orthodontic problems. Much of our knowledge about bonding materials has come from the bottom layer of the pyramid and in terms of clinical relevance might be thought to come above the three categories above it for this type of problem. Equally, animal research has contributed significantly to our understanding of how functional appliances work and might arguably be placed above Ideas, Editorials and Opinions and Case Reports.

Figure 1.1: The evidence based triangle (adapted from SUNY Downstate Evidence Based Medicine

Course)

A good overview of systematic reviews is given by Hemingway and Brereton under the title of What is a systematic review?

This article comes from Bandolier’s Learning Zone which has a number of excellent articles on evidence based thinking about healthcare. Some criticism of randomised controlled trials has been made by Meikle (2005); it is worth remembering that for some aspects of orthodontic treatment, unlike many medical interventions, the clinician can easily see the results of

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Experimental Control Figure 1.2: model

T0 O O

Intervention X

T1 O O

The clinical research model, sometimes known as the OXO

treatment and so the conclusions of such investigations do not always come as a surprise to experienced clinicians.

However, the results of systematic reviews and randomised controlled trials are frequently inconclusive or give less information than expected. Professor Shaw, in a lecture entitled Clinical Uncertainty and Evidence-Based Dentistry given at the 2008 AAO Annual Session in Denver, suggested that orthodontic reviews carried out by the Cochrane Collaboration all concluded that:

• • • •

trials were too small better trials were needed results were inconclusive and recommendations for practice cannot be made

The clinical research model was described by Campbell and Stanley (1963) and is shown in Figure 1.2. In this model, the experimental and control groups are assumed to be identical and differ only in the applied intervention, X. The applied intervention is therefore assumed to be responsible for any difference in outcome between the experimental and control groups. This theory of causation is successionist in that the causation between treatment and outcome is inferred by repeated succession of one event by another. This technique is ideally suited to laboratory studies or those in which all variables can be tightly controlled. However, in complex socio-technical situations it may work less well. In their book on the evaluation of sociological research, Pawson and Tilley attack the use of the OXO model as follows: ... for us, the experimental paradigm constitutes a heroic failure, promising so much and yet ending up in ironic anticlimax. The underlying logic seems meticulous, clear headed and militarily precise, and yet findings seem to emerge in a typically noncumulative, low impact, prone to equivocation sort of way.

There is however an alternative – the generative theory of causation. Whereas the clinical research model tries to describe what happened, generative theory attempts to explain why something happened. It is exemplified by the following equation: context (C) + mechanism (M) = outcome (O)

Figure 1.3: model

Orthodontics as a complex, non-linear socio-technical

It acknowledges that mechanism on its own might not be enough to produce the outcome but an external influence (context) is required in addition to the mechanism to produce the required outcome. For example, a removable orthodontic appliance requires operator skill and patient compliance in order to work but compliance is not binary, patient response is variable and operator skill difficult to quantify – the combination of patient compliance, biological response and operator skill required to produce a successful outcome in an individual patient is difficult to determine. Pawson and Tilley would claim that experimentalists have pursued too singlemindedly the question of whether an intervention works at the expense of why it works and that the traditional clinical research model removes information about the ‘what’ of context and the ‘why’ of mechanism in an attempt to produce generalisable knowledge. What makes the clinical

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research model very strong in some circumstances makes it very weak in others.

This problem is not confined to orthodontics. Don Berwick in his presentation, Eating Soup with a Fork, at the IHI National Forum in 2007 cites a similar problem in relation to the deployment of rapid response teams in acute hospitals and argues that randomised controlled trials may be less effective in providing information about complex, non-linear relationships in social systems. Whether orthodontic treatment is a complex, non-linear social system is debatable but one model is given in Figure 1.3 but there seems good case to support this suggestion.

There is no suggestion that this should be a less rigorous approach but simply that consideration should be given to broadening the methods of inference and finding a wider, but no less rigorous, range of ways to gain knowledge. The evidence based pyramid may not in fact be a pyramid but a flat-topped cone with multiple methods of obtaining gold standard evidence depending on the type of problem to be tackled.

Another aspect worth consideration is the speed of technical development; medical, dental and orthodontic technology changes increasingly rapidly with many products having only a four to five year life. Evaluation of new products and product related techniques requires a response rate shorter than the product cycle in order maintain currency.

Critical appraisal Critical appraisal is an important tool for bridging the gap between research and practice and involves systematic evaluation of research to assess its validity, results and relevance. Several tools are helpful and Hill and Spittlehouse (2001) is a useful starting point. CASP (Critical Appraisal Skills Programme) gives more detailed information.

Peer review If you are ever asked to peer review an article, then the British Medical Journal offers an excellent Training Package on how to do this.

MindMaps Some parts of the Course Manual and some lectures use maps, which have been created with MindJet’s MindManager 9 Mac software based on Tony Buzan’s mind mapping techniques.

We find this an extremely useful software package for brainstorming both content and structure for lectures and chapters. A MindMap of the structure of this chapter is shown in Figure 1.4. If you are not familiar with MindMaps then the following notes may be helpful:

• the MindMap title appears in the centre of the spine • read the mind map downwards • each main branch is equivalent to a level 1 heading with subordinate branches being equivalent to lower level headings Referencing

Figure 1.4: MindMap of this chapter created with MindJet’s MindManager Pro 9 software

Considerable discussion has taken place about the relative merits of the Vancouver and Harvard systems of referencing citations. After much careful thought, we have decided to continue with the Harvard system as we feel that many course delegates will feel that being able to associate a specific viewpoint with the relevant citation is important to them.

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A comprehensive resource on citation styles for both print and electronic citations is provided by Glasgow University Library at http://www.lib.gla.ac.uk/researchskills/citationstyle.shtml.

We have included links to medical and journal databases beside most references. The source of these is identified by an icon as shown in Appendix 2. The hyperlinks to Pub Med are either blue if the original journal or the National Library of Medicine PubMed has an abstract of the article, or orange if they only give the title (normal for older references). Links are still given if the title only is displayed as you may want to look at the Related Articles, Links hyperlink in PubMed.

Education Continuing Professional Education (CPE) This two day course is recognised for 12 verifiable CPE points. A certificate of attendance in the style recommended by the General Dental Council, verifying the CPE points awarded, will be issued to all participants who attend the course.

Postgraduate Education Allowance This two day course no longer requires approval for the Postgraduate Education Allowance by the Department of Postgraduate Dentistry, Thames Postgraduate Medical and Dental Education, University of London, 33 Millman Street, London WC1N 3EJ. In your registration pack you will find a pre-printed FP-84-0306 form; please sign the register at the course (it is normally at the front of the lecture theatre) if you wish to claim this allowance. It has been a condition of approval in the past that a post course report and attendance register is sent to the Regional Postgraduate Dental Dean.

Questionnaire and Feedback On the second day, we will ask you to complete and return a short questionnaire on the course. This can be found in this manual at Appendix A. This has proved a great help in planning future courses to be as relevant, useful and enjoyable as possible and we would encourage you to complete and return these immediately whilst things are still fresh in your minds - preferably before you leave for home. Meanwhile, we hope you enjoy the course and find this manual useful both during and after the course.

We find the feedback from delegates invaluable in improving all aspects of both the Lecture Course and the Course Manual. If you have any comments that spring to mind after you have handed in the questionnaire, then please send these either to David Birnie or Nigel Harradine.

Future Excellence in Orthodontics Lecture Courses Due to the redevelopment and refurbishment of The Royal Society of Medicine, we moved the course from The Royal Society of Medicine to the Royal College of Physicians in 2003 and in 2006 we moved to The Royal College of Obstetricians and Gynaecologists.

Excellence in Orthodontics Courses are an awkward size for the Royal College of Physicians, being slightly too big for the Seligman Lecture Theatre and too small for the Wolfson Lecture Theatre although both the facilities and the audio-visual support there were and are excellent.

Since 2006, we have used The Royal College of Obstetricians and Gynaecologists’ conference facility, again pleasantly situated on Regents Park. At the moment, this venue offers Excellence in Orthodontics the best balance of facilities available to meet its needs in central London.

INTRODUCTION EXCELLENCE IN ORTHODONTICS 2012

References Berwick DM (2007) Eating Soup with a Fork Keynote Presentation IHI National Forum Available from http://www.ihi.org/offerings/VirtualPrograms/OnDemand/SoupwithFork/Pages/default.aspx Accessed 22 February 2012 Campbell DT and Stanley JC (1963) Experimental and quasi-experimental designs for research Chicago, Rand McNally Critical Skills Appraisal Programme (CASP) Available from http://www.sph.nhs.uk/what-we-do/public-health-workforce/resources/critical-appraisals-skillsprogramme Accessed 22 February 2012 Hemingway P and Brereton N (2009) What is a systematic review?

Available from http://www.medicine.ox.ac.uk/bandolier/painres/download/whatis/Syst-review.pdf Accessed 22 February 2012 Burls A (2009) What is critical appraisal?

Available from http://www.medicine.ox.ac.uk/bandolier/painres/download/whatis/What_is_critical_appraisal.pdf Accessed 22 February 2012 Meikle MC (2005) Guest Editorial: What do prospective randomized clinical trials tell us about the treatment of Class II malocclusions? A personal viewpoint European Journal of Orthodontics 27: 105-114 Pawson R and Tilley N (1997) Realistic evaluation London, Sage Publications State University of New York (SUNY) Downstate Medical Center Evidence Based Medicine Course Available from http://library.downstate.edu/EBM2/contents.htm Accessed 22 February 2012 Training package for BMJ peer reviewers Available from http://www.bmj.com/about-bmj/resources-reviewers/training-materials Accessed 22 February 2012 University of Glasgow Library (online) Citation styles Available from http://www.gla.ac.uk/services/library/howtofindinformation/findingusinginformation/howtocitereferences/ Accessed 22 February 2012

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OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

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Occlusal treatment goals Nigel Harradine

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Introduction This chapter is the first of three chapters focussing on aspects of treatment planning in relation to evidence-based treatment goals.

When treating patients, we may have many goals; eg: a short treatment time, lack of discomfort for the patient and avoidance of damage to the oral tissues. In terms of tooth position, there are only two groups of goals: occlusal goals and facial aesthetic goals. The former describe the relationships of the teeth in the intercuspal position and during function and are considered in this chapter. The latter are concerned with the position of the occlusion within the face and are covered in the chapter on Diagnosis and Treatment Planning and the chapter on Facial Appearance, the Smile and Tooth Aesthetics.

In addition to specifically occlusal goals, there has also been a large amount of interest in, and strongly held opinion expressed about, the most desirable position of the condyle within the glenoid fossa and the position of the articular disc. It has been asserted that orthodontic treatment can influence both of these positions with clinically important consequences and that orthodontic treatment can cause mandibular dysfunction by a variety of mechanisms. We clearly need to decide what treatment goals we should have in these respects and these topics are also covered in this chapter.

Intercuspal goals Andrews' Six Keys to normal (or optimal) occlusions – published by Andrews (1972) - are a widely quoted set of static occlusal goals for tooth relationships in the intercuspal position and can be summarised as follows: Andrews Six Keys

Characteristic

Key 1

correct interarch relationships

Key 2

correct crown angulation (tip)

Key 3

correct crown inclination (torque)

Key 4

no rotations

Key5

tight contact points

Key 6

flat curve of Spee (0.0 - 2.5 mm)

It is important to remember that these keys were not created as a total definition of ideal static occlusion, they were a summary of the most frequent ways in which 1150 post-treatment study casts presented at the American Association Orthodontists, the Tweed Foundation and the Angle Society differed from the 120 “non-orthodontic normals”.

Key point: Andrews’ six keys are not definers of success, they were common causes of failure.

The six keys were designed to assist in focusing a clinician's mind on common errors with interlinking and inexorable consequences. In fact, the variety of tooth form makes the consequences of failure to achieve a Key not as inexorable as Andrews originally implied and Andrews' subsequently published book, Straight-Wire The Concept and Appliance (1989) recognises this point. That book also most usefully contains the previously unpublished data concerning the magnitude of arch length changes arising from errors in the six keys. The data show that these arch length changes are frequently smaller than might be imagined. A paper by O’Higgins et al. (1999) also investigates the size of some of these effects. An interesting average rule of thumb is suggested - that every 5 degrees of upper incisor torque increases the total arch length by 1 mm. This finding has been strongly supported by Sangcharearn and Ho (2007) who found every 5 degrees of incisor torque increased the upper arch length by 0.92 mm. They found a close linear relationship between arch length and incisor inclination over a range from 90 degrees to 130 degrees.

This means that a 10 degree change in torque will alter the molar relationship by approximately 1 mm on each side.

We prefer a routine upper central incisor prescription with a fairly high (23 degrees) torque value in view of the ‘slop’ or lay in the slot which studies show to approximate 11 degrees in practice for a 19/25” wire. O’Higgins et al also reported that the extra 2 degrees of tip (angulation) in the Roth prescription for the upper canine (13 degrees)

OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

Crosby and Alexander (1989) Freeman et al (1996) Santoro et al (2000) Bernabe et al (2004) Othman and Harradine (2007)

Anterior Ratio 23 31 28 20 17

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compared to Andrews standard (11 degrees) requires an approximate extra 0.5 mm. of arch length per side. We prefer a smaller upper canine angulation (the Damon prescription has 6 degrees) and this might be expected to have a similar size of effect per degree in reducing the upper arch length, although the effect may not be linear over a range of angles due to the shape of the canine. The combined effects of these results suggest that our preferred routine prescription values (see the chapter on The Development of Preadjusted Edgewise Appliances) might require 0.5 mm less upper labial segment space per side

Overall ratio 13 11 5 5

Table 2.1: Percentages of potential patients with “substantial” Bolton discrepancies (more than 2 SDs of ratio from Bolton’s original study)

than Andrews’ original standard prescription.

Inter-arch tooth-width discrepancies - Bolton ratios The 1989 textbook by Andrews also differentiates between “normal” and “optimal” occlusions. Abnormal malocclusions are those which cannot be treated to an optimal result which fulfils the six keys without orthognathic surgery to produce an optimal skeletal pattern or restorative work to produce teeth of matching dimensions throughout both arches. The disclaimer about skeletal pattern seems overstated to those clinicians treating a majority of patients who have an abnormal skeletal pattern, but tooth width discrepancies between the arches or between different parts of the same arch may well be an under-recognised cause of inability to produce a six-keys occlusion in an individual case.

The study of discrepancies in tooth size between the arches was given a quantitative basis by Bolton (1958, 1962, 1985). A review of tooth-size discrepancies by Othman and Harradine (2006), can be recommended with due modesty. Several studies e.g. Freeman et al (1996) have reported a substantial proportion of patients with potentially significant discrepancies in Bolton ratios. For anterior teeth in that study, the excess tooth tissue was twice as likely to be in the lower jaw and this is again a frequent finding.

Other authors have also found significant percentages of subjects with such discrepancies. In these papers, the percentage of significant discrepancies is usually defined in terms of standard deviations of ratio in Bolton’s original study. These are summarised in Table 2.1. It will be noticed that these papers found more discrepancies in the anterior ration than in the overall ratio. The paper by Othman and Harradine (2007) was carried out on a random sample of orthodontic patients in the United Kingdom. The clinical significance of these large numbers of patients with outlying ratios is discussed later in this section.

Measuring Bolton ratios - convenience and reproducibility One reason why tooth size discrepancies are not more frequently measured is the time required to carry out the analysis. The advent of computer programs and electronic callipers greatly facilitates the measurement of Bolton ratios. A paper by Tomassetti et al (2001) reported that the electronic callipers and software of the Hamilton Arch Tooth System (HATS) was much quicker than using vernier callipers and ‘manual’ calculation. This has been confirmed by Othman and Harradine (2007b). The random error of measurement in relation to the size of discrepancy considered to be clinically important is poorly reported in most papers and Othman and Harradine report very significant measurement error in relation to discrepancies of a clinically significant size.

Key point: Because of the poor reproducibility, several repeat measurements should be made of a Bolton ratio before committing to active alteration of tooth size.

Before

Four 4s

Four 5s

Mean (mm)

0.89

1.25

0.84

sd (mm)

0.59

0.91

0.77

Max (mm)

2.01

3.70

2.58

Table 2.2: Premolar extractions and the effect on Bolton discrepancies (Saatci and Yukay 1997)

Bolton ratios and extraction patterns The situation is further complicated when planning orthodontic treatment, by the findings of an interesting paper by Saatci and Yukay (1997) who examined the effect on the Bolton ratio and Bolton discrepancy in millimetres of various premolar extraction patterns (Table 2.2). In a sample of patients who initially all had

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OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

Bolton ratios close to Bolton’s average, all combinations of premolar extraction placed some ratios outside this range. The extraction of four first premolars had a statistically and possibly clinically significant effect, whilst extraction of four second premolars had very little average effect. The extraction of four first premolars placed 31 of the sample of 50 outside the normal range of Bolton values, whilst second premolar extractions only placed 17 outside the normal range and indeed lowered the average Bolton discrepancy. Cases outside the normal range erred strongly in the direction of mandibular excess. The question of the clinical significance of discrepancies of this magnitude will again be discussed later.

Bolton ratios in different malocclusions Several authors have compared Bolton ratios in different malocclusions. It is worth noting the findings of Nie and Lin (1999) who reported a tendency to maxillary tooth-size excess in class 2 patients and mandibular tooth-size excess in class 3 patients. Araujo and Souki (2003) also found a significantly higher mean ratio (mandibular tooth excess) in class 3 cases and a lower percentage of significant Bolton discrepancy in class 2 cases. It is interesting to speculate whether this indicates that such discrepancies contribute slightly to the establishment of the corresponding incisor relationship or alternatively whether the relative ‘overgrowth’ of a jaw is associated with growth control mechanisms which also cause relatively large teeth in that jaw.

Bolton ratios and ethnic groups Several studies have investigated differences in ratios in different ethnic groups. Smith et al. (2000) found small but statistically different ratios between black, Hispanic and white groups. They also found gender differences and suggest that Bolton’s ratios only apply well to white females who probably made up Bolton’s entire original sample.

A study in Saudi nationals by Alkofide and Hashim (2002), found different overall ratios to those in Bolton’s original sample. Also, there were statistically significantly different ratios for the class 2 sub-sample and between the genders in that malocclusion. It is clear that the original Bolton ratio norms are unlikely to be an ideal guide to the presence or absence of a clinically significant problem in all populations.

Bolton ratios and PAR scores A very interesting experimental study by Heusdens et al (2000) investigated the effect in typodont setups of different extraction patterns and quite extreme variations in Bolton ratio on PAR scores. They found only modest increase in PAR scores with severe tooth size discrepancies and concluded that generalised tooth size discrepancy is not of great importance after all. However, this finding must reflect the insensitivity of the PAR score to several aspects of poor occlusal fit as much as it indicates any lack of importance of tooth size discrepancies. In the method employed in this paper, discrepancies of 12 mm (!) did not result in a significant change in the PAR score, but would surely affect the occlusal result to a substantial degree. Harradine and Othman (2006), suggested in a literature review that a better means of determining clinical significance would be to use the method employed in development of the PAR index namely the correlations of expert opinions of quality of occlusal fit with the measured level of tooth-size discrepancy.

Another paper exploring the relationship between Bolton discrepancies and features of malocclusion is by Redahan and Lagerstrom (2003). This is an interesting paper, but is possibly one which is asking the wrong question. The authors examine the relationship between Bolton discrepancy and several features of both the pre-treatment and post-treatment alignment and occlusion. They conclude that Bolton discrepancy has very little correlation with these aspects of the start or finishing occlusion and is therefore of very little diagnostic assistance. Several points would question this conclusion. Firstly, features such as crowding and intercanine width would not be expected to correlate significantly with Bolton discrepancy. Secondly, few patients had a significant discrepancy, so statistically significant demonstration of a relationship would be unlikely. Thirdly, the post-treatment overjet – which is a feature potentially affected by the Bolton ratio- did indeed show a weak correlation with Bolton discrepancy, whilst the buccal segment relationship was not examined. It would, of course, be possible for a potential increased overjet with a decreased Bolton ratio to be masked by a slightly class 3 molar relationship. Both of these interesting papers address an important subject – how much do tooth-size discrepancies actually matter – but do not resolve the issue.

The clinical significance of Bolton discrepancies and the appropriateness of Bolton’s original sample All of the above discussion highlights the importance of deciding the clinical significance of inter-arch tooth width discrepancies and especially of the expression of such discrepancies in terms of Bolton’s original sample and standard deviations of ratio. Potential limitations of Bolton’s original sample in terms of sex, race and malocclusion

OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

Key

%

Comment

Key 1

80%

though most had 'class 1'

Key :

91%

usually 632/236

Key 3

68%

estimated from incisor angle

Key 4

67%

usually translated teeth

Key 5

43%

spaces

Key 6

56%

increased curve of Spee

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type have already been mentioned but there is another highly important consideration. That sample consisted entirely of “excellent occlusions”. Therefore, all the cases by definition had Bolton ratios which did not prevent a good occlusion. A Bolton ratio which falls outside the standard deviation for that original sample may therefore not indicate a tooth size discrepancy which is clinically significant.

One way for clinicians to get a much better feel for the clinical significance of a discrepancy is for investigators to focus more on the actual size of the discrepancy rather than the Bolton ratios alone. We strongly advocate such an approach. Several papers have suggested that 2-3 mm is a level at which a clinically significant effect may result. Proffit suggested 1.5 mm. Proffit and many other authors do not say whether this applies to the total ratio or the anterior ratio or both and this is a very important point. Also, the discrepancy in millimetres is larger in the maxilla than in the mandible for the same Bolton ratio. Rather than expand at length here on this subject, readers are referred to the discussion section of the paper by Bernabe, Major and Flores-Mir (2004) which covers the most important aspects of this debate very clearly. You will see for example that if 1.5 mm is taken as the marker of clinical significance then Bolton’s original standard deviations of ratio markedly underestimates the percentage of cases in Peru with such a discrepancy, particularly in the posterior segments.

Othman and Harradine (2007), recommended 2 mm of correction as a threshold for clinical significance and, in a random sample of British orthodontic patients, found 25% of patients required such a correction for an ideal total arch ratio and 12% for the anterior ratio (averages for upper and lower arches). These are significant percentages of a representative population of orthodontic patients. Reassuringly, this figure of 2mm was also recommended as a threshold for clinical significance by Endo et al (2009).

Table 2.3: Percentages of cases failing to satisfy each of Andrews' six keys in 1150 American board cases

Bolton discrepancies – conclusions • they are a relatively frequent cause of inability to obtain a perfect occlusion without adjustment of • •

•

tooth size. modern methods of measurement make assessment rapid and we should take advantage of this, but the method error for an individual measurement is substantial in relation to the size of a significant discrepancy, so repeat measurements are advisable. discrepancies should be expressed in millimetres, not in terms of the standard deviations of Bolton’s original ratios. We would suggest that an anterior discrepancy of less than 2 mm (1 mm per side) is unlikely to change our treatment although it might be noted as an explanation of a less-than-perfect anterior occlusion differences in mean ratios between different sexes, races, malocclusions and extraction patterns are small in relation to clinical significance

Failure to achieve the six keys Andrews (1989) also gives the percentages of failure to satisfy each key in 1150 American Board of Orthodontics cases (Table 2.3). This chapter discusses and illustrates the common reasons for these failures.

Key % Reason Key 1

87%

AP molars

Key 2

99%

angulation

Key 3

90%

inclination

Key 4

81%

rotations

Key 5

69%

spaces

Key 6

0%

Spee

Table 2.4: Percentage of 120 cases failing to meet the six keys in a study by Kattner and Schneider (1993)

A further study of the rate of failure to achieve the six keys was performed by Kattner and Schneider (1993) (Table 2.4). In all respects except the curve of Spee, they found an even lower rate of success than Andrews had found in his study even though half the cases were treated with the Straight-Wire Appliance (Roth prescription). However, their sample was also different in being selected from routinely treated cases according to availability of records from two practitioners and might

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be expected to be produce less perfect occlusions than those examined by Andrews which were submitted to the American Board of Orthodontics for board certification. The difference in curve of Spee findings is also interesting in that Andrews measured the occlusal plane to the second molars and Kattner and Schneider to the first molars, the second molars being unerupted in some of their cases. It can be seen that this makes a large difference to the measured flatness of the curve of Spee.

It is worth noting that in 1150 American Board cases studied by Andrews, only three achieved all six keys! It is clear that these goals can be rigorously applied by their original author, but Kattner and Schneider found that none of the 120 cases in their study met all six keys. This very low success rate may be largely explained by an increasing emphasis over the years by Andrews and by others, including Kattner and Schneider, on the lingual aspect of the posterior occlusion which was frequently found wanting, the upper palatal cusps being out of contact with the lower fossae at the end of active treatment stage. This point is of interest in several respects. The torque values in the Roth prescription (very widely favoured for upper molars) deliberately overcorrect the tendency of upper molar palatal cusps to hang down and at the end of active treatment, a lack of complete palatal cusp intercuspation would not be surprising. This assists the elimination of non-working side 'interferences' (vide infra). The paucity of good studies of post-treatment settling is also highlighted. It is conceivable that such post-treatment settling might improve the compliance with the six keys but also increase the incidence of non-working side contacts. Clearly, assessment of the details of an occlusion will be affected by the timing of post-treatment records. Roth made this point (in his letter following the paper by Kattner and Schneider), emphasising the appropriate intention of slightly overcorrecting some aspects of the occlusion in the confident expectation that they will settle back to a better eventual result. So what you see depends on when you look.

Conclusion The six keys are a very hard target if you look closely enough, but remain a very useful clinical aid to achieving an intercuspal occlusion that would be widely accepted as ideal. In addition, the majority of the keys are derived primarily from the labial tooth surface where we attach our brackets and this makes the keys more clinically relevant than a description of occlusion based solely on the occlusal surfaces of the teeth.

Benefits of class 1 occlusion Good alignment of the teeth is a desirable goal from aesthetic and dental health points of view. However, it is worth being a devil’s advocate for a moment and asking why we should aim for a class 1 occlusion. What is wrong with a well-aligned mild class 2 division i or class 2 division ii? Three possible answers should be considered.

•

teeth in an optimal occlusion may perform their basic masticatory function more efficiently. Work by Luke and Lucas (1985) supports this view. An interesting paper by Owens et al (2002), demonstrated a increasing area of occlusal contact or very-near contact from a class 3 malocclusion group, through a class 2 group, a class 1 group to the most occlusal contact in subjects with good occlusion • well-intercuspated occlusions may be more stable. Work by Lloyd and Stephens (1979) supports this hypothesis.

• a six keys occlusion may make it easier to produce the pattern of functional occlusal contacts that is currently widely held to be the most desirable - namely a mutually protective occlusion. This view has been strongly propounded by some authors. However, the work by Tipton and Rinchuse (1991) throws doubt on this association between static and functional occlusion and this point is covered later in this chapter.

A final point might be that since the teeth seem clearly designed to fit together in a class 1 relationship and have a strong natural tendency to intercuspate maximally, then whilst we are aligning them it would be sensible to also aim for such a relationship, unless other considerations outweigh this reasoning, which they sometimes do. However, a paper entitled “The Philadelphia fable: How ideal occlusion became the philosophers stone of orthodontics” by Ackerman et al (2007) gives a lucid summary of the origins of occlusal goals in orthodontics over the last century and argues that we are in danger of valuing a concept of perfect occlusion too highly in relation to other goals of dental health and facial appearance which will be valued more highly by our patients.

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Functional occlusal goals ICP and RCP Most orthodontists would readily agree that the intercuspal position should coincide fairly closely with the retruded contact position. However, the precision of this coincidence has become something of an orthodontic virility test in some circles and an exact coincidence is strongly championed by Roth amongst others. He felt that the “correct” condylar position can never be detected by simple clinical observation because occlusal contacts condition the condylar position and extensive efforts are necessary to reveal the extent of this effect. Williamson et al (1978) have shown that on average, this discrepancy is < 1 mm, but that some individuals (notably with class 2 occlusions) have much larger and clinically significant discrepancies.

Since over 99% of the population have been shown to have an RCP-ICP discrepancy, it seems sensible to treat discrepancies of approximately 1 mm in an anteroposterior direction as entirely normal and their elimination as not a sensible occlusal goal. The question arises as to how we should view RCP-ICP discrepancies of greater magnitudes.

Utt et al (1995) found that approximately 20% of orthodontic patients had a discrepancy of >2 mm prior to treatment. (An interesting side question is whether the advocated ‘power centric’ condylar position produced with firm biting pressure into a pre-contact wax incisor jig is the ‘natural’ or ‘gold standard’ condylar position – especially vertically). The evidence that RCP-ICP discrepancies of 2 mm (measured at the condyle) are harmful is scarce, although Roth felt purely from clinical experience that TMD, periodontal disease, pulpitis and tooth wear are all associated with such discrepancies and that the initial tooth contacts are by definition “interferences”. Small RCP-ICP discrepancies of the condyle are hard to detect without a pre-contact bite registration and articulator mounting.

This is discussed further in a section below.

ICP/RCP discrepancies and cephalometrics Williamson (1978) and others have explored the differences in cephalometric analysis that exist in the RCP and ICP positions and conclude that if the goal is to treat to a zero discrepancy then discrepancies of >2 mm give rise to a clinically significant cephalometric error and should be measured and corrections to the analysis made. If a clinician considers that antero-posterior displacements of < 1 mm which cannot be detected by routine skilful clinical examination are important then he must take on board the necessity to use articulator mounted models with a precontact registration on all cases and to strongly consider adjusting the cephalometric analysis for all patients with a discrepancy > 2 mm.

ICP/RCP discrepancies and articulators

Figure 2.1: A flow diagram of articulator logic. Consistent adherence to this chain of logic would lead to several trips around the orange circuit with repeated mounting of models

Utt et al (1995) reported that only 13% of orthodontists in the USA routinely mount their pretreatment study casts. If it is felt that discrepancies which cannot be detected without pre-contact registration and articulator mounting are important, then repeat records of this type should also be taken prior to the end of treatment to ensure that the displacement has been eliminated and if found to exist at that stage, then additional anchorage from headgear or class 2 elastics would need to be used to eliminate the discrepancy. Utt found that only 3.9% of orthodontists routinely mounted progress records. Successful elimination of the discrepancy would logically need to be checked again with further articulator-mounted models in order to be certain that no discrepancy greater than say the 1 mm average commonly found, is present. This process might well require more than one check. Utt also reported that only 6.5% of orthodontists mounted casts at the end of treatment. This must mean that half of the orthodontists who feel it is

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OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

important to detect discrepancies prior to treatment, do not take the necessary steps to ensure that any such discrepancy is absent at the end of treatment. It can be seen that the logical pursuit of such a viewpoint is a potentially very arduous clinical load for the patient and the clinician (see Figure 2.1). Is there good evidence that such a workload is justified in terms of better results? The excellent study by Ellis and Benson (2003) supports the view that the routine mounting of study casts is not justified by its effect on clinical decisions. They also report the poor reproducibility of recording the “two-piece power centric relationship” even with particularly careful technique.

ICP/RCP discrepancies and “Sunday bites” Perhaps the important question is:- at what size does a discrepancy cease to be part of the normal variation in condylar position and become a “Sunday bite” which we should definitely detect before treatment and eliminate during treatment? One answer might be that if we can detect an occlusal discrepancy by clinical examination which is > 2 mm then this is a clinically significant discrepancy. Of relevance is that Egermark et al (2003) chose > 1.5 mm as their definition of a potentially significant A-P discrepancy. Frequently, such displacements are associated with an ICP which is cuspally ill-defined (e.g. a class 2 case with anterior open bite) and sometimes there is one clearly abnormally placed tooth (e.g. a tipped terminal molar following uncontrolled extraction of a more mesial molar) which is causing the displacement. Such mandibular displacements are perhaps a good example of something which is easy to detect and treat if you keep remembering to look for it. A sound clinical technique for determining the most comfortably rearmost and uppermost condylar position will almost always reveal such discrepancies, whilst simple additional aids such as the leaf gauges popularised by Williamson serve to remove the feedback from occlusal contacts and can sometimes be useful. With this viewpoint, a clinically detectable post-treatment discrepancy of < 1 mm would be a sensible treatment goal at the end of any treatment which can alter the occlusion. It is a fact that quantification of condylar position in all three planes of space requires skilful precontact registration and articulator mounting of casts. It is interesting that Milosevic and Samuels (1998) employed clinical, intra-oral detection of ICP/RCP discrepancies in their scientific investigation of this topic when looking for discrepancies of this size as did Egermark et al (2003) who regarded antero-posterior discrepancies of >1.5 mm and lateral discrepancies of >0.5 mm to be potentially significant. We currently feel that the evidence is weak that occlusal discrepancies which are only detectable by articulator mounting are frequently harmful and we therefore adopt the approach outlined in this paragraph rather than the view which would logically require repeated articulator mountings on all cases.

A particularly interesting contribution to the debate on this topic is the article by Utt et al (1995) and the Point/Counterpoint articles by Roth (1995) and Rinchuse (1995).

Functional tooth contacts

It has frequently been proposed that the following problems can result from certain patterns of functional tooth contact.

• • • •

mandibular dysfunction bruxism periodontal disease instability of tooth position

It is therefore clearly important to examine this topic and decide on the best functional occlusal goals. A bilaterally balanced occlusion is the most popular goal for prosthetists constructing full dentures and a unilaterally balanced (group function) pattern has its advocates for natural dentitions, but the most commonly proposed goal for optimal tooth contacts during functional movements is the Mutually Protective Occlusion (MPO). This is usually defined as an immediate but gentle disclusion of all posterior teeth on leaving the intercuspal position. The working side canine (or canine plus incisors) should be the only teeth in contact. In ICP the anterior teeth should in turn be slightly out of contact. Any other contacts between teeth are termed occlusal “interferences” and it has been proposed that these interferences predispose to one of the problems listed above. In this chapter, the current evidence relating to these hypotheses will be summarised.

OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

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Mandibular dysfunction (MD) and functional occlusion

Large cross-sectional studies such as those by Egermark-Erikson et al (1983), Riolo et al (1987) and Seligman et al (1988, 1991) have all failed to provide convincing evidence that there is a relationship between mandibular dysfunction and occlusal interferences. The highly impressive 20-year follow-up longitudinal study by Carlsson et al (2002), found no strong predictors of later TMD and the only occlusal factor was a weak association with deep overbite at an early age. The study by Egermark et al (2003) did show some weak correlations between previous unilateral crossbite and current lateral displacements and current TMJ clicking (r=0.35 and r=0.31 respectively). In general, however, correlation between features of malocclusion and MD signs and symptoms were “weak and few”.

This excellent paper is well worth a careful read. Some studies (e.g. Pullinger and Seligman 1991) support a clinical impression that anterior open bite - which is the antithesis of a mutually protected occlusion - is a modest predisposing factor to mandibular dysfunction. With respect to the effects of occlusal equilibration, the placebo effect of such equilibration has long ago been documented (Goodman et al 1976), but more thought-provoking and impressive evidence comes from the double blind prospective controlled study by Magnusson and Enbom (1984) who showed not only this placebo effect but also that experimentally created interferences were associated with additional signs and symptoms of dysfunction. Anecdotal evidence from clinical experience with individual cases often seems to support a causative link, but this source of evidence must be viewed with great caution. A concise and recent review of systematic reviews by Huang (2004) is well worth the read. He concludes that there is no convincing evidence that occlusal adjustment prevents or treats TMD better than no treatment or placebo treatment. A further long-term follow-up study by Egermark, Carlsson and Magnusson (2005), found the same very low incidence of TMD in patients who had received orthodontic treatment as in those who had not. This was in spite of a high prevalence in both groups of functional tooth contacts frequently described as “interferences”. The short article by Rinchuse, Rinchuse and Kandasamy (2005), is a typically plain-talking and hard-hitting essay comparing evidence-based and experience-based viewpoints on the relationship between occlusion and TMD.

Bruxism and functional occlusion

As mentioned above, there is a clinical impression that mandibular displacements may predispose to damage from attrition, but studies have shown that so-called parafunctional activity is almost universal and should not therefore be considered abnormal except when present to a marked degree when it is referred to as bruxism. Studies such at that by Egermark-Erikson (1983) failed to show any connection between bruxism and the pattern of functional occlusal contacts, although Carlsson et al (2001) found that parafunction and tooth wear at an early age were risk factors for TMD 20 years later.

Periodontal disease and functional occlusion The view that periodontal disease may be exacerbated by non-working side contacts is strongly propounded by some speakers, but there is very little work to support it. The work by Ericsson, Thilander and Lindhe (1978) on beagle dogs with experimental periodontitis and severe occlusal trauma remains – with its definite experimental limitations - almost the only firm evidence in this area and the occlusal stress in that study was extreme and unlike any probable effect from a non-working side contact.

Tooth stability and functional occlusion Several clinicians, e.g. Roth (1981 and succeeding articles) very firmly proposed that much post-treatment relapse can be blamed on the absence of a mutually protective occlusion. For example, recurrence of lower incisor crowding has been blamed on undesirable lateral forces on the canine teeth resulting from occlusal interferences. There is very little evidence to support this view. More plausibly, we might feel that upper incisors that are unduly retroclined following inappropriate overjet reduction with a removable appliance might lead to overjet relapse due to functional occlusal forces with excessively steep occlusal guidance. However, there is no evidence to support this hypothesis either and in any case, such treatment would not be advised on static occlusal grounds.

Summary of current evidence on functional occlusion In summary, there is little hard evidence to support the view that a mutually protective occlusion confers benefit in these respects. For good and certainly trenchant reviews of this topic, the article “A contemporary and evidencebased view of canine protected occlusion” by Rinchuse et al (2007) and a further paper entitled “Myths of orthodontic gnathology” by Rinchuse and Kandasamy (2009) are comprehensively referenced and well worth a read.

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OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

In view of this current evidence, the adoption of the MPO as our functional occlusal goal should probably depend to a significant degree on the extra effort involved for operator and patient. How difficult is it to consistently produce an MPO?

Stability of functional occlusal contacts

There is also the question of the long-term stability of orthodontically created functional occlusal patterns. It is natural to wonder what were the functional occlusal contacts of Andrews' original 120 NONs and indeed Andrews (1989) himself has wondered this, but in the 1960s and early 1970s when the cases were being collected, functional occlusion was not yet such an issue and Andrews did not take functional occlusal records. Clark and Evans (1998) and Milosevic and Samuels (1998) both reported on interferences immediately after the end of treatment and in retention, but little is known about post-orthodontic functional occlusion in the longer term. Recall of patients for such studies is of course more difficult. Egermark et al (2003) report that long after orthodontic treatment, eruption of third molars can create new non-working side contacts. Olsson and Linqvist (2002), did investigate the prevalence of interferences after orthodontic treatment. They found that 54.4% of patients had interferences after treatment and that this could be reduced over the next year to 13.8% by occlusal grinding. Some patients required 6 sessions of occlusal grinding to prevent recurrence of interferences at the next recall visit! This suggests that such tooth contacts may be hard to eliminate for the long term. We do not advocate occlusal grinding to remove non-working side contacts.

Suggested functional goals Balancing the evidence concerning benefit of an MPO and the practical consequences of aiming to achieve it, we would suggest the following approach. Aim for an MPO within reasonable limits of treatment and chairside time and patient discomfort:

• take advantage of preadjusted appliances to achieve more frequently a “six keys” intercuspal

occlusion, since it is still possible that such an occlusion is more likely to fulfil functional occlusal goals as well.

• choose a prescription for upper molar attachments (adequate buccal root torque e.g. Roth, Damon, MBT prescriptions) that facilitate adequate elevation of upper molar cusps and flattening of the curve of Spee on the second molars.

• plan ahead, check the functional occlusion during treatment and choose the most efficient moment to align the second molars if this is required. If in doubt, place attachments earlier rather than later. If bonding all the molars, the best time is usually at the first visit whilst bonding all the other teeth.

Other anatomical goals relating to the functioning occlusion Condylar Position

Conflicting opinions have been expressed concerning the desired condylar position within the fossa and this question is closely related to that of RCP-ICP discrepancies discussed earlier. At one end of the spectrum for example, Roth (1995) advocated a relatively posterior position, often described as “rearmost, uppermost and midmost” with recently more emphasis on the ‘uppermost’ component. Lysle Johnston (1988) points out that rearmost and uppermost are contradictory terms in the TMJ, but essentially what is implied is that there is no discrepancy between RCP and ICP and the earlier consideration of RCP-ICP discrepancies is therefore relevant to this goal. Alternatively, the holders of the “functional” viewpoint (e.g. Witzig 1987) advocate a forward position with a minimum of 3 mm joint space behind the condyle on X-ray. Such a forward position is claimed to trap the disc on top of the condyle and therefore prevent anterior displacement of the disc that will cause internal derangement of the joint and pain. Orthodontic treatment that changes condylar position in either direction will therefore be incriminated by holders of one of these views as predisposing to mandibular dysfunction. Luecke and Johnston (1992) have shown that conventional fixed appliance orthodontic treatment causes a transitory more forward position of the condyle in the intercuspal position with a return to the pre-treatment position after treatment i.e. orthodontic treatment with fixed appliances did not change the condylar position. In the longer term, the jaw

OCCLUSAL TREATMENT GOALS EXCELLENCE IN ORTHODONTICS 2012

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influences tooth position (as in dentoalveolar compensation), rather than the converse. Also, no relationship was found between condylar position and the craniomandibular index (CMI) in this study.

Condylar position and functional appliances In several studies, Hans Pancherz (see chapter on Functional Appliances) has demonstrated that the Herbst appliance also does not change the condylar position even after seven months of full-time forward posturing in the appliance.

A careful MRI analysis by Chintakanon et al (2000), also found that the condyles were essentially unchanged by functional treatment in their concentricity within the fossa. This finding is supported by a report by Joondeph (1999) of cases in which attempted anterior repositioning of the condyle to alleviate TMD symptoms returned completely to the previous position in the long term.

Clinical tip: At present it does not seem necessary or practicable to have a specific condylar position as a treatment goal, other than aiming for a clinically detectable discrepancy between RCP and ICP of 1 mm or less.

Articular disc position This has become much easier to assess following the introduction of MRI scans which do not involve ionising radiation and can be ethically used on any subject. Studies on cadavers have revealed that in skilled hands, MRI and arthrography are both very good at diagnosing disc position - although both were capable of false positive diagnoses of anterior displacement. Many studies with these techniques have shown that there is almost no relationship between disc position and symptoms of mandibular dysfunction. Thirty-one per cent of totally asymptomatic volunteers were found in a study by Kircos (1987) using MRI to have an anteriorly displaced disc. This percentage has since been found in several other studies on asymptomatic volunteers - for example the study by Alexander (1993). In this latter study it was interesting that of the 13% who had an anterior disc position only half had a posterior condylar position - the two features do not therefore coincide. Also Alexander found five subjects with normally related discs who had joint sounds, whilst only two of the seven with anteriorly placed discs had joint sounds. It seems appropriate to conclude that in spite of strong advocacy by some clinicians for designing orthodontic treatment to produce a particular relationship between condyle and disc, this is not with our current knowledge a sensible treatment goal. Although disc position is very probably an important aspect of the problem for some patients with mandibular dysfunction, orthodontic treatment has not been shown to be capable of altering or preventing the alteration of disc position and the relationship between disc position and dysfunction continues to appear complex and very incompletely understood.

Mandibular dysfunction following orthodontic treatment Regardless of specific treatment goals in relation to mandibular function, we should be aware of the evidence concerning the effect of orthodontic treatment on MD however mediated. The studies by Egermark and Thilander (1992), Wadhwa et al (1993), Kremenak et al (1992) and Sadowsky et al (1991) for example have all failed to find any harmful effects in the short or long term and the review by Sadowsky (1992) is equally reassuring. In fact the results tend to suggest a modest beneficial effect from orthodontic treatment with respect to MD. More recent studies continue to support these findings. Egermark et al (2003) reported a 20-year follow-up study of an original random sample of 400 of whom 320 (85%) were still providing data at 20 years â&#x20AC;&#x201C; a remarkable achievement. They found a trend (not statistically significant) for those who had received orthodontic treatment in childhood (32% of the original random sample) to have less symptoms of MD. A further long term follow-up study by Egermark, Carlsson and Magnusson (2005), found the same very low incidence of TMD in patients who had received orthodontic treatment as in those who had not. A cross-sectional study by Conti et al (2003) presented results which would support the view that in the short-term, orthodontic treatment has no effect on the incidence or severity of MD. However, this study suffers from the inherent shortcomings of a comparison between two groups of different patients of different ages and highlights the benefits as well as the difficulties of a long-term prospective study such as that by Egermark. Further reports have appeared on the impressive long-term follow up of 1018 Welsh children (Mohlin et al 2004); McFarlane et al (2009) 337 subjects were followed from the age of 11 years to 30 years. These papers rewards a thorough reading. The orthodontic treatment received by these children was rather old fashioned and unsatisfactory by modern standards, yet there was no relationship between TMD and this treatment or of any feature of the treatment (such as extractions). Whilst acknowledging that all this weighty evidence does not totally

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preclude the possibility that some treatment in certain cases might precipitate problems, such a possibility would seem to be small in relation to the prevalence of TMD. NB: The American Journal of Orthodontics and Dentofacial Orthopaedics of January 1992 was devoted entirely to papers on TMJ research many of which were part of the AAO TMJ Research Programme started in response to the settlement of the Brims versus Malloy lawsuit. The American Academy of Orofacial Pain has published an excellent small book entitled ‘Temporomandibular Disorders’ and edited by Charles McNeill. It has now been superseded by a slightly expanded version entitled ‘Orofacial Pain’ edited by Jeffrey Okeson. Both are excellent publications, are admirably concise, have excellent bibliographies and repay careful study.

References Ackerman JL, Ackerman MB, Kean MR (2007) A Philadelphia Fable: How ideal occlusion became the philosopher's stone of orthodontics The Angle Orthodontist 77: 192–194 Alkofide E and Hashim H (2002) Intermaxillary tooth size discrepancies among different malocclusion classes: A comparative study Journal of Clinical Paediatric Dentistry 26: 383-388 Andrews LF (1972) The six keys to normal occlusion American Journal of Orthodontics 62: 296-309 Andrews LF (1989) Straight Wire. The concept and appliance Published by LA Wells Co. San Diego ISBN 0-9616256-0-0 Araujo E and Souki M (2003) Bolton anterior tooth size discrepancies among different malocclusion groups Angle Orthodontist 73:307-313 Bernabe E, Major PW and Flores-Mir C (2004) Tooth-width ratio discrepancies in a sample of Peruvian adolescents American Journal of Orthodontics and Dentofacial Orthopaedics 125:361-5 Bolton WA (1958) Disharmony in tooth size and its relation to the analysis and treatment of malocclusion American Journal of Orthodontics 28:113-30 Bolton WA (1962) The clinical application of tooth size analysis American Journal of Orthodontics 48:504-529 Carlsson GE, Egermark I and Magnusson T (2002) Predictors of signs and symptoms of temporomandibular disorders: a 20-year follow-up study from childhood to adulthood Acta Odontologica Scandinavica 60: 180-185 Chintakanon K, Sampson W, Wilkinson T and Townsend G (2000) A prospective study of Twin-block appliance therapy assessed by magnetic resonance imaging American Journal of Orthodontics and Dentofacial Orthopaedics 118: 494-504 Clark JR and Evans RD (1998) Functional occlusion relationships in a group of post-orthodontic patients: preliminary findings European Journal of Orthodontics 20: 103-110 Conti A, Freitas M, Conti P, Henriques J and Janson G (2003) Relationship between signs and symptoms of temporomandibular disorders and orthodontic treatment: a cross-sectional study Angle Orthodontist 73: 411-417 Crosby DR and Alexander CG (1989) The occurrence of tooth size discrepancies among different malocclusion groups American Journal of Orthodontics and Dentofacial Orthopaedics 95:457-461 Egermark I and Thilander B (1992) Craniomandibular disorders with special reference to orthodontic treatment. An evaluation from childhood to adulthood American Journal of Orthodontics and Dentofacial Orthopaedics 101: 28-34

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Egermark I, Magnusson T and Carlsson G (2003) A 20-year follow-up of signs and symptoms of temporomandibular dysfunction and malocclusions in subjects with and without orthodontic treatment in childhood Angle Orthodontist 73: 109-115 Egermark-Erikson L, Ingervall B, and Carlsson GE (1983) The dependence of mandibular dysfunction in children on functional and morphologic malocclusion American Journal of Orthodontics 83: 187-194 Egermark I, Carlsson GE, Magnusson T (2005) A prospective long-term study of signs and symptoms of temporomandibular disorders in patients who received orthodontic treatment in childhood Angle Orthodontist 75: 645-650 Ellis P and Benson PE(2003) Does articulating study casts make a difference to treatment planning?

Journal of Orthodontics 30:45-49 Endo T, Uchikura K, Ishida K, Shundo I, Sakaeda K and Shimooka S(2009) Thresholds for clinically significant tooth-size discrepancy Angle Orthodontist 79: 740-746 Ericsson I, Thilander B and Lindhe J (1978) Periodontal conditions after orthodontic tooth movements in the dog.

Angle Orthodontist 48: 210-218 Freeman JE, Maseroni AJ and Lorton L (1996) Frequency of Bolton tooth-size discrepancies among orthodontic patients American Journal of Orthodontics and Dentofacial Orthopaedics 110: 24-27 Goodman P, Greene CS, and Laskin DM (1976) Response of patients with myofascial pain-dysfunction syndrome to mock equilibration Journal of the American Dental Association 92: 955-9 Heusdens M, Dermaut L and Verbeeck R (2000) The effect of tooth size discrepancy on occlusion: An experimental study American Journal of Orthodontics and Dentofacial Orthopaedics 117: 184-191 Huang GL et al (2004) Occlusal adjustment for treating and preventing temporomandibular disorders American Journal of Orthodontics and Dentofacial Orthopaedics 126:138-139 Johnston LE (1988) Gnathologic assessment of centric slides in post-retention orthodontic patients Journal of Prosthetic Dentistry 60: 712-715 Joondeph D (1999) Long-term stability of mandibular orthopaedic repositioning Angle Orthodontist 69: 201-209 Kattner PF and Schneider BJ (1993) Comparison of Roth appliance and standard edgewise appliance treatment results American Journal of Orthodontics and Dentofacial Orthopaedics 103: 24-32 Kircos LT, Ortendahl DA, Mark AS, and Arakawa M (1987) Magnetic resonance imaging of the TMJ disc in asymptomatic volunteers.

Journal of Oral and Maxillofacial Surgery 45: 852-854 Kremenak CR, Kinser DD, Melcher TJ, Wright GW, Harrison SD, Ziaja RR, Harman HA, Ordahl JN, Demro JG, Menard CC, Doleski KA and Jakobsen JR (1992) Orthodontic risk factors for temporomandibular disorders (TMD) II. American Journal of Orthodontics and Dentofacial Orthopaedics 101: 21-27 Lloyd TG and Stephens CD (1979) Spontaneous changes in molar occlusion after extraction of all first premolar teeth - a study of class II/I cases treated with removable appliances British Journal of Orthodontics 6: 91-94 Luecke PE and Johnston LE (1992) The effect of maxillary first premolar extraction and incisor retraction on mandibular position: testing the central dogma of â&#x20AC;&#x153;functional orthodonticsâ&#x20AC;?

American Journal of Orthodontics and Dentofacial Orthopaedics 101: 4-12

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Luke DA and Lucas PW (1985) Chewing efficiency in relation to occlusal and other variations in the human dentition British Dental Journal 159: 401-403 MacFarlane T, Kenealey P, Kingdon HA, Mohlin BO, Pilley R, Richmond S and Shaw WC (2009) Twenty year cohort study of health gain from orthodontic treatment: Temporomandibular disorders.

American Journal of Orthodontics and Dentofacial Orthopaedics 135: 692.e1-692.e8 Magnusson T and Enbom L (1984) Signs and symptoms of mandibular dysfunction after introduction of experimental balancing side interferences Acta Odontologica Scandinavica 42: 129-134 Milosevic A and Samuels RHA (1998) Functional occlusion after fixed appliance orthodontic treatment: a UK three-centre study European Journal of Orthodontics 20: 561-568 Mohlin BO, Derweduwen K, Pilley R, Kingdon A, Shaw WC, Kenealy P (2004) Malocclusion and temporomandibular disorder: A comparison of adolescents with moderate to severe dysfunction with those without signs and symptoms of temporomandibular disorder and their further development to 30 years of age Angle Orthodontist 74:319-327 Nie Q and Lin J (1999) Comparison of intermaxillary tooth size discrepancies among different malocclusion groups.

American Journal of Orthodontics and Dentofacial Orthopaedics 116: 539-44 O’Higgins E, Kirschen R and Lee RT (1999) The influence of maxillary incisor inclination on arch length.

British Journal of Orthodontics 26: 97-102 Olsson M and Linqvist B (2002) Occlusal interferences in orthodontic patients before and after treatment, and in subjects with minor orthodontic need.

European Journal of Orthodontics 24: 677-687 Othman SA and. Harradine NWT (2006) Tooth-size discrepancy and Bolton’s ratios: a literature review Journal of Orthodontics 33: 45-51 Othman SA and Harradine NWT (2007) Tooth size discrepancies in an orthodontic population Angle Orthodontist 77: 668–674.

Othman SA and Harradine NWT (2007b) Tooth-size discrepancy and Bolton’s ratios: the reproducibility and speed of two methods of measurement Journal of Orthodontics 34: 234-242 Owens S, Buschang PH, Throckmorton GS, Palmer L, English JD (2002) Masticatory performance and areas of occlusal contact and near-contact in subjects with normal occlusion and malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 121: 602-610 Proffit WR (2000) Contemporary Orthodontics Mosby Inc. St Louis page 170 Pullinger AG and Seligman DA (1991) Overbite and overjet characteristics of refined diagnostic groups of temporomandibular disorders American Journal of Orthodontics and Dentofacial Orthopaedics 100: 401-415 Redahan S and Lagerstrom L (2003) Orthodontic treatment outcome: the relationships between anterior dental relations and anterior inter-arch tooth size discrepancy Journal of Orthodontics 30:237-244 Rinchuse D, Kandasamy S and Sciote J (2007) A contemporary and evidence-based view of canine protected occlusion.

American Journal of Orthodontics and Dentofacial Orthopaedics 132: 90-102 Rinchuse DJ (1995) Counterpoint A three-dimensional comparison of condylar position changes between centric relation and centric occlusion using the mandibular position indicator American Journal of Orthodontics and Dentofacial Orthopaedics 107: 319-28

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Rinchuse DJ, Rinchuse DJ, and Kandasamy S (2005) Evidence-based versus experience-based views on occlusion and TMD American Journal of Orthodontics and Dentofacial Orthopaedics 127: 249-254 Rinchuse DJ and Kandasamy S (2009) Myths of orthodontic gnathology American Journal of Orthodontics and Dentofacial Orthopaedics 136: 322-330 Riolo ML, Brandt D and TenHave TR (1987) Association between occlusal characteristics and signs and symptoms of TMJ dysfunction in children and young adults American Journal of Orthodontics 92: 467-477 Roth RH (1995) Point/Counterpoint: A three-dimensional comparison of condylar position changes between centric relation and centric occlusion using the mandibular position indicator American Journal of Orthodontics and Dentofacial Orthopaedics 107: 315-318 Saatci P and Yukay F (1997) The effect of premolar extractions on tooth-size discrepancy American Journal of Orthodontics and Dentofacial Orthopaedics 111: 428-34 Sadowsky C, Theisen TA, and Sakols EI (1991) Orthodontic treatment and temporomandibular joint sounds - a longitudinal study American Journal of Orthodontics and Dentofacial Orthopaedics 99: 441-7 Sadowsky C (1992) The risk of orthodontic treatment for producing temporomandibular mandibular disorders: A literature overview.

American Journal of Orthodontics and Dentofacial Orthopaedics 101: 79-87 Sangcharearn Y and Hob C (2007) Maxillary incisor angulation and its effect on molar relationships The Angle Orthodontist 77: 221-225 Santoro M, Ayoub ME, Pardi VA and Cangliosi TL (2000) Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition of Dominican Americans Angle Orthodontist 70: 303-397 Seligman DA and Pullinger AG (1991) The role of intercuspal occlusal relationships in temporomandibular disorders: a review.

Journal of Craniomandibular Disorders and Facial Oral Pain 5: 96-106 Seligman DA, Pullinger AG, and Solberg WK. (1988) Temporomandibular disorders Part III: occlusal and articular factors associated with muscle tenderness Journal of Prosthetic Dentistry 59: 483-489 Smith S, Buschang PH and Watanabe E (2000) Interarch tooth size relationships of three populations: “Does Bolton’s analysis apply?”

American Journal of Orthodontics and Dentofacial Orthopaedics 117: 169-174 The American Academy of Orofacial Pain (1993) Temporomandibular disorders Guidelines for Classification, Assessment and Management Chicago, Quintessence Publishing Co Inc., Editor Charles McNeill The American Academy of Orofacial Pain (1996) Orofacial Pain Guidelines for Assessment, Diagnosis and Management Chicago, Quintessence Publishing Co Inc., Editor Jeffrey Okeson Tipton T and Rinchuse DJ (1991) The relationship between static occlusion and functional occlusion in a dental student population Angle Orthodontist 61: 57-63 Tomassetti JJ, Taloumis LJ, Denny JM, and Fischer JR (2001) A comparison of 3 computerised Bolton tooth-size analyses with a commonly used method Angle Orthodontist 71:351-357 Utt TW, Meyers CE Jr, Wierzba TF, and Hondrum SO (1995) A three-dimensional comparison of condylar position changes between centric relation and centric occlusion using the mandibular position indicator American Journal of Orthodontics and Dentofacial Orthopaedics 107: 298-308

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Wadhwa L, Utreja A, and Tewari A (1993) TM dysfunction in normal, untreated and treated malocclusions American Journal of Orthodontics and Dentofacial Orthopaedics 103: 54-61 Williamson EH, Caves SA, Edenfield RJ, and Morse PK (1978) Cephalometric analysis: Comparison between maximum intercuspation and centric relation American Journal of Orthodontics 74: 672-677 Witzig JW and Spahl TJ (1987) The clinical outline of maxillofacial orthopaedic appliances 1st ed. Littleton, Mass: PSG Publishing: 167-216

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Chapter

3

Diagnosis and treatment planning Nigel Harradine

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Introduction The chapter on Occlusal Treatment Goals considers what our occlusal goals should be. This chapter addresses further important questions of diagnosis and treatment planning:

• • • •

where would we ideally like to place this occlusion horizontally and vertically within the face? exactly what aspects of the appearance and function of the teeth and face are a source of dissatisfaction to the patient? what are the diagnostic features, which we need to observe to decide how we can find the best means of satisfying these requirements? how do extractions affect aesthetics, stability and ease of treatment?

With regard to the first point, the vertical position of the occlusion is also important to remember and we should ensure that our treatment mechanics avoid unwanted extrusion of the molars or incisors. The scope for altering the vertical position of the occlusion orthodontically is covered in other chapters. This chapter will discuss the anteroposterior position of the occlusion and the width of the occlusion. Decisions need to be reached as to what is desirable and what is achievable.

In relation to the second point, a gummy smile is a good example of a dentofacial feature which may or may not bother the patient.

A list of diagnostic features relating to these aspects is clearly required and also decisions about how best to assess them.

The last part of this chapter focuses on extraction decisions, which are such an important part of the planning process.

It is inappropriate in this manual to deal in detail with all the potentially relevant features, such as measuring the overjet or assessing the molar relationship. Nor is a level of detail appropriate for orthognathic cases included here. Rather, this section is a core checklist to avoid important categories of data being neglected and to suggest appropriate measures in some categories.

The occlusion

Important aspects of occlusal planning have been covered in the chapter on Occlusal Treatment Goals. However, other factors, notably dental disease or missing or previously extracted teeth will alter the potential choice of occlusal goals.

Features important in diagnosis The facial soft-tissue profile The two most important features are probably the prominence of the lips relative to the nose and chin (assessed via the lower lip to E line distance or using Merrifield’s line) and the nasolabial angle (NLA). These have their limitations but are also quick and easy to apply and therefore stand a good chance of being incorporated in routine orthodontic diagnosis. One of the limitations of the NLA (Figure 3.1) is that it comprises both the angle of the lower surface of the nose and also the inclination of the upper lip and facial aesthetics in profile may be more influenced by the latter. An angle between a tangent to the upper lip and the facial horizontal (Figure 3.2) might be a better measure of the aesthetics of upper lip profile but is not in common use and the NLA with intelligent interpretation may therefore be preferred.

The Holdaway angle is another well-known measure of balance in facial profile. It has been used in the British Orthodontic Society national audit of successively treated orthognathic cases (Johnston et al 2006), and is now officially recommended by the BOS clinical effectiveness committee as one of seven cephalometric measures to

DIAGNOSIS AND TREATMENT PLANNING EXCELLENCE IN ORTHODONTICS 2012

Figure 3.1: The nasolabial angle (NLA). This is a well established aesthetic indicator, but may not be the best guide to aesthetics of the upper lip profile

Figure 3.2:

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A suggested alternative to NLA. The lip inclination

audit the outcome of orthognathic cases. OPAL, which is produced on behalf of the British Orthodontic Society, was used to measure and extract the data and the Holdaway angle is now included in the OPAL analysis. This angle is open to a little confusion both from differences in definition and also depending on whether the correction factor for the skeletal convexity is applied. The original papers (Holdaway 1983, Holdaway 1984) are recommended and fully explain his thoughts with plenty of examples. The norm is entirely his opinion. A paper by Basciftci et al (2003) used this angle and is a good example of the angle in action as a measure of balance in facial profile. The angle in its conventional definition is between soft tissue nasion-soft pogonion and soft pogonion-labrale superius. The larger the facial convexity (i.e. the more skeletal class 2), the larger the angle should be, according to Holdaway. Interestingly, both the Turkish dental students in this paper and the Bolton norms have Holdaway angles at the very upper end of ‘normal’ according to Holdaway.

OPAL gives both the uncorrected value and the value corrected for convexity according to Holdaway’s formula.

An important point about Merrifield’s line and the Holdaway angle are that they do not include nose prominence in the assessment of facial balance whereas the Rickets E line does.

A relatively straightforward and interesting analysis for assessing soft tissue balance has been proposed by Bass (2003). The anteroposterior positions of the lips and chin are assessed in relation to a perpendicular from subnasale. This analysis is linear as is Ricketts E line assessment but like the Holdaway analysis, disregards the nose. An appealing aspect in principle is the use of a natural vertical obtained from posing during a lateral photograph, which is then transferred to the cephalometric x-ray. This uses a simple protractor and the E line as a reference common to photograph and cephalogram. A simple method of recording natural head posture is intuitively a sensible way to view aesthetics of the soft tissues. Some digitising programs such as OPAL, permit the recording of natural vertical and then make antero-posterior measurements - e.g. of the nose and chin - in relation to it. This method may increase the popularity of using a natural head posture.

Figure 3.3: The Holdaway angle. A measure of facial balance which excludes the nose

The lips

The vertical resting and smiling (upper lip) lip lines are important in

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relation to appearance and in some cases to the stability of overjet reduction. These can be measured in mm relative to the upper incisor tip. If any upper gum is shown during smiling, this may be a cause of concern to the patient and this possibility should be explored. Interestingly, Johnson and Smith (1995) propose, in a study on smile width, that the most important feature of a smile that both affects aesthetics and is also affected by orthodontics, is the amount of maxillary gingivae displayed. Their examples of smiles judged to have a poor appearance by a lay panel seem to support this view.

The A-P and vertical skeletal pattern and the incisor inclinations A well-known variety of cephalometric parameters exist for these assessments.

Temporomandibular joint dysfunction

Although clinically significant signs and symptoms seem uncommon and there is good evidence that orthodontic treatment does not cause this potential problem, it is quick and easy to at least be aware of the existence and extent of any signs and symptoms.

• • •

joint noises? discomfort with jaw movement / muscle tenderness? amount of opening and lateral excursion in mm. This can be recorded in the notes in simple diagrammatic form and is a good objective sign of a change in actual joint dysfunction. Opening is usually > 40 mm and lateral excursion > an upper incisor width.

The patient's actual complaints For example: Is the patient bothered by the prominent upper teeth or also by the receding chin? This may profoundly affect the chosen plan in cases of borderline skeletal severity. Is the patient bothered by the appearance or function of an anterior open bite or is it the long face or the gummy smile that are the main concern? This may strongly influence the choice between Young Kim type orthodontic mechanics and a Le Fort osteotomy.

Patient compliance The literature has to date been largely unhelpful in identifying predictors of lack of patient compliance. Midtreatment indicators such as a failure to attend or to progress in the early stages of treatment are of some help, but we still have almost no scientific ability to pick winners in advance. The study by O’Brien et al (2003) did show that a geographical measure of likely social deprivation (the postcode) did significantly predict levels of compliance with functional appliances. However, it is debatable as to how much we would alter the treatment plan in the light of the patient’s address.

Age and sex

Spontaneous space closure has been clearly shown by Stephens and Houston (1985) to be highly related to the rate and amount of remaining growth. Johnston has shown (e.g. Livieratos and Johnston 1995) in studies using his pitchfork analysis (Johnston 1996) that in a growing patient, a significant part of the correction of a class 2 molar relationship in a non-extraction case is, on average, due to temporary inhibition of maxillary growth and continuing mandibular growth. This is clearly a large factor to consider when choosing mechanics in a patient with little or no remaining growth.

The problem list Having gathered all the relevant data, we would strongly advocate the compilation of a problem list before deciding on treatment aims and subsequently, treatment means. The advantages of a problem list can be summarised as follows:

• •

it turns a mass of data into a short and relevant list no problems are forgotten – at the treatment planning stage or later

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• •

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it focuses thought on the actual problems it enables problems to be recorded as fully noted, even if the subsequent list of treatment aims includes a decision to accept a problem rather than to attempt to resolve it.

These are powerful advantages in making good plans, in keeping track of treatment aims during treatment and in recording the limitations of treatment aims. A list of treatment aims will of necessity address all the problems in the list and will lead to a rational selection of the best means of treatment for that patient The sequence of forming a plan should therefore be:

• • •

compile a problem list list the treatment aims list the treatment means

General and specific treatment aims

Any specific list of treatment aims will be compiled against an underlying set of general treatment aims or principles. For example, we need to have answers to all the following questions:

• • • • •

what final occlusion do I normally aim for? what general aims do I have about changes in arch width and shape? what do I believe is desirable/achievable regarding vertical tooth position? what general aims do I have for antero-posterior lower incisor position? what are my general views about the effects of extractions and what factors influence my choice of extractions?

All these questions are addressed in one of the chapters of this manual, with the last two being a particular focus of this chapter. It will not surprise readers to hear that we feel that every orthodontist needs views on these questions that are based on the best available evidence, although it needs to be recognised that the current evidence is far from ideal on many of these points. A paper by Lysle Johnston (1998) is typically iconoclastic on this subject and very well worth a read. It is entitled “The value of information and the cost of uncertainty: who foots the bill?”

Antero-posterior incisor position This is a highly important part of any treatment plan. Given that our occlusal goals usually include a class I incisor relationship, the question becomes one of where to aim to put the lower incisors. This should be considered first in its own right and then in relation to extraction philosophy since this a very important determinant of final lower incisor position. This question is very amenable to cephalometric analysis and many well-known cephalometric goals for lower incisor position have been advocated. Those by Tweed, Steiner, Merrifield, (1996) Ricketts, Downs, Mills (1966) and Holdaway are representative (see the book by Athanasiou 1995). The questions that should be asked about any goal for incisor position are:

• • • • •

does it produce results that are more stable? are the results more aesthetic? does it facilitate a good occlusion? can the planned position be more easily achieved than others? is the planned incisor position conducive to long-term dental health?

Stability and lower incisor position The most crucial questions are the first three. Regarding stability, few people now dispute that no treatment goal is likely to produce more stable results than those obtained when following Mills’ goal (1968) of aiming to leave

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the average incisor labiolingual position unchanged during treatment. The question is whether other guides to end-of-treatment incisor position will produce results that are equally stable anteroposteriorly. In the past, many have claimed or implied - contrary to Mills’ findings - that their analysis or goal will consistently produce substantial and stable labiolingual change in lower incisor position. The evidence to support this is very slim although individual cases of such a stable change undoubtedly occur. Mills (1966) found that lower incisors which were proclined or retroclined by a minimum of 7 degrees during treatment relapsed by an average of 50% posttreatment. The extent of these post-treatment changes correlated significantly with the amount of labiolingual movement, although there were unpredictable individual exceptions. A study by Houston and Edler (1990) provided strong evidence that the APo line is not a position of lower incisor stability. They also found that in 62% of cases the incisors tended to return towards their starting A-P position. In the remaining cases, the posttreatment A-P changes were haphazard. More recent studies have produced similar findings. Hansen, Koutsonas and Pancherz (1997) found that incisors proclined an average of 11 degrees or 3.2 mm retroclined an average of 8 degrees or 2.5 mm in the following six months when no appliances were in place. Stucki and Ingervall (1998) found that on average 70% of the proclination produced by Jasper Jumpers subsequently relapsed.

Sims and Springate (1995) investigated more modest A-P alterations in lower incisor position and found a similar tendency for incisors moved labially during treatment to return towards their starting position, but found that modest retroclination of incisors was stable or even increased post-retention. This is one of several hints in the literature that invasion of the space previously occupied by the tongue is more stable than invasion of lip or cheek space. These authors also commented on the wide standard deviation of post-treatment change around the average changes.

A study by Williams and Andersen (1995) investigated the very interesting idea that lower incisor proclination might prove to be stable in those patients in whom the mandible is expected to develop in an anterior rotational pattern according to the morphological features described by Bjork. The treatment would in effect be taking advantage of the natural tendency for lower incisors to compensate by proclining as the mandible rotates anteriorly. The authors found an average proclination during treatment of 9 degrees with an average relapse of 3.4 degrees and an average treatment change relative to APo of 2.7 mm with an average relapse of 1.2 mm. The degree of relapse was very significantly related to the amount of labial movement or proclination although some cases were a marked exception to the general rule. Disappointingly, anterior rotators are no more likely to permit stable lower incisor proclination than other groups.

This paper therefore supports the previous studies, but can similarly be interpreted in two ways:

•

proclination tends to be unstable

or alternatively,

•

approximately 60% of the proclination remains

Both these statements are true, but many clinicians seem to recall only one of them. Several details of the study

by Anderson and Williams are worth noting. Firstly, all cases were retained until skeletal maturity (hand-wrist radiographs) - an average of 3.3 years. Secondly, the post-retention Little’s index was much better than most of those reported by Little (1990) (2.8 mm vs. 4.7 mm). Was this due to the long retention until cessation of growth or is it related to the anterior growth rotation? Thirdly, the relapse in lower incisor labial movement was not related to the relapse in Little’s index, which again proved hard to statistically attribute to any parameter other than expansion during treatment of the intercanine width. Finally we should note that not all of those predicted to rotate anteriorly, actually did. Also, marked pogonial growth made some cases appear to have no linear movement of the lower incisors in spite of definite proclination relative to the mandibular plane. An interesting paper!

Key point: Stability of A-P incisor change is not statistically related to stability of irregularity. “Stability” can mean different things.

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Paquette et al (1992) also found that cases which had been treated with an average of 2.8 mm. more lower incisor proclination than another matched group of cases, finished with slightly greater irregularity (Little’s index) out of retention. The difference in post-treatment relapse of irregularity between the two groups was very small (0.6 mm), but the findings did suggest that labial movement of lower incisors during treatment does, on average, increase the chance of subsequent relapse.

No study has demonstrated consistent anteroposterior stability in a group of orthodontic cases in which the lower incisors have been significantly changed in their A-P position during treatment. Reviewing current knowledge on the ability of the soft tissues to adapt to lower arch expansion, Ackerman and Proffit (1997) propose an approximate limit of 2 mm for labial movement of the lower incisors if anteroposterior stability is the main factor influencing our decision.

It is of interest to detour for a moment and note that Artun et al (1990) found that substantial (>10 degrees) proclination of lower incisors was not associated with greater subsequent relapse than a group treated without proclination. However, these were severe Class 3 patients who, subsequent to lower incisor proclination, had a backward mandibular sagittal split osteotomy; i.e. if the soft tissue environment is radically changed by surgical repositioning of the jaw, the usual soft tissue effects do not seem to apply.

An interesting suggestion is the one formally advocated by Selwyn-Barnett (1996) who points out that in effect the lips cannot ‘know’ which incisor is touching them and that we can therefore procline the lower incisor in class 2 division ii cases to touch the lower lip at the same A-P position as was occupied before treatment by the extruded upper incisor. The stability of the results of such a philosophy has not been well tested, but the resulting plan is often required in any case to achieve occlusal goals (Andrews’ keys 3 and 6) and is a useful way of structuring a plan to procline the lower incisors in such cases, as well as a sensible hypothesis about stability.

However, Canut and Arias (1999) found that proclining lower incisors in class 2 division ii cases leads to much more relapse of arch irregularity than when the arch length was not increased. This is salutary evidence that a plausible hypothesis may be incorrect. We aim to retain with particular care Class 2 division 2 cases in which we have substantially proclined the lower incisors and with increasing emphasis on informed consent, prior information about the need for and importance of retention is especially relevant in these cases.

An impressive long-term study by Jonsson and Magnusson (2010) over 25 years found that treatments involving extractions produced much less relapse of crowding in both arches when compared with non-extraction cases, particularly in the lower arch. Cephalometrics was not included in this study but it is probable that non-extraction cases involved labial movement of the incisors.

Aesthetics and incisor position

Most proponents of a particular anteroposterior goal for the dentition have based their advocacy primarily on the aesthetic advantages. There is, however, very little direct evidence concerning this question. An opinion may be formed based on the fact that the Tweed analysis frequently retroclines lower incisors and the Ricketts analysis frequently plans for labial movement of lower incisors, but what also matters aesthetically in this respect is the anteroposterior position of the overlying lips and this is extremely variable. Park and Burstone (1986) have shown in a very elegantly conceived study that the soft tissue appearance of the lips in relation to a soft - tissue APo line varies enormously even when the Ricketts hard tissue APo line goal is exactly achieved. Achievement of a particular lower incisor position will therefore produce an enormous variety of profiles, although it is still probably true that for any given patient, some lower incisor positions will produce a more aesthetic lip position than others.

Even here, opinions vary as to what is an aesthetically desirable goal, treatment to Merrifield’s profile line tending to produce less prominent lips than treatment to Ricketts’ E line for example.

Variability of soft tissue response Quite separate from this question of variability in soft tissues for a given hard tissue position is the fact of the variability of soft tissue response to tooth movement. This is also well documented. Staggers (1990), for example, comparing premolar and second molar extractions, found definite differences in the A-P changes in incisor position between the two groups, but no differences in the changes in soft-tissue facial convexity or of the upper lip relationship to a soft-tissue APo line. Almost all studies show that the soft tissues move much less than the

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underlying teeth. For example, Paquette, Beattie and Johnston (1992) found an average 1.4 mm posterior movement of the upper lip when the upper incisors were retracted by an average of 5.0 mm – an average ratio of 28%. Large tooth movements are therefore required on average to produce clinically substantial soft tissue change, but the variability is huge. In this paper, the range of upper lip anteroposterior change associated with upper incisor retraction was 10.0 mm! Pancherz and Anehus-Pancherz (1993) reported that there was no correlation (r=0.02) between the hard and the soft tissue changes brought about by treatment with the Herbst appliance. More recent papers have continued to find poor correlation between incisor movement and change in the overlying lips. Kusnoto and Kusnoto (2001) found a correlation coefficient of r=0.39 for the upper lip. In other words, the change in incisor position accounted for r2 = 16% of the variation in lip change. The average ratio of movement was 1:4 for lip: incisor change. A paper by Lai et al (2000) suffers from choices in cephalometric values, which greatly lessen the potential usefulness of the results, but still reveals “a large variation in the soft tissue response to dental movements”. The paper includes the result that two groups which differed in their change in upper incisor inclination during treatment by an average of 20 degrees, differed in their change in upper lip to E line distance by an average of only 0.5 mm. This large variation in soft tissue response was emphasised again in a more recent study by Tadic et al (2007) which focused on predictors of change in lip shape and NLA with upper incisor correction in class II cases. They found a large range of change in NLA (40 degrees) and no correlation with incisor A-P change.

Key Point: Changes in anteroposterior incisor position clearly result in much smaller and highly variable changes in the prominence and shape of the overlying lips. Prediction of changes in lip profile is prone to substantial error.

What degree of lip prominence is considered attractive?

A final factor when weighing the aesthetic consequences of incisor prominence is the variety of opinion as to what is an attractive degree of lip prominence. This has been investigated in several studies and a good paper which includes a good summary of the literature is the one by Nomura et al (2009). Lay judges from different racial groups were asked to rate lips of varying prominence in silhouette profiles of disclosed racial groups. Several useful findings emerged. For example all judges of all racial groups prefer the lips to be behind Ricketts E line in all racial groups. Hispanic and Japanese judges prefer more retruded lips and white and Kenyan judges have very similar views on lip prominence. This paper repays a read and may help set a target for lip prominence which is more likely to be appropriate for a given patient.

A suggested lower incisor target position

All orthodontists need to look at the available evidence and decide their general aims in relation to this important target. As a starting point, the evidence relating to stability indicates that we should aim not to change the antero-posterior position significantly during treatment unless there is a good reason. Most orthodontic cases (as opposed to orthognathic surgical cases) can be treated without significantly altering the labiolingual position of the lower incisors. Also, the aesthetic consequences of changing their position are unpredictable and usually small. However, if this goal of aiming for little change in the initial antero-posterior position is unwaveringly followed, there are several categories of patient where this would have substantial disadvantages.

•

• •

in some cases, the aesthetic concerns of lip prominence or inclination are sufficiently marked that they outweigh considerations of stability. For example, in a well-aligned class 1 bimaxillary proclination case, excessive lip and tooth prominence is probably the only potential indication for treatment. Equally, some class 2 cases have a very obtuse nasolabial angle. This can be a strong factor to tip the treatment plan towards surgery. Where surgery is not an option, this factor may sometimes lead to a decision to plan for significant lower incisor proclination to maintain upper lip support whilst reducing the overjet. some cases (e.g. some class 2 division ii patients) are impossible to treat to our chosen occlusal goals without substantial lower incisor proclination. some cases with reduced or negative overbite require extractions to retrocline the incisors and achieve an overbite

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• • •

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correction of class 3 cases without orthognathic surgery frequently requires significant lower incisor retroclination. many cases with mild lower arch crowding are very demanding on the wear of class 2 traction if lower arch extractions are prescribed and unwanted incisor retroclination is to be avoided. It is better to move the lower incisors labially to the modest extent required. from a purely pragmatic viewpoint, some cases become extremely anchorage demanding if the lower incisors are not moved labially. This point is less frequently mentioned than others such as considerations of profile, but can undoubtedly be a powerful if unstated motive.

Aesthetics versus stability?

Small anteroposterior changes in lower incisor position are of little consequence for either appearance or stability.

The evidence is that the larger the change, the more these two factors will - on average - conflict. Choosing a position that is less likely to be stable means more emphasis on ‘permanent’ retention and this is the source of a philosophical dilemma. The work of Little and others quoted above has shown that although larger lower incisor changes in position are less stable, lower incisor alignment tends to deteriorate after retention whether or not the anteroposterior lower incisor position has been maintained. Little personally advocates fixed indefinite retention for lower incisors after all orthodontic treatment. In the light of this, two tenable viewpoints have emerged.

Since tooth alignment tends to deteriorate even if we put the teeth where stability is most probable:

•

all cases should have indefinite retention and if this is the case, then why should the orthodontist be concerned with minimising spontaneous relapse when all case are to be retained forever anyway?

Or alternatively

•

for one reason or another few young patients wear retainers for the rest of their life and it is therefore best practice to try to leave the lower incisors in a position that minimises the probability of relapse when retention is discontinued.

These two approaches are both entirely tenable. At present we favour the second viewpoint as a starting point, but with some definite exceptions for the aesthetic, occlusal and anchorage reasons listed above. A complicating factor for those looking for certainties in life is that all these exceptions are relative and thus open to weighting which varies even between clinicians who would subscribe to the same choice between the two opposing viewpoints. The chapter on Stability and Retention discusses further the evidence about stability in general and the best practical approach to retention in the light of this evidence.

The question of a suitable goal for lower incisor position is inextricably entwined with extraction philosophy and the merits and disadvantages of extractions per se should now be examined - a subject of recently revived controversy.

Extractions versus non - extraction treatment This ancient debate about the possible benefits and disadvantages of extractions is almost as old as orthodontics itself, but has resurfaced more recently with all the heat and fury that apparently occurred at the time of Angle vs.

Case (see the articles by Bernstein 1992). In the USA, the debate has on occasion become markedly acrimonious.

It is clearly important to look as objectively as possible at the evidence concerning the issues relating to extractions.

Reasons for elective extractions in orthodontics Before examining possible disadvantages of extractions, it is worth reminding ourselves of the reasons for wanting to remove teeth electively.

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•

relief of crowding space is provided for crowded teeth without expanding the arches laterally or anteriorly (or in the upper arch, without transferring the crowding to a more distal part of the arch).

• correction of incisor relationship o overjet reduction o lower incisor retroclination to correct a class 3 relationship o providing the space required to move upper labial segment contact points distally as retroclined upper teeth are torqued to a correct inclination in the correction of a class 2 division ii relationship o correction of bimaxillary proclination o increase in overbite if the incisors are proclined and the overbite reduced • provision of anchorage in addition to providing the space for tooth movement, extractions frequently provide additional space which is harnessed to provide intraoral anchorage. Mesial movement of anchor teeth in response to reciprocal forces is therefore possible without the arch having to be expanded anteriorly to accomplish the desired occlusion. Without extractions, no intraoral anchorage is available for distal movement of teeth (except in naturally spaced dentitions or with Temporary Anchorage Devices - TADs) unless incisors are moved labially in one arch or the other. In nonextraction treatment (discounting unpredictable favourable growth), anchorage must be gained extra-orally or from TADs or alternatively, incisors must move labially or buccal teeth must expand.

These increases in arch circumference are not always desirable.

Proposed disadvantages of extractions Several potential disadvantages have been proposed:

• • • •

mandibular dysfunction a less attractive dental and facial appearance longer, more difficult treatment (in some cases) pain, anxiety and other possible adverse effects of the actual extraction procedure

Key thought: The last three considerations on this list have all contributed to a general downward trend in the rate of elective extractions in orthodontics

Extractions and mandibular dysfunction It has been suggested that extractions may cause mandibular dysfunction by two mechanisms.

• •

the effect on condylar position within the fossa loss of vertical face height.

Regarding condylar position, such authors as Witzig and Spahl (1987) and Bowbeer (1987) have proposed that extractions cause “over-retraction” of the upper incisors and that this leads to the condyles being forced posteriorly and hence the articular disc becomes anteriorly placed and hence mandibular dysfunction. The work previously quoted in the chapter Occlusal Treatment Goals demonstrates the paucity of evidence of an association between condylar position and mandibular dysfunction and indeed the inability of orthodontics or restorative dentistry to alter it permanently. With specific reference to extractions, Gianelly (1991a and 1991b) has found no difference in condylar position between those treated with the extraction of four premolars and those receiving no orthodontic treatment. This has been supported by work by Kundinger et al (1991). Luecke and Johnston (1992) found that the temporary effect of orthodontic treatment on condylar position was highly correlated with the mesial movement of buccal segments but not at all with the retraction of incisors. Major et al (1997) used tomography to show that condylar position was unchanged by treatment in both non-extraction and extraction groups. With regard to the view held, for example, by Bowbeer (1987) that extraction of premolars causes a loss of

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vertical dimension and that this causes mandibular dysfunction, Staggers (1990) was unable to find any such effect in a study of premolar and second molar extractions. Kocadereli (1999) also found no difference in change in vertical facial dimensions between 40 cases treated non-extraction and 40 cases treated with first premolar extractions.

It remains possible that extractions predispose to mandibular dysfunction by some other unknown mechanism.

However, studies by such workers as Kremenak et al (1992) have found no differences between groups treated with loss of upper premolars, four premolars and non-extraction. Beattie et al (1994) also found no difference in the CMI values for non-extraction cases and extraction cases. In this clever study, the principle of equipoise was used to get two groups matched for all the variables which discriminant analysis had shown to be able to account for the decision to extract or not. In other words, a rare and necessary feat was achieved - to compare the results of extraction versus non-extraction in groups of comparable cases.

Key Point: There appears to be very little evidence to support either of the proposed mechanisms for causation of mandibular dysfunction by extractions or indeed to support any other unknown mechanism. There is therefore no reason to avoid extractions because of concerns about mandibular dysfunction.

Extractions and facial aesthetics Orthodontic treatment involving extraction has also been accused of producing unpleasantly retrusive lips relative to the nose and chin. Studies have certainly shown that it is possible to achieve a degree of long term retroclination of the lower incisors and that this will be associated with the lips being more posterior than would have been the case if the incisors were more procumbent. The variability of soft tissue (lip) position for a given underlying incisor position and the variability of soft tissue response to anteroposterior movement have already been discussed, but it remains true that for a given individual, more posterior incisors means more posterior lips to an unpredictable extent. However, studies comparing the soft tissue changes in patients with differing extraction patterns inevitably encounter the fact that the groups are very unlikely to be balanced in terms of requirements for space and anchorage. For example, Staggers (1990), comparing first premolar and second molar extractions, found that the anteroposterior changes in lower incisor position were only minutely different and the soft tissue changes were very variable, but on average, identical. This would not be at all surprising if the second molar extraction group had much less initial crowding. This study at least shows that it is nonsensical to generalise about the effects of extractions on lower incisor position regardless of other features of the malocclusion and treatment.

Similarly, the studies by Luppanapornlap et al (1993) and by James (1998), both demonstrated that patients treated with extractions had on average slightly more prominent lips at the end of treatment than those treated on a non-extraction basis. This reflected the fact that initial lip prominence was a significant factor in the extraction/non-extraction decision of the orthodontists planning that group of patients. A recent study by Zierhut et al (2000) again showed the small extra lip retraction with extractions (1.7 mm for the lower lip and 1.0 mm for the upper lip) when compared with non-extraction cases, but since extractions had been chosen in cases with slightly more prominent lips, the final average soft tissue profile was identical in both groups. Finally, the study by Shearn and Woods (2000) was notable for showing the wide variety of anteroposterior changes in lower incisor position, which result for all combinations of premolar extractions. This is simply a reflection of all the other variables in the treatment - notably the amount of crowding, of class 2 elastics, of headgear and of differential growth. An opinion that extractions or non-extraction are “good” or “bad” for the profile is clearly simplistic and uninformed.

Key point: All the published data strongly supports the view that orthodontic treatment involving good planning and execution produces very similar profiles in extraction and non-extraction cases.

Lay opinion A good study by Bishara and Jakobsen (1997) involved assessment by lay people of profile changes in class 2 division i malocclusions treated with and without extractions. Lay judges:

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• • • •

preferred the profile of normals to the pre-treatment profile of Class 2 division i patients immediately after treatment, preferred the changes in profile in the extraction group to the changes in the non-extraction group two years after treatment, showed no preference for the profiles of either treatment group or for the untreated normal group considered the changes with treatment to be very favourable in both treatment groups.

Key point: All the published data strongly supports the view that orthodontic treatment with good planning and execution produces changes in profile which are viewed favourably by the lay public whether or not extractions are involved.

Differences in soft tissue appearance if the same case is treated extraction or non-extraction Of course, the answers to these questions will also be different for different types of malocclusion. Not much evidence, as opposed to opinion, exists on any of the questions, but the study by Paquette et al (1992) referred to above, gave some extremely useful information for one type of malocclusion. The equivalent groups of cases assembled by the equipoise analysis as being equally susceptible to extraction or non-extraction, were unsurprisingly, mild to moderate class 2 division i malocclusions with mild lower arch crowding. The cases averaged 14.5 years post-retention and were recalled and compared aesthetically, for mandibular dysfunction and for stability. Cephalometric analysis of the long term results revealed that the extraction group had lower incisors averaging 2 mm more posterior than the non-extraction group and the lower lip was 1.2 mm further behind E line in the extraction group. However, these measurable and statistically significant differences produced no detectable aesthetic or stability effects. Regarding aesthetics, various assessments of the patients' opinion of the aesthetic changes in their silhouettes and facial photographs both before and after treatment revealed no difference between the groups. Regarding stability, the Little index in the lower labial segment at recall was 2.9 mm in the extraction group and 3.4 mm in the non-extraction group. This difference was again not significant, although the overall reduction in lower labial irregularity was slightly greater in the extraction group (by 1.9 mm.), which happened to be slightly more crowded initially and relapsed fractionally less.

It would seem that in such mildly crowded cases, if they are treated using non-extraction mechanics which only produce mild labial movement of the lower incisors, (average 0.4 mm in this group), it does not matter significantly whether the cases are treated with or without extractions from the viewpoint of aesthetics or stability.

Twenty years later a very similar study has been reported by Konstantonis (Angle on line early for 2012). The same equipoise discriminant analysis was used to compare extraction and non-extraction, this time in a sample of class 1 cases. Analysis showed that the extraction decision was based on initial crowding, facial convexity and lower incisor protrusion. This confirms that clinicians were basing their extraction decision on actors relating respectively to stability, facial aesthetics and occlusal fit. Interestingly, the extraction rate in the parent sample was 30% which compared to 55% for the sample treated in the 1970s from which Paquette derived his borderline group In the derived borderline sample, extraction lead to an average of 2 mm greater retraction of the lower lip relative to E line and an increase of 5 degrees in the NLA compared to no change for this angle in the nonextraction group. The superimposed average profiles in that paper show that these differences have a small effect on the facial profile.

These two studies of borderline cases firmly indicate that if it is felt that treatment will be quicker, easier or more pleasant if carried out on a non-extraction basis, then this would be the sensible approach in this type of case. The studies did not investigate these latter aspects, but it seems reasonable to assume for now that if all things are genuinely equal for a given type of case, we should not extract.

An interesting prospective study by Heiser et al (2004), compared two groups with equivalent starting irregularity index (averaging 5.1 and 5.8) treated with and without premolar extractions. It is very probable that the nonextraction group had some labial movement of the lower incisors relative to the extraction group. They measured areas bounded by different parts of the dental arch. The increase in the area bounded by the lower labial segment relapsed more in the non-extraction group, but interestingly, the relapse in Irregularity index was the same in both groups. The connection between change in lower incisor proclination and irregularity index is clearly not a close

DIAGNOSIS AND TREATMENT PLANNING EXCELLENCE IN ORTHODONTICS 2012

% of cases with > 2mm crowding Treatment Extraction

Pre - treatment 16%

25 yrs+ posttreatment 0%

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one. For relatively mild crowding, treated in the permanent dentition, extractions possibly confer no significant additional stability of alignment.

However, the impressive long-term study by Jonsson and Magnusson (2010) of cases reviewed Non-extraction 8% 15% more than 25 years after treatment, found that No treatment 4% 6% treatments involving extractions produced much Extraction 16% 11% less relapse of crowding of greater than 2mm Non-extraction 3% 28% Mandible when compared with non-extraction cases, in No treatment 9% 16% both arches but particularly in the lower arch.

Table 3.1: Jonsson and Magnusson (2010) long term changes in Such a long-term study is rare and for crowding. Percentages of cases with > 2mm crowding understandable reasons.

The authors understandably conclude that non-extraction cases should receive proportionately more rigorous long-term retention.

Maxilla

In his long-term studies of dental irregularity, Little (1990) identified “lower arch development in the mixed dentition” (i.e. expansion and proclination of the labial segment) as the only treatment regimen to show significantly worse results than others in this respect. Little (2002), again referred to this work in his paper contributing to the section on early treatment which followed the American Association meeting on that subject.

The core of his conclusions was that whilst you can hold and use the Leeway space without any detriment to stability, lateral and anterior expansion of the arches at an early age caused a degree of relapse which was “significant and alarming” and this was for cases which only had to have mild proclination to be included in the “expansion” group. Conversely, a paper by Ferris, Alexander, Boley and Buschang (2005), showed that patients with mild crowding but significant irregularity, when treated in the late mixed dentition with RME, arch expansion, interdental stripping and without extractions, had very acceptable stability more than 4 years out of retention.

There was no availability of cephalometric data on incisor labiolingual movement, but the arch width measurements showed that a substantial percentage of premolar expansion was stable in this age group. The effect of extraction choices on lateral stability and smile aesthetics is considered below and in the following chapter on Facial Appearance, the Smile and Tooth Aesthetics. It is worth recalling that Little advocates indefinite fixed retention after all treatments whatever the final tooth positions.

Extractions and smile width So far, this section has dealt chiefly with the antero-posterior effects of extractions. Interestingly, the clever study

by Spyropoulos et al.(2001) that used computerised modification of photographs, concluded that factors other than profile outline may be more important in facial aesthetics for lay people and it is orthodontists who pay particular attention to the profile. Orthodontic treatment involving extractions has been accused in recent years of causing larger dark intraoral spaces lateral to the buccal segments - a “dark buccal corridor”. However, the study by Johnson and Smith (1995) found no evidence of this and also no evidence that extractions produced less attractive smiles in the opinions of lay judges.

Two more recent studies by Gianelly have looked at the relationship between extractions and width of dentition.

In the first, (Gianelly 2003a), he compared a non-extraction group with an extraction of four first premolars group.

The principal finding was that post-treatment, canine, premolar and widest molar widths were essentially the same in the two groups. The second similar study (Gianelly 2003b) is more interesting. The first point of note is that he added a measurement at constant arch depth from the upper central incisors and this depth corresponded to the average depth of the molar-premolar contact in a group of non-extraction patients. This is a sound idea, since measurement at a constant arch depth overcomes the problem that non-extraction may well involve distal movement and therefore molar expansion whilst conversely there is frequently molar constriction in extraction case just because the molars move mesially into a narrower part of the arch. The results for this measurement at constant arch depth showed that the extraction group was slightly wider after treatment than were the non-extraction group. This is a good measurement for future studies. The second part of the study was similar to that by Johnson and Smith. Fifty lay judges were asked to rate close up photos of 12 extraction and 12 non-extraction smiles. There were no differences in the aesthetic scores between the groups. Interestingly, the lay judges again seemed unaware of ‘dark buccal corridors’ as an aesthetic factor in smiles, since only one of them

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mentioned it at all. Also there was no difference in the number of teeth displayed in the two groups whilst smiling.

Key Point: When comparing extraction and non-extraction cases, measurement of arch width at a constant arch depth is more informative than measurement of changes in width of a specific tooth These two studies are similar in many respects to many studies comparing profiles in extraction and nonextraction groups. They are useful in that they look at (and indeed refute) the idea that extraction results in a narrow arch at the dental smile width, but this leaves unanswered what would result if the same cases were treated with the two regimens – especially if the space requirements were substantial. The Gianelly studies naturally involved cases where clinicians had picked horses for courses when choosing to treat extraction or nonextraction. The cases were not matched. One of the conclusions in a thoughtful systematic review by Janson et al (2011) discussed below is that the studies by Gianelly are good research which does indeed support the view that premolar extractions per se do not have a detrimental effect on smile aesthetics.

Studies of buccal corridor spaces Studies using digitally-altered buccal corridor spaces (BCS) are well worth a look, but the results are not yet strongly convincing. A paper by Moore et al (2005), supported the view that the appearance of small buccal corridors is preferred by lay judges, whilst the similar study by Roden-Johnson et al (2005), showed no such effect.

Details of study design, such as the extent of the digital alteration or the definition of buccal corridor, are probably important in these investigations. We feel that the measurement and design used by Moore is the more sound. A recent study by Yang et al (2008) is also to be recommended for its innovative but very accessible method of measuring the BCS and found no effect of extractions on BCS. Importantly and understandably, the cases were not randomised for extraction or matched in any way. The following chapter on Facial Appearance, the Smile and Tooth Aesthetics gives a thorough overview of smile aesthetics, but it is helpful here to note the study by McNamara et al (2008), which found no relationship between BCS or upper incisor exposure and smile aesthetics as rated by both lay persons and orthodontists. Here again, we have to be cautious about that finding because BCS was measured using the Smilemesh software program which defines BCS as the distance between the canines and the outer commissure. We would generally prefer to define BCS as the distance from the widest tooth to the inner commissure. Finally, it is worth looking at the illustrations in the paper by Ioi et al (2009) which also used digital alteration of BCS. They found that lay judges preferred smaller BCS. However, in our opinion, their digital manipulation produced a highly unrealistic imitation of a naturally occurring narrow arch, which gave an appearance of extraction of all buccal teeth. A further point in this paper is that the judges were all orthodontists and dental students. Genuinely lay judges are much more appropriate in such a study. These were used in a study

by McLeod et al (2011) and interestingly, lay opinion was more fussy in Canada than in the USA about acceptable limits for BCS and for gum exposure on smiling. The illustrations in that paper clearly show the ideal and acceptable ranges for these and other smile features. The authors point out that the narrow focus on the smile area and the specific use of a ‘slider’ to mark the chosen illustrations may well have made the lay judges give a ore stringent view of acceptability that in real life. This question of realistic portrayal of variations in BCS concerned Janson et al (2011) in their thoughtful systematic review of factors influencing smile aesthetics. They concluded that based on studies of actual subjects, BCS on its own has not yet been shown to be a factor in smile attractiveness.

Key Point: Interpretation of research requires scrutiny of the actual dimension which was measured and the specific experimental setup.

Extractions and aesthetics - the study that is needed There are several good studies discussed above that have compared both profile and smile aesthetics in patients who have been treated with or without extractions. In all of these studies, the extraction pattern has – very understandably – not been randomly assigned. Whilst these have been extremely informative, they leave unanswered the question: “How do the smile and profile aesthetics compare if very crowded cases are treated with or without extractions?” This question has recently become much more relevant because some clinicians

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treat virtually everything non-extraction. This change in their practice has in some instances been facilitated by the apparent ease with which crowded teeth can be accommodated using self-ligating brackets. For this study, matched cases are required with large space requirements which are treated with or without extractions. Using the discriminant analysis methods so pertinently applied by Lysle Johnson, such a study must be possible with the cooperation of clinicians of differing philosophies. The results would still leave the question of the stability of expansion as a factor in treatment planning, but would more thoroughly examine the aesthetics of arch expansion.

Planning extractions In the light of the previous scrutiny of the current evidence, we can now produce suggested guidelines for the practical implementation of extraction planning (assuming a full complement of healthy teeth). This section is a series of rules of thumb with supporting explanation and references. It is hoped that this provides a straightforward sequence of evidence-based thoughts which will produce a sensible extraction plan in the large majority of cases.

Plan the lower arch first This adage still seems very sensible as a way of a systematic thought process. However, it should be noted that factors relating to the upper incisors (such as the NLA) may strongly influence the planned A-P incisor position.

Almost always, if we extract in the lower arch, there is some residual space to close. If the lower incisors are not to be retroclined (and this is rarely desired), then class 2 traction is required.

Assessing the lower arch crowding As discussed earlier, the factors which influence a target A-P position for the lower incisors should all be considered.

• • • • •

A-P incisor stability – even though indefinite retention is planned facial aesthetics o profile o smile width achievement of a good occlusion ease of achievement long-term periodontal health

The amount of crowding is frequently a sufficiently strong factor to narrow the choice by itself to one of two lower extraction patterns in many cases.

The recommendations in Table 3.2 imply a differential anchorage effect between extraction of first or second premolars. This differential has long been assumed from the differential force theory, but is supported by a paper

by Saelens and de Smit (1998) where the extraction of first premolars successfully accommodated twice the crowding than did the extraction of second premolars. The average lower incisor anteroposterior change was the same in both groups (0 mm) and the molars moved mesially 1 mm more in the second premolar extraction group.

This convincing evidence is supported by the paper by Ong and Woods (2001) which clearly showed more anchorage is provided in the upper arch by extraction Category Millimetres of crowding Extraction pattern of 4s than by extraction of 5s. Creekmore (1997), reviewing this subject concludes that as a rule of 1 to 4 mm Non-extraction or Mild second premolars thumb, extraction of first premolars provides 5 to 8 mm First premolars or Moderate approximately 66% of the space for aligning/retracting second premolars the anterior teeth, whereas extraction of second 9+ mm First premolars Severe premolars provides approximately half of the space.

Table 3.2: Common extraction patterns related to category of crowding.

Other factors may significantly modify this starting point.

Other factors will significantly influence the choice of

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extractions within each category.

• • • •

desired antero-posterior incisor position (factors listed above) any planned canine expansion canine angulation curve of Spee

The effect on available space of antero-posterior expansion/retraction The ‘traditional’ rule of thumb is that 1 mm of labial movement will provide sufficient space for 2 mm of crowding (1mm on each side of the arch). This rule of thumb assumes a rectangular arch form. In fact, with a much more realistic parabolic archform, the situation is more complicated and in general the labial movement will need to be greater than 1 mm to produce 2 mm of space. The paper by Steyn et al (1996) demonstrates this and interestingly, also calculates the effect of different arch depths and widths on the anterior movement of incisors required to accommodate a given amount of crowding. In general, the wider the intercanine distance and the shallower the arch depth from the canines to the mid-incisor point, the greater the A-P expansion required to accommodate a given amount of crowding (or conversely the greater the A-P retraction of incisors for a given amount of interdental stripping) and in cases presenting a specific dilemma, inspection of the table in the paper by Steyn is recommended .

In a given instance, the labial movement of lower incisors in a non-extraction case is frequently greater than that required to accommodate the crowded teeth. This reflects the additional use of class 2 traction and the degree of control of lower incisor inclination with occlusal plane levelling. For example, in non-extraction cases Saelens and De Smit (1998) found that to accommodate crowding of only 4 mm required an average of 5 mm of labial movement of lower incisors and not the 2 mm which the rule of thumb would have estimated. It will be seen in the chapter on self-ligation that there may possibly be less incisor proclination and greater lateral arch expansion if light forces and self-ligating brackets are employed to align crowded arches, but this has yet to be supported by strong evidence.

The effect on available space of lateral expansion Lateral expansion has been found to have less effect on arch perimeter than A-P expansion. An interesting paper

by Noroozi et al (2002), demonstrates the ability of an algorithm based on two measurements of arch width and two of arch length to predict the arch perimeter increase which will result for any given A-P or lateral expansion.

These authors again find that A-P expansion is much more effective than lateral expansion in providing space.

Their formula again predicts approximately 1mm of arch length gain for 1mm of incisor labial movement. This is half of the ‘rule of thumb’. In the lateral dimension, each mm of canine expansion gives 0.6 mm of space and each mm of second molar expansion gives 0.3 mm.

Key point: Because dental arches are far from rectangular, 1 mm of labial incisor movement gives approximately 1 mm of extra arch length, not 2 mm. i.e. more labial movement of incisors is required to accommodate crowding than you might think.

The amount of curve of Spee The historical rule of thumb for this factor was 1 mm of space required for every 1 mm depth of curve of Spee.

This has been shown to be an excessive calculation of space required. Germane and Staggers (1992) found a nonlinear relationship and a less than one to one ratio for curves shallower than 9 mm. A more recent study by Braun et al (1996) found an even smaller effect - namely that a very deep curve of 9 mm only requires 2 mm of additional space. The strong tendency for labial flaring of lower incisors associated with non-extraction levelling of curves of Spee is therefore mainly due to choices in the biomechanics employed rather than to the space requirements.

This will be discussed further in the chapter on Managing Overbites and is also referred to in the section on bracket prescriptions in the chapter on The Development of Preadjusted Appliance Systems.

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If the lower arch is non extraction:-

Then non-extraction is our treatment of choice in the upper arch. If the case is suitable for functional appliance treatment then this is our preferred option if class 2 correction is required. If the upper second molars have erupted, the upper third molars are present and of good size and at least half a unit of distal movement is proposed, then the extraction of upper second molars can be considered. Waters (2001) has reported that this achieved 1.2 mm additional distal movement of the upper first molar and 5 degrees less incisor proclination, but this should be weighed against the long -term disadvantage of having a smaller more conically rooted third molar in place of a second molar. We almost never extract upper or lower second molars. (One exception is when intruding molars with TADS in the presence of unerupted 8s).

Although non-extraction is our treatment of choice if the lower arch is non-extraction, extraction of upper first premolars is much less demanding on anchorage and the occlusal disadvantages of a class 2 molar relationship are slight (see Andrews 1989: Straight Wire: The Concept And Appliance pages 182-187). If the initial molar relationship is more than half a unit class 2 and the case is not ideal for functional appliances, we would usually advocate extraction of upper first premolars. This does carry an increased chance of small residual spaces in the extraction sites. This is due partly to the difference in mesiodistal width between two premolars and one first molar and partly to the second premolars being teeth that are more frequently disproportionately small. This was discussed in the chapter on Occlusal Treatment Goals. Such occlusal imperfections may be considered much more acceptable than the consequences of insufficient anchorage to correct a class 2 relationship. A recent new factor in this decision between aiming for a class 1 or class 2 molar relationship is our ability to distalise buccal segments with miniscrews (See chapter on Temporary Anchorage Devices in Orthodontics)

If lower premolars are extracted:Then upper premolars are almost always extracted. If the upper canines are at an ideal angulation or more distally angulated and must move distally by half a unit or more, then extraction of upper first premolars is recommended.

Therapeutic diagnosis

Extractions are irreversible. Treatment response can be unpredictable. In a number of cases, it is sensible to start non-extraction and align the arches before making a decision on extraction. If extractions are then carried out, very little treatment time has been lost and the need for the extractions has been demonstrated to clinician and patient. The potentially different response to alignment with very gentle wires and self-ligating brackets has in our view increased the occasions when this approach is sensible. It is important to start such treatment with the clear understanding that if the clinician decides after some visits that extractions are required that this is a decision that must be implemented.

References Ackerman JL and Proffit WR (1997) Soft tissue limitations in orthodontics: Treatment planning guidelines Angle Orthodontist 67: 327-336 Andrews LF (1989) Straight Wire. The concept and appliance Published by LA Wells Co. San Diego ISBN 0-9616256-0-0 Artun J, Krogstad O and Little RM (1990) Stability of mandibular incisors following excessive proclination: a study in adults with surgically treated mandibular prognathism.

Angle Orthodontist 60: 99-106 Athanasiou AE (1995) Orthodontic cephalometry London, Mosby-Wolfe Basciftci FA, Uysal T and Buyukerkmen A (2003) Determination of Holdaway soft tissue norms in Anatolian Turkish adults.

American Journal of Orthodontics and Dentofacial Orthopaedics 123:395-400

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Bass NM (2003) Measurement of the profile angle and the aesthetic analysis of the facial profile Journal of Orthodontics 30:3-9 Beattie JR, Paquette DE and Johnston LE (1994) The functional impact of extraction and non-extraction treatments: A long-term comparison in patients with â&#x20AC;&#x153;borderlineâ&#x20AC;?, equally susceptible Class II malocclusions American Journal of Orthodontics and Dentofacial Orthopaedics 105: 444-9 Bernstein L (1992) Edward H. Angle versus Calvin S. Case: Extraction versus non-extraction. Part I. Historical revisionism American Journal of Orthodontics and Dentofacial Orthopaedics 102: 464-470 Bishara SE and Jakobsen JR (1997) Profile changes in patients treated with and without extractions: Assessments by lay people American Journal of Orthodontics and Dentofacial Orthopaedics 112: 639-44 Bjork A and Skieller V (1977) Growth at the maxilla in three dimensions as revealed radiographically by the implant method British Journal of Orthodontics 4: 53-64 Bowbeer GR (1987) The sixth key to facial beauty and TMJ health Functional Orthodontics 4: 10-35 Braun S, Hnat WP and Johnson BE (1996) The curve of Spee revisited American Journal of Orthodontics and Dentofacial Orthopaedics 110: 206-10 Canut JA and Arias S (1999) A long-term evaluation of treated Class II division 2 malocclusions: a retrospective study model analysis.

European Journal of Orthodontics 21: 377-386 Case CS (1964) The question of extraction in orthodontia. REPRINT American Journal of Orthodontics and Dentofacial Orthopaedics 50: 660-691 Creekmore TD (1997) Where teeth should be positioned and how to get them there.

Journal of Clinical Orthodontics 31:586-608 Ferris T, Alexander RG, Boley J and Buschang PH (2005) Long-term stability of combined rapid palatal expansion-lip bumper therapy followed by full fixed appliances American Journal of Orthodontics and Dentofacial Orthopaedics 128:310-325 Germane N and Staggers JA (1992) Arch length considerations due to the curve of Spee: a mathematical model American Journal of Orthodontics and Dentofacial Orthopaedics 102: 251-5 Gianelly AA, Cozzani M, Boffa J et al (1991a) Condylar position and maxillary first premolar extraction American Journal of Orthodontics and Dentofacial Orthopaedics 99: 473-476 Gianelly AA, Anderson CK and Boffa J (1991b) Longitudinal evaluation of condylar position in extraction and non-extraction treatment American Journal of Orthodontics and Dentofacial Orthopaedics 100: 416-420 Gianelly AA (2003) Arch width after extraction and non-extraction American Journal of Orthodontics and Dentofacial Orthopaedics 123:25-8 Gianelly AA (2003) Extraction vs non-extraction: Arch width and smile aesthetics Angle Orthodontist 73:354-358 Hansen K, Koutsonas TG and Pancherz H (1997) Long-term effects of Herbst treatment on the mandibular incisor segment: A cephalometric and biometric investigation American Journal of Orthodontics and Dentofacial Orthopaedics 112: 92-103 Heiser W, Niederwanger A, Bancher B, Bittermann G, Neunteufel N and Kulmer S (2004) Three-dimensional dental arch and palatal form changes after extraction and non-extraction treatment. Part 1. Arch length and area American Journal of Orthodontics and Dentofacial Orthopaedics 126:71-81

DIAGNOSIS AND TREATMENT PLANNING EXCELLENCE IN ORTHODONTICS 2012

Holdaway RA (1983) Soft tissue cephalometric analysis and its use in orthodontic treatment planning. Part 1 American Journal of Orthodontics and Dentofacial Orthopaedics 84:1-28 Holdaway RA (1984) Soft tissue cephalometric analysis and its use in orthodontic treatment planning. Part 2 American Journal of Orthodontics and Dentofacial Orthopaedics 85:279-293 Houston WJB and Edler R (1990) Long term stability of the lower labial segment relative to the A-Pog line European Journal of Orthodontics 12: 302-310 Ioi H, Nataka S and Counts AL (2009) Effects of buccal corridors on smile esthetics in Japanese Angle Orthodontist 79: 628-636 James RD (1998) A comparative study of facial profiles in extraction and non-extraction treatment American Journal of Orthodontics and Dentofacial Orthopaedics 114: 265-76 Janson G, Branco NC, Fernandes TMF, Sathler R, Garib D, Lauris JRP(2011) Influence of orthodontic treatment, midline position, buccal corridor and smile arc on smile attractiveness Angle Orthodontist 81: 153-161 Johnson DK and Smith RJ (1995) Smile aesthetics after orthodontic treatment with and without extraction of four first premolars American Journal of Orthodontics and Dentofacial Orthopaedics 108: 162-7 Jonsson T and Magnusson TE (2010) Crowding and spacing in the dental arches: long term development in treated and untreated subjects American Journal of Orthodontics and Dentofacial Orthopaedics 138:384e1-384e7 Johnston C, Burden D, Kennedy D, Harradine N, Stevenson M (2006) Class III surgical-orthodontic treatment: A cephalometric study American Journal of Orthodontics and Dentofacial Orthopaedics 130:300-9 Johnston LE (1996) Balancing the books on orthodontic treatment: an integrated analysis of change British Journal of Orthodontics 23: 93-102 Johnston LE (1998) The value of information and the cost of uncertainty: who foots the bill?

Angle Orthodontist 68: 99-102 Kocadereli Ä° (1999) The effect of first premolar extraction on vertical dimension American Journal of Orthodontics and Dentofacial Orthopaedics 116: 41-45 Konstantonis D (online early for 2012) The impact of extraction vs nonextraction treatment on soft tissue changes in Class I borderline malocclusions The Angle Orthodontist Kremenak CR, Kinser DD, Harman HA, Menard CC and Jakobsen JR (1992) Orthodontic risk factors for temporomandibular disorders (TMD) 1:premolar extraction American Journal of Orthodontics and Dentofacial Orthopaedics 101:13-20 Kundinger KK, Austin BP, Christensen LV, Donegan SJ, Ferguson DJ et al (1991) An evaluation of temporomandibular joints and jaw muscles after orthodontic treatment involving premolar extractions.

American Journal of Orthodontics and Dentofacial Orthopaedics 100: 110-115 Kusnoto J and Kusnoto H (2001) The effect of anterior tooth retraction on lip position of orthodontically treated adult Indonesians American Journal of Orthodontics and Dentofacial Orthopaedics 120: 304-307 Lai J, Ghosh J and Nanda RM (2000) Effects of orthodontic therapy on the facial profile in long and short vertical facial patterns American Journal of Orthodontics and Dentofacial Orthopaedics 118: 505-13 Little RM (1990) Stability and relapse of dental arch alignment British Journal of Orthodontics 17:235-41

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Little RM, Riedel RA and Stein A (1990) Mandibular arch length increase during the mixed dentition. Post retention stability and relapse.

American Journal of Orthodontics and Dentofacial Orthopaedics 97: 393-404 Little RM (2002) Stability and relapse: early treatment of arch length deficiency American Journal of Orthodontics and Dentofacial Orthopaedics 121:578-581 Livieratos FA and Johnston LE Jr. (1995) A comparison of one-stage and two-stage non-extraction alternatives in matched Class II samples.

American Journal of Orthodontics and Dentofacial Orthopaedics. 108:118-31 Luecke PE and Johnston LE (1992) The effect of maxillary first premolar extraction and incisor retraction on mandibular position: testing the central dogma of “functional orthodontics” American Journal of Orthodontics and Dentofacial Orthopaedics 101: 4-12 Luppanapornlap S and Johnston LE (1993) The effects of premolar extraction: a long term comparison of outcomes in “clear-cut” extraction and non-extraction Class II patients Angle Orthodontist 63: 257-272 Major P, Kamelchuk L, Nebbe B, Petrikowski G and Glover K (1997) Condyle displacement associated with premolar extraction and non-extraction orthodontic treatment of Class I malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 112: 435-40 McLeod C, Fields HW, Hechter F, Wiltshire W, Rody W and Christensen J (2011) Esthetics and smile characteristics evaluated by laypersons Angle Orthodontist 81: 198-205 McNamara L, McNamara JA, Ackerman M, Baccetti T (2008) Hard- and soft-tissue contributions to the aesthetics of the posed smile in growing patients seeking orthodontic treatment American Journal of Orthodontics and Dentofacial Orthopaedics 133: 491-499 Merrifield LL (1966) The profile line as an aid in critically evaluating facial aesthetics American Journal of Orthodontics 52: 804-822 Mills JRE (1966) Long-term results of the proclination of lower incisors British Dental Journal 120: 355-363 Mills JRE (1968) The stability of the lower labial segment Dental Practitioner 18: 293-306 Moore T, Southard K, Casko JS, Qian F, Southard TE (2005) Buccal corridors and smile aesthetics American Journal of Orthodontics and Dentofacial Orthopaedics 127:208-13 Nomura M, Motegi E, Hatch JP, Gakung PT, Ng’ang’a PM, Rugh JD, Yamaguchi H (2009) Esthetic preferences of European American, Hispanic American, Japanese, and African judges for soft-tissue profiles American Journal of Orthodontics and Dentofacial Orthopaedics 135: S87-S95 Noroozi H, Djavid GE, Moeinzad H and Teimouri AP (2002) Prediction of arch perimeter changes due to orthodontic treatment.

American Journal of Orthodontics and Dentofacial Orthopaedics 122:601-607 O’Brien K et al (2003) The effectiveness of early treatment for Class II malocclusion with the Twin Block appliances: A multicentre randomized controlled trial. Part 1:dental and skeletal effects American Journal of Orthodontics and Dentofacial Orthopaedics 124:234-43 Ong HB and Woods MG (2001) An occlusal and cephalometric analysis of maxillary first and second premolar extraction effects Angle Orthodontist 71: 90-102 Pancherz H and Anehus-Pancherz M (1993) The headgear effect of the Herbst appliance: A cephalometric long-term study American Journal of Orthodontics and Dentofacial Orthopaedics 103: 510-520

DIAGNOSIS AND TREATMENT PLANNING EXCELLENCE IN ORTHODONTICS 2012

Paquette DE, Beattie JR and Johnston LE Jr (1992) A long-term comparison of non-extraction and premolar extraction edgewise therapy in “borderline” Class II patients.

American Journal of Orthodontics and Dentofacial Orthopaedics 102: 1-14 Park and Burstone (1986) Soft - tissue profile - fallacies of hard tissue standards in treatment planning American Journal of Orthodontics 90: 52-56 Roden-Johnson D, Gallerano R and English J (2005) The effects of buccal corridor spaces and arch form on smile aesthetics American Journal of Orthodontics and Dentofacial Orthopaedics 127:343-50 Sarver DM and Ackerman MB (2003a) Dynamic smile visualisation and quantification: Part 1. Evolution of the concept and dynamic record for smile capture American Journal of Orthodontics and Dentofacial Orthopaedics 124:4-12 Sarver DM and Ackerman MB (2003b) Dynamic smile visualisation and quantification: Part 2. Smile analysis and treatment strategies American Journal of Orthodontics and Dentofacial Orthopaedics 124:116-27 Saelens NA and De Smit AA (1998) Therapeutic changes in extraction versus non-extraction orthodontic treatment European Journal of Orthodontics 20:225-230 Selwyn-Barnett BJ (1996) Class II/Division 2 Malocclusion: A method of Planning and Treatment British Journal of Orthodontics 23: 29-36 Sims AP and Springate SD (1995) Stability of the lower labial segment following orthodontic treatment--a comparison of treatment with Andresen and Begg appliances British Journal of Orthodontics 22: 13-21 Shearn BN and Woods MG (2000) An occlusal and cephalometric analysis of lower first and second premolar extraction effects American Journal of Orthodontics and Dentofacial Orthopaedics 117:351-61 Spahl TJ Letter to the editor American Journal of Orthodontics and Dentofacial Orthopaedics (2003); 124:16A-17A Spyropoulos MN and Halazonetis DJ (2001) Significance of the soft tissue profile on facial aesthetics American Journal of Orthodontics and Dentofacial Orthopaedics 119: 464-71 Staggers JA (1990) A comparison of second molar and first premolar extraction treatment.

American Journal of Orthodontics and Dentofacial Orthopaedics 98: 430-436 Stephens CD and Houston WJB (1985) Factors affecting the rate of spontaneous space closure at the site of extracted mandibular first premolars European Journal of Orthodontics 7: 157-62 Steyn CL, Harris AMP and du Preez RJ (1996) Anterior arch circumference adjustment - how much?

Angle Orthodontist 66: 457-462 Stucki N and Ingervall B (1998) The use of the Jasper Jumper for the correction of Class II malocclusion in the young permanent dentition European Journal of Orthodontics 20: 271-281 Tadic N and Woods MG (2007) Incisal and soft tissue effects of maxillary premolar extraction in class II treatment (2007) The Angle Orthodontist 77: 808–816 Waters D and Harris EF(2001) A cephalometric comparison of maxillary second molar extraction and non-extraction treatment in patients with Class 2 malocclusions American Journal of Orthodontics and Dentofacial Orthopaedics 120: 608-613 Williams S and Andersen CE (1995) Incisor stability in patients with anterior rotational mandibular growth Angle Orthodontist 65: 431-442

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Witzig JW and Spahl TJ (1987) The clinical outline of maxillofacial orthopaedic appliances 1st ed. Littleton, Mass: PSG Publishing: 167-216 Yang I-H, Nahm DS and Baek H-S (2008) Which hard and soft tissue factors relate with the amount of buccal corridor space during smiling?

The Angle Orthodontist; 78: 5â&#x20AC;&#x201C;11 Zierhut EC, Joondeph DR., Artun J and Little RM (2000) Long-term profile changes associated with successfully treated extraction and non-extraction Class II division I malocclusions.

Angle Orthodontist 70: 208-219

Useful related references not referred to in this chapter Proffitt WR (1994) Forty-year review of extraction frequencies at a University orthodontic department Angle Orthodontist 64: 407-413

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Chapter

4

Facial appearance, the smile and tooth aesthetics David Birnie "The apple-hat she which wore, surmounted with black willow plumes, concealed from view a face so facelike in its appearance as to be positively facial."

Gertrude the Governess: or Simple Seventeen in Nonsense Novels by Stephen Leacock (1911)

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Introduction This chapter emerged from a request to talk on whether orthodontic treatment could change facial appearance.

Like many such requests, the search for knowledge proved both fascinating and informative. Topics covered are:

• • • • • • • • •

why are we interested in facial appearance? how do we define facial appearance and what are its components is there agreement on concepts of facial attractiveness? does society’s concept of facial appearance change with time? what are the attractive and unattractive features of facial appearance? how is facial appearance measured? does facial appearance change with age? can orthodontics change facial appearance? is there a difference between smile analysis in orthodontics and restorative dentistry?

All these questions are of topical interest to orthodontists but the answers are frequently rather ‘soft’ and subtle.

Restorative dentistry has a more standardised approach to smile analysis and diagnosis probably because patients are more likely to be adults and therefore the restorative dentist works in a less dynamic environment in terms of growth, development and age related changes (Sarver 2003a).

Facial appearance Components of facial appearance We are interested in facial appearance because we believe that orthodontic treatment can influence facial appearance either positively or negatively. In this chapter, the components of facial appearance are examined as well as the effect of animation on facial appearance. Is there general agreement on what constitutes an attractive face and if so, is this concept static or does it change with time? What are the attractive and unattractive features of facial appearance? How can we measure facial appearance? How does age affect facial appearance and how does this affect orthodontic treatment plans?

The orthodontist’s interest in facial appearance has increased in recent years as it has been realised that soft tissues are important diagnostic features and represent boundaries in treatment – perhaps more challenging boundaries than hard tissues. We know that orthodontic treatment may affect facial appearance either positively or negatively and increasingly, orthodontists are able to measure soft tissues and thus derive soft tissue outcome measures for orthodontics. Orthodontists (and oral surgeons) often move hard tissues to effect soft tissue change and yet we know that hard tissue changes have a variable effect on soft tissues; it makes sense therefore to concentrate more on soft tissues and to develop more sophisticated methods of measuring and analysing them at the diagnostic stage and at the end of treatment.

The following books are excellent texts on facial and dental appearance and aesthetics and provide a sound basis for further reading and thought:

• • • • •

Proportions of the Aesthetic Face by Powell and Humphries Fundamentals of Esthetics by Claude Rufenacht Esthetic Orthodontics and Orthognathic Surgery by David Sarver Facial and Dental Planning for Orthodontists and Oral Surgeons by William Arnett and Richard McLaughlin The Art of the Smile by Rafi Romano

are excellent texts on facial appearance which provide a sound basis for further reading and thought.

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The components of facial appearance are: hair

hairline

forehead

eyes and eyebrows

cheeks

ears

nose

upper lip

teeth

lower lip

teeth

chin

throat and neck

skin

bone structure

soft tissue drape

expression

animation

A systematic analysis of facial appearance can be divided into five regions:

• • • •

forehead and orbit cheek and nose maxilla mandible

Each of these areas need to be evaluated:

• • •

vertically horizontally and for symmetry

This can be done by examining the patient from the following aspects:

• • •

frontal profile 45°(oblique) profile

However the rigid division of the face into zones or components does cause problems – such as in considering the smile which straddles the border between maxilla and mandible. Not only does the smile involve the maxillary and mandibular zones, but it involves the orbital area as well!

And so as orthodontists move their focus from static hard tissue analysis to a combination of soft tissue and hard tissue analysis, it is important to remember that facial animation can dramatically affect facial appearance instantaneously and that age provides constant and, to a certain extent, predictable change. We struggle to come to terms with the analysis of facial dynamics and the extent to which these can be changed.

Important concepts in facial appearance The eyes are an important concept in facial appearance as these are used to gain attention.

However, the mouth is probably even more important. It has associations with:

• • •

survival o feeding socialisation o communication self-fulfilment o acting and singing

Much of the fashion in facial appearance is related to a wish to preserve or re-create youthfulness. This is characterised by a large forehead, large eyes, a foreshortened lower face and full lips. Why the preoccupation with youthfulness? Almost certainly because of its associations with fertility.

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Evolutionary psychology ….

• facial cosmetic surgery procedures performed on female patients have increased 35% since 1997 • one of the most common procedures is the injection or insertion of foreign material into the lips to increase their fullness • men have evolved a preference for younger women thus narrowing the range of mates to those young enough to bear children • as women's reproductive capacities drop off, so do men's ratings of attractiveness for them, even if they are shown only pictures of women's faces …. and concealed ovulation?

• Although ovulation in human females is generally accepted as concealed (unlike other mammals), there is evidence that subtle cues to ovulation may exist. Roberts et al (2004) tested the hypothesis that female facial attractiveness might be subject to cyclical variation and be perceived by potential mates. They tested preferences for photographs of women during the follicular and luteal stages of the cycle. They showed that women’s facial appearance varied during the menstrual cycle and was higher in the periovulatory than the luteal phase. Not surprisingly and conversely, women in the fertile phase are more attracted to men possessing facial features with high genetic quality (ie: more masculine features) than during the rest of the cycle.

Extractions and facial appearance

Lip support is dependent on the presence of teeth. Inappropriate extractions will reduce lip support and inappropriate non-extraction treatment will result in excessive lip fullness. Thus the best facial profile for an individual is obtained by the appropriate choice of extraction or non-extraction treatment. Done correctly, orthodontics should leave no scars on facial appearance. Rushing et al (1995) carried out an interesting study in to how dentists perceive the effects of orthodontic extraction on facial appearance. The extraction of permanent teeth is commonly undertaken in orthodontics to produce results that improve tooth alignment, masticatory function, periodontal health and facial aesthetics as well as being a basis for the establishment of a stable result.

The study carried out by Rushing et al (1995) sought to determine whether dentists could distinguish between patients who had received orthodontic treatment and those who had not and between patients who had had extractions for orthodontic purposes and those who had not. In addition, the study looked at whether orthodontists evaluate facial appearance differently from general dental practitioners.

The results of this study showed that general dental practitioners and orthodontists were only approximately 50% accurate in identifying:

• whether a patient had received orthodontic treatment or had not from the patient’s facial profile • whether a patient had had extractions or not as part of their orthodontic treatment Interestingly, there was no difference between orthodontists and general dental practitioners in their judgement of whether patients who had a concave facial profile had had extractions or not but practitioners who limited their practice to orthodontics with a non-extraction emphasis were more likely to associate concave profiles with orthodontic treatment involving extractions.

Frontal and profile analysis Several methods of profile analysis exist and these gradually become more refined with time. The measurement of soft tissues from a cephalometric radiograph is not always satisfactory and measurement from facial photographs may sometimes be preferable.

One of the most influential contributors to the science of facial analysis in recent years has been William Arnett.

The facial keys to orthodontic diagnosis and treatment planning were originally described in 1993. (Arnett and Bergman 1993a and 1993b). The use of these keys to perform a soft tissue cephalometric analysis is described by Arnett et al (1999).

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A synthesis of these concepts, with some updating, is given in Arnett and McLaughlin (2004).

The integration of cephalometric radiographs and facial photographs gives more scope for useful analyses.

Key concepts are the use of a natural head position for both cephalometric radiography and horizontal and vertical reference lines.

Frontal reference lines The interpupillary line is used as a horizontal reference line and a vertical line through soft tissue nasion and the middle of the philtrum as a vertical reference line.

Facial asymmetry is difficult to quantify; frequently the asymmetry involves multiple structures and twodimensional measuring techniques are inadequate descriptors. Edler et al (2004) have described useful outcome measurement for the correction of facial asymmetry. The inferior insertions of the ears were used as baseline and this line bisected perpendicularly to produce an ideal facial midline; the outline of the mandible was traced from a full-face photograph to produce right and left areas of the mandible. The following measurements were then taken:

• • • •

the area of the right side was divided by the area of the left side to produce an area ratio the perimeter of the right side was divided by the perimeter of the left side to produce a perimeter ratio the compactness of the shape was determined by squaring the perimeter and dividing it by its area.

The value for the right hand side was divided by the value for the left hand side to give a compactness ratio the centres of areas (or moments) of the right and left sides are combined and then measured as a horizontal distance to the bisecting perpendicular of the baseline. This measurement is then expressed as a percentage of the length of the baseline and referred to as the moment ratio.

The value for ideal symmetry would unity for the first three measurements and zero for the moment ratio. Of more interest perhaps is the difference in the ratios between the right and left sides of the face in individual patients. This can be determined from the following formula: Difference index = Since in cases of ideal (or perfect) symmetry there would be no differences between the right and left sides of the mandible, the normal value for this measurement is zero. The authors found that the highest correlations between clinicians’ judgements and metrics were for the difference index for area and compactness – essentially measuring size and shape.

Meyer-Marcotty et al (2011) assessed the three dimensional perception of facial asymmetry. The identification of asymmetry in virtual 3D faces was independent of the profession of the raters - orthodontists, oral and maxillofacial surgeons and lay people. Lay people were able to detect asymmetries when located near the midline of 3D faces. Asymmetries of the nose were judged as more negative than asymmetries of the same degree of the chin. The location and architecture of the nose play a crucial role in perception of symmetry. The authors detected a left/right bias of facial asymmetry. A deviation of the nose to the left led to more negative rating of facial perception, whereas a deviation of the chin to the right was judged more negatively.

Profile reference line The position of the vertical reference line for the face in profile is a matter of debate. Arnett and McLaughlin (2004) suggest the use of a vertical line (True Vertical Line - TVL) through subnasale. It is probable that no single point suits every malocclusion and in cases of maxillary retrusion, Arnett and McLaughlin suggest moving the TVL 1 to 3 mms anteriorly.

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Figure 4.1: Horizontal and vertical reference lines in the frontal view

Figure 4.2: Arnett and McLaughlin’s True Vertical Line (TVL) through subnasale

Figure 4.3: Nasal morphology. Note the straight dorsum and supratip break

Bass (2003) has published an interesting article on norms for the aesthetic analysis of the lower face which is well worth reading. This includes a useful method of clinically establishing a true horizontal head position and then relating the anteroposterior position of the lips and dentition to verticals dropped from this line. Bass suggests that:

• • •

the chin point should lie on a vertical line drawn halfway between subnasale and A point the upper lip should be vertical and its vermilion border should just project in front of a vertical line through subnasale a vertical tangent to the labial face of the upper incisor should pass through a point 25% of the distance from A point to subnasale

The nose Soft tissue nasion is also the area of the start or radix of the nose; a line through soft tissue nasion should pass through the subnasal area. If a rhinoplasty is considered as an adjunct to orthognathic surgery, then it is easier to augment the radix than to make it deeper.

The dorsum is divided into an upper bony part and a lower cartilaginous part. The removal of a dorsal hump is a common procedure in rhinoplasties but augmentation is also possible. Towards the lower part of the cartilaginous dorsum is the supra tip break and then the nasal tip. Passing on to the underside of the nose, the points are infratip, columella and subnasale. Arnett and McLaughlin 2004 describe nasal tip projection relative to TVL as being 14.6 mm to 17.4 mm in adult females and 15.7 mm to 19.1 mm in adult males.

The nasolabial angle is normally in the range 90° to 120°. Its value is a combination of maxillary protrusion or retrusion, the position of the maxillary teeth and the vertical position of the nasal tip. Perhaps of more importance is the drape of the upper lip which should be at least 90° to a true horizontal; a backward sloping upper lips look particularly unaesthetic.

The midface Much is made of the effects of orthodontic treatment on the midface. Quantifying these effects is particularly difficult as they represent subtle change across a moderate area rather than movements of individual points.

Arnett and McLaughlin 2004 describe four points which may assist in describing the midface: the soft tissue cheekbone, the soft tissue orbital rim, the subpupil point and the nasal base point.

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Concepts of facial appearance

Agreement on concepts of facial appearance Is there agreement on concepts of facial appearance? An excellent review article on facial aesthetics through the ages has been published by Peck and Peck (1970).

Although we may believe that beauty is in the eye of the beholder, the evidence points in the other direction.

Iliffe (1960) published 12 photographs of young women aged 20-25 years, representing different facial types photographed under the same conditions, in an English newspaper. Readers were asked to rank the photographs in order of attractiveness or ‘prettiness’. Each response was correlated as to the age, sex and occupation of the respondent and 4,300 replies were obtained. The positive correlations obtained were high and significant suggesting that in the United Kingdom, a common basis for judging facial attractiveness existed and that it was shared by both men and women regardless of age.

The same study, with 100,000 responses, was repeated in the United States of America by Udry (1965) who found that not only was there significant agreement as to whom the most attractive facial appearance belonged, but that the top three selections were the same in both Great Britain and the United States of America. After the first three selections, the order differed only slightly.

In a study by Xu et al (2008) study, the agreement and disagreement between pairs of Chinese and US orthodontists in ranking the facial attractiveness of end-of-treatment photographs of growing Chinese and white orthodontic patients was determined. Each orthodontist independently ranked standard clinical sets of profile, frontal, and frontal-smiling photographs of 43 white patients and 48 Chinese patients. The resulting correlations ranged from +0.004 to +0.96 with a median of +0.54. Of these, 18.7% were lower than 0.4; 41.0% were lower than 0.5; 68.8% were lower than 0.6; 91.6% were lower than 0.7; and only 8.4% were greater than 0.7. As had been anticipated, correlations between judges were higher when they ranked patients of their own ethnicity than when they ranked patients of different ethnicity, but the differences were smaller than had been expected. The rankings of no pair of judges correlated negatively. The distribution of levels of agreement between pairs of orthodontists did not differ substantially according to whether the pairings were from the same or different continents although judges from the same continent had better agreement when judging patients from that continent. This study again demonstrates consistency in the evaluation of facial attractiveness.

Oh et al (2009) studied the concordance between rankings of facial attractiveness and 21 cephalometric measurements on US and Chinese patients at the end of orthodontic treatment. Among US patients, higher rank for photographic facial attractiveness was strongly associated with higher values for profile angle, chin prominence, lower lip prominence, and Z-angle, and also with lower values for angle of convexity, H-angle, and ANB. Among Chinese patients, higher rank for photographic facial attractiveness was strongly associated with higher values for Z-angle and chin prominence, and also with lower values for angle of convexity, H-angle, B-line to upper lip, and mandibular plane angle. Chinese patients whose lower face height values approximated the ethnic “ideal” (54%) tended to rank higher for facial attractiveness than patients with either higher or lower values of lower face height. Surprisingly, many cephalometric measures believed by clinicians to be indicators of facial attractiveness failed to correlate with facial attractiveness rank for either ethnicity at even the P <0.05 level, including SN-pogonion angle, lower incisor to mandibular plane angle, and Wits appraisal.

Racial studies Interestingly, a similar study was undertaken by Martin (1964) to determine how males judged female beauty according to racial group membership. A panel of judges were asked to rank ten photographs of black females from the least Negroid (most Caucasian) to the most Negroid. Three groups of men (50 American whites, 50 American blacks and 50 African (Nigerian) blacks) were then asked to rank the photographs by facial attractiveness. The results support the proposition that American whites and American blacks share a common aesthetic standard for female facial attractiveness – that of the Caucasian facial model. The African blacks rated Caucasian features less often attractive than did either American whites or American blacks.

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The effect of time on concepts of facial attractiveness Although it has been suggested that standards of facial attractiveness are based on classical values and have remained unchanged over several centuries, several authors (Farkas et al 1984, Pogrel 1991) have suggested that changes in facial aesthetic standards have taken place. Auger and Turley (1994) studied profile photographs of adult Caucasian females from fashion magazines with publication dates covering a 100 year period and found that standards of facial attractiveness had changed with a trend towards more protrusive lips and increase in vermilion display.

A similar study on the male facial profile was done by Nguyen and Turley (1998). As in female profiles, an increasing tendency towards lip protrusion, lip curl and vermilion display was found in male profiles in fashion magazines over 65 years.

Perhaps surprisingly, a similar trend to increasing anteroposterior lip position, nasiolabial angle and interlabial angle with increased fullness and more anteriorly positioned lips has been found in African American females during the last century (Yehezekel and Turley 2004).

Unattractive features of facial appearance The flowing features of facial appearance are generally rated as unattractive:

• • • • • • •

severe class 2 or class 3 malocclusions little show of vermilion border an upper lip that slopes backwards a very high or very low smile line lack of a well defined labiomental fold an everted lower lip extreme bilabial protrusion

The smile The aesthetic zone is composed of the size, shape, position and colour of the displayed teeth, the gingival contour, the buccal corridors and the framing of the lips. The range of the aesthetic zone is defined by the movements of the upper and lower lip during smiling, facial expression and speech and the essentials of the smile involve the interaction and relationships between:

• • •

the teeth the framework of the lips the gingival scaffold (Garber and Salama 1996, Ackerman and Ackerman 2002, van der Geld et al 2008)

Smiling involves:

• • • • • •

the development of prominent nasolabial folds flaring of the nostrils inferior movement of the nasal tip display of the teeth pronounced lip movement squinting of the eyes

Squinting of the eyes is the final part of the smiling process and denotes a natural and spontaneous smile; smiles which do not involve squinting of the eyes appear as joyless.

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A very good review of the smile in orthodontics is given by Sarver (2001).

Rigsbee et al (1988) looked at the influence of animation on smile characteristics. They determined that women showed greater facial animation than men and that during smiling, the nasal width increased by 14%, there was 20% shortening of the upper lip, and the mouth width increased to 130% of the original. The upper lip length was greater for males than females by 2.6 mm at rest and 3.2 mm when smiling. On average, for the total sample, upper incisor exposure was 9.7 mm and the interlabial gap was 11.8 mm. Orthodontically treated patients had more upper incisor exposure on smiling and also a greater interlabial gap.

Characteristics of the normal smile The characteristics of the normal smile are:

• normal incisor show • • • • • •

o almost all cervicoincisal length of tooth of maxillary anterior teeth displayed o only interproximal gingiva displayed the upper incisors do not touch the lower lip the incisal edges are parallel to the lower lip the smile displays at least the first premolars or the first and second premolars the upper incisors are approximately the width of the philtrum the upper central incisors, lateral incisors and canines are in the golden proportion (1:0.618) (Levin 1978) midline coincides with harmonious and balanced smile

Measuring the smile Ackerman et al (1998) have described a reliable and repeatable method of recording the unstrained posed smile.

The smile may be unposed, a result of happiness or emotion, or posed, which indicates a greeting, appeasement or self-assurance. The posed smile can be subdivided into strained – forced and unnatural – or unstrained which looks natural and can be sustained. Both Hulsey (1970) and Rigsbee et al (1988) have concluded that both the unstrained and the strained smile are reproducible. Frush and Fisher (1958) discussed the relationship between the curvature of the incisal edges of the upper anterior teeth and the curvature of the upper border of the lower lip. They also defined the buccal corridor as the space developed when a patient smiles, between the buccal surfaces of the posterior teeth and the commissure of the lips. The method of smile measurement described by Ackerman et al (1998) depends on drawing vertical and horizontal lines on a photograph of an unstrained posed smile. The vertical lines correspond to the commissures of the lips, the distal embrasure of the upper canines (thus establishing a second method of defining the buccal corridors originally described by Hulsey (1970) and the dental midline. The horizontal lines correspond to the upper border of the upper lip, the lower border of the upper lip, the incisal edge of the right central incisor, the upper border of the lower lip and the lower border of the lower lip. The following measurements can then be obtained:

• • • • • •

maximum upper incisor exposure upper lip drape lower lip to upper incisor interlabial gap at rest and smiling commissure (smile) width smile index The smile index was described by Ackerman et al (1998). It is defined as follows: Figure 4.4: The method of smile measurement recommended by Ackerman et al (1998). Scaling can be achieved by measuring vertical and horizontal tooth size and applying vertical and horizontal scaling factors.

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FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

The lower the smile index, the less youthful the smile appears (because there is relatively less tooth display).

• frontal intercanine width the intercanine width as measured from a full-face photograph • right and left buccal corridor the buccal corridor is measured from the mesial line angle of the maxillary first premolars to the inner aspect of the commissure • buccal corridor ratio Van der Geld et al (2007) have described a reliable way in which to capture the spontaneous smile using a video camera. The spontaneous smile usually produces greater incisor and gingival display than the posed smile.

Buccal corridor ratios The two ways of measuring buccal corridor width merit some discussion. The method described by Hulsey (1970) is described as:

whereas that of Frush and Fisher (1958) is

The Frush and Fisher method is strongly preferred as a more valid measure of buccal corridor ratio. Moore et al (2005) described a measure of smile fullness as:

and smile breadth as:

The study of Moore et al (2005) characterised smile fullness by buccal corridor ratio as shown in Table 4.1.

Digitally altered photographs of smiling faces with different categories of smile fullness were judged by a panel of lay members who concluded that having minimal buccal corridors (broad smile) was a preferred aesthetic feature in men and women.

However, this contrasts with the study of Roden-Johnson et al (2005) who suggested that lay people had no preference between treated (narrow-tapered and normal-broad) archforms and untreated controls; furthermore, they argued that buccal corridor width did not affect smile rating by Percentage BCR Smile category orthodontists, dentists or lay people.

28%

narrow

22%

medium-narrow

15%

medium

10%

medium-broad

2%

broad

Table 4.1: Smile fullness categorised by percentage buccal corridor ratio

Parekh et al (2006) investigated the attractiveness of smile arc and buccal corridor width and found that excessive buccal corridors and smile arcs were rated less attractive by both orthodontists and lay persons. In addition, flat smile arcs decreased attractiveness regardless of the buccal corridor width.

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Martin et al (2007) determined that both lay people and orthodontists prefer smiles with smaller buccal corridors.

Orthodontists were more discriminating than lay people and detected smaller differences between smiles than lay people as supported by Kokich et al (1999). Martin et al suggest that studies which have found no difference in preference between large and small buccal corridors have used intercanine width rather than visible maxillary dentition for calculating buccal corridor ratios.

Yang et al (2008) carried out an interesting study to determine which hard and soft tissue factors were related to buccal corridor area ratio (BCAR).

Long faces tended to have less buccal corridor area and buccal corridor area was negatively associated with increased soft tissue height (subnasale to soft tissue menton), the amount of upper incisor exposure and the sum of tooth widths from upper left to upper right first molar. There was no difference in buccal corridor area between extraction and non-extraction groups. Note that this study used upper intercanine width rather than the visible dentition to determine where the buccal corridor started.

Ioi et al (2009) confirmed, using a group of orthodontists and a group of dental students, that both groups preferred broader smiles (buccal corridor ratio < 10%) and that above 10%, the difference in perception became clinically significant.

Springer et al (2011) used a novel method involving digital manipulation of smile components by lay people using a slider. One finding was the poor reliability of the results for measurement of buccal corridor spaces. It is interesting to note that Janson et al (2011) in their review of the factors influencing smile attractiveness were critical of many of the studies into buccal corridors on the grounds that many had an unrealistic representation of the smile and/or an insufficient number of lay judges. They concluded that there is as yet no convincing evidence that buccal corridors affect smile attractiveness.

Tjan et al (1984) and Dong et al (1999) have useful summaries of some of the aesthetic factors relating to the smile as described below.

Upper lip position (smile line) The three categories of upper lip position on smiling are given in descending order of aesthetic rank.

The term gingival smile line (GSL) refers to the show of a contiguous band of gingivae. Gingival smile lines are often thought to be unattractive; however, a small band of contiguous gingivae (up to 25% of incisor height) is acceptable. Females, on average, show 1 mm of gingival smile line and males show –1 mm. In addition, round faces tolerate gingival smile lines better than long thin faces. Normally, both patients with gingival smile lines and those without have normal upper lip lengths.

The gingival margin of the upper canine should be at the height of the upper lip when smiling.

Sarver and Ackerman (2003a) suggests a more detailed analysis of the morphology of the upper lip and its relationship to the upper incisors. These include:

•

•

height of the philtrum the height of the philtrum is measured from subnasale to the lowest point of the upper lip midway between the philtral columns. The relative height of the philtrum in relation to the height of the commissures is the important measurement rather than the absolute height of the philtrum. In adolescents, the height of the philtrum is usually shorter than the commissure height but this differential decreases as the face matures height of the commissures the height of the commissures is measured perpendicular to a horizontal line through subnasale

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FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

Aesthetic Rank

Upper lip position

% Occurrence

Description of incisor and gingival show

1

Average

56%

75% to 100% of maxillary anterior teeth and interproximal gingivae only

2

High

29%

maxillary anterior teeth and a contiguous band of gingivae

3

Low

15%

less than 75% of anterior teeth

Table 4.2: Table of upper lip position on smiling in descending order of aesthetic rank Aesthetic Rank

Upper lip curvature

% Occurrence

Description

1

Upward

12%

the corner of the mouth is higher than the centre of the lower border of the upper lip

2

Straight

45%

the corner of the mouth is level with the centre of the lower border of the upper lip

3

Downward

43%

the corner of the mouth is lower than the centre of the lower border of the upper lip

Table 4.3: Table of upper lip curvature on smiling in descending order of aesthetic rank Aesthetic Rank

Upper lip curvature

% Occurrence

Description

1

Parallel

60%

incisal edges of upper anterior teeth are parallel to the upper border of the lower lip

2

Straight

35%

the incisal edges of the upper anterior teeth are horizontal

3

Reverse

5%

the incisal edges of the upper anterior teeth are curved in reverse to the upper border of the lower lip

Table 4.4: Table of parallelism of upper incisor curve to lower lip on smiling in descending order of aesthetic rank Aesthetic Rank

Upper lip curvature

% Occurrence

Description

1

Not touching

54%

the incisal edges of the upper teeth do not touch the lower lip

2

Touching

36%

the incisal edges of the upper teeth just touch the lower lip

3

Slightly covered

10%

the incisal edges of the upper teeth are slightly covered by the lower lip

Table 4.5: Table of relationship between upper incisors and lower lip on smiling in descending order of aesthetic rank

• • • • •

interlabial gap at rest and when smiling 'at rest' value is only measured when lip incompetence is present maxillary incisor exposure at rest and smiling maxillary central incisor crown height gingival display smile arc

Van der Geld et al (2008) have described how maxillary lip line heights during spontaneous smiling tended to be higher in the premolar area and, for a considerable number of patients, the posterior maxillary region was also part of the aesthetic zone. During orthodontic treatment however, more attention is given to incisor lip line heights but with a risk of overexposure of the posterior gingiva. During speech, less maxillary incisor and gingiva were displayed compared with spontaneous smiling but more lower incisor was displayed. In van der Geld’s study, the coherence of lip line heights during spontaneous smiling, speech, and tooth display in the natural rest position was determined eg: patients showing higher lip line heights during spontaneous smiling, also showed higher lip line heights during speech as well as a greater amount of tooth display in the natural rest position. This means that these problems can be addressed by a single orthodontic strategy. For the upper central incisor, lip line heights during spontaneous smiling decreased by 2 mm. Maxillary tooth display decreased by and upper lip length increased by almost 4 mm in the natural rest position. Where considerable perioral muscular activity is required such as in spontaneous smiling, additional muscle activity slows the age-effects. In the natural rest position with the least perioral musculature activity, mandibular tooth display increased because of ‘sagging’ of the lower lip with age. During speech no significant age effects were found but during spontaneous smiling, lip line heights decreased, which means that the lower lip was elevated somewhat higher in the older age group. All in all, an excellent and interesting paper which adds considerably to our knowledge about age related changes in

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the smile. Desai et al (2009) carried out a cross-sectional study on changes in the dynamic smile; they found that maxillary incisor display decreased with age but that the smile index increased significantly. No subject in the 50 and over age group had a high smile, and no subject in the 15-to-19 year group had a low smile. All dynamic measurements indicated a pattern of decreasing change from rest to smile, especially evident after ages 30 to 39 years. As a person ages, the smile gets narrower vertically and wider transversely and the ability of the perioral muscles to create a smile decreases with increasing age.

Van der Geld et al (2011) has proposed the following useful semi-quantitative categorisation of smile the line:

• • • •

< than 75% of incisor crown height showing is a low smile line between 75% and 100% of the incisor crown height showing is a normal smile height showing the total incisor crown length of a tooth and a continuous band of gingiva (minimum, 1 mm) is classified as a high smile line a lip line height that showed more than 4mm of gingiva is classified as a gummy smile line

Upper lip curvature The three categories of upper lip curvature on smiling are given in descending order of aesthetic rank.

Parallelism of upper incisor curve with lower lip (smile arc) David Sarver (2001) has devoted a whole paper to this topic. The three categories of parallelism of upper incisor curve to lower lip are given in descending order of aesthetic rank.

It can be seen that the parallel or consonant smile is both the most attractive and the most common. Ackerman (1998) compared a group of treated and untreated patients; 40% of the treated patients showed a change in smile arc and 32% showed flattening of the smile. In the untreated group, 13% had a change in smile arc and 5% exhibited flattening.

Relationship between upper incisors and lower lip The three categories of relationship between upper incisors and lower lip are given in descending order of aesthetic rank in Table 4.5. It should be noted that Janson et al (2011) in their thoughtful systematic review of research into factors influencing smile attractiveness concluded that no research on actual subjects as yet supports the view that smile arc, as an individual factor, influences smile attractiveness.

The oblique view Sarver and Ackerman (2003b) suggest that useful information can be obtained from an oblique or three-quarter photograph. In particular, the relationship of the occlusal plane to the curve of the lower lip and the display of the upper maxillary teeth, including the premolars and molars which are not visible from the frontal view. The relationship of the smile arc to the incisal edges and the cusp tips of the upper incisors is uncertain; while the suggested relationship is consonance, in the illustration by Sarver, the lower lip covers half of the second premolar and most of the first molar.

70

60

per cent

50 40 30 20 10 0 Canine

First premolar Yoon et al (1992)

Figure 4.5:

Second premolar

First molar

Tjan et al (1984)

Number of teeth displayed on smiling

Second molar

The number of teeth displayed on smiling The number of teeth displayed on smiling has been described by Tjan et al (1984) and Yoon et al (1992).

The results are shown in Figure 4.5. In aesthetic rank, smiles which show first molar to first molar are judged the most attractive and these are closely followed by smiles which show second premolar to second premolar and second molar to second molar.

Smiles which show only the six anterior teeth are very uncommon (< 7% in both samples).

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Kim and Giannelly (2003) compared the aesthetics of smiles in extraction and non-extraction cases without arch expansion and could find no difference between the two groups.

Lip asymmetry Gazit-Rappaport et al (2003) measured the asymmetry and length of the lips in patients with functional side shifts (crossbites with lateral displacements). They used clinical photographs and divided the upper and lower lips into right and left hand sides with a vertical line down the centre of the philtrum; this line was used to measure vertical lip length. Horizontal lip length was measured along the junction of the upper and lower lips. The results for each quadrant were expressed as a percentage of the total surface area and length of each lip. In addition an absolute measure of lip asymmetry was used involving the difference between the right and left quadrants expressed as a percentage of the total lip surface area. Functional side shifts were shown to demonstrate measurable lip asymmetry characterised by thickening of the lower lip and thinning of the upper lip on the side of the shift.

Videographic smile recording Sarver and Ackerman (2003a and 2003b) have advanced the concept of videographic recording of smile dynamics and speech. Given the dynamic nature of facial expression, this is a logical way to progress. At the moment however, while it is technically possible to record this data, analysing it is more difficult and less certain. Sarver records smile and speech form both frontal and oblique aspects for about 5 seconds each which yields about 2 x 4 Mb or 2 x 150 frames of video data. The video clip is then reviewed and the frame that best represents the patient's social smile is selected for static analysis.

The effect of age The effect of age is shown in Figures 4.6 and 4.7. As a person ages, gravity exerts its inevitable effect. Upper incisor exposure becomes less and lower incisor exposure becomes greater (Choi et al 1995, quoted in Dong et al 1999).

Maxillary cant

The plane of the maxilla should be parallel to the interpupillary line when the patient is viewed in a full-face orientation. In fact the maxilla has two planes – a posterior occlusal plane and anterior (incisal) plane. If the posterior occlusal plane is not parallel to the interpupillary line, then it is likely that there is mandibular asymmetry (due to condylar hyperplasia?) with compensatory overdevelopment of the maxilla on one side. This situation is, of course, only treatable with surgery. However, if the posterior occlusal plane is parallel to the interpupillary line and the anterior occlusal plane is not, then this should be manageable by orthodontic treatment alone. Whether this requires extrusion or intrusion of the anterior teeth will depend on the crown lengths of the anterior teeth.

The diagnosis and management of maxillary cant therefore depends on the interplay of four factors:

• •

interpupillary line posterior occlusal plane

8

3.5

7

3

6

2.5

4

mm

mm

5

3 2

1.5 1

1

0.5

0 -1

2

20-29

30-39

40-49

50-59

60-69

0 20-29

Age

-2 Resting

Figure 4.6: smiling

40-49 Age Resting

Smiling

Exposure of upper incisors by age: at rest and

30-39

Figure 4.7: smiling

50-59

60-69

Smiling

Exposure of lower incisors by age: at rest and

FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

Gingival or mucosal display

Degree

Treatment options

2-4 mm

1

orthodontic intrusion orthodontics and periodontics periodontics periodontics and restorative dentistry

4-8 mm

2

periodontics and restorative dentistry orthognathic surgery

> 8 mm

3

orthognathic surgery, with periodontics and restorative dentistry where necessary

Table 4.6: Categorisation and treatment options for increased gingival display

Diagnosis and treatment planning involves assessing the following factors:

• • • • •

• •

61

anterior occlusal plane maxillary incisor crown

length Kokich (1993b) has published an excellent article describing this in more detail.

Increased gingival display Some of the concepts relating to increased gingival display (gummy smile) have already been discussed.

the relative vertical relationship between the posterior and anterior occlusal plane the amount of gingival display the crown lengths of the maxillary incisors the facial type the likely effect of future facial growth and aging

It is probable that orthodontists and oral surgeons have been too quick to treat mild amounts of gingival display – it is frequently much less unattractive than previously thought and of course naturally decreases with age.

Where the anterior occlusal plane has increased vertically (over-erupted) relative to the posterior occlusal plane, then orthodontic intrusion of the maxillary incisors will lift the gingival margins of the anterior teeth as intrusion occurs thus improving the amount of gingival display. If in the same situation, the crowns of the maxillary incisors are short due to tooth surface loss or trauma, then intrude the anterior teeth to get the correct gingival margin relationships and have the teeth restored as appropriate (Kokich 1993b).

Deguchi et al (2008) compared the effects of J-hook headgear and miniscrews on incisor intrusion; the force to intrude the incisors was generated by ligatures, rather than an elastic force (elastomeric or spring), to give a discontinuous force. There were significantly greater reductions in overbite, maxillary incisor to palatal plane, and maxillary incisor to upper lip in the implant group than in the J-hook headgear group; mean intrusion for the miniscrew group was 3.6 mm and 1.1 mm for the J-hook headgear group. The miniscrews produced a more force in the vertical force vector and smaller vector, than the J-hook headgear group. Furthermore, significantly less root resorption was observed in the implant group compared with the J-hook headgear group; this was attributed to a long rest/healing period due to the discontinuous force produced by the ligatures.

Treatment of increased gingival display Garber and Salama (1996) have suggested the following categorisation and treatment options for increased gingival display as shown in Table 4.6. Waldrop (2008) has an interesting and up-to-date article on the challenges of managing gingival excess.

Botulinum toxin type A (Botox) Many patients with excessive gingival display have excessive muscle contraction. The use of Botulinum toxin A (BTX-A) to reduce gingival display is described by Polo (2008). Botulinum toxin type A is the most potent and most commonly used of the seven serotypes of BTX. BTX-A blocks neuromuscular transmission by binding to acceptor sites on motor or sympathetic nerves and thus preventing the release of acetylcholine. It therefore produces partial chemical denervation of the muscle with a consequent decrease in muscle activity. The muscles injected were the elevators of the upper lip – levator labii superioris alaeque nasi, levator labii superioris and zygomaticus minor. The BTX-A was diluted by adding 4.0 mL normal saline solution to 100 units of vacuum dried BTX-A to give 2.5 units per 0.1 mL. Under sterile conditions, 2.5 units were injected into the overlapping points of the right and left levator labii superioris alaeque nasi and levator labii superioris, and levator labii superioris and

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FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

zygomaticus minor (two injections per side, four injections per individual). The injection sites were identified by observation during smiling and palpation.

Measurements of gingival display and upper central incisor height were recorded for each patient with a full, unposed, spontaneous smile. The results are shown in Figure 4.8; completers were patients who attended all seven follow-up appointments.

6

Gingival exposure (mm)

5 4 3 2 1

The results showed that from a mean preinjection exposure of 5.2 mm, the gingival All Patients display declined to 0.09 mm two weeks postinjection â&#x20AC;&#x201C; a reduction in gingival display of 5.1 Figure 4.8: Gingival exposure after injection of botulinum toxin type A mm.

At the 24 week review, the mean gingival (BTX-A) (from Polo 2008) display had risen to just under three mm. We have not tried this technique but this is an interesting and thought-provoking paper and the comments of Niamtu (2008) are worth reading.

0

Baseline

2

4

8 12 Weeks after injection

16

20

24

The relationship between occlusal outcome and smile aesthetics One of the tenets of Angleâ&#x20AC;&#x2122;s teaching was that if the teeth were put in the right place, then good soft tissue aesthetics would follow. Not all orthodontists necessarily accept this and Schabel et al (2008) studied the correlation between post-treatment smile aesthetics and the ABO Objective Grading System. They found no correlation between post-treatment smile aesthetics and the ABO Objective Grading System scores and that none of the individual components or summed scores of the system could predict attractive or unattractive smiles.

Dental aesthetics Tooth factors

Tooth proportions A good paper on tooth aesthetics is provided by Sarver (2004).

The anterior teeth should present a symmetrical display with the actual tooth widths in the relative proportions given in Figure 4.9. This table gives the mean maximum mesiodistal tooth widths (on the crown) and the mean mesiodistal tooth widths at the cervical margin (on the root). Abnormalities in this symmetrical relationship occur particularly when the lateral incisors are of an anomalous shape. It should also be remembered that when viewed from the full-face position, the appearance of the widths of the anterior teeth should be in the golden proportion (1:0.618). Practically this is not very helpful as it is an apparent view rather than an actual measurement.

Many clinical problems focus on abnormalities of width or height of the upper central and lateral incisors. The ratio of width to height of the clinical crown the incisors is normally in the range 65% to 85% and normally approximately 80%; if it is possible to achieve this by tooth reshaping them then this should be done, if this ratio cannot be achieved then restoration of the teeth is required.

Figure 4.9: Maximum mesiodistal crown widths (on crown) and crown widths at cervical margin (on root) of maxillary and mandibular teeth

Where a single tooth is missing, then the tooth on the contralateral side can be used as a guide to the space

FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

Figure 4.10: This photograph shows the gingival heights of the upper central incisors and canines to be level and slightly higher than the lateral incisors. Between the central incisors, the papilla and the apparent contact pint (or connector) are approximately the same height. The connectors (Morley and Eubank 2001) decrease in height as one moves distally along the arc and between the lateral incisor and the canine, it is only 30%.

63

Figure 4.11: The occlusal embrasures increase in size as the height of the connectors decreases. Note also that the zenith, or highest point of the gingival contour coincides with the long axis of the tooth on the lateral incisors and canines whereas on the central incisors and canines, the zenith is slightly distal to the long axis of the tooth.

to be provided for the absent tooth. As a general rule, the canines should be placed in the position where they will function best and the incisors in the position where their aesthetics are best. Discrepancies in the relative width of teeth such as lateral incisors are not noticed so much if the discrepancy is unilateral rather than bilateral.

In positioning a diminutive or peg shaped lateral incisor for subsequent restoration, it is sensible to place it slightly mesial in the space as it is easier to get a good emergence profile this way. For veneers, place the lateral incisor in contact with the lower incisors so as to minimise the amount of facial preparation necessary. Conversely, if a crown is to be placed, then position the lateral incisors so that there is at least 1 mm of space between the palatal surface of the lateral incisor and the lower incisors to minimise the amount of palatal preparation required.

Dental midlines The dental midlines should coincide with the facial midlines. The upper dental midline, identified by the position of the gingival papilla between the upper central incisors, should coincide with the midline of the face as defined by a line through soft tissue nasion and the middle of the philtrum of the upper lip. The mandibular dental midline can then be judged against this reference point.

â&#x20AC;˘

the correction of dental centrelines is an integral part of establishing the symmetry of the appearance of the upper anterior teeth. The most important aspect is to keep the dental midline parallel to the true vertical when viewed in the full-face position; discrepancies of the midline under these circumstances may not be detectable until the midline is off by 4 mm. If the midline is angulated however, then the midline discrepancy is noticed at about 2 mm discrepancy. Janson et al (2011) point out the importance of measuring the limit of acceptable discrepancy rather than the smallest discrepancy that can be detected. They conclude in their systematic review that a limit of 2.2 mm can be considered acceptable for midline deviation. Concerning the axial midline angulation, they concluded that 10° (2 mm measured from the midline papilla and the incisal edges of the incisors) is already very apparent. Springer et al (2011), in their novel research into smile aesthetics also measured both the ideal and the acceptable ranges for the lay judges of all the variables investigated. They found a fairly wide range of acceptability for all the variables.

Tooth angulation Where teeth have tilted and are at an abnormal angulation, the level of the incisal edge may not be at the correct relationship to the facial axis of the clinical crown due to incisal edge wear. In these cases, it is necessary to alter the position of the teeth to their correct angular position within the dental arch and then restore the incisal edges to their original morphology.

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FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

Aspects of asymmetry of the anterior teeth, dental centrelines and the problems of tooth angulation and incisal wear are discussed by Kokich (1993c).

Key Point: Midline discrepancies are aesthetically acceptable if less than 2 mm and may not be readily noticed unless they are 4 mm off.

Mesiodistal angulation of the upper incisors makes a midline discrepancy much more noticeable.

Tooth inclination The inclination of the upper canines and premolars should be upright (zero inclination). Canines with either positive or negative buccal root torque look unattractive.

When viewed from a sagittal direction, increased tooth inclination may decrease the amount of incisor display; conversely, decreased inclination may increase incisor display due to lengthening of the tooth as the crown is retroclined.

Gingival aesthetics

Biologic width Biologic width refers to the combined connective tissue – epithelial attachment from the crest of the alveolar bone to the base of the gingival sulcus. This is made up of the supra-alveolar connective tissue fibres (on average 1.07 mm) and the junctional epithelium (mean 0.97 mm) making a total average biologic width of 2.04 mm.

The placement of restorations requires 1-2 mm of sound tooth structure coronal to the epithelial attachment and thus the minimum distance between alveolar crest and the margin of the restoration should be 3-4 mm (allowing a gingival sulcus of 1 mm).

Gingival contour and levels For patients who are combined orthodontic and restorative patients, it is important to get the gingival contour and levels correct during orthodontic treatment.

Kokich and Spear (1997) give four criteria to evaluate during orthodontic treatment:

• •

the gingival levels on contralateral teeth (e.g.: right lateral incisor and left lateral incisor) should be the same the height of the gingival contour on the lateral incisors should be very slightly lower than on the central incisors and canines • the height of the gingival contour of the central incisors and the canines should be the same • half the contact area between central incisors is tooth to tooth contact and the gingival half is filled with interproximal papilla The zenith (highest point) of the gingival contour on the maxillary central incisors and canines coincides with the long axis of these teeth; for the lateral incisor, the zenith lies distal to the long axis.

In evaluating problems of gingival level, the following factors should be evaluated:

Figure 4.12: Average root lengths and crown heights in the permanent dentition

•

height

the actual and original clinical crown

FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

• •

65

o look at the incisal edges for signs of wear or dentine showing through the sulcus depth the position of the amelocemental junction Crown height History

If a discrepancy in crown height exists between contralateral teeth, then it is helpful to have some history as to why this has occurred if known. Has there been any history of incisor damage as a result of trauma? Is the difference in crown height reflected in a difference in the height of the gingival contour?

Diagnosis In addition to the history, the key diagnostic features are:

•

•

what is the correct anatomical crown length for the tooth type? Where both teeth have suffered a reduction in anatomical crown length as a result of trauma or non-carious tooth surface loss (abrasion or erosion) this can be difficult to determine; the height of other teeth in the arch may however provide some indication by using a chart of crown heights (see Figure 4.12). It is helpful to identify the amelocemental junction for this stage. what is the clinical crown height for the tooth type in the mouth? Is there excessive sulcular depth or false pocketing as a result of gingival enlargement? How much attached gingiva is there?

What is the relationship between tooth crown and lip line both at rest and smiling?

No difference in height of gingival contour

• for minor differences in crown height, it may be possible to remove tooth tissue from the longer tooth to correct the discrepancy • larger discrepancies will require restoration

Difference in height Equalisation of the heights of the gingival contour can be achieved in one of three ways: of gingival contour present • gingival surgery to increase the height of the gingival contour of the shorter crown. The type of surgery (gingivectomy or apically repositioned flap) will depend on the width of attached gingiva • extrusion of the tooth with the higher gingival contour height • intrusion of the tooth with the lower gingival contour height The movement of the gingival margin is a 1:1 linear relationship with tooth instruction or extrusion (Kokich 1993a).

Kokich and Kokich (2004) distinguish between altered passive eruption where the sulcus is abnormally deep due to gingival hyperplasia and active altered eruption where the amelocemental junction is usually positioned at the alveolar bone crest. This occurs in females (who stop growing earlier) with long crown heights and deep overbites (allowing supraeruption of the teeth) and requires periodontal surgery to correct.

Open gingival embrasures

Diagnosis

Open gingival embrasures, or black triangles are unsightly. There are a number of methods of dealing with these.

They are essentially either papilla problems or connector problems (remember that between the central incisors, the papilla and the connector are the same vertical height). An excellent review of open gingival embrasures is given by Zachrisson (2004a).

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FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

The prevalence of open gingival embrasures is cited as 38% in adult orthodontic patients by Kurth and Kokich (2001). Interestingly, they concluded that maxillary central incisor rotation or overlap was not associated with an increased prevalence of open gingival embrasures. Tarnow et al (1992) investigated the relationship between crestal bone height and the position of the interdental contact point. An increased distance from the alveolar bone crest to the interproximal contact point was associated with the prevalence of open gingival embrasures with the suggestion that a height of 5mm had a 2% prevalence, 6mm had a 44% prevalence and 7mm, a prevalence of 75%. The height from alveolar crest to amelocemental junction was not however significant. Short and more incisally positioned contact points have a higher risk of open gingival embrasures. Finally, patients with open gingival embrasures tend to have larger gingival embrasure areas than those that do not.

The most common causes of open gingival embrasures are:

• • • •

incisal contact points that are located too far occlusally loss of papilla tissue due to o periodontal disease o traumatic oral hygiene practices divergent or triangular crown forms divergent roots Management

It is important to check root angulation carefully as this is one of the commonest causes of open gingival embrasures, particularly where the incisors are overlapped. In this situation, it is also common to have abnormal wear of the incisal edges so make sure that the gingival levels and contours are correct to allow restoration of the incisal edges.

Teeth with triangularly shaped crowns are a particular problem. Reducing the width of the teeth can reduce the size of the embrasure and also ‘squeezes’ the papilla downwards. Check that any tooth reduction will leave a tooth that conforms to the rules of tooth proportion ie: width to height ratio of 65% to 85%. If this cannot be achieved then the alternative is to restore the tooth. Tooth extrusion may also help to develop a small papilla.

The following Brasseler Komet disc and bur are recommended:

• •

interdental diamond coated perforated disc #8934A.220 diamond coated cone shaped bur #8833

In summary,

• • • • •

correct root angulations (this may mean over-angulating the brackets on the incisors) relocate the contact point more gingivally by crown recontouring remember the 50-40-30 rule for connectors consider moving the alveolar crest more occlusally by tooth extrusion consider relocation of the contact point by restorative means

It is not always possible to completely eliminate close the open gingival embrasure; this does not always matter.

Kokich et al (1999) have shown that an open space between incisors had to be 2 mm wide before orthodontists perceived it as unattractive and the lay people did not notice an open gingival embrasure until it was 3 mm long.

FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

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Complex aesthetic problems

The missing lateral incisor – closing space In patients who have missing lateral incisors where a decision has been made to close the space(s), several issues arise. A good review of this subject is given by Zachrisson (2004b) and further information is given in Zachrisson (2007).

Gingival emergence profiles The necessity for correcting the gingival emergence profiles is increased in patients who show the full height of the anterior tooth crowns on smiling and in cases where space closure is unilateral only.

The gingival emergence profiles in space closure spaces should mimic the natural dentition’s high-low-high. This means that the canine substituting for the lateral incisor should have a low emergence profile and the first premolar, substituting for the canine, requires a high emergence profile.

Low emergence profiles can be achieved by tooth extrusion. High emergence profiles can be achieved by:

• • •

tooth intrusion o bracket positioning (may affect torque) o step-up bends (less effect on torque) simple gingival surgery (no osseous recontouring) surgical crown lengthening (including osseous recontouring) Simple gingival surgery

A simple gingivectomy of the marginal gingival to the base of the probing depth can be used to increase crown height. Some regrowth of gingival always occurs and this is about 45% of the tissue removed (Monefeldt and Zachrisson (1977). The use of soft tissue lasers is becoming increasingly popular in orthodontics; useful papers on this subject are Sarver and Yanosky (2005a and 2005b) and Kravitz and Kusnoto (2008).

Surgical crown lengthening This provides more crown height than is possible with simple gingival surgery. The bone level should be adjusted to be 3 mm apical to the planned gingival margin to allow 2 mm of biologic width and 1 mm of sulcus depth. The amount of crown height gain is variable; patients with a thick gingival biotype tend to have more regrowth than patients with a thin gingival biotype. Some patients may show further gingival recession.

Tooth aesthetics The canine The canine needs to be shaped to be more like a lateral incisor by reduction of the tip and the labial surface. This has been described comprehensively by Zachrisson and Mjör (1975) and Thorderson et al (1991). Composite can be used to add a mesial corner if required.

The first premolar Intrusion of the first premolar to adjust the gingival emergence profile provides space occlusally to build up the premolar crown to look more like a canine crown. This has been described by Rosa and Zachrisson (2001). The build-up can carried out by using a hybrid composite or an ultrathin porcelain laminate veneer.

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Functional occlusion It is legitimate to ask whether closing the lateral incisor space has any functional occlusion consequences in view of the loads to be taken by the first premolar functioning in the canine position because the first premolar has smaller and thinner roots. Nordquist and McNeill (1975) compared 33 patients with at least one missing incisor and 19 patients who had space reopening and fixed prosthodontic replacement. The mean examination period post-orthodontics was 9 years 8 months. They found that patients who had space closure:

• •

were periodontally healthier did not have any difference in adequacy of occlusal function

and that there was no evidence to support the hypothesis that a class 1 canine relationship was a preferred occlusal outcome. Robertsson and Mohlin (2000) examined 50 patients with missing lateral incisors, 30 of whom had had orthodontic space closure and 20 who had prosthetic replacement with a porcelain bonded to gold or resin bonded prosthesis, at an average duration of 7.1 years after treatment. The patients who had had\space closure were more satisfied with their treatment than patients who had prostheses and no difference could be found between the groups with respect to TMJ signs and symptoms. Furthermore, patients with prosthetic replacements had poorer gingival health with build-ups of plaque and calculus.

References Ackerman JL, Ackerman MB, Brensinger CM and Landis JR (1998) A morphometric analysis of the posed smile Clinical Orthodontics and Research 1: 2-11 Ackerman MB and Ackerman JL (2002) Smile analysis and design in the digital era Journal of Clinical Orthodontics 36: 221–236 Arnett GW and Bergman RT (1993a) Facial keys to orthodontic diagnosis and treatment planning. Part 1 American Journal of Orthodontics and Dentofacial Orthodontics 103: 299-312 Arnett GW and Bergman RT (1993b) Facial keys to orthodontic diagnosis and treatment planning. Part 2 American Journal of Orthodontics and Dentofacial Orthodontics 103: 395-411 Arnett GW, Jelic JS, Jone K, Cummings DR, Beress A, Worley CD, Chung B and Bergman RT (1999) Soft tissue cephalometric analysis: diagnosis and treatment planning of dentofacial deformity American Journal of Orthodontics and Dentofacial Orthopaedics 116: 239-253 Arnett GW and McLaughlin RP (2004) Facial and Dental Planning for Orthodontists and Oral Surgeons Edinburgh, Mosby Auger TA and Turley PK (1994) Esthetic soft tissue profile changes during the 1900s Journal of Dental Research (IADR Abstracts) 73: 2128 Bass NM (2003) Measurement of the profile angle and the aesthetic analysis of the facial profile Journal of Orthodontics 30: 3-9 Chio TR, Jin TH and Dong JK (1995) A study on the exposure of maxillary and mandibular central incisor in smiling and physiologic rest position Journal of Wonkwang Dental Research Institute 5: 371-379 Desai S, Upadhyay M and Nanda R (2009) Dynamic smile analysis: Changes with age American Journal of Orthodontics and Dentofacial Orthopaedics Dong J-K, Jin T-H, Cho H-W and Oh S-C (1999) The aesthetics of the smile: a review of some recent studies International Journal of Prosthodontics 12: 9-19

136:310.e1 -310.e10

FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

Deguchi T, Murakami T, Kuroda S, Yabuuchi T, Kamioka H and Takano-Yamamoto T (2008) Comparison of the intrusion effects on the maxillary incisors between implant anchorage and J-hook headgear American Journal of Orthodontics and Dentofacial Orthopaedics 133: 654-660 Edler R, Wertheim D and Greenhill D (2004) Outcome measurement in the correction of mandibular asymmetry American Journal of Orthodontics and Dentofacial Orthopaedics 125: 435-443 Farkas LG, Katic MJ, Hreczko, Deutsch C and Munro IR (1984) Anthropometric proportions in the upper lip-lower lip-chin area of the lower face in young white adults American Journal of Orthodontics and Dentofacial Orthopaedics 86: 52-60 Frush JO and Fisher RD (1958) The dynesthetic interpretation of the dentogenic concept Journal of Prosthetic Dentistry 8: 558-581 Garber DA and Salama MA (1996) The aesthetic smile: diagnosis and treatment Periodontology 2000 11: 18â&#x20AC;&#x201C;28 Gazit-Rappaport T, Weinreb M and Gazit E (2003) Quantitative evaluation of lip asymmetry in functional side asymmetry European Journal of Orthodontics 25: 443-450 Hulsey CM (1970) An aesthetic evaluation of lip-teeth relationships present in smile American Journal of Orthodontics 57: 132-144 Iliffe AH (1960) A study of preferences in feminine beauty British Journal of Psychology 51: 267-273 Ioi H, Nakata S and Counts AL (2009) Effects of buccal corridors on smile esthetics in Japanese Angle Orthodontist 79: 628-633 Janson G, Branco NC, Fernandes TMF, Sathler R, Garib D and Lauris JRP (2011) Influence of orthodontic treatment, midline position, buccal corridor and smile arc on smile attractiveness Angle Orthodontist 81: 153-161 Kim E and Giannelly AA (2003) Extraction versus non-extraction: arch widths and smile aesthetics Angle Orthodontist 73: 354-358 Kokich VG (1993a) Esthetics and anterior tooth position: an orthodontic perspective. Part 1: Crown length Journal of Esthetic Dentistry 5: 19-23 Kokich VG (1993b) Esthetics and anterior tooth position: an orthodontic perspective. Part 2: Vertical position Journal of Esthetic Dentistry 5: 174-177 Kokich VG (1993c) Esthetics and anterior tooth position: an orthodontic perspective. Part 3: Mediolateral relationships Journal of Esthetic Dentistry 5: 200-207 Kokich VG and Spear FM (1997) Guidelines for managing the orthodontic-restorative patient Seminars in Orthodontics 3: 3-20 Kokich VO, Kiyak HA and Shapiro PA (1999) Comparing the perception of dentists and lay people to altered dental esthetics Journal of Esthetic Dentistry 11: 311-324 Kokich V and Kokich V Jr (2004) Anterior dental aesthetics: what every clinician needs to know!

AAO 104th Annual Session Doctors Session Disk 1 Kravitz ND and Kusnoto B (2008) Soft-tissue lasers in orthodontics: An overview American Journal of Orthodontics and Dentofacial Orthopaedics 133: S110-S114

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Kurth JR and Kokich VG (2001) Open gingival embrasures in adults after orthodontics treatment: prevalence and etiology American Journal of Orthodontics and Dentofacial Orthopaedics 120: 116-123 Levin EI (1978) Dental esthetics and the golden proportion Journal of Prosthetic Dentistry 40: 244-253 Martin AJ, Buschang PH, Boley JC, Taylor RW and McKinney TW (2007) The impact of buccal corridors on smile attractiveness European Journal of Orthodontics 29: 530-537 Martin JG (1964) Racial ethnocentrism and judgement of beauty Journal of Social Psychology 63: 59-63 Meyer-Marcotty P, Stellzig-Eisenhauer A, Bareis U, Hartman J and Kochel J (2011) Three dimensional perception of facial asymmetry European Journal of Orthodontics 3: 647-653 Monefeldt I and Zachrisson BU (1977) Adjustment of clinical crown height by gingivectomy following orthodontic space closure Angle Orthodontist 47: 256-264 Moore T, Southard KA, Casko JS, Qian F and Southard TE (2005) Buccal corridors and smile esthetics American Journal of Orthodontics and Dentofacial Orthopedics 127:208-13 Morley J and Eubank J (2001) Macroaesthetic elements of smile design Journal of the American Dental Association 132: 39-45 Nguyen DD and Turley PK (1998) Changes in the Caucasian male facial profile as depicted in fashion magazines during the twentieth century American Journal of Orthodontics and Dentofacial Orthopaedics 114: 208-217 Niamtu J (2008) Botox injections for gummy smiles American Journal of Orthodontics and Dentofacial 133: 782-783 Nordquist GG and McNeill RW (1975) Orthodontic versus restorative treatment of the congenitally absent lateral incisors â&#x20AC;&#x201C; long term periodontal and occlusal evaluation Journal of Periodontology 46: 139-143 Oh HS, Korn EL, Zhang X, Yan Liu, Xu T, Boyd R and Baumrind S (2009) Correlations between cephalometric and photographic measurements of facial attractiveness in Chinese and US patients after orthodontic treatment American Journal of Orthodontics and Dentofacial Orthopaedics â&#x20AC;¨136:762.e1 -762.e14 Parekh SM, Fields HW, Beck M and Rosenstiel S (2006) Attractiveness of variations in the smile arc and buccal corridor space as judged by orthodontists and laymen Angle Orthodontist 76: 557-563 Peck H and Peck S (1970) A concept of facial esthetics Angle Orthodontist 40: 284-317 Polo M (2008) Botulinum toxin type A (botox) for the neuromuscular correction of excessive gingival display on smiling (gummy smile) American Journal of Orthodontics and Dentofacial Orthopaedics 133: 195-203 Pogrel MA (1991) What are normal aesthetic values?

Journal of Oral and Maxillofacial Surgery 49: 963-969 Powell N and Humphries B (1984) Proportions of the aesthetic face New York, The American Academy of Facial, Plastic and Reconstructive Surgery, Thieme-Stratton Inc. Rigsbee OH, Sperry TP and BeGole EA (1988) The influence of facial animation on smile characteristics International Journal of Adult Orthodontics and Orthognathic Surgery 3: 233-239

FACIAL APPEARANCE, THE SMILE AND TOOTH AESTHETICS EXCELLENCE IN ORTHODONTICS 2012

Roberts SC, Havlicek J, Flegr J, Hruskova M, Little AC, Jones BC, Perrett DI and Petrie M (2004) Female facial attractiveness increases during the fertile phase of the menstrual cycle Proceedings of the Royal Society of London B (Supplement) 271, S270–S272 Robertsson S and Mohlin B (2000) The congenitally missing upper lateral incisor. A retrospective study of orthodontic space closure versus restorative treatment European Journal of Orthodontics 22: 697-710 Roden-Johnson D, Gallerano R, and English J (2005) The effects of buccal corridor spaces and arch form on smile esthetics American Journal of Orthodontics and Dentofacial Orthopaedics127: 343-50 Romano R (2005) The art of the smile: integrating prosthodontics, orthodontics, periodontics, dental technology and plastic surgery in the esthetic dental treatment Chicago, Quintessence Publishing Co, Inc Rosa M and Zachrisson BU (2001) integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors Journal of Clinical Orthodontics 35: 221-234 Rufenacht CR (1990) Fundamentals of esthetics Chicago, Quintessence Publishing Co, Inc Rushing SE, Silberman SL, Meydrech EF and Tuncay OC (1995) How dentists perceive the effects of orthodontic extraction on facial appearance Journal of the American Dental Association 126: 769-772 Sarver DM (1998) Esthetic orthodontics and orthognathic surgery St Louis, Mosby-Year Book, Inc Sarver DM (2001) The importance of incisor positioning in the esthetic smile: the smile arc American Journal of Orthodontics and Dentofacial Orthopaedics 120: 98-111 Sarver DM and Ackerman MB (2003a) Dynamic smile visualization and quantification: Part 1. Evolution of the concept and dynamic records for smile capture American Journal of Orthodontics and Dentofacial Orthopaedics 124: 4-12 Sarver DM and Ackerman MB (2003b) Dynamic smile visualization and quantification: Part 2. Smile analysis and treatment strategies American Journal of Orthodontics and Dentofacial Orthopaedics 124: 116-127 Sarver DM (2004) Principles of cosmetic dentistry in orthodontics: Part 1. Shape and proportionality of anterior teeth American Journal of Orthodontics 126: 749-753 Sarver DM and Yanosky M (2005a) Principles of cosmetic dentistry in orthodontics: Part 2. Soft tissue laser technology and cosmetic gingival contouring American Journal of Orthodontics and Dentofacial Orthopaedics 127:85 -90 Sarver DM and Yanosky M (2005b) Principles of cosmetic dentistry in orthodontics: Part 3. Laser treatments for tooth eruption and soft tissue problems American Journal of Orthodontics and Dentofacial Orthopaedics 127: 262-264 Schabel BJ, McNamara JA, Baccetti T, Franchi L and Jamieson SA (2008) The relationship between post-treatment smile aesthetics and the AABO Objective Grading System Angle Orthodontist 78: 579-584 Springer NC, Chang C, Fields HW and Beck FM,(2011) Smile esthetics from the lay perspective American Journal of Orthodontics and Dentofacial Orthopaedics 139: e91-e101 Tarnow DP, Magner AW, and Fletcher P (1992) The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal papilla Journal of Periodontology 63: 995-996 Thorderson A, Zachrisson BU and Mjör IA (1991) Remodelling of canines to the shape of lateral incisors by grinding: a long term clinical and radiographic evaluation American Journal of Orthodontics and Dentofacial Orthopaedics 100: 123-132

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Tjan AHL, Miller GD and The JGP (1984) Some aesthetic factors in a smile Journal of Prosthetic Dentistry 51: 24-28 Udry JR (1965) Structural correlates of feminine beauty preferences in Britain and the United Sates: a comparison Sociology and Social Research 49: 330-342 van der Geld PA, Oosterveld P, van Waas MA and Kuijpers-Jagtman AM (2007) Digital videographic measurement of tooth display and lip position in smiling and speech: reliability and clinical application American Journal of Orthodontics and Dentofacial Orthopaedics 131: 301.e1-8 van der Geld P, Oosterveld P and Kuijpers-Jagtman AM (2008) Age-related changes of the dental aesthetic zone at rest and during spontaneous smiling and speech European Journal of Orthodontics 30: 366-373 van der Geld P, Oosterfield P, Schols J and Kuipers-Jagtman AM (2011) Smile line assessment comparing quantitative measurement and visual estimation American Journal of Orthodontics and Dentofacial Orthopaedics 39: 174-180 Waldrop TC (2008) Gummy smiles: the challenge of gingival excess: prevalence and guidelines for management Seminars in Orthodontics 14: 260-271 Xu T, Korn EL, Liu Y, Oh HS, Lee KH, Boyd RL and Baumrind S (2008) Facial attractiveness: Ranking of end-of-treatment facial photographs by pairs of Chinese and US orthodontists American Journal of Orthodontics and Dentofacial Orthopaedics 134:74 -84 Yang I-H, Nahm D-S and Baek S-H (2008) Which hard and soft tissue factors relate with the amount of buccal corridor space during smiling?

Angle Orthodontist 78: 5-11 Yehezekel S and Turley PK (2004) Changes in the African American female profile as depicted in fashion magazines during the 20th century American Journal of Orthodontics and Dentofacial Orthopaedics 125: 407-417 Yoon ME, Jin TH and Dong JK (1992) A study on the smile in Korean youth Journal of the Korean Academy of Prosthodontics 30: 259-270 Zachrisson BU and Mjör IA (1975) Remodelling of teeth by grinding American Journal of Orthodontics 68: 545-553 Zachrisson BU (2004a) Interdental papilla reconstruction in adult orthodontics World Journal of Orthodontics 5: 67-73 Zachrisson BU (2004b) First premolars substituting for maxillary canines – esthetic, periodontal and functional considerations World Journal of Orthodontics 5: 358-364 Zachrisson BU (2007) Improving the esthetic outcome of canine substitution for missing maxillary lateral incisors World Journal of Orthodontics 8: 72-79

THE EXTRACTION NON-EXTRACTION DECISION EXCELLENCE IN ORTHODONTICS 2012

Chapter

5

The extraction non-extraction decision David Birnie and Nigel Harradine

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Introduction The decision as to whether to extract to not to extract permanent teeth in orthodontic treatment has been vigorously debated since the days of Edward Angle and Charles Tweed. The heart of this debate probably lies in this excerpt from The Tweed Years.

Angle and Tweed worked closely together for the last two years of Angle's life. Tweed banded his patients with an edgewise appliance and Angle acted as the advisor. The system worked in the following manner: Tweed made progress records of his patients every 4 months. He packed the records in a suitcase and took them to Pasadena, where Angle studied them and outlined a treatment plan for the next 4 months. This was repeated every 4 months for the next 2 years. This was a very productive time during Tweed's education and for the evolving edgewise appliance. Angle was so pleased with Tweed's work, that he was instrumental in making it possible for Tweed to be invited to give lectures at several orthodontic meetings.

In 1932, Tweed published his first article in The Angle Orthodontist. It was titled "Reports of Cases Treated with the Edgewise Arch Mechanism." Tweed held to Angle's firm conviction that the practitioner must adhere to the line of occlusion concept and never extract teeth.

This conviction lasted for 3 years after Angle's death.

After 5 years of orthodontic practice, Tweed became disheartened with his work for two reasons: (1) the protrusive faces that he was creating, and (2) the unstable dentitions. He became so disappointed that he almost left orthodontics. He resolved to study his many failures and his few successes by devoting each morning he was in his office to the making of progress records of his patients. After studying these records, he came to realize that the patients who had pleasing facial balance and harmony also had mandibular incisors that were upright over basal bone. He selected some failures, extracted first premolars, and retreated them. He reached the conclusion that carefully planned extractions allowed him to improve appearance as well as stability. Tweed wrote, "Foresight caught up with hindsight," and the diagnostic facial triangle was born.

Orthodontic extractions in perspective The percentage of teeth extracted for orthodontic reasons varies according to how studies were carried out. Reich and Hillier (1993) reported on the reasons for tooth extraction in the western states of Germany. This was a questionnaire study involving 68 dentists who were asked to record extractions in their practices over a two week period. In all, 1215 teeth in 882 patients were extracted and the reasons for extraction are given in Table 5.1. The extraction of third molars was included as a reason, when caries, periodontal reasons and others Table 5.1: The reasons for tooth extraction in Reich and were not indicated. According to the participating Hillerâ&#x20AC;&#x2122;s 1993 study dentists periodontal disease is the most frequent cause of tooth extraction for people over 40 years of age, while for those below 40 years of age, caries and third molar extractions are the most frequent reasons.

Reason Caries Periodontal disease Caries and periodontal disease Third molars Prosthetic reasons Orthodontic reasons Trauma Other

Percentage 20.7% 27.3% 18.7% 14.7% 11.2% 4.1% 0.4% 2.9%

In a study involving every fourth general dentist in Scotland, McCaul et al (2001) asked dentists to record the number and reasons for tooth extraction over a one week period. During this time, 2,558 teeth were extract or 7.3 per dentist. The study that was designed to establish whether the reasons for tooth loss had changed between 1999 and 1984, found that in 1999 in the 0â&#x20AC;&#x201C;20 years of age, orthodontics had replaced caries as the commonest reason for extraction as shown in Figure 5.1 with 50% of extractions being for this reason. Overall, orthodontic extractions represented 10% of extractions across all age groups.

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In a similar study carried out in Ontario by Murray et al (1996), orthodontic extractions represented 86% of extractions in the 0-12 year old age group and 35.4% in the 13-19 year old age group.

100% 90% 80% 70% 60% 50%

Where should orthodontists put teeth?

40% 30% 20% 10% 0% 0-10

11-20

Caries

21-30 Perio

31-40

41-50

Orthodontics

51-60

61-70

Pre-prosthetic

71+

Other

Figure 5.1: Data from McCaul et al (2001) showing that in the 0-20 year old groups, half of tooth extractions are for orthodontic reasons 100% 90% 80% 70% 60%

per cent

50% 40% 30% 20% 10% 0% 0-12

The size of the mandibular dental arch is traditionally used as the basis for planning the arch length and arch width and the maxillary dental arch is then fitted around that mandibular dental arch and orthodontists aim to try and position the teeth upright over the basal bone.

Given that the ability to change the size of the mandibular basal bone is extremely limited, this makes good sense. However, a difficulty arises in knowing what the size of the mandibular bone actually is as it is extremely difficult to measure by available methods.

Given the inability to measure this directly, a proxy measure is often used – the shape and size of the lower dental arch. The correlation between the size of the basal mandibular bone, the amount of alveolar bone and the size and length of the mandibular arch is uncertain.

13-19 20-39 40-59 Age group (years) Periodontal disease Orthodontic Trauma Pericoronitis Patient request Other

It is assumed that when treatment planning using the initial shape and length of the mandibular arch, the shape of the arch will be unchanged, arch length will be created by extractions and the teeth will be placed at Figure 5.2: Data from Murray et al (1996) showing the approximately average inclination values over the basal high percentage of orthodontic extractions in the 0-12 and 13-19 year old age groups. bone. Figure 5.3 illustrates how difficult (or impossible this may be in some cases; the orthodontist can either maintain the original posterior arch width and have the posterior teeth lingually inclined or expand the posterior arch width, position the teeth with the correct torque inclination over basal bone. So, maintaining original mandibular arch shape and placing the teeth over basal bone may not always be achievable at the same time.

Caries Prosthodontic Impacted

Will Andrews and Larry Andrews’ WALA line is the band of soft tissue immediately superior to the mucogingival junction in the mandible. It is at or nearly at the same superior-inferior level as the horizontal centre-of-rotation of the teeth. Andrews’ sees the WALA Ridge as the primary landmark for arch width and form and for archwire width and form. This is perhaps a better indicator of mandibular basal bone position than the pretreatment mandibular arch width.

Figure 5.3: Lingually inclined lower molars; it will be difficult to put the lower molars at the correct inclination without expanding the posterior arch width

There is no doubt that evolution has resulted in progressive reduction in jaw and tooth size in humans but that does not wholly account for the amount and rate of increase in ‘crowding’ that has been seen in recent time.

Nevertheless this is a prevalent, conventional paradigm on which to base treatment planning and results in the majority of patients being treated with extractions.

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Figure 5.4: arch

AG start of treatment 2002; crowded lower

Figure 5.5: AG seven years after end of active nonextraction treatment; uncrowded lower arch

So while crowding may be caused by evolutionary and genetic causes, it may also be caused by other factors such as early loss of deciduous teeth and soft tissue pressures which are most obvious in some class 2 division ii malocclusions.

What is crowding?

Once again a definition of crowding is not easy to find although every orthodontist knows what it is. It should not be confused with irregularity. It is a mismatch in size between the existing arch length and the mesiodistal widths of the teeth to be accommodated in the alveolar bone. This assumed to be a permanent state which is often only manageable by extractions. In fact patients can exist in a crowded or uncrowded state at different times of their lives as shown in Figure 5.4 and Figure 5.5.

In some malocclusions, such as class 2 division ii malocclusion, facial musculature has an obvious effect on tooth position and in some patients, this affects the buccal segments and the lower buccal segments have a marked lingual inclination. In these cases the width of the basal bone of the mandible in the posterior segments may be wider that the mandibular dental arch suggesting that the these teeth can be uprighted through posterior expansion to place the teeth over the basal bone.

Crowding may be caused by premature loss of deciduous teeth due to caries; this is not a problem of a mismatch in size between teeth and alveolar bone. Initially the arch was uncrowded and then, due to deciduous tooth loss it becomes crowded. Is that space recoverable?

It can be seen that the definition of crowding is not clear cut.

Why do orthodontists extract teeth?

Surprisingly, It is sometimes difficult to find a list of reasons why orthodontists extract permanent teeth or a list of situations in which extractions are advisable. There are four principal reasons why extractions might be required.

• • • •

to make space within the arch to align the remaining teeth the reduce the fullness of the lips to assist in providing a stable result for pathological reasons

Making space within the arch to align teeth This is one of the commonest causes of tooth extraction; the teeth are crowded and so teeth are extracted in order to align the teeth within the existing arch length.

THE EXTRACTION NON-EXTRACTION DECISION EXCELLENCE IN ORTHODONTICS 2012

Figure 5.6: This patient seems to have both severe crowding and spacing in the same arch

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Figure 5.7: The same patient post-treatment; it is almost possible to align teeth however crowded and irregular. The question is, under what circumstances should we?

The decision to do this may result both from a particular diagnostic philosophy but also the type of appliance system available. Given a simple appliance system such as a removable appliance, the patient in Figure 5.4 is untreatable without extractions; given modern fixed appliance however, it becomes possible. The decision to extract therefore can be not only a result of the diagnostic process, but also as result of the appliances available to manage the malocclusion and the patient’s ability to manage those tools.

The danger with any approach is that it is applied excessively; those in favour of extraction extract too much and those in favour of non-extraction, do not extract often enough. In Figure 5.6, the lower arch is severely crowded in the lower incisor region but has spacing in the premolar regions, particularly on the left. Note the difference in the thickness of the alveolus between Figure 5.6 and Figure 5.7 as a result of remodelling subsequent to tooth alignment. Almost any amount of crowding or irregularity can be aligned and so the question becomes when, and under what circumstances should the teeth be aligned without extractions?

Reducing the fullness of the lips In countries with a high proportion of bimaxillary protrusion, extractions are often carried out to produce a flatter profile. Unless the mechanics are carefully designed to maintain lip fullness, extractions invariably result in flattening of the facial profile.

In contrast, non-extraction treatment does not always result in an increase in lip protrusion and the effect is variable. Whether this happens or not seems to depend on the strength of the perioral musculature; strong musculature prevents protrusion (and makes retention more challenging), weaker muscles allow more protrusion.

In addition, apparent lip fullness in the early adolescent will reduce towards the end of the teens as nose and lip growth occur.

If a treatment goal is to reduce lip fullness, then extractions can be carried out at the start of treatment. For nonextraction treatment, it should not be assumed that an increase in lip protrusion will necessarily occur as the effects are variable. Assess the tonicity of the lips and if in doubt, wait until the end of the alignment phase before making a final decision remembering to factor in the effects of growth and maturation.

Extractions and stability Although one of our ‘mental models’ is that the extraction of teeth in orthodontics aids or guarantees stability, that is not the case as was demonstrated by the Seattle studies. The teeth do sit in a position of balance between the lips, cheeks and tongue at any moment in time, but those forces almost certainly change over time resulting in a marginally different neutral zone with associated tooth movement; there are of course other factors that contribute to post-treatment tooth movement.

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No orthodontist gives any post-treatment guarantee of stability and the best advice on how to maintain posttreatment alignment is low level maintenance through prolonged retainer wear. The less compliance this required on the part of the patient, the more likely it is to happen. Fortunately, the ability of retainers to maintain tooth alignment has increased significantly over the past two decades and the use of fixed retainers and nighttime wear of vacuum formed retainers is a much more reliable form of retention than Hawley retainers.

Extractions for pathological reasons This is a justified reason for extraction provided the pathology is severe enough and the sequelae of the extractions are less than the consequences of alternative methods of managing the pathology. It may include:

• • • • • • •

caries root resorption fracture, trauma and ankylosis periodontal disease ectopic teeth impaction other oral pathology such as cysts and tumours

The effects of extractions Extractions result or may result in:

• • • • • •

loss of tooth substance shortening of the arch length narrowing of the arch width a decrease in inclination of the anterior and posterior teeth increase in overbite lip retraction

Non-extraction treatment results in or may result in:

• • • • • •

retention of tooth substance maintenance of arch length maintenance or widening of arch width increase in inclination of anterior and posterior teeth decrease in overbite maintenance or increase in lip fullness

Outcome PAR percentage reduction Anterior ratio Overall ratio

Incisor extraction Mean sd 80.3a 18.0 81.7 a 4.5 94.2 a 2.9

Premolar extractions Mean sd 87.7 ab 10.2 79.3 a 2.3 92.2 b 2.2

Non extraction Mean sd 91.2 a 9.2 76.9 b 2.3 91.2 b 2.0

Table 5.2: The PAR percentage reduction for each group and Bolton ratios. The superscripted letters indicate groups with the same letter are not significantly different at the 0.05 level of significance (from Ileri et al 2011)

Ileri et al (2011) compared treatment outcome of class 1 cases treated without extractions, with four premolar extractions and a single incisor extraction. This was a retrospective study involving 60 patients with 20 patients in each group and all patients were treated with the Edgewise appliance. The PAR index was used to calculate outcome and the Bolton discrepancy was also calculated from the T1 study models. These results are shown in

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Table 5.2. The authors concluded that orthodontic treatment without extraction has a better treatment outcome than the four-first premolar extraction and single lower incisor extraction protocols in Class I cases with moderate to severe mandibular anterior crowding.

The patient perspective

Patients do not like having extractions and it is often the part of orthodontic treatment that most concerns them.

The loss of what is often four perfectly sound and healthy teeth needs careful consideration in an age where most specialties have abandoned the removal of healthy body parts! As life expectancy increases (10 million Britons living are now expected to reach 100 years of age), people may, in later life, be glad of the teeth an orthodontist removed in their teenage years.

References Ileri Z, Basciftci FA, Malkoc S, and Ramoglu SI (2011) Comparison of the outcomes of the lower incisor extraction, premolar extraction and non-extraction treatments European Journal of Orthodontics first published online July 10, 2011 doi:10.1093/ejo/cjr064 McCaul LK, Jenkins WMM and Kay EJ (2001) The reasons for extraction of permanent teeth in Scotland: a 15-year follow-up study British Dental Journal 190: 658-662 Murray H, Locker D and Kay EJ (1996) Patterns of and reasons for tooth extractions in general dental practice in Ontario, Canada Community Dentistry and Oral Epidemiology 23: 196-200 Reich E and Hiller KA (1993) Reasons for tooth extractions in the western states of Germany Community Dentistry and Oral Epidemiology 21: 379-383 The Tweed Years The Charles H Tweed International Foundation for Research and Education Available from http://www.tweedortho.com/about/tweedyears.asp Accessed 19 January 2011

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BRACKET PLACEMENT, BONDING AND DEBONDING TECHNIQUES EXCELLENCE IN ORTHODONTICS 2012

Chapter

6

Bracket placement, bonding and debonding techniques David Birnie

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Bracket placement Theory of bracket siting and slot siting

Angulation landmarks The five traditionally used landmarks are the facial axis of the crown, the long axis of the tooth, the incisal edges, marginal ridges and contact points. Andrews feels that many of these landmarks are difficult to observe or are too far from the bracket slot to be used as effective bracket siting guidelines.

Inclination landmarks Inclination landmarks reported in the literature show bizarre variation. Tweed (1966) recommends that the brackets should be placed a specified distance from the incisal edge. Saltzmann suggests that the brackets should be placed in the middle third of the crown.

Holdaway (1952) suggests that the brackets be placed on the gingival third of the crown if there is an anterior open bite, in the middle third of the crown if the overbite is normal and in the occlusal third of the crown if there is an increased overbite. Jarabak uses crown form as a predictor as to where to place brackets: in ovoid crowns the brackets should be placed in the middle third of the crown, in tapering crown forms 1-2 mm from the incisal edge and in square crowns as close to the incisal edge as possible. According to Andrews, slot inclination can vary by up to 45 degrees according to a bracket's site.

Using the Straight-Wire Appliance, accurate bracket siting is all that is required from the clinician. Once the bracket is sited in its correct location, Andrews claims that the slot is automatically correctly positioned.

Characteristics of an ideal bracket site The ideal bracket site is such that:

• • •

a bracket located there will not interfere with the gingivae or opposing teeth during occlusion the angulation and inclination of the crown at the site will have a consistent angular relationship to each tooth's occlusal surface and occlusal plane at all times the middle of each bracket site must share the same plane or surface when teeth are optimally positioned.

The bracket siting method recommended by Andrews is therefore keyed to the occlusal plane, the facial axis of the clinical crown and the facial axis point.

Slot siting The faciolingual position of the slot is determined by the crown's prominence plane. This is the sum of the molar prominence (1 mm) and the bracket stem prominence and is the same for all crowns in one arch. The slot target point is the midpoint of the slot site for each tooth type. It is located at the junction of the crown's prominence plane and the facial extensions of the crown's midsagittal and midtransverse planes.

Fowler (1990) looked at variations in ideal bracket location and concluded that the variability was greatest for FACC angulation, then FA point height and finally for FA point mesiodistal location but that these variations had few clinical implications.

Slot Siting Features

• • • • •

midtransverse plane of bracket slot, bracket stem and crown are coincident bracket base inclination occlusogingival base contour midsagittal plane of bracket slot, bracket stem and crown are coincident plane of bracket base at 90 degrees or 100 degrees (maxillary molars only)

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• • •

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mesiodistal base contour parallel vertical bracket components equal stem prominence Slot Siting Features For Translation Brackets

• • •

counterrotation countermesiodistal tip counterbuccolingual tip (maxillary molars only)

The FACC and the FA point The FACC (facial axis of the clinical crown) is for all teeth except for molars, the most prominent portion of the central lobe on each crown's facial surface. On molars, the FACC is represented by the buccal groove that separates the two mesial buccal cusps.

The FA (facial axis) point is the midpoint of the FACC. In his textbook, Andrews has used the terms FACC and FA point to denote the facial axis of the clinical crown and the facial axis point. These replace the older nomenclature LACC (long axis of the clinical crown) and LA point (long axis point).

Andrews designed the Straight-Wire Appliance such that, in order to express the treatment built into the bracket correctly, the base point of each bracket should be positioned over the FA point of the corresponding tooth with the bracket aligned parallel to the FACC. Advantages The advantage of this method of positioning brackets is that it is simple, relatively accurate and requires no special measuring device. It does result in the brackets being positioned slightly further gingivally than normal and this helps to move the point of force application closer to the centre of resistance of the tooth.

Pitfalls The disadvantage is that Andrew's method of bracket positioning does not take into account the fact that the clinical crown is of variable length, particularly in adolescence and nor does it take account of abnormal crown morphology such as obtuse incisal edge/FACC angles. In addition, it takes no account of biological variability. For example, discrepancies often exist between the marginal ridges of premolars and molars; these are not necessarily corrected by repositioning either the molar or the premolar tube or bracket as, due to the curvature of the buccal surfaces, repositioning the tube or bracket may dramatically affect torque. The only real solution here is to have vertical steps in the archwire to adjust the relative tube or bracket positions to produce level marginal ridges and with the teeth at the correct torque.

Bracket placement studies Fowler (1990) studied the variability both within and between clinicians in placing upper incisor and canine brackets. The variability was greatest for FACC angulation, FA point height and FA point mesiodistal location.

Training and experience reduced variability and Fowler concluded that the clinical implications were small.

Balut et al (1992) found similar findings with mean vertical variability of 0.34 mm and angular variability of 5.54 degrees. The teeth with greatest angular variation were the upper and lower canines and the upper anterior teeth. The teeth with the greatest vertical variation were the upper second premolars.

Taylor and Cook (1992) also showed that angulation was the most variable factor but also that inclination error frequently exceeded the 2° limit. This may be influenced by the variability in angulation.

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Armstrong et al (2007) compared bracket placement methods using the centre of the clinical crown and measurement from the incisal edge and concluded that measurement from the incisal edge was marginally better on incisors but less good on premolars; however there was little difference between the two techniques.

However, the authors also concluded that bracket placement errors occurred regardless of which technique was used and that therefore archwire bends or bracket repositioning was necessary to achieve acceptable treatment results. Whichever method is used, Suàrez and Vilar (2009) have shown the marginal ridge alignment can deteriorate during treatment due to variation in the buccal curvature of the teeth; this effect is particularly evident in the lower molar and lower premolar region.

Theoretical bracket placement charts McLaughlin and Bennett (1995) have suggested the use of theoretical bracket placement charts. McLaughlin and Bennett determined ideal bracket placement positions based on the midpoint of the clinical crown using data on:

• • • •

anatomical crown heights clinical crown heights American Boards or Angle Society cases debonded cases that had settled into a good six keys occlusion

They found minor deviations of the centres of the clinical crowns on the:

• • • •

upper premolars the upper second molars lower canines lower first molars

From this data, a theoretical bracket placement chart was devised from which the user selects the row of bracket heights which most closely corresponds to the half clinical crown height of the dentition to be bonded. This is an interesting method that deserves further consideration and evaluation; it is however too time consuming for everyday clinical use.

Recommended method of bracket placement Bracket positioning remains as much an art as a science - perhaps more so. Bracket positioning is usually based on Andrew's method using the FA Point and the FACC. Upper incisors should be bonded so that the incisal edges of the lateral and central incisors are at the same level; the lateral incisors may be fractionally higher (up to 0.5 mm) but never longer. Upper and lower canine tips should be slightly longer than the adjacent teeth to facilitate canine guidance. In general aim to put the bracket in the centre of the clinical crown, but err on the side of placing it more gingivally to keep the bracket:

• •

closer to the centre of resistance of the tooth away from upper arch interferences (in the lower arch)

The following method is recommended: For incisors and canines:

• •

check that clinical crown heights approximate to anatomical crown heights check for abnormal incisal edge/FACC angles

For premolars and molars: • check location of FA point, cusp height and marginal ridge height; aim to position bracket so as to get marginal ridges level

millimetres

BRACKET PLACEMENT, BONDING AND DEBONDING TECHNIQUES EXCELLENCE IN ORTHODONTICS 2012

6 5

millimetres

4 3

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Then for all teeth: • visualise FACC • place bracket so that tiewings straddle FACC (or so that slot is parallel to incisal edge if preferred) • position base point on FA Point (or specified distance from incisal edge or cusp tip) • seat bracket o check placement • from facial surface • from occlusal surface with mirror • with contralateral side • relative to incisal edge An excellent description of bracket positioning is given by Swain (1986).

Approximate measurements used by Swain (1986), Wick Alexander (1986) and McLaughlin and Bennett (1995) from 1 the slot point to the incisal edge are given in Figure 6.1.

Careful attention should be paid to looking at the 0 L1 L2 L3 L4 L5 L6 L7 morphology of each tooth and minor variations made in Swain Alexander Bennett and McLaughlin the position of each bracket to ensure that optimal tooth positioning is obtained. In the case of incisor teeth with Figure 6.1: Bracket placement in the upper and lower arches fractured edges, it is better to try and establish a satisfactory bracket height from the contralateral tooth and then measure down from the gingival margin for the damaged tooth.

2

A more modern take on bracket positioning is given by Pitts (2009). Pitts places brackets more gingivally than normal and using the mesiodistal contact points of the teeth as a reference line (the M-D contact line) and this is illustrated and described in Figure 6.2. Always check bracket position form the occlusal and if right handed, Upper incisors Upper canine Upper premolars

Upper molars

Lower incisors

Lower canines

Figure 6.2: Pitts recommends placing brackets more gingivally using the tooth contact points as a reference line (the M-D contact line). The line of the brackets should create a wedge opening moving anteriorly

Lower premolars

Lower molars

Occlusogingival

Progressively more gingival keying off canine Edge of occlusal tiewings on M-D contact line Edge of occlusal tiewings on M-D contact line

Occlusal edge of pad on M-D contact line but second molar 1.5 mm more occlusal Open bite: 5 mm from incisal edge Deep bite: 3.5 mm from incisal edge Edge of occlusal tiewings on M-D contact line Edge of occlusal tiewings 0.5 mm gingival to on M-D contact line Edge of occlusal tiewings 0.5 mm gingival to on M-D contact line

Mesiodistal

On FACC at height of contour 0.5 mm mesial to FACC at height of contour On FACC at height of contour. First premolar usually too distal; second premolar too mesial so check from occlusal Centre buccal tube pad over buccal groove of tooth On FACC at height of contour On FACC at height of contour On FACC at height of contour Centre buccal tube pad over buccal groove of tooth

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consider sitting on the left of patient to bond left-hand quadrants.

Further tips and refinements • on lower canines, it is worth positioning the bracket slightly mesially to ensure that the mesial edge of the canine does not tuck behind the distal edge of the lateral incisor.

• it is often difficult to get marginal ridges level; one tip is to align an imaginary line on the buccal surface of the teeth, which joins the marginal ridges, and align the occlusal edge of the bracket with this line. Focus primarily on trying to place buccal segment bonds so as to get marginal ridges level • a common error is to bond premolars too occlusally resulting in lateral open bites at finishing • to improve accuracy of angulation, bond with a current DPT radiograph easily available for viewing • bond upper second molars fractionally more occlusally than is ideal to keep these teeth just out of occlusion during treatment and prevent interferences. They will settle into place after debond • the bracket positioning chart shown on page 87 can be used either at the start of treatment to select torques and make notations about individual bracket positions or can be used in the last few months of treatment to identify tooth movement required during the finishing phase.

Variations in use of brackets

Vertical position of brackets The vertical positioning of brackets may be adjusted to facilitate treatment. Thus in deep bite cases the brackets may be placed slightly occlusally and in open bite cases slightly gingivally on the incisors. Incisors have relatively flat labial surfaces and so adjustments of vertical position have little if any effect on torque. It should be remembered that these adjustments alter the distance between the centre of effort and the centre of resistance of the tooth which will alter the tooth mechanics.

Vertical adjustment on teeth with curved buccal surfaces results in alteration of torque depending on how curved the surface is and the extent of the vertical adjustment.

Over angulating brackets Where teeth have to be translated a significant distance (such as in pseudotransposition cases) there is an increased tendency to tip and so the brackets should be angulated to prevent this; this often requires a significant overangulation of the bracket. A similar situation occurs where implants are to be placed post orthodontic treatment and the tooth roots must be parallel to one another to leave room for the implant.

Inverting brackets Inverting a bracket changes its torque and rotation but not it’s in/out or tip. The brackets commonly inverted are lateral incisors and canines. In general, inverting a bracket on its own rarely produces enough torque to correct the problem one is trying to deal with and additional torque needs to be bent into the archwire to optimise the final position of the tooth; that being the case, one might question if it is worth doing at all.

It is perhaps less advisable to use this technique with self-ligating brackets which are not symmetrical along the slot axis unless one is happy to cope with an inverted slide or clip.

Inverting Roth prescription lateral incisor brackets changes their torque from +8° to -8° which is helpful when moving a palatally placed lateral incisor into the line of the arch. Standard prescription brackets change from +3° to -3° which is less useful.

If a decision is made to close an upper lateral incisor space then the upper canine brackets may be inverted to produce palatal rather than buccal root torque. This is more relevant to the standard prescription which has -7° of inclination in the maxillary canine in which case inverting produces a change in torque of 14° whereas the Roth prescription has only -2° producing a change in inclination of only 4° when inverted. In these cases the use of an inverted standard prescription canine bracket may harmonise better with the central incisor root position than a Roth prescription bracket.

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Most class 3 patients demonstrate considerable proclination of the upper labial segment at the end of treatment.

Although we have not tried it often, the use of labial root torque (achievable by inverting the upper incisor brackets) with advancement of the upper labial segment is worth consideration. The case published by Catania et al (1990) demonstrates significant maxillary development with only mild to moderate proclination of the incisors using this technique.

Band or bond?

We routinely bond incisors, canines, premolars and molars; banding molars is now a very, very rare event.

The reasons against bonding molars are as follows:

• • • • •

the inferior quality of etch pattern obtained on molars the difficulty in obtaining and maintaining adequate moisture control during bonding inadequate adaptation of the attachment base thus producing an uneven adhesive layer the vertical bulk of molar tube designs with tiewings the larger masticatory forces found on the posterior regions of the mouth

Millett et al (1999) has published an excellent retrospective review of first molar bond failure. The median survival time was 699 days and the overall failure rate was 21%. The tubes were placed with light-cured Transbond. Age at the start of treatment (the older the better) and operator were significant factors in determining bond failure rate, but patient’s gender or the presenting malocclusion was not.

A further study by Millett et al (2001) compared the shear bond strength of molar tubes bonded with either a compomer (Ultra Band-Lok), a resin modified glass ionomer cement (3M Multi-Cure or Fuji Ortho LC and a light cured resin adhesive (3M Unitek Transbond). Interestingly, the mean shear bond strength of tubes bonded with 3M Transbond was significantly less than those bonded with 3M Multi-Cure or Fuji Ortho LC. Ultra Band-Lok gave significantly lower shear bond strengths than Fuji Ortho LC. This suggests that compomers or resin modified glass ionomer cements are viable alternatives to the use of a light cured resin adhesive for bonding molar tubes.

We now bond all teeth including molars routinely unless bands are specifically required for the attachment of a palatal or lingual intraoral auxiliary. The use of low profile bonding tubes, improved moisture control, discluders such as MiniMolds, bond enhancers and improved adhesives make this an achievable goal.

Moisture control Moisture control remains critical in the bonding process.

It is still preferable to bond in a clean dry and uncontaminated field. Steps to achieve this include:

Figure 6.3: The Kerr Optiview retractor gives excellent retraction in all areas of the mouth

• consider the use of an atropine sulphate tablet as suggested for indirect bonding. Although not everybody will wish to do this, it does provide a very dry field which almost eliminates the need for a saliva ejector, cotton wool rolls or Dri-Angles. The patient is given a 600 microgram tablet of atropine sulphate to take one hour before bonding as a TTO drug (to take out) to dry up salivary secretions.

(Contra-indications are: pregnancy, glaucoma, and severe asthma. Wearers of contact lenses should be asked to remove them and not replace them until the following day). Children under the age of 12 years are not given atropine.

BRACKET PLACEMENT, BONDING AND DEBONDING TECHNIQUES EXCELLENCE IN ORTHODONTICS 2012

Figure 6.4:

• • •

89

The sequence of placing and curing brackets (modified from Pitts 2009)

the Kerr Optiview (see Figure 6.3) retractor is an excellent retractor which is entirely perioral and therefore is unobtrusive while giving excellent overall retraction when bonding upper molars, ask the patient to move their mandible to the same side to carry the soft tissues of the cheek away from the bonding site isolate and bond a sextant at a time; use a high speed light and cure first and second molars once placed; the remainder of the sextant can then be cured as a unit

Bonding technique Our bonding technique has changed over time and with improved retraction, it is now possible to bond multiple teeth and cure them as a single unit. Pitts (2009) again has useful advice on bonding technique.

• •

• •

consider reshaping teeth as necessary prior to bonding o eg: tips of upper canines bond the lower arch first o bond second molar to canine on the lower left o then second molar to canine on the lower right o followed by the lower incisors repeat sequence for maxillary arch consider using two nurses to help you bond; one to butter the bracket pads and the other to cure the brackets and aspirate is necessary o using this technique it is possible to bond second molar to second molar in both arches in about 20 minutes

Curing lights The curing light market is developing rapidly. The following types of light are available:

• • •

conventional curing lights high performance halogen curing lights (Optilux 501) LEDs

A good summary of the various different types of light is given by Mayes (2000).

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Light guides

Light guides collimate visible light to increase its intensity and thus reduce the curing time and increase the depth of polymerisation (cure). Bishara et al (2001) investigated the effectiveness of light guides on the shear bond strength of orthodontic brackets and found that when using a reduced cure time, the bond strength of the brackets was significantly reduced.

However, Evans et al (2002) compared the effects of the Reliance Power Slot light guide and the Ormco Turbo-Tip light guide with conventional curing lights. They found that the light guides significantly reduced curing times by 10 seconds per bracket while maintaining the same bond strength. Light guides can be retro-fitted to existing curing lights.

Conventional curing lights Conventional curing lights use halogen bulbs filtered to produce blue light. They cure adhesive under metal brackets in 20-30 seconds.

High performance halogen curing lights The Demetron Optilux 501 is a high performance curing light with an 80-watt tungsten/quartz/halogen bulb whose performance does not degrade with time. This has an 8 mm light guide which emits a full spectrum light filtered as blue light with a range of 400 to 505 nanometres. It cures under metal brackets in 8 seconds and under ceramic brackets in 5 seconds.

The light has Boost mode which increases the light output to 1,000 mWatt/cm2 in 10 second cycles with a five second beep. This allows adhesive under metal brackets to be cured with 5 second exposure in each interdental space. The light is intense and at the tip of the guide, some discomfort on skin or mucosa may occasionally be felt.

This light was the cutting edge of modern light technology and offered excellent performance/cost ratio. The reduced time required to cure the adhesive significantly increases the attractiveness of a light cure material compared to a dual cure. It has now been superseded by LED lights.

LED lights

Quartz tungsten halogen lights have disadvantages:

• • •

halogen bulbs have a life of about 50 hours the bulb, reflector and filter degrade over time halogen bulbs generate significant heat

Light emitting diodes (LEDs) have lifetimes of 10,000 hours and undergo little light degradation during their life.

In addition, no filters are required to produce blue light, LEDs are robust and require little power. Low power LEDs based on silicon carbide technology have been available for many years but their power output was only 7μW per LED which was insufficient to cure dental resins. The introduction of gallium-nitride technology in 1995 saw the development of 3mW LEDs which represents a 400 times increase in power over the former technology. The spectral output of these blue LEDs falls within the absorption spectrum of the camphorquinone photoinitiator (400nm to 500 nm) of dental composites (Mills et al 1999).

Parr and Rueggeberg (2002) (see Figure 6.1) have compared the spectral emission profiles of LEDs and quartz tungsten halogen lights normalised for the absorption requirements of Light Unit Peak λ (nm) Power (mW) Normalised Effectiveness camphorquinone. They concluded power (mW) (%) 465 120 102 85 Apollo that while all LED lights produced 465 68 85 85 CoolBlu lower power than quartz tungsten 469 52 42 82 Lux-O-Max halogen lights, 80% of the light 478 409 277 68 Optilux 501 produced by the LED lights met the Table 6.1: Comparison of quartz halogen curing light with three LED lights demonstrating the needs of the camphorquinone relative effectiveness of LED lights (from Parr and Rueggeberg 2002)

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photoinitiator whereas less than 70% of the light from the quartz halogen light did.

Fay et al (2002) looked at several of the mechanical properties of composite cured with LED and quartz halogen lights and concluded that there was no statistical difference in the mechanical properties of composites cured with either light. A similar conclusion was reached by Bishara et al (2003) who compared the Ultradent UltraLume 2 with the 3M Unitek OrthoLux Visible Light Curing Unit. Mills et al (1999) concluded that a significantly greater depth of cure was achieved using quartz halogen lights. Niepraschk et al (2007) investigated the depth of cure in vitro with halogen, plasma arc and LED lights for periods of 10 and 20 seconds. They found that the greatest depth of cure was given by the halogen and the LED lights used for 20 seconds. There was no difference in the depth of cure between the plasma arc light and the LED light when used for 10 seconds.

Bouschlicher et al (2002) looked at intrapulpal temperature rise during photoinitiation with LED, quartz tungsten halogen and plasma arc lights. It was suggested that the narrow spectral emission of blue LED light curing units would generate less heat than more conventional lights. They found that the LED, plasma arc and newer quartz tungsten halogen lights (such as the Optilux 501) produced less intrapulpal temperature rise than the older conventional quartz tungsten halogen lights.

Dunn and Taloumis (2002) compared the shear bond strength of orthodontic brackets bonded to teeth with conventional halogen-based light-curing units and commercially available LED curing units. They studied two LED lights (Lumalite LumaCure and Centrix VersaLux) and two halogen lights (Demetron Optilux 501 and Demetron ProLite). The study involved bonding orthodontic brackets with Transbond XT to extracted third molar teeth and then measuring the sear bond strength of the brackets using an Instron testing machine. No significant difference in bond strength was found between the four lights; the range of mean bond strengths were from 8.8 to 8.5 MPa and the range of standard deviations from 1.0 to 1.2 MPa and so neither the means nor the standard variations changed much between the groups. The curing time used for each light was however 40 seconds.

Cacciafesta et al (2002) compared shear bond strengths produced with a high power halogen light (1,200 mW/cm2) with the GC E-light (1,500 mW/cm2). Using bovine teeth and Transbond XT adhesive, they found that the shear bond strength was no different between the LED and halogen light groups using a 10 second curing time.

Mavropoulos et al (2005) have shown that the shear bond strengths achievable with the newer intensive LED lights with a 10 second exposure is almost comparable with that achieved with high intensity halogen lights with an exposure of 40 seconds. Thind et al (2006) compared the bond strength generated by high power halogen lights, a plasma arc light and an LED used for their recommended periods and found no difference in bond strengths between the three lights.

We routinely use the Ormco Demi (successor to the CoolBeam) (Figure 6.5) which has a feature called Periodic Level Shifting (PLS) which intermittently increases the light output from an impressive base of 1100 mW/cm2 to a peak of 1330 mW/cm2 to reduce curing time without raising intrapulpal temperature. Curing times as low as five seconds are possible with the correct adhesive. This light is small, lightweight and has excellent battery life.

In a randomised controlled trial, Krishnaswamy and Sunitha (2007) demonstrated equivalent bond failure rates over a 15 month period in a contralateral quadrant study with halogen and LED lights. The overall bond failure rate was 7.0% for the LED light and 8.1% for the halogen light. Pandis et al (2007) carried out a study (again over 15 months) which compared a plasma arc light with LED lights and found a 2.5 times greater bond failure rate with the LED light (2.8% for the plasma arc light compared with 6.7% for the LED light). Mandibular teeth showed an almost 150% higher failure incidence compared with maxillary teeth. No effect from the arch side (right vs left) and location (anterior vs posterior) was identified in this study. This contrasts with Koupis et al (2008) who Figure 6.5: Ormco Demi light with charger and metal compared light curing for 10 seconds with an LED light hydride battery with 20 seconds for a conventional halogen light on 30

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patients with 600 brackets. The overall failure rate for the halogen light was 3.3% and for the LED light 5.0% and these were not significantly different. Significantly more failures were found in boys compared with girls, in the mandibular dental arch compared with the maxillary arch, and in posterior segments compared with anterior segments although no significant difference was found between the right and left segments.

Mirabella et al (2008) found no difference in bond failure rates using 3M APC brackets cured with a conventional halogen light and an LED light; fewer bond failures were experienced in the maxillary (1.7%) compared with the mandibular arch (4.4%). In the mandibular arch, more bond failures occurred in the premolar region (7.5%) than the anterior region (2.2%).

LED curing light technology has made enormous strides in just a few years and would seem to be currently the curing light technology of choice.

Curing technique Wendl and Droschl (2004) investigated the effect of curing technique on the shear bond strength of brackets using a light-cured resin (Enlight LV), a RMGIC (Fuji Ortho LC) and a chemically cured composite (Concise) as a control. Four different types of light were used (halogen, high performance halogen, plasma arc and LED) and two different types of curing (two sided and four sided). All lights produced adequate bond strengths of 5 to 8 MPa. The bond strength of Enlight LV (but not Fuji Ortho LC) depended on the duration of the light exposure with the highest bond strength being achieved with 40 second cure and the halogen light. The bond strengths of the light cured adhesive and the resin modified glass ionomer adhesive were similar although less than Concise. Four sided curing was better than two sided curing and all adhesives had higher bond strengths after 24 hours than after one hour. For Enlight this was 19%, for Fuji, 6.6% and for Concise 16%; the largest increase in bond strength occurred for the light cured composite suggesting that the curing process continues once light exposure has ceased (dark cure).

Indirect bonding Indirect bonding was originally described as an experimental technique by Silverman et al (1972). The method involved applying mixed cement to each bracket in a transfer tray, a process requiring a slow setting adhesive and subsequently necessitating flash removal of set adhesive.

Why indirect bonding?

The advantages of indirect bonding are:

• • • • • •

more accurate bracket and tube placement better use of the orthodontist’s time no need for separators; avoids band fitting on posterior teeth makes it easier to bond posterior teeth improved bond strength due to better moisture control and shorter bonding period improved patient comfort and hygiene

The disadvantages of indirect bonding are:

• • • •

it is technique sensitive an additional set of impressions may be required bonded posterior attachments more vulnerable than bands may require the use of an anti-sialagogue

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The development of indirect bonding

The following key stages can be identified in the development of indirect bonding:

•

•

•

•

a significant advance was the Thomas technique, which used set composite on the bracket bases (custom bases) which were then placed on the teeth using only a primer as the final stage adhesive (Thomas 1979). This avoided the need to place composite on the bracket bases immediately before tray insertion the introduction of a two tray system (Nakaji and Sheffield 1981), in Hickham J H, 1993). This meant that the tray system could be sufficiently rigid to seat the brackets but sufficiently flexible to allow easy removal of the transfer tray once the brackets had been placed on the teeth and the adhesive had set. Using a Bioplast/Biocryl combination seems to work well although Moskowitz et al (1996) have described using a vinyl polysiloxane (Caulk Reprosil) impression material as the flexible undertray. the introduction of a no mix adhesive for the custom base that gives a consistent and complete cure. This can be done using either a thermally cured adhesive, such as Reliance Thermacure, (Sinha et al 1995) or a light-cured adhesive, such as 3M-Unitek APC brackets, (Sondhi 1999). These techniques make it much easier for the orthodontists to position the brackets on the models without the need for repeated mixing of adhesive. Conventional no mix adhesives do not work well as an incomplete cure is obtained because the catalyst is only applied to the bracket base. the introduction of custom indirect bonding adhesives for the final positioning of brackets on the teeth, such as Reliance Custom IQ (Indirect Quickset) and 3M-Unitek Sondhi Rapid-Set. These adhesives should be chemically cured and have a fairly short working time. Light cure adhesives would seem to have little place at this stage of the indirect bonding process as unlimited working time is not required.

Indirect bonding versus direct bonding

Accuracy of bracket placement Several studies have looked at the accuracy of bracket placement comparing the two techniques - Aguirre et al (1982) and Koo et al (1999). It is perhaps surprising that there have not been more studies. It would seem that indirect bonding has a slight advantage but this is not as marked as perhaps would have been expected; Aguirre found that vertical bracket position was more accurate with the indirect technique on upper canines and more accurate on lower second premolars with the direct technique. Angular positioning was very variable and more accurate on upper and lower canines with the indirect technique. Koo found that indirect bonding was better in bracket height but that there was no difference in either angulation or mesiodistal positioning between the two techniques.

Hodge et al (2004) concluded that there was no mean difference in the accuracy of bracket placement with either a direct or indirect technique but the variability of placement was less with an indirect system. Very generally, this study found that with both techniques, vertical errors were greater than mesiodistal errors which were in turn greater than angulation errors.

Shpack et al (2007) compared the accuracy of lingual and labial bonding using both direct and indirect technologies particularly looking at rotational and torque error. The authors concluded that the indirect bonding technique was significantly twice as accurate as the direct technique for all teeth in both labial and lingual techniques. This was valid for both torque error and rotational error. For both torque error and rotational error, no statistical difference was found between the labial and lingual systems for direct and indirect techniques.

There was systematic distal off-center rotational error in the mandible is most likely caused by the Ponzo visualization illusion (qv) which caused mandibular teeth to be mesially rotated.

Time utilisation Aguirre et al (1982) looked at bonding second premolar to second premolar in the upper and lower dental arches.

They determined that the average time for direct bonding was 42 minutes and for indirect bonding 54 minutes for both laboratory and clinical phases. The clinical phase of indirect bonding took 24 minutes. Kalange (1999)

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studied bonding second molar to second molar in the upper and lower arches and found that the clinical phase of indirect bonding took 25 minutes and the laboratory phase 60 minutes. Hodge et al (2001) have published a persuasive article on the efficiency of indirect bonding.

Bond strength In the early days of indirect bonding, prior to the introduction of the Thomas technique, Zachrisson and Brobakken (1978) showed that direct bonding had a lower failure rate than indirect bonding. Using the Thomas technique, however, Hocevar and Vincent (1988) showed that there was no difference in in vitro bond strength between the indirect and direct bonding techniques. Aguirre et al (1982) had similar findings with clinical failure rates of 4.5% for the indirect technique and 5.3% for the direct technique. Thiyagarajah et al (2006) showed that there were no differences in bond failure rate using direct and indirect technique in a large sample followed over one year. The bond failure rate was a commendably low 2.5% although the study did not include bonded molar tubes.

The Thomas technique introduced an interface not previously encountered in orthodontics - that of the aged composite interface. Does the custom composite base, aged between set up and indirect bonding, adhere as well as a conventional immediate mix adhesive? Shiau et al (1993) showed that an aged composite interface up to seven days old was unlikely to affect bond strengths.

Specialty Appliances have a useful website with lots of practical information about indirect bonding.

Debonding The increase in effectiveness of bonding procedures and the advances in bonding technology now make it possible to generate enamel fractures when debonding metal brackets; this has, of course, always been possible in teeth with severely compromised crowns as a result of extensive restoration. Manufacturers can now make adhesion enhancers and adhesives that are far stronger than is necessary for orthodontic use. And so the quest is to maximise bond strengths without endangering the integrity of the enamel surface.

In addition, self-ligating brackets have much more rigid bracket bodies which are harder to deform on debonding.

The conventional method of 'snapping off' directly bonded brackets with a small, sharp rotation of the wrist works well on siamese brackets but less well on more rigid brackets.

The best way to removed self-ligating brackets is to squeeze firmly but gently on one pair of tiewings only as shown in Figure 6.6 to distort the bracket; the bracket will (noiselessly!) separate from the enamel surface. It is not necessary to twist or rotate the bracket â&#x20AC;&#x201C; it just floats off the tooth! Situations where particular care needs to be taken include teeth with large restorations including molars with moderate sized buccal amalgam restorations. Some brackets have specific debonding pliers and in these cases, these are generally the plier of choice for that bracket.

Damon Clear brackets have a specific debonding plier and protocol.

A comprehensive paper on enamel surfaces after orthodontic bracket debonding and Campbell (1995) has published the optimum method of debonding. As a result of the findings of this paper the following technique is recommended:

Figure 6.6:

Debonding technique for self-ligating brackets

â&#x20AC;˘ use of fluted tungsten carbide bur to remove gross adhesive. Can use disclosing

BRACKET PLACEMENT, BONDING AND DEBONDING TECHNIQUES EXCELLENCE IN ORTHODONTICS 2012

• •

95

solution to improve visibility of adhesive. Do not touch the enamel surface with bur. use abrasive points or cups to remove residual adhesive final polish with prophylaxis paste or pumice slurry

Another paper by Hong and Lew (1995) compared:

• • • • •

band removing pliers slow speed tungsten carbide bur high speed ultrafine diamond bur high speed tungsten carbide bur high speed white stone finishing bur

High speed ultrafine diamond burs and white stone finishing burs were found to be unsuitable for removing composite adhesive. The high-speed burs were used with a water spray, which made it more difficult for the operator to distinguish between composite and enamel surface. The high-speed tungsten carbide bur produced the smoothest surface (Surface Roughness Index) but was fourth in the Composite Remnant Index (CRI).

A good review of debonding is given by Banks (2004).

Ireland et al (2005) carried out an interesting study which compared enamel loss at bonding, debonding and enamel clean-up using 37% ortho-phosphoric acid and Transbond and 10% polyacrylic acid and Fuji Ortho LC using four different debonding methods:

• • • •

debonding pliers ultrasonic scaler slow speed tungsten carbide bur high speed tungsten carbide bur

The authors found that using 37% ortho-phosphoric acid removed more enamel than 10% polyacrylic acid and that post debond, more Transbond than Fuji Ortho LC remained on the enamel surface. The least enamel was removed using a slow speed tungsten carbide bur (up to approximately 5 μm) with both materials and the most with an ultrasonic scaler or high speed tungsten carbide bur (up to approximately 30 μm). More enamel was lost using Transbond that Fuji Ortho LC for all debonding methods.

Figure 6.7: L*a*b* colour space

The CIE (Commission Internationale d’Eclairage)

Trakyal et al (2009) looked at colour changes with five different adhesive systems after debonding, finishing procedures (polishing with Stainbusters) and after photo-aging. The colour change was measured using the CIE L*a*b* colour space; this is a uniform colour space in the shape of a cube. The L* axis runs vertically from 0 to 100; the a* axis left to right with a* + values being red and a* - values green and the b* axis in and out with b* + being blue and b* - yellow.

The a* and b axes have no maximum or minimum values. The difference in colour values within the space is given by ΔE; note that this does not specify how the colour values differ (ie: it does not segment L*, a* and b* values). The CIE L*a*b* colour space is illustrated in Figure 6.7. This was an in vitro study and colourimetric measurements were made after bonding, photo-aging, debonding and adhesive

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removal with a high speed tungsten carbide bur, after polishing with a composite removing/polishing bur (Stainbuster) and after a second period of photo-aging. Colour change was estimated using Vita EasyShade. The authors concluded that no clinically detectable colour change of enamel took place as a result of photo-aging but that polishing with the Stainbuster but may improve reflectance by reducing surface irregularities.

Karamouzos et al (2010) studied in vivo colour change in natural teeth following fixed appliances when the teeth had been bonded with chemically cured and light cured adhesives. They measured the colur changes using a reflectance spectrophotometer and the colour changes were recorded using the CIE L*a*b* colour space. After active treatment, the mean L* value decreased by 2.01 ΔL* units, whereas the mean a* and b* values increased by 0.31 Δa* units and 1.80 Δb* units. So, the teeth became darker, redder and yellower. It was found that 12.98% of the bonded teeth had visible, clinically significant color changes, whereas the distribution of these teeth among the subjects showed that approximately 80% of the patients had at least one tooth with an unacceptable colour change. The possible reasons for the colour change were:

• • • • • •

the etching process roughens the tooth surface and affects reflectance remineralisation does not result in the same quality of enamel as originally present alteration of the enamel surface during debonding which is not restored during the polishing phase irreversible penetration of resin tags into the enamel surface the variations of blood flow in the dental pulp and the adjacent gingival tissue as a result of orthodontic forces from alteration of the resting salivary flow rates during orthodontic treatment that affect tooth hydration and thus tooth colour

References Aguirre MJ, King GJ, and Waldron, JM (1982) Assessment of bracket placement and bond strength when comparing direct bonding and indirect bonding techniques American Journal of Orthodontics and Dentofacial Orthopaedics 82: 269-276 Alexander RG (1986) The Alexander Discipline: Contemporary concepts and philosophies Glendora, Ormco Corporation Armstrong D, Schen G, Petocz P and Darendeliler MA (2007) A comparison of accuracy in bracket positioning between two techniques—localizing the centre of the clinical crown and measuring the distance from the incisal edge European Journal of Orthodontics 29: 430-436 Balut N, Klapper L, Sandrik J and Bowman D (1992) Variations in bracket placement in the preadjusted appliance American Journal of Orthodontics and Dentofacial Orthopaedics 102: 62-67 Banks PA (2004) Efficient debonding Orthodontics 1: 251-253 Bouschlicher MR, Whalen SR and Dawson DV (2002) Intrapulpal temperature increases with LED, QTH and Plasma arc photoinitiation The IADR/AADR/CADR 80th General Session (March 6-9, 2002) San Diego, California, Dental Materials VIII: Others – Nonmetallic http://iadr.confex.com/iadr/2002SanDiego/techprogram/abstract_13520.htm Accessed: 15 February 2012 Cacciafesta V, Süßenberger U, Jost-Brinkman P-G and Miethke R-R (1998) Shear bond strengths of ceramic brackets bonded with different light-cured glass-ionomer cements: an in vitro study European Journal of Orthodontics 20: 177-187 Cacciafesta V, Jost-Brinkman P-G, Süßenberger U and Miethke R-R (1998) Effects of saliva and water contamination on the enamel shear bond strength of a light-cured glass ionomer cement American Journal of Orthodontics and Dentofacial Orthopaedics 113: 402-407

BRACKET PLACEMENT, BONDING AND DEBONDING TECHNIQUES EXCELLENCE IN ORTHODONTICS 2012

Cacciafesta V, Sfondrini MF, Jost-Brinkmann PG and Boehme A (2002) LED Curing lights prove effective for orthodontic bonding Journal of Clinical Orthodontics 36: 461-465 Campbell PM (1995) Enamel surfaces after orthodontic bracket debonding Angle Orthodontist 65: 103-110 Catania JA, Cohen BD and Deeney MR (1990) The use of labial root torque and the tie-forward technique in the treatment of maxillary skeletal retrusion and severe arch length discrepancy American Journal of Orthodontics and Dentofacial Orthopaedics 98: 12-18 Dunn WJ and Taloumis LJ (2002) Polymerization of orthodontic resin cement with light-emitting diode curing units American Journal of Orthodontics and Dentofacial Orthopaedics 122: 236-241 Evans LJ, Peters C, Flickinger C, Taloumis L and Dunn W (2002) A comparison of shear bond strengths of orthodontic brackets using various light sources, light guides and cure times American Journal of Orthodontics and Dentofacial Orthopaedics 121; 510-515 Fay R-M, Lu H and Powers JM (2002) Mechanical properties of composite cured with LED and QTH curing lights The IADR/AADR/CADR 80th General Session (March 6-9, 2002) San Diego, California, Dental Materials VI: Polymer Materials – Mechanical Properties and Degradation Program http://iadr.confex.com/iadr/2002SanDiego/techprogram/abstract_10107.htm Accessed: 15 February 2012 Fowler PV (1990) Variation in the perception of ideal bracket location and its implication for the preadjusted appliance British Journal of Orthodontics 17: 306-310 Hickham JH (1993) Predictable indirect bonding Journal of Clinical Orthodontics 27: 215-217 Hocevar RA and Vincent HF (1988) Indirect versus direct bonding: bond strength and failure location American Journal of Orthodontics and Dentofacial Orthopaedics 94: 367-371 Hodge TM, Dhopatkar AA, Rock WP and Spary DJ (2001) The Burton approach to indirect bonding Journal of Orthodontics 28: 267-270 Hodge TM, Dhopatkar AA, Rock WP and Spary DJ (2004) A randomized clinical trial comparing the accuracy of direct versus indirect bracket placement Journal of Orthodontics 31: 132-137 Hong YH and Lew KKK (1995) Quantitative and qualitative assessment of enamel surface following five composite removal methods after bracket debonding European Journal of Orthodontics 17: 121-128 Ireland AJ, Hosein I and Sherrif M (2005) Enamel loss at bond-up, debond and clean-up following the use of a conventional light-cured composite and a resinmodified glass polyalkenoate cement European Journal of Orthodontics 27: 413–419 Kalange JT (1999) Ideal placement with APC brackets and indirect bonding Journal of Clinical Orthodontics 33; 516-526 Karamouzos A,Athanasiou AE, Papadopoulos MA and Kolokithas G (2010) Tooth-color assessment after orthodontic treatment: A prospective clinical trial American Journal of Orthodontics and Dentofacial Orthopaedics 138: 537.e1-537.e8 Koo BC, Chung C-H and Vanarsdall R (1999) Comparison of the accuracy of bracket placement between direct and indirect bonding techniques American Journal of Orthodontics and Dentofacial Orthopaedics 116: 346-351 Koupis NS, Eliades T and Athanasiou AE (2008) Clinical evaluation of bracket bonding using two different polymerization sources Angle Orthodontist 78: 922–925

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Krishnaswamy NR and Sunitha C (2007) Light-emitting diode vs halogen light curing of orthodontic brackets: A 15-month clinical study of bond failures American Journal of Orthodontics and Dentofacial Orthopaedics 132: 518-523 Mavropoulos A, Staudt CB, Kiliaridis S and Krejci I (2005) Light curing time reduction: in vitro evaluation of new intensive light-emitting diode curing units European Journal of Orthodontics 27: 408–412 Mayes JH (2000) Curing lights: an overview Clinical Impressions 9: 15-28 McLaughlin RP and Bennett JC (1995) Bracket placement with the preadjusted appliance Journal of Clinical Orthodontics 29: 302-311 Millett DT, Letters S, Roger E, Cummings A and Love J (2001) Bonded molar tubes – an in vitro evaluation Angle Orthodontist 71: 380-385 Mills RW, Jandt KD and Ashworth SH (1999) Dental composite depth of cure with halogen and blue light emitting diode technology British Dental Journal 186: 388-391 Mirabella D, Spena R, Scognamiglio G, Luca L, Gracco A and Siciliani G (2008) LED vs halogen light-curing of adhesive-precoated brackets Angle Orthodontist 78: 935–940 Moskowitz EM, Knight LD, Sheridan JJ, Esmay T and Tovilo K (1996) A new look at indirect bonding Journal of Clinical Orthodontics 30: 277-281 Nakaji NK and Sheffield (1981) Table Clinic, AAO Annual Session Niepraschk M, Rahiotis C, Bradley TG, Eliades T, Eliades G (2007) Effect of various curing lights on the degree of cure of orthodontic adhesives American Journal of Orthodontics and Dentofacial Orthopaedics 132: 382-384 Parr GA and Rueggeberg FA (2002) Spectral analysis of commercial LED dental curing lights The IADR/AADR/CADR 80th General Session (March 6-9, 2002) San Diego, California, Dental Materials VIII: Others – Nonmetallic http://iadr.confex.com/iadr/2002SanDiego/techprogram/abstract_19567.htm Accessed: 12 February 2011 Pandis N, Strigous S and Eliades T (2007) Long-term failure rate of brackets bonded with plasma and high-intensity light-emitting diode curing lights. A clinical assessment Angle Orthodontist 77: 707-710 Pitts TR (2009) Begin with the end in mind: bracket placement and early elastics protocols for smile arc protection Clinical Impressions 17: 2-11 Shiau J-Y, Rasmussen ST, Phelps AE, Enlow DH and Wolf GR (1993) Bond strength of aged composites found in brackets placed by an indirect technique Angle Orthodontist 63: 213-220 Shpack N, Geron S, Floris I, Davidovitch M, Brosh T, and Vardimon AD (2007) Bracket placement in lingual vs labial systems and direct vs indirect bonding Angle Orthodontist 77: 509–517 Silverman E, Cohen M, Gianelly AA and Dietz VS (1972) A universal direct bonding system for both metal and plastic brackets American Journal of Orthodontics 62: 236-244 Sinha PK, Nanda RS, and Ghosh J (1995) A thermal-cured, fluoride releasing indirect bonding system Journal of Clinical Orthodontics 29: 97-100 Sondhi A (1999) Efficient and effective indirect bonding American Journal of Orthodontics and Dentofacial Orthopaedics 115: 352-359

BRACKET PLACEMENT, BONDING AND DEBONDING TECHNIQUES EXCELLENCE IN ORTHODONTICS 2012

SuĂ rez C and Vilar T (2009) The effect of constant height bracket placement on marginal ridge levelling using digitized models European Journal of Orthodontics 32: 100-105 Swain BF (1986) Straight wire design strategies: five year evaluation of the Roth modification of the Andrews Straight-Wire Appliance In: Graber LW ed. Orthodontics State of the Art Essence of the Science: St Louis, The CV Mosby Company Taylor NG and Cook PA (1992) The reliability of positioning preadjusted brackets: an in vitro study British Journal of Orthodontics 19: 25-34 Thind BS, Stirrups DR and Lloyd CH (2006) A comparison of tungsten-quartz-halogen, plasma arc and light-emitting diode light sources for the polymerization of an orthodontic adhesive European Journal of Orthodontics 28: 78-82 Thiyagarajah S, Spary DJ and Rock WP (2006) A clinical comparison of bracket bond failures in association with direct and indirect bonding Journal of Orthodontics 33: 198-204 Thomas RG (1979) Indirect bonding: simplicity in action Journal of Clinical Orthodontics 13: 93-106 Trakyal G, Ă&#x2013;zdemir FI and Arun T (2009) Enamel colour changes at debonding and after finishing procedures using five different adhesives European Journal of Orthodontics 31: 397-401 Wendl B and Droschl H (2004) A comparative in vitro study of the strength of directly bonded brackets using different curing techniques European Journal of Orthodontics 26: 535-544 Zachrisson BU and Brobakken BO (1978) Clinical comparison of direct versus indirect bonding with different bracket types and adhesives American Journal of Orthodontics and Dentofacial Orthopaedics 74: 62-78

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ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Chapter

8

Archwires and biomechanics David Birnie

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Introduction A variety of archwires is now available to the orthodontist and it can be difficult to decide which archwire has the desired properties for a particular clinical situation.

Archwire properties point of arbitrary clinical loading

10

yield point

failure point

The properties of conventional archwires are shown in Figure 8.1 and the terms describing the wires behaviour familiar to most.

proportional limit

Resilience is indicated by the area under the curve to the left of the proportional limit and formability by the area under the curve between the yield and the failure points and is the capacity of a material to absorb energy while undergoing elastic deformation.

Stress

0

Range

0

Springback

8

Strain

Figure 8.1:

Properties of conventional archwires

The modulus of elasticity (E) is given by the slope of the graph.

Stiffness is proportional to E and springiness to its reciprocal (1/E). Range is measured from a point 0.1% along the x-axis to the yield point.

Typically, orthodontic archwire materials are required to have the following properties: strength

formable

resilience

toughness

weldable

aesthetics

good range

springiness

biocompatibility

low friction

springback

poor biohostability

As the cross-section of a wire is altered:

• • •

range is affected proportionally springiness changes as a fourth power function strength changes as a cubic function.

As the length of a wire supported at one end is altered:

• • •

range is affected as a square springiness as a cubic function strength changes proportionally

Archwire materials Archwires may be classified by:

• • •

material stainless steel, Elgiloy, titanium alloys, glass, polymers coated or non-coated ion implantation, spray coating, sleeving morphology round, rectangular, single, multistrand or braided

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Cobalt chromium Elgiloy

Stainless steel

Titanium alloys

Nickel copper chromium Copper NiTi

Nickel titanium

Martensitic stabilised

Austenitic active (pseudoelastic)

Martensitic active (thermoelastic)

pseudoelastic 27°C

Glass Optiflex

Titanium molybdenum TMA

141

UFRP Unidirectional fibre reinforced composites

Titanium Niobium TiNb/FA

thermoelastic 35°C and 40°C

Graded martensitic active

Figure 8.2:

•

Orthodontic archwires classified by material. Stainless steel and titanium alloys are the commonly used archwire types

composite o made of more than one morphology (e.g.: Wonder Wire which is round in the buccal segments and rectangular in the anterior segment) o made of one or more materials with a mechanical join or material having different properties in different sections of the archwire (e.g.: GAC Bioforce, Forestadent TripleForce). TSA (Tri-Sectional Archwires from Modern Arch ) are archwires made with reduced section stainless steel (eg: 0.018” x 0.018”) in the buccal segments and NiTi, TMA or Elgiloy (untorqued or pretorqued 20 degrees) 0.019” x 0.025” in the anterior segments.

Evans and Durning (1996a, 1996b) have produced a useful and well-accepted classification of orthodontic alloys.

Stainless steel Stainless steel archwires are used as working archwires. Standard grade stainless steel wires are quite adequate for use with current fixed appliances. Highly resilient or “Australian” type wires are not required.

Elgiloy

The Elgin Watch Company developed a cobalt chromium alloy (40% cobalt, 20% chromium, 5% iron and 15% nickel) in the 1950s which Rocky Mountain Orthodontics marketed as Elgiloy. Elgiloy’s advantage is related to the ability to increase its resilience and strength, but not its stiffness, after formation, by heat treatment. It is now of limited use because of the extensive use of preformed archwires and the lack of need to place complex bends in archwires; despite this, cobalt chromium archwires are sold as Remaloy (Dentaurum), Forestaloy (Forestadent), Bioloy (GAC), Masel (Masaloy) and of course Rocky Mountain Orthodontics (Elgiloy).

Titanium alloys The following titanium alloys are used in orthodontics:

•

• • •

nickel-titanium alloys o martensitic stabilised alloys o martensitic active alloys • martensitic graded archwires o austenitic active alloys nickel titanium copper chromium titanium molybdenum alloys titanium niobium alloys

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Nickel-titanium alloys The field of nickel titanium alloys is confusing and remains so despite profuse information within the literature.

Helpful explanations have been given by Kusy (1991, 1997), Matasa (1997) and Santoro (2001a, 2001b) and the following terms require explanation.

Definitions active alloy an alloy which is capable of undergoing its anticipated phase transformation; i.e.: in which an SME can be mechanically or thermally induced As and Af The start and finish temperatures at which austenite is formed in a nickel titanium alloy austenite historically, a specific phase of iron; also a high temperature metallurgical phase of nickel titanium with a face centred structure (hexagonal close packed) which can transform to martensite martensite historically, a metastable phase of iron resulting from the diffusionless transformation of austenite following rapid cooling; also a low temperature metallurgical phase of nickel-titanium with a body-centred (cubic or tetragonal) structure Ms and Mf The start and finish temperatures at which martensite is formed in a nickel titanium alloy passive alloy an alloy that is incapable of undergoing its anticipated phase transformation because extensive plastic deformation has suppressed the transformation phase transformation a change in the number or character of the phases that constitute the microstructure of an alloy by a change in crystalline structure pseudoelasticity the mechanical analogue of thermoelasticity in which, at constant temperature, the austenitic-martensitic phase transformation occurs with increasing applied force; the effect by which a material recovers the induced plastic strain on loading. Clinically, it is useful to think of this as a local stress-related superelastic effect generated by tying in an irregular tooth R structure a metastable rhombohedral structured intermediate phase between austenite and martensite (Khier et al 1991).

The R structure always seems to be present in an austenite to martensite transformation but not always in the reverse transformation (Bradley et al 1996). As of 2011, R phase is considered a martensitic phase which may appear in certain testing of alloys upon incremental heating or stressing. The diffusionless reorientation of atoms in the material must proceed on the minimal energy pathway, this may or may not include intermediate R phase existence between austenite and martensite. Traditional evaluation of these alloys does not consider the R phase due to lack of cohesive agreement among the academic and industrial communities. Thus only austenite and martensite are considered, R phase being swept up in the martensite regime (Alauddin S, 2011, Personal communication). resistivity amount of resistance to the passage of electrical currents; because austenite and martensite have different resitivities (see Table 8.1), the phase transformation temperatures can be inferred from the resistivity of a

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particular alloy. Other methods of inferring phase transformation are radiographic diffraction and differential scanning calorimetry shape memory effect (SME) the ability of a wire to return to undergo deformation and then return to its prior shape when triggered by a mechanical or thermal stimulus. This phenomenon is a combination of thermoelasticity and pseudoelasticity.

Strictly speaking this is a one-way shape memory effect as only austenite retains the memorised shape stabilised alloy an alloy in which a predetermined amount of wire deformation has occurred during processing suppressing the SME (q.v.) stress induced martensitic transformation (SIM) the mechanical analogue of SME. The ability of a wire to revert to its original shape when subjected to mechanical deformation superelasticity the martensite-austenite phase transformations, generated by mechanical stress or heat, which result in a segment of the loading curve for nickel titanium alloys in which stress is independent of applied strain. It only exists when both phases of the alloy are present. thermoelasticity the thermal analogue of pseudoelasticity in which the martensitic phase transformation occurs from austenite as the temperature decreases. The phase transformation can be reversed by increasing the temperature to its original value (pseudo-shearing). In most metals and alloys, an equivalent amount of stress usually generates an irreversible shearing deformation transition temperature range (TTR) the temperature range over which the alloy structure changes from the martensitic to the austenitic phase The mode of action of nickel titanium alloys Nickel titanium can exist in two different crystalline forms; facecentred (hexagonal close-packed) 2.1 GPa 1.4-1.7 GPa 0.84 GPa Yield Strength austenite and body-centred (cubic 200 GPa 31-35 GPa 84-98 GPa Elastic Modulus or tetragonal) martensite. The Resistivity 76 µohm-cm 82 µohm-cm physical difference between Thermal Conductivity 0.085 watt/cm-°C 0.18 watt/cm-°C austenite and martensite are given 3.7 x 10-6 emu/g 2.4 x 10-6 emu/g Magnetic Susceptibility in Table 8.1.

The process of phase Thermal Expansion 11 x 10-6/°C 6.6 x 10-6/°C transformation has been examined Table 8.1: Physical properties of nickel titanium alloys as a function of their phase by measuring resistivity, using radiographic diffraction and differential scanning calorimetry (Bradley et al 1996). A newer method, temperature modulated differential scanning calorimetry (TMDSC) gives further information about phase transformation of nickel titanium alloys and its complexity (Brantley et al 2003).

Property

Stainless steel

Martensite

Austenite

Transformation can be induced either by change in temperature or by change in applied stress. Temperature change induced transformation between the phases can be brought about by cooling (austenite to martensite) or heating (martensite to austenite). From this it is apparent that martensite is a low temperature form of the alloy and austenite the high temperature form of the alloy. Another transformation to an intermediate phase can occur between the austenitic and martensitic phases known as the R phase; this has rhombohedral symmetry and a simple hexagonal lattice. Thus the transformation may be austenite - R-phase - martensite and the reverse on

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heating. Not all transformations pass through the R-phase however and the R-phase has a lower elastic modulus than austenite.

Mf

Resistivity

Ms

A review of superelastic nickel titanium archwires has been published by Waters (1992), Evans and Durning (1996) and Santoro et al (2001a, 2001b).

As Af

Temperature transition ranges (TTRs) In Figure 8.3, the phase changes of nickel titanium archwires are demonstrated. At low temperatures, the archwire is completely martensite; as the temperature Figure 8.3: Resistivity against temperature for superelastic rises, progressive transformation into austenite occurs nickel titanium archwires (after Santoro 2001a) until finally, the alloy is wholly composed of austenite.

The period during which the phase transformation occurs (martensite to austenite) generates the shape memory effect. For this to be clinically detectable, the Af has to be just below mouth temperature so that the alloy is mostly in its austenitic form; however, if it is all austenite then the alloy simply obeys Hooke’s Law (stress and strain are proportional). So ideally, the Af should be set above mouth temperature and nickel titanium alloys should have temperature transition ranges that correspond to the temperatures of the oral environment.

Temperature

If the Af is below mouth temperature, then intraorally, the alloy is principally austenite. In order to effect superelasticity, more martensite is necessary; this is produced by archwire deflection. This is stress induced martensitic (SIM) transformation. Interestingly, SIM shifts the TTR to higher values since as a result of the changes in the lattice structure, more energy is required to reverse the martensitic transformation. Accordingly, in clinical practice one of the important characteristics of nickel titanium alloys is their stress-related Af; this is the temperature at which thermally active wires are ‘activated’. Thus the stress-induced (pseudoelasticity) and the thermal (thermoelasticity) properties of nickel titanium alloys are related (Santoro and Beshers 2000).

In laboratory studies, the type of loading should simulate the clinical situation as closely as possible. At the moment the three bracket bending test is the most appropriate (Santoro et al 2001b).

The force generated by superelastic behaviour varies with temperature. In a paper by Filleul (1997), three out of four tested “superelastic” wires showed superelasticity at 22°C, two out of four at 39°C and none of the four at 44° C. The start of the superelastic plateau occurs at different force levels according to temperature; lower temperatures generate a plateau at a lower force. This is an illuminating paper which repays careful reading. This variability has been re-emphasised by Nakano et al (1999) who tested 42 brands of nickel titanium wires and found large differences in the loads exerted in three point bending tests as shown in Table 8.2 as well as in the plateau behaviour of different archwires. Similar variability has been found by Gurgel et al (2001). Bolender et al (2010) have suggested that most NiTi wires do not exhibit in torsion the superelastic effect traditionally described in bending and that the optimal constant moments necessary to gain third-order control of tooth movement early in treatment are not present in a preadjusted edhewise-rectangular NiTi archwire system. A braided stainless steel rectangular archwire displayed better torsional behavior at 35°C than most NiTi archwires of the same dimensions.

It is important to remember that: 0.016" wire: load at 1.5 mm activation

0.016" wire: difference in load between 0.5 mm and 1.5 mm activation

0.016 x 0.022" wire: load at 1.5 mm activation

0.016 x 0.022" wire: difference in load between 0.5 mm and 1.5 mm activation

A Company Align

153

100

340

200

Ormco CuNiTi 35

17

17 3

3

Ormco CuNiTi 40 Table 8.2:

Load characteristics of different nickel titanium wires (in grams)

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Product

Dimension(s)

Manufacturer

Abbreviation

Smart SE

0.016”

Beijing Smart Tech Co Ltd

Smart

Keen Pak Ni-Ti

0.016”

Ormco

Ormco

CY16

0.016”

Grikin Advanced Materials Co

Youyan 1

Nitinol heat activated

0.016”

3M Unitek

3M

Smart SE

0.016” x 0.022”

Beijing Smart Tech Co Ltd

Smart

Damon CuNiTi

0.016” x 0.022”

Ormco

Damon

L&H Titan

0.016” x 0.022”

Tomy International

L&HR

CF1616

0.016” x 0.022”

Grikin Advanced Materials Co

Youyan 1

RF1616

0.016” x 0.022”

Grikin Advanced Materials Co

Youyan 2

Table 8.3:

• •

145

Types of NiTi wire used in the study by Ren et al (2008)

thermoelastic wires make archwires easier to tie in superelasticity in the mouth comes from stress induced martensitic transformation

Differential scanning calorimetry (DSC) method (measures the amount of energy (heat) absorbed or released by a sample as it is heated or cooled) was used by Ren et al (2008) to study the phase transformation temperatures and the phase transition processes of nine commonly used clinical NiTi alloys in China (0.016” and 0.016” x 0.022”) (Figure 8.3). The Af of the Smart, Ormco and 3M NiTi round wires were lower than room temperature and no phase transformation was detected during oral temperature indicating that these archwires do not possess shape memory. No phase transformation was seen for Youyan 1 round wire from -80° to +80°. For the rectangular wires, the Af of Smart, L&HR and Youyan 2 were close to mouth temperature whereas at room temperature they were mixture of martensite and austenite suggesting these wires had a shape memory effect. No phase transformation for the rectangular Youyan 1 was seen from -80° to +80° suggesting this wire had no shape memory effect. The 0.016” x 0.022” Damon CuNiTi wire existed as a mixture of martensite and austenite at room temperature but its Af was much higher than mouth temperature at 61.5°C and was therefore almost completely martensitic at mouth temperature. One slightly puzzling feature about this paper is that we were not aware that a 0.016” x 0.022” Damon CuNiTi wire has ever been made. The somewhat strange results reported by this paper are as a result of differeing test data definitions related to the existence of the R-phase.

Three types of nickel titanium alloys are available now: Martensitic stabilised alloys An example of these alloys is Nitinol. Nitinol undergoes 8-10% deformation during processing which suppresses the shape memory effect. This alloy has a mainly martensitic structure at room temperature.

The alloy delivers one-fifth to one-sixth the force per unit activation thus giving a light, continuous and linear force.

Austenitic active alloys The introduction of super-elastic nickel titanium alloys (Miura et al 1986) has been an important step forward in wire technology. Earlier nickel-titanium alloys were work hardened and possessed a high elastic limit and a low elastic modulus giving excellent spring back. Super-elastic nickel titanium wires have excellent springback, shape memory and superelasticity. These archwires have primarily austenitic grain structure with some martensitic Ni-Ti present. A phase called the R structure, which is an intermediate metastable rhombohedral phase, may exist in the transformation between austenite to martensite.

These alloys are, by definition, predominantly in the austenitic phase at room temperature and are engineered not to undergo thermal phase transformation at mouth temperature. If the austenitic transformation temperature is

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below mouth temperature then a stress induced martensitic transformation can however be induced by deformation. This phenomenon is variously called pseudoplasticity or pseudoelasticity (a subset of super elasticity) because of the flat force deactivation curve. Since austenite has a higher elastic modulus, on loading, the slope of the graph starts with a slope three times that of martensitic stabilised alloy; this then gives way to plateau behaviour and finally a further positive slope characteristic of martensitic nickel titanium.

Both types of active alloys can exhibit this type of stress-induced transformation and thus be superelastic.

Austenitic active alloys, then, deform elastically within the austenite phase when an initial strain is applied to them. Strain induces martensitic transformation during which increasing strain is not accompanied by an increase in stress. Once martensitic transformation is complete, then the material again behaves elastically within the martensitic phase.

Martensitic Active Alloys Martensitic active archwires are, by definition, predominantly martensitic at room temperature and are thermoelastic – often referred to as thermal wires. Thermoelastic archwires change their properties according to temperature such as martensitic active alloys. Bishara et al (1995) have produced a useful list of the ideal properties of thermoelastic archwires. These are:

• • • • •

highly ductile at room temperature instantaneous activation at mouth temperature ability to develop forces that will produce tooth movement once fully activated, the wire is not further activated by the heat of the mouth a narrow temperature transition range such that the wire is highly ductile at room temperature and highly active at mouth temperature

For two wires of equal dimensions, one composed of austenite would have an initial stiffness four times greater than one composed of martensite.

GAC's Sentalloy wire is an example of a martensitic active alloy. It is subject to a thermoelastic effect triggered by the temperature of the mouth that raises the Phase Start/Finish Temperature °C martensitic alloy through its critical temperature range start 14 Martensitic causing the alloy to transform to austenite and return to its original shape and stiffness.

Technical finish 7 improvements in the ability to control precisely the start 34 Austenitic composition of alloys has produced alloys in which the finish 43 start and finish of martensitic and austenitic Table 8.4: Example start and finish transformation transformations may be carefully controlled. Typical temperatures for martensitic active alloys values for this type of alloy are given in Table 8.4.

Thus these archwires are ligated, in theory, in their malleable martensitic form and then undergo austenitic transformation as the body heat increases. This induces a thermally activated shape memory effect which returns the archwire to its original (austenitic) archform.

The shape memory effect has been investigated by Hurst et al (1990). This demonstrated 89% to 94% recovery for most archwires. Sentinol (heavy) showed a mean recovery of 41.3% probably because its transition temperature range was close to room temperature. This paper, however, investigated the laboratory behaviour of these wires and a study that is closer to the clinical situation is necessary before firm conclusions can be drawn.

NeoSentalloy is similar to Sentalloy but has greater heat sensitivity and a higher shape memory effect. Sentalloy Bioforce gives differential forces rising from 100g anteriorly in the midline to 320 g in the molar region as shown in Figure 8.4. A similar alloy is produced by Forestadent (TripleForce).

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Tonner and Waters (1994) have compared various superelastic nickel-titanium wires using a three point bending test.

350 300 250

In the articles, they make several important points:

grams

200 150

• wire of the same diameter from different manufacturers has highly variable performance.

This varies at 35°C between 20 and 130 cN/mm • superelastic wires have to be deflected at least 2 mm before exhibiting plateau behaviour • superelastic wires show significant temperature sensitivity over the range form 5°C to 30°C

100 50 0 0

Figure 8.4:

147

9

18 27 mms from midline

36

48

GAC Sentalloy Bioforce wire

Nickel Titanium Copper Chromium Alloys (CuNiTi) The addition of copper to nickel titanium alloys increases strength, reduces hysteresis (the energy lost between activation and deactivation) and allows greater precision in the setting of the austenitic transformation temperature. The addition of copper, however, increases the transformation temperature to above that of the oral cavity and to compensate for this, 0.2 to 0.5% chromium is added to reduce the transformation temperature.

CuNiTi was originally produced with four different austenitic transformation temperatures covering both pseudoelastic and thermoelastic archwires.

CuNiTi type 1

• • • • • •

austenitic transformation temperature 15°C pseudoelastic infrequently used very heavy forces few clinical indications not commercially available CuNiTi type 2

• • •

austenitic transformation temperature 27°C pseudoelastic in patients o who have an average or high pain threshold o with normal periodontal health o where rapid tooth movement is required and the forces generated by the archwire are constant CuNiTi type 3

• • •

austenitic transformation temperature 35°C thermoelastic in patients o who have a low to normal pain threshold o whose periodontium is normal to compromised o where relatively low forces are desired

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CuNiTi type 4

• • •

austenitic transformation temperature 40°C thermoelastic in patients o who are sensitive to pain o who have compromised periodontal conditions o where tooth movement is slowed down o good as initial rectangular wire

Whilst the ability to later transition temperatures is important, contemporary CuNiTi wires have a variety of transition temperatures. The addition of copper makes for a more consistent wire; Ormco have recently released a 0.013” CuNiTi wire is claimed to have 65% of the force of an 0.014” CuNiTi wire.

Pandis et al (2009) investigated whether 0.016” 35° CuNiTi or 0.016” NiTi archwires resolved mandibular anterior crowding at different rates in a double blind randomised control trial. Using In Ovation-R active self-ligating brackets with an 0.022” slot, they found that wire type had no effect on the rate of resolution of anterior mandibular crowding (129.4 vs 121.4 days). Patients with an irregularity index < 5 took a shorter time to resolve anterior mandibular crowding than those with an irregularity index > 5 (138.5 vs 113.1 days) – not surprisingly.

Clinical effectiveness of superelastic wires There is little published work on the effectiveness of superelastic nickel-titanium wires. O'Brien et al (1990) showed no significant difference in contact point alignment between Nitinol (MSA) and Titanol (AAA) archwires over a five-week period. A later paper (West et al 1995) compared 0.0155" multistrand stainless steel round wire with an 0.014" NiTi superelastic wire. The superelastic wire gave improved alignment in the lower labial segment only and with doubtful cost benefits.

A further paper (Evans et al 1998) compares the performance of three aligning archwires: an 0.016" x 0.022" active martensitic wire (American Orthodontics Titanium Heat memory Wire), a graded 0.016" x 0.022" active martensitic wire (GAC Bioforce Sentalloy) and a 0.015" multistrand wire (Dentaurum Dentaflex). Patients were included in the study if they were having upper and lower fixed appliances and under 18 years of age. Impressions were taken at the prealignment phase, 4 weeks into treatment and 8 weeks into treatment and the study models analysed at each time period using a three dimensional Reflex microscope. Although visual inspection of the data would suggest that the active martensitic wires were superior in obtaining arch alignment, this apparent finding was not supported by statistical analysis which found no difference between the performances of the three wires. Yet again, researchers have found it impossible to demonstrate clinically the supposed benefits of modern nickel titanium alloys. Some of the reasons for these findings are given by Riley and Bearn (2008).

At the present time, some authors suggest chilling superelastic archwires before insertion to allow the tying in of thicker archwires. This can be done with an ‘Ice’ aerosol or by leaving the archwires in a refrigerator or freezer. It may be that such wires are best tied in with steel ligatures rather than elastomerics. Additionally, some orthodontists recommend that their patients use daily warm water rinses while superelastic archwires are in place.

In reality, none of these measures seems necessary.

The effect of stress Nickel titanium archwires are commonly used during the aligning phase of orthodontic treatment; we are therefore particularly interested in the performance of these wires in situations of maximum load.

Segner and Ibe (1995) threw some doubt upon the clinical relevance of superelasticity when they tested sixteen superelastic wires from nine manufacturers. Several of the archwires tested showed no pseudo-elastic properties.

None of the materials had a plateau that extended below 0.28 mm and 0.5 mm was considered a good value.

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For small archwire deflections therefore, none of the materials will behave superelastically. It is known that the presence of stress increases the Af value. With large deflections, the considerable load applied to the wire may result in localised SIM formation thus elevating the TTR. The TTR may move out of the oral temperature range thus rendering the archwire non-superelastic at mouth temperature. Santoro and Beshers (2000) compared five different archwires with minimum (1 mm) and maximum (6 mm loading). The specimens were placed in a temperature bath and the temperature raised from 4°C to 60°C and the phase determined by measuring resistivity. The results are shown in Table 8.5. It can be seen that Ormco’s CuNiTi 27° and 3M Unitek’s Nitinol Heat Activated provide a wide TTR, corresponding to mouth temperature changes, and unchanged by maximum loading.

The effect of temperature Whilst thermoelastic archwires demonstrate exciting and unusual properties in relation to their physical behaviour, the clinical relevance of this is a matter of conjecture.

Santoro et al (2001b) suggest that at least 2 mm of deflection are necessary for the formation of SIM in austenitic wires; below 2 mm may result in a higher force delivery due to the continued presence of the austenitic phase.

The disappointing clinical results of superelastic archwires are attributed to the fact that many superelastic archwires:

• • • •

do not exhibit plateau behaviour require excessive deflection to achieve plateau behaviour deliver excessive force on the plateau a combination of the above factors

In several articles by Meling and Ødegaard (1998a, 1998b, 1998c), the effect of temperature changes on thermoelastic wires has been investigated. These papers looked at the effect of temperature on the elastic properties of thermoelastic wires (1998a), the effect of temperature on longitudinal torsion (1998b) and the effect of temperature on bending (1998c).

In 1998a, Meling and Ødegaard confirmed Segner and Ibe’s suspicions when they found that only four out of eight superelastic nickel-titanium wires showed superelastic behaviour when deactivated from 25 degrees of torsional twist. Only one wire had a wide plateau at twist angles present in conventional prescriptions. The other wires demonstrated deactivation plateaus when deactivated from 45 to 60 degrees of torsion which is outside the range employed in orthodontics; in addition, the thermal responsiveness of the wires was variable between wires.

In 1998b, the effect of short-term temperature changes was investigated in archwires in torsion. Meling and Ødegaard found that the torsional stiffness of superelastic nickel titanium wires was significantly influenced by the short-term application of hot (80°C) or cold (10°C) water. The changes induced by hot water were transient but cold water induced a reduction in torsional stiffness which persisted for at least five minutes after the application of the water. Repeated application of cold water resulted in incremental reductions in torsional stiffness which was still present 60 minutes later.

Unloaded

1 mm Load

GAC Neo-Sentalloy

9-22

9-28

6 mm Load 9-28

Ormco CuNiTi 27°

16-31

4-33

4-33

Ormco CuNiTi 35°

7-35

7-37

23-41

Ormco CuNiTi 40°

13-38

21-38

21-38

3M Unitek Nitinol Heat Activated

8-38

4-38

4-38

Table 8.5: Stress related TTRs for various archwires under two different load conditions (Santoro 2000)

Similar effects were found in bending (1998c) although martensitic stabilised archwires, which are relatively temperature insensitive, showed minimal changes.

Rucker and Kusy (2002a) compared the elastic flexural properties of multistranded stainless steel wires with those of conventional (stabilized martensitic) nickel titanium archwires. The nickel titanium archwires showed non-linear elasticity thus underestimating the elastic properties of strength

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ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

and range. Multistranded stainless steel wires did not match the strength and range of conventional NiTi alloys; however, the paper suggests that it should be possible to enhance the performance of multistranded stainless steel wires by decreasing their yield strengths.

Rucker and Kusy (2002b) also compared resistance to sliding for multistranded stainless steel and single stranded wires. They found that there was almost no difference between the kinetic coefficients of friction for stainless steel wires, regardless of configuration, in the passive region (<θc). In general, nickel titanium archwires had higher coefficients of kinetic friction. In the active region (>θc), the multistrand wires behaved as follows compared with single strand wires: coaxial wires had low friction, three-strand round and eight strand rectangular medium friction and three strand rectangular wires had high friction.

Rucker and Kusy (2002c) have shed some light on why nickel titanium archwires are instinctively preferred by orthodontists in the early stages of treatment and yet it has been difficult to demonstrate the benefits of nickel titanium archwires over other initial aligning archwires scientifically. Rucker and Kusy argue that an initial aligning archwire requires:

• • •

high strength to prevent permanent deformation low stiffness to deliver low forces on activation high range to maximize activations

The authors tested three groups of archwires: wires with similar overall wire diameters (0.018"); group wires with stainless steel cores of polymer coated wires with single-stranded SS wires; and braided wire configurations with corresponding single stranded wires. These groups were compared with 0.016" nickel titanium archwire and the elastic property ratios calculated. The behavior of superelastic nickel titanium wires can be divided into three distinct regions: the A (austenitic) region in which the elastic properties can be predicted from linear elastic models, where the E measurements for these archwires typically vary from 33 to 55 GPa; the SP (superelastic plateau) region in which wires deliver a nearly constant force over a range of activation, the extent of which depends on the initial content of the A phase; and the M (martensitic) region in which the magnitudes of E should be less than those of the A region and typically equal 31 to 35 GPa. Here, the elastic behavior can also be predicted by a linear elastic model. In this study, the elastic properties of single stranded nickel titanium wires, were superior to all the other levelling wires. This outcome is independent of whether the wires are clinically operating in the austenitic region or in the superelastic plateau region.

Interestingly, the paper also points out that bevelling and rounding of rectangular archwires can impact the flexural properties. For example, an 8% decrease in cross-sectional area (i.e., 2% from each corner) results in nearly a 20% decrease in stiffness.

In contrast, Badran et al (2003) used photoelastic models to simulate the shear stresses involved in aligning moderately crowded lower incisors and a palatally displaced upper canine using 0.015" and 0.0175" multi-strand, 0.014" and 0.016" martensitic stabilised (classic) nickel titanium and 0.014" and 0.016" austenitic active (stress induced superelastic) nickel titanium archwires. The martensitic stabilised nickel titanium archwires delivered forces 15-20% higher than the forces produced by the multi-strand and martensitic stabilised archwires which delivered similar forces. This paper then again shows that it is difficult to conclusively demonstrate the superiority of nickel titanium archwires over multi-strand archwires. In contrast, Weilland (2003) in a rather ingenious clinical experiment using 0.016" stainless steel solid archwires and 0.016" GAC (blue) Sentalloy superelastic alloy. Weilland found that the superelastic archwire moved teeth significantly further than stainless steel (median 3.5 mm compared with 2.3 mm on an activation of 4.5 mm) over a period of 12 weeks. However this came at the price of statistically significantly more root resorption in the teeth treated with the superelastic wire.

Gatta et al (2011) investigated load-deflection characteristics of superelastic and thermal nickel titanium archwires using a three point bending technique. The authors concluded that thermal archwires demonstrated significantly lower working forces than superelastic archwires at both 2 mm and 4 mm deflections. Increase in wire size produced an increase in working force. In the unloading phase, a statistically significant decrease in force with increasing wire deflection occurred for all archwire types. Superelastic wires at 2 mm of deflection showed curves

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

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with a smaller hysteresis than thermal wires of the same size. At 4 mm deflection, the superelastic and thermal wires of the same size demonstrated similar behaviour, characterized by wide hysteresis curves but with different force levels.

Titanium molybdenum alloys (TMA) Stabilised beta-titanium alloys (TMA) contain 80% titanium as well as 10% molybdenum, 6% zirconium and 4% tin.

TMA is twice as stiff as martensitic stabilised nickel titanium alloys and a third as stiff as stainless steel. It is formable and weldable. Proffit (1986) cites the use of TMA wires to provide root paralleling at the end of treatment; these archwires are probably more useful for the delivery of localised tip and torque. It is therefore suited to obtaining more precise individual tooth movements such as in-out, tip, torque and rotation, particularly at the end of treatment.

Originally, titanium molybdenum alloys were protected by patent; however this expired a few years ago and several variants of the alloy are now available. These have been described by Verstrynge et al (2006) as follows:

• • • •

Ti-11.5, Mo-6, Zr-4.5,Sn o beta III – β-alloy Ti-3, Al-8, V-6, Cr-4, Mo-4, Zr o beta C – β-alloy Ti-6, Al-4, V o α-β alloy Ti-45 Nb o titanium niobium

Twelve TMA archwires were tested and most were from the first category (Beta III). The archwires differed in their elastic modulus, hardness, yield strength and ductility. One archwire (α-β alloy) demonstrated the highest elastic modulus, the highest yield strength and the highest hardness. A Beta III alloy demonstrated the greatest ductility.

TMA has a higher rigidity and lower recoverable deformation than nickel titanium allows. Laheurte et al (2007) have described a method of improving the pseudoelasticity of TMA by controlling the grain size. This produces an archwire with mechanical properties midway between martensitic stabilised NiTi and active NiTi alloys. The modified TMA does not however exhibit plateau behaviour.

Reverse curve TMA asymmetric T-loop archwires TMA archwires are good at delivering the range of their activation. Reverse curve TMA asymmetric T-loop archwires are a useful method of intruding and retracting upper incisors. A presentation of how to use reverse curve TMA asymmetric T-loop archwires by Jim Hilgers is on the Ormco website at http://www.ormco.com/learning/seminarsOnline/seminarDetailPage.cfm?SEMINARNUM1=5 .

Titanium niobium finishing arches (TiNb/FA) Titanium niobium archwires are available and are a variant of TMA. These wires have 60% of the stiffness of TMA and are easy to bend. They are recommended by the manufacturer for use as finishing archwires.

Archwire morphology and treatments Supercable Supercable 1 (Strite Industries Ltd) is a seven strand super elastic nickel titanium coaxial wire. It is claimed to have one fifth the force of an equal diameter round single strand nickel titanium wire and one third of the force of an equal diameter round stainless steel (Figure 8.5). This develops very low forces in the initial stages of treatment, approximately one third of the force of an equal diameter round nickel titanium wire, as described by Berger (2008).

1

SPEED System Orthodontics, Strite Industries Ltd, 298 Shepherd Avenue, Cambridge, Ontario, N3C 1V1 Canada

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Dual dimension archwires

450 400 350 300

grams

250 200 150 100 50 0 Damon CuNiTi Heat activated NiTi Supercable NiTi 0.012" 0.013" 0.014" 0.016" 0.018" 0.020"

Figure 8.5: Unloading forces for various types and dimensions of archwires with 3 mm of activation. Supercable delivers approximately one third of the force of an equal diameter round nickel titanium archwire (after Berger 2008)

Dual dimension archwires normally have a rectangular section in the anterior region and round wire posteriorly. Wonder Wire (Wonder Wire Corporation) was the first archwire to have this feature but the company no longer seems to be in business; we have used this wire and while an interesting diversion, we were not sufficiently enthused by it to become a regular part of our archwire sequencing. The Hills Dual-Geometry 2 wire (see Figure 8.6) has a square anterior section and a round posterior section – the archwire dimensions are therefore 0.018” x 0.018” x0.018” for 0.018” slots and 0.021” x 0.021” x 0.021” for 0.022” slots and the concept of dual dimension wires remains an interesting one.

Reverse curve nickel titanium archwires

The use of reverse curve nickel titanium archwires is an effective method of dealing with reluctant overbites. Although slightly awkward to place and requiring some 3 months or so to act, they are a useful adjunct to treatment. The 0.019" x 0.025" size is preferred. If left in place too long the labial segment develops a semilunar curve; this, however, is easily removed with a flat archwire.

Pretorqued nickel titanium archwires It is now possible to purchase nickel titanium archwires with 20° of torque in the anterior segment only. These archwires are available as flat archwires and archwires with a reverse curve and are known as SET (SuperElastic Torqued) Titan archwires and are available from several orthodontic suppliers.

Ion implantation Ion implantation is a technique used to modify surfaces exposed to corrosion or wear. Nitrogen ions are produced in a source chamber from collisions between atoms and electrons emitted from a heated filament. The beam of ions is accelerated and sent into an evacuated implantation specimen where it penetrates the specimen (Mizrahi et al 1991).

GAC (Spire Ion Implantation) and Ormco (TMA Low Friction) have produced wires treated by ion implantation to try and reduce friction. Ormco claims a reduction in friction of 54% for Low Friction TMA. Ryan et al (1997) investigated the effects of ion implantation on various wires in vitro and determined that stainless steel produced the least frictional force, followed by ion implanted nickel titanium, ion implanted beta titanium, untreated nickel titanium and untreated beta titanium. The interesting point about this article is that stainless steel still performed better than nickel titanium alloys whether ion implanted or not.

Figure 8.6: The Hills Dual-Geometry wire has a square anterior section and polished round posterior section to allow space closure in the posterior segments while maintaining torque control anteriorly.

2

Kula et al (1998) have cast some doubts on this and other studies in reporting that the rate of space closure in vivo was not different for implanted and unimplanted beta titanium wires and furthermore that the rate of space closure was not significantly different between beta-titanium and stainless steel wires. The brackets used were not implanted. It may be that both archwire and bracket surfaces need to be implanted in order to produce significant reductions in friction. This used a split archwire design where one side only of a 0.019" x 0.025" TMA archwire was implanted with

SPEED System Orthodontics, Strite Industries Ltd, 298 Shepherd Avenue, Cambridge, Ontario, N3C 1V1 Canada

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nitrogen ions by Spire Corporation. The computed monthly rate of space closure for TMA was 0.12 to 2.46 mm per month compared with 0.76 to 1.75 mm per month for stainless steel.

Aging and archwire fracture Eliades and Bourauel (2005) have published an interesting review on the effect of intraoral aging on orthodontic materials. The mechanism whereby archwires may be affected by aging are the effects on:

• • • •

friction force delivery superelasticity and fracture resistance

Age changes on the surface of the bracket slot or archwire due to calcified biofilm may affect the friction between the bracket slot and archwire. In addition, the actual structure of the archwire or bracket may be affected thus altering their mechanical properties.

Ni-Ti archwires show pitting, corrosion and biofilm deposits as a result of aging; this however is very difficult to simulate in vitro and considerable caution should be taken in extrapolating laboratory findings to the clinical situation.

It has been speculated that the superelasticity of NiTi wires may be affected by intraoral aging although there is no evidence to support this; it is known however that significant temperature changes can adversely affect the superelastic properties of NiTi wires.

The fracture resistance of NiTi wires is however significantly reduced by intraoral aging and that this affects NiTi more than stainless steel or TiMb wires.

Zinelis et al (2007) have studied the fracture mode of nickel titanium archwires because retrieved archwires have a much higher fracture incidence in contrast to laboratory experiments which showed that these wires were practically unbreakable. Most fractures were located in the posterior region of the arch, probably because of highmagnitude masticatory forces. Brittle fracture without plastic deformation was observed in most specimens regardless of the type of nickel titanium archwire. There was no increase in the hardness of the intraorally exposed specimens regardless of wire type which suggests that hydrogen embrittlement was not the cause of fracture.

Archwire sequences We know that for a given nominal size, different nickel titanium archwires have different properties. Our preferred high technology archwire is copper nickel titanium. The manufacturing process for nickel titanium archwires struggles to keep a consistent temperature transition range and so for any nickel titanium archwire, variability of physical properties is a problem. Copper NiTi overcomes variability in transition temperature and with careful manipulation of its transition temperature can provide an adequately stiff wire.

Archwire sequences can be classified in different ways; the preferred method is by archwire type. The four archwire phases are:

• • • •

phase 1 o light round high technology archwires phase 2 o rectangular high technology archwires phase 3 o major mechanics phase 4

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ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

o

finishing

Phase 1:

Light round high technology archwires Aim

Archwires

10 weeks

Normal Level

Appointment intervals

Duration 10 to 20 weeks

0.014” CuNiTi

Align

Alternatives

Correct majority of rotations

0.013” CuNiTi (more crowded cases)

Initiate arch form

0.016” CuNiTi (following 0.013” CuNitTi)

Phase 1 uses high technology archwires to level, align, almost fully correct all anterior rotations and partially correct posterior rotations. It also begins to initiate arch form. Normally this phase lasts 10 weeks; however, very crowded and irregular cases require 20 weeks with 10 weeks in 0.013” CuNiTi and 10 weeks in 0.016” CuNiTi. There is no rush to get into larger dimension wires – almost all major tooth alignment can be achieved with these archwires.

Phase 2:

Rectangular high technology archwires Aim

Archwires

Appointment intervals

20 to 30 weeks

Normal Fully resolve all rotations

0.014” x 0.025” CuNiTi

Begin torque control arch

8-10 weeks

0.018” x 0.025” CuNiTi

Anterior space consolidation Continue development

Duration

form

Alternatives

4-6 weeks

0.016” x 0.025”CuNiTi (cases with minimal irregularity) Intrusion and bite opening 0.017” x 0.025” RCOS CuNiTi 0.019” x 0.025” RCOS CuNiTi Torque 0.019” x 0.025” CuNiTi + 20°

Phase 2 fully resolves all rotations; posterior rotations are slowest and most difficult to correct, particularly if they are the terminal tooth on the archwire. Phase 2 also is the beginning of torque control. It is important to use an archwire that is 0.025" in the first order dimension to ensure first order alignment of the teeth before progressing to working archwires if using self-ligating brackets; otherwise the change into the major stainless steel working archwires will be difficult because of lack of first order alignment.

The 0.016" x 0.025" CuNiTi archwire is used in cases (normally class 2 division i) with very mild irregularity instead of the 0.014” x 0.025” and 0.014” x 0.025” CuNiTi archwires.

Intrusion and bite opening is also largely completed at this stage using nickel titanium archwires with reverse curves of Spee. Additional torque can be achieved using wires with 20° of torque added.

Phase 3:

Rectangular working archwires

Preposted stainless 0.019” x 0.025” stainless steel archwires are the preferred archwires for this stage. Preposted archwires are less expensive than crimpable hooks and never slip. Their disadvantage is that there may be some softening of the wire at the point where the hook is soldered to the archwire. Depending on the needs of the case, TMA archwires can be substituted for stainless steel particularly where the additional rigidity of the stainless steel wires is not required.

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Aim

Archwires

Appointment intervals

155

Duration

Normal Maintain archform integrity

0.019” x 0.025” stainless steel preposted

6-8 weeks

Finish torque control

0.019” x 0.025” TMA

4 weeks if wearing elastics

Consolidate posterior space Corrections anteroposterior buccolingual vertical

Phase 4:

Alternative

20 weeks

0.016” x 0.025” stainless steel preposted and crossbite correction with cross elastics

Finishing archwires

The finishing stages of treatment involves the optimisation of final tooth positions. Minor tooth adjustments can be made in 0.019” x 0.025” stainless steel archwires. TMA is more resilient and this material is better for larger corrections. Careful archwire bending and the use of posterior-V elastics can be used to develop interdigitation. If only minor vertical adjustment without wire bending is required, then 0.014” x 0.025” CuNiTi archwires can be used to improve buccal segment fit.

Aim

Archwires

Appointment intervals

Duration

Normal Make remaining adjustments to: in-out angulation inclination rotation Develop interdigitation

0.019” x 0.025” stainless steel preposted

4-6 weeks

10-20 weeks

Alternative 0.019” x 0.025” TMA for minor adjustments of tooth position 0.014” x 0.025” CuNiTi allows more vertical settling while maintaining first order alignment

Two different archwire sequences are commonly used. The three wire archwire sequence is used in relatively well aligned arches and the four wire archwire sequence used in more irregular arches.

The 0.016" x 0.025" nickel titanium archwire is used as a transitional wire between the initial aligning wires and the working archwires. It does not provide any torque control except on very poorly aligned teeth. It is important to use an archwire that is 0.025" in the first order dimension to ensure first order alignment of the teeth before progressing to working archwires; the reduced slot depth of the Damon System bracket and the precise nature of the closure mechanism make this more critical.

In the initial aligning and transition stages of treatment, archwires should be left in place for ten weeks. There is no need to see the patient more frequently than this; if you are uncomfortable with this length of time between patient appointments then see the patient for a review visit at five weeks but do not change the archwire!

Additional archwires are given in the same table and these may be useful on occasion. Additional information is given in the chapter on Self Ligating Brackets: Theory And Practice.

Mandall et al (2006) have undertaken a randomised clinical trial on archwire sequences which measured time taken to get into an 0.019” x 0.025” working archwire, discomfort and root resorption. The archwire sequences were:

• • •

0.016” NiTi, 0.018” × 0.025” NiTi and 0.019” × 0.025” stainless steel 0.016” NiTi, 0.016” stainless steel, 0.020” stainless steel and 0.019” × 0.025” stainless steel 0.016” × 0.022” CuNiTi, 0.019” × 0.025” CuNiTi and 0.019” × 0.025” stainless steel

The authors found no difference in discomfort or amount of root resorption but the sequence with four archwires took a greater number of visits (although not a statistically significant time) to reach 0.019” × 0.025” stainless steel although this was not explained by the increased number of archwires. Although these are not archwire

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sequences we use, this is an interesting paper that raises many questions about our conceptions of archwire sequences.

Archwire error First order error

This occurs when an archwire rotates in a first order direction within a molar tube or an Activa bracket. The error is given by the formula:

where: w is the width of the bracket d is the depth of the bracket dim1 is the first order dimension of the archwire.

A working stainless steel archwire has about 4 degrees of freedom in a 0.022" slot.

Second order error Tip or second order error occurs because of the use of undersized archwires. The error is related to the diameter of a round wire or the height of a rectangular wire and the bracket width but becomes negligible in working archwires as shown in Figure 8.7.

The error is given by the formula:

where: w is the width of the bracket h is the height of the bracket dim2 is the second order dimension of the archwire.

Third order error

Torque or third order error again occurs because of the use of undersized archwires.

The error is due to the fact that the archwire can rotate within the bracket before applying any force to the bracket.

This error is not negligible in working archwires and is of considerable significance in any case that requires palatal movement of the upper incisor roots. The magnitude of this error is given in Figure 8.8.

8 7 6

degrees

5 4 3 2 1 0 2

2.5 0.022"

Figure 8.7:

0.020"

3 bracket width (mm) 0.018"

0.016"

3.5 0.014"

4 0.012"

Tip error for various bracket widths and archwire sizes

The error is given by the formula:

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

157

18 16 14

Deviation angle

12 10 8 6 4 2 0 16-22

17-25 18-25 19-19 19-25 Archwire size (inches x 0.001)

21-25

21-28

where: h is the height of the bracket dim1 is the first order dimension of the archwire dim2 is the second order dimension of the archwire.

It can be seen that an 0.016" x 0.022" archwire gives minimal third order control. An 0.018" x 0.025" archwire gives 10 degrees of play while a 0.019" x 0.025" archwire only reduces this play by 2 degrees. Full sized archwires are therefore required if the torque built into the bracket is to be fully expressed.

Figure 8.8:

Torque error for various sizes of rectangular archwire

However, the actual situation is worse than this as in addition a further 40% of the torque can be lost if the actual amount of torque transmitted to the bracket is measured (Sebanc et al 1984). Gioka et al (2004) have cited five variables which may affect the amount of torque loss between archwire and bracket. These are:

• • • • •

play between archwire and bracket slot lack of stiffness of bracket structure or slot inadequate archwire stiffness incomplete ligation manufacturing variability

All of these factors can be controlled by the clinician except for manufacturing variability. The amount of torque loss can therefore be reduced by:

• • • •

specifying a (substantially) higher value prescription than the final tooth inclination target using metal or ceramic brackets or composite brackets with metal slots using large cross section stainless steel archwires using secure ligation. Elastomeric ligatures lose 40% of their force within the first 24 hours in vitro and due to enzymatic degradation and thermal cycling, the in vivo situation is likely to be worse.

This is a good reason to use passive self ligation (or wire ligatures).

Pain from initial archwires Again little work has been carried out on discomfort from archwires. Jones (1984) and Jones and Chan (1992) looked at the discomfort caused by initial aligning archwires (multistrand and superelastic NiTi) using tooth extraction as a control and found that:

• • • •

the pain from archwires was greater than from tooth extraction the pain lasted 5-6 days the amount of discomfort increased with age there was little difference in the discomfort produced by either archwire

This contrast with the findings of Ngan (1989) who found no difference in discomfort between patients under and over 16 years of age. This may be explained by the fact that Jones used a verbal scale to determine pain levels compared with Ngan’s visual analogue scale (VAS).

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Ngan (1994) has compared the effectiveness of a single dose of a placebo, aspirin and ibuprofen in reducing pain after the placement of separators and initial orthodontic archwires. Both aspirin (650 mg) and ibuprofen (400 mg) reduced discomfort with ibuprofen being significantly more effective than aspirin.

Leavitt et al (2002) have published an interesting paper which looks at pulpal pain during orthodontic treatment – in the past it has been assumed that the pain associated with tooth movement was periodontal pain. This evaluated detection and pain thresholds in the dental pulp and compared them with a pain visual analogue scale (VAS) completed by the patient. There was a significant difference between the experimental and control groups at post-archwire insertion day 1 followed by a small but non-significant difference at post-archwire insertion day 7.

Despite finding a non-significant but suggestive (there was an outlier in the data) negative correlation between pain scores, the investigators were unable to find significant differences in the detection or pain threshold at any of the assessment periods. This paper is strongly suggestive of the fact that pulpal pain is involved in the pain from orthodontic appliances but does not quite manage to show it!

Erdinç and Dincer (2004) showed that pain was initiated approximately two hours after initial archwire placement, that 90% of patients experienced pain in the first week and that the mean pain intensity peaked at 24 hours and thereafter gradually declined over 7 days.

Bartlett et al (2005) demonstrated that a telephone call from the orthodontic provider reduced patient’s selfreported pain and anxiety scores. This was a well designed and interesting study having two experimental groups and one control group which were asked to complete pain intensity and anxiety state questionnaires in the week following appliance placement. The first experimental group received a structured telephone call within 24 hours of appliance placement covering:

• • • • • • •

the patient’s well being the pain and discomfort experienced reassurance that the patient’s discomfort was within normal limits the need to maintain excellent oral hygiene the need for a soft diet a reminder to use analgesics if necessary and the importance of maintaining a positive attitude

The second experimental group also received a similarly timed telephone call but this simply thanked the patient for agreeing to participate in the study and reminding them to fill in the questionnaire. The control group received no telephone call.

Both groups receiving a telephone call reported lower pain intensity scores and lower anxiety states than the control group – the content of the telephone call was not important.

Pringle et al (2009) have demonstrated that the mean pain intensity in the first week after initial archwire placement is lower with the Damon passive self-ligating appliance than with conventional appliances.

Tooth movements

Management Tooth movement is often described as first, second and third order; however this can be misleading. Tooth movement can occur in each of three directions at right angles to one another – the x, y and z axes. In addition, these movements can occur as bodily movement or a moment about the axis. These movements are shown in Figures 8.9 and 8.10.

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Figure 8.9: Translational movement in the x, y and z axes corresponds to mesiodistal, up and down and in-out movements of teeth

159

Figure 8.10: Moments around the x, y and z axes correspond to angulation, inclination and derotation of teeth

Basic wire bending skills Although the Straight-Wire Appliance greatly reduces the amount of wire bending required during active treatment, orthodontists using the appliance still require basic wire bending skills. These should include:

• • • • •

an understanding of first, second and third order bends the ability to bend flat, symmetrical and co-ordinated archwires the ability to bend and adjust bayonet bends and various designs of loop the ability to incorporate and adjust progressive and continuous torque the ability to bend and adjust curves of Spee

Ligation Proper ligation technique is as important as accurate band and bracket positioning.

Wire ligature ties Operators should be familiar with the use of conventional ties, rotation ties and lacebacks tied with 0.010" wire ligatures and Coon pattern ligature lockers. In practice however these are now rarely used as the use of elastomeric ligatures is preferred in conventional ilgation.

Elastomeric ties Elastomeric ligatures have for many years been used routinely as the predominant method of ligation. These are best placed with Orthopli 018R or Microna forceps and are used in a figure of eight pattern where additional force is required to obtain full bracket engagement. Figure of eight elastomeric ligatures should be used selectively to fine tune bracket engagement and resistance to sliding. The use of figure of eight ligatures increases the fictional resistance by approximately one and a half times for most working archwires and by over three times for 0.016" x 0.022" archwires (Sims et al 1993).

Hain et al (2006) studied the effects of different types of ligation on sliding friction with an 0.0119” x 0.025” stainless steel archwire. The ligation methods tested included Damon 2 and SPEED self-ligating brackets, TP SuperSlick, silicone impregnated and conventional elastomeric ties. The Damon 2 self-ligating brackets demonstrated the least friction followed by the TP SuperSlick elastomeric ligatures whose coating seemed resistant to wear in a simulated clinical setting.

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Kobayashi ligatures

3.5

Kobayashi ligatures are used to add hooks to brackets.

These ligatures should be reasonably soft but all proprietary Kobayashi ligatures are unsuitable for use on ceramic brackets - it is better to make up a hook from an 0.010" wire tie instead for these cases. The use of Kobayashi ligatures is declining.

3 2.5

ratio

2 1.5 1 0.5

Archform

0 016 x 022

017 x 025

018 x 025

019 x 025

Figure 8.11: Comparison of ratio of frictional resistance between figure of eight and conventional elastomeric ligation (from Sims et al 1993)

Archform is usually interpreted as meaning the two dimensional shape of the dental arch viewed from the occlusal; a little further thought would elicit the comment that size was also important.

The development of pre-adjusted edgewise appliances has stimulated the wish for preformed archwires which simulate “ideal” archform to be commercially available. Many manufacturers offer archwires in different sizes (widths) and some in both different widths and shapes.

Much has been written on the shape and size of the ideal natural dental arch and the derivation of archforms for orthodontic use. Archform has generally been described using:

•

•

simple mathematical descriptions o segments of a circle linked to straight lines (Hawley 1905) o ellipses (Brader 1972) o parabolas (Jones and Richmond 1989) o catenary curve (Pepe 1975) complex mathematical curve-fitting formulae o conic sections (Sampson 1981) o cubic spline (BeGole 1979) o polynomial function (Lu 1966) o “mixed” functions (Ferrario et al 1994) o beta function (Braun et al 1998)

Knox et al (1994) provide a thought-provoking look at the possibility of an ideal preformed archwire. The notion of an ideal orthodontic archform, with its implications of symmetry and mathematical description, does not accord with what is found in nature. In particular, symmetry is not a tenable assumption. Furthermore, the development of the preadjusted edgewise appliances means that archwires no longer follow the contour of the buccal cusps and incisal edges. As manufacturers make more sophisticated appliances, archform may well deviate further from the smooth archform described in an “ideal” arch (see Orthos archform where CIS creates a sharp bend in the canine region). When comparing arches used with the Straight-Wire Appliance with edgewise arches, it is also important to remember that to produce core arch lines of the same shape and size, a preadjusted edgewise appliance arch must be wider in the premolar region. This reflects the built in molar offset.

The shape of dental arch that we should adopt as our treatment goal has long been a topic for lively discussion.

Particular archforms have been advocated on grounds of producing better intercuspal occlusion, better functional occlusion, better stability and better aesthetics.

Because differences in arch shape are so noticeable to the eye, it is important to have a more accurate idea of the extent to which differences in arch shape produce differences in arch dimension. Superimposing arches of different shape reveals that arch widths vary by less than might be guessed and that the differences are frequently in the premolar and not the canine region. Measurements on typodonts quantify the effects of various shapes on intercanine, interpremolar and intermolar widths.

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Tooth

1

2

3

4

5

6

Mean

-1.21

-0.88

-0.32

0.59

1.78

2.77

sd

1.24

1.07

1.63

1.28

1.10

0.89

Table 8.6: al 2008)

161

The mean difference and standard deviations between corresponding FA and WALA points in the mandible (n=70) (from Ronay et

The paper by Felton in 1987 investigated different archforms with regard to the natural occurrence of the various shapes in untreated malocclusions and the stability of the change of shape produced by the different archforms during treatment. No archform was the closest match for more than 20% of cases. Regarding stability, of the 65% that had a change of shape during treatment, 70% returned to the pre-treatment shape. Felton did not report whether this was associated with a return of dental irregularity, but the paper did support the concept of not expanding intercanine width and suggests that some customising of arch shape may produce more stable results.

Leaving aside archform, there is much evidence over many years to support the practice of not significantly altering arch widths during treatment, although almost all orthodontists do! Huntley (1990) has provided interesting additional evidence in his study of cases all treated with arches of the same size. Approximately half these cases had a significant increase in intercanine width. If preformed arches are left unaltered in size, they should therefore be purchased in different sizes.

Ricketts has developed an approach that combines variability in shape with variation in size. He felt that larger arches also tend to be of a different shape. A combination of three different shapes and smaller sizes of two of the shapes therefore comprise a “Pentamorphic” system. This is based on studies of ideal and stable treated occlusions and in particular on one study of only 40 patients. The basis for choosing an arch for a patient is not very clear. A “rough estimate can be made from gross facial form”, but analysis of lateral and frontal cephalometric radiographs by the Rocky Mountain Diagnostic Services is advocated as an “immense advantage”.

Robnett (1980) said that “A universal archform probably does not exist. Years of seeking such a form have resulted in limited improvements in orthodontic care, and yet the ideal form remains elusive.” Customising archform is therefore essential.

However, conebeam CT images show that the teeth are frequently not positioned over the apical bases but inclined lingually. This raises questions about whether in fact the arches can be expanded to reposition the teeth over the basal bone or whether the original arch shape reflects the size of underlying dent-alveolar arches. Ronay et al (2008) have investigated the relationship between the dental and basal archform using the FA points to represent the dental arch and the WALA points to represent the basal arch. The WALA points were described by Andrews and Andrews (2000) described the WALA ridge as the most prominent point on the soft-tissue ridge immediately occlusal to the mucogingival junction. It is located at or nearly at the same vertical level as the horizontal centre of rotation of each tooth.

Ronay et al (2008) found that the arch form derived from the WALA points was much broader in the premolar and molar regions and that all archforms were highly individual and could not be generalised by a single shape. There was significant correlation between the FA and WALA points particularly in the canine and molar regions and that the WALA points could be used to indicate basal archform.

40

mm

20

0 -40

-20

0 mm WALA points

20

40

FA points

Figure 8.12: Superimposition of the FA point and WALA curves for the lower arch (after Ronay et al 2008)

A questionnaire study carried out at Bristol Dental Hospital (McNamara et al 2009) to determine the choices made by clinicians with respect to archwires and arch form during the early and late stages of treatment with fixed appliances. Most clinicians felt that maintenance of the pretreatment arch form,

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ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

particularly intercanine width, was important in the later stages of treatment although it was not considered so important in the early stages of treatment when NiTi archwires were used. There was however no consistency as to how arch form should be measured or determined, and methodologies were used in different ways by different clinicians.

McNamara et al (2010) further reported that comparing the intercanine and intermolar width measurements on archwires fabricated on three sets of standardized typodonts models demonstrated differences in the mean values of each dimension, even though there were no differences on the models. In treated patients, large variations in intercanine and intermolar widths were also observed for both intraoperator and interoperator figures. Some clinicians contracted the intercanine and intermolar widths, others expanded them. Although most clinicians aimed to maintain pretreatment arch forms, this study showed that this was not often transferred to clinical practice

Archform and arch width Lee (1999) has given a good review of archform and arch width. This gives a good summary of conventional thought on the possibilities for obtaining stable arch expansion. It emphasises that arch expansion is likely to be more stable in the absence of extractions, the immutability of lower canine width, correction of class II arch relationships may result in some stable expansion and that arch expansion produces space of only 33% of the expansion in the posterior region.

References Andrews LF and Andrews WA (2000) The six elements of orofacial harmony Andrews Journal 1: 13-22 Badran SA, Orr JF, Stevenson M and Burden DJ (2003) Photo-elastic stress analysis of initial alignment archwires European Journal of Orthodontics 25: 117-125 Bartlett BW, Firestone AR, Vig KWL, Beck M and Marucha PT (2005) The influence of a structured telephone call on orthodontic pain and anxiety American Journal of Orthodontics and Dentofacial Orthopaedics 128: 435-441 BeGole EA (1980) Application of cubic spline function in the description of dental arch form Journal of Dental Research 59: 1549-1556 Berger JL (2008) The SPEED System: an overview of the appliance and clinical performance Seminars in Orthodontics 14: 54-62 Bishara SE, Winterbottom JM, Suleiman A-HA, Rim K and Jakobsen JR (1995) Comparisons of thermodynamic properties of three nickel titanium orthodontic archwires Angle Orthodontist 65: 117-122 Bolender Y, Vernière A, Rapin C and Filleul M-P (2010) Torsional superelasticity of NiTi archwires: myth or reality?

Angle Orthodontist 80: 1100-1109 Brader AC (1972) Dental arch form related with intraoral forces: PR = C American Journal of Orthodontics 61: 541-61 Bradley TG, Brantley WA and Culbertson BM (1996) Differential scanning calorimetry (DSC) analysis of superelastic and nonsuperelastic nickel-titanium orthodontic wires American Journal of Orthodontics and Dentofacial Orthopaedics 109: 589-597 Brantley WA, Iijima M and Grentzer TH (2003) Temperature-modulated DSC provides new insight about nickel titanium wire transformations American Journal of Orthodontics and Dentofacial Orthopaedics 124: 387-394 Braun S, Hnat WP, Fender DE and Legan HL (1998) The form of the human dental arch Angle Orthodontist 68: 29-36

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Eliades T and Bourauel C (2005) Intraoral aging of orthodontic materials: the picture we miss and its clinical relevance American Journal of Orthodontics and Dentofacial Orthopaedics 127: 403-12 Erdinç AM and Dincer B (2004) Perception of pain during orthodontic treatment with fixed appliances European Journal of Orthodontics 26: 79-85 Evans TJW and Durning P (1996a) Orthodontic Products Update British Journal of Orthodontics 23: 1-4 Evans TJW and Durning P (1996b) Orthodontic Products Update Aligning archwires, the shape of things to come? - A fourth and fifth phase of delivery British Journal of Orthodontics 23: 269-275 Evans TJW, Jones ML and Newcombe RG (1998) Clinical comparison and performance perspective of three aligning archwires American Journal of Orthodontics and Dentofacial Orthopaedics 114: 32-39 Felton JM, Sinclair PM, Jones DL and Alexander RG (1987) A computerised analysis of the shape and stability of mandibular archform American Journal of Orthodontics and Dentofacial Orthopaedics 92: 478-583 Ferrario VF, Sforza C, Miani A and Tartaglia G (1994) Mathematical definition of the shape of dental arches in the human permanent healthy dentitions European Journal of Orthodontics 16: 287-294 Filleul MP and Jordan l (1997) Torsional properties of Ni-Ti and Copper-Ni-Ti wires: the effect of temperature on physical properties European Journal of Orthodontics 19: 637-646 Gatto E, Matarese G, Di Bella G, Nucera R, Borsellino C and Cordasco G (2011) Load-deflection characteristics of superelastic and thermal nickel-titanium archwires European Journal of Orthodontics first published online October 23, 2011 doi:10.1093/ejo/cjr103 Accessed 23 January 2012 Gioka C and Eliades T (2004) Materials-induced variation in the torque expression of preadjusted appliances American Journal of Orthodontics and Dentofacial Orthopaedics 125: 332-338 Gurgel J de A, Herr S, Powers JM and LeCrone V (2001) Force-deflection characteristics of superelastic nickel titanium archwires American Journal of Orthodontics and Dentofacial Orthopaedics 120: 378-382 Hain M, Dhopatkar A and Rock P (2006) A comparison of different ligation methods on friction American Journal Orthodontics Dentofacial Orthopaedics 130: 666-670 Hawley CA (1905) Determination of the normal arch and its application to orthodontics Dental Cosmos 47: 541-557 Hilgers JJ (1999) Reverse curve TMA with T-loops http://www.ormco.com/index/ormco-education-video-reverse-curve-tma-with-t-loops Accessed: 12 February 2011 Hurst CL, Duncanson MG, Nanda RS and Angolkar PV (1990) An evaluation of the shape-memory phenomenon of nickel-titanium orthodontic wires American Journal of Orthodontics and Dentofacial Orthopaedics 98: 72-76 Huntley P (1990) The effects of preformed ‘ideal’ archwires upon arch dimensions British Journal of Orthodontics Research Report 16: 64 Jones ML (1984) An investigation into the initial discomfort caused by placement of an archwire European Journal of Orthodontics 6: 48-54 Jones ML and Richmond S (1989) An assessment of the fit of a parabolic curve to pre- and post-treatment dental arches British Journal of Orthodontics 16: 85-93

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Jones ML and Chan C (1992) The pain and discomfort experienced during orthodontic treatment: a randomised controlled trial of two initial aligning archwires American Journal of Orthodontics and Dentofacial Orthopaedics 102: 373-381 Khier SE, Brantley WA and Fournelle RA (1991) Bending properties of superelastic and nonsuperelastic nickel-titanium orthodontic wires American Journal of Orthodontics and Dentofacial Orthopaedics 99: 310-318 Knox J, Jones ML and Durning P (1994) An ideal preformed archwire?

British Journal of Orthodontics 20: 65-70 Kula K, Phillips C, Gibilaro A and Proffitt WR (1998) Effect of ion implantation of TMA archwires on the rate of orthodontic sliding space closure American Journal of Orthodontics and Dentofacial Orthopaedics 114:577-580 Kusy RP (1991) Nitinol alloys: so, who's on first? (Letter to the editor) American Journal of Orthodontics and Dentofacial Orthopaedics 100: 25A Kusy RP (1997) A review of contemporary archwires; their properties and characteristics Angle Orthodontist 67: 197-207 Laheurte P, Eberhardt A, Philippe MJ and Deblock L (2007) Improvement of pseudoelasticity and ductility of Beta III titanium alloy—application to orthodontic wires European Journal of Orthodontics 29: 8-13 (Open access article) Leavitt AH, King GJ, Ramsay DS and Jackson DL (2002) A longitudinal evaluation of pulpal pain during orthodontic tooth movement Orthodontics and Craniofacial Research 5: 29-37 Lee RT (1999) Arch width and form: a review American Journal of Orthodontics and Dentofacial Orthopaedics 115: 305-313 Lu KH (1966) An orthogonal analysis of the form, symmetry and asymmetry of the dental arch Archives of Oral Biology 11: 1057-1069 Mandall NA, Lowe C, Worthington HV, Sandler J, Derwent S, Abdi-Oskouei M and Ward S (2006) Which orthodontic archwire sequence? A randomized clinical trial European Journal of Orthodontics 28: 561–566 Matasa CG (1997) NiTi alloys; two metals in one The Orthodontic Materials Insider 10: 1; 2-7 McNamara C, Drage KJ, Sandy JR and Ireland AJ (2009) An evaluation of clinicians’ choices when selecting archwires European Journal of Orthodontics 32: 54-59 McNamara C, Sandy JR and Ireland AJ (2010) Effect of arch form on the fabrication of working archwires American Journal of Orthodontics and Dentofacial Orthopaedics 138: 257.e1-257.e8 Meling TR and Ødegaard J (1998a) The effect of temperature on the elastic responses to longitudinal torsion of rectangular nickel-titanium archwires Angle Orthodontist 68: 357-368 Meling TR and Ødegaard J (1998b) The effect of short-term temperature changes on the mechanical properties of rectangular nickel-titanium archwires tested in torsion Angle Orthodontist 68: 369-376 Meling TR and Ødegaard J (1998c) Short-term temperature changes influence the force exerted by superelastic nickel-titanium archwires activated in orthodontic bending American Journal of Orthodontics and Dentofacial Orthopaedics 114: 503-509 Miura F, Masakuni M, Ohura Y and Hamanaka H (1986) The super-elastic property of the Japanese NiTi alloy wire for use in orthodontics American Journal of Orthodontics and Dentofacial Orthopaedics 90: 1-10

ARCHWIRES AND ARCHWIRE TECHNOLOGY EXCELLENCE IN ORTHODONTICS 2012

Mizrahi E, Cleaton-Jones PE, Luyckx S and Fatti LP (1991) The effect of Ion implantation on the beaks of orthodontic pliers American Journal of Orthodontics and Dentofacial Orthopaedics 99: 513-519 Nakano H, Satoh K, Norris R, Jin T, Kamegai T, Ishikawa F and Katsura H (1999) Mechanical properties of several nickel-titanium alloy wires in three point bending tests American Journal of Orthodontics and Dentofacial Orthopaedics 115: 390-395 Ngan P, Kess B and Wilson S (1989) Perception of discomfort by patients undergoing orthodontic treatment American Journal of Orthodontics and Dentofacial Orthopaedics 96: 47-53 Ngan P, Wilson S, Shanfield J and Amini H (1994) The effect of ibuprofen on the level of discomfort in patients undergoing orthodontic treatment American Journal of Orthodontics and Dentofacial Orthopaedics 106: 88-95 O'Brien K, Lewis D, Shaw W and Coombe E (1990) A clinical trial of aligning archwires European Journal of Orthodontics 12: 380-384 Pandis N, Polychronopoulou A and Eliades T (2009) Alleviation of mandibular anterior crowding with copper-nickel-titanium vs nickel-titanium wires: A double-blind randomized control trial American Journal of Orthodontics and Dentofacial Orthopaedics 136: 152.e1-152.e7 Pepe SH (1975) Polynomial and catenary curve fits to human dental arches Journal of Dental Research 54: 1124-1132 Pringle AM, Petrie A, Cunningham SJ and McKnight M (2009) Prospective randomised clinical trial to compare pain levels associated with two orthodontic fixed bracket systems American Journal of Orthodontics and Dentofacial Orthopaedics 36: 160-167 Proffit WR (1986) Contemporary Orthodontics St Louis, The CV Mosby Company Ren C, Bai Y, Wang H, Zheng Y and Li S (2008) Phase transformation analysis of varied nickel-titanium orthodontic wires Chinese Medical Journal 121: 2060-2064 Ricketts RM (1979) Design of archform and details for bracket placement Distributed by Rocky Mountain Orthodontics Riley M and Bearn D (2008) A systematic review of clinical trials of aligning archwires Journal of Orthodontics 36: 42-51 Robnett JH (1980) Segment concept in arch pattern design American Journal of Orthodontics and Dentofacial Orthopaedics 77: 355-367 Ronay V, Miner RM, Will LA and Arai K (2008) Mandibular arch form: The relationship between dental and basal anatomy American Journal of Orthodontics and Dentofacial Orthopaedics â&#x20AC;¨134:430-438 Rucker BK and Kusy RP (2002a) Elastic flexural properties of multistranded stainless steel versus conventional nickel titanium archwires Angle Orthodontist 72: 302-309 Rucker BK and Kusy RP (2002b) Resistance to sliding of stainless steel multistranded archwires and comparison with single-stranded levelling wires American Journal of Orthodontics and Dentofacial Orthopaedics 122: 73-83 Rucker BK and Kusy RP (2002c) Elastic properties of alternative versus single stranded levelling archwires American Journal of Orthodontics and Dentofacial Orthopaedics 122: 528-541 Ryan R, Walker G, Freeman K and Cisneros GJ (1997) The effects of ion implantation on rate of tooth movement: an in vitro model American Journal of Orthodontics and Dentofacial Orthopaedics 112: 64-68

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Sampson PD (1981) Dental arch shape: a statistical analysis of arch shape using conic sections American Journal of Orthodontics 79: 535-548 Santoro M, Nicolay OF and Cangialosi TJ (2001a) Pseudoelasticity and thermoelasticity of nickel titanium alloys: a clinically oriented review. Part 1: Temperature transitional ranges American Journal of Orthodontics and Dentofacial Orthopaedics 119: 587-593 Santoro M, Nicolay OF and Cangialosi TJ (2001b) Pseudoelasticity and thermoelasticity of nickel titanium alloys: a clinically oriented review. Part 1: Deactivation forces American Journal of Orthodontics and Dentofacial Orthopaedics 119: 594-603 Santoro M and Beshers DB (2000) Nickel-titanium alloys: stress related temperature transitional range American Journal of Orthodontics and Dentofacial Orthopaedics 118: 685-692 Sebanc J, Brantley WA, Pincsak JJ, and Conover JP (1984) Variability of effective root torque as a function of edge bevel on orthodontic arch wires American Journal of Orthodontics 86: 43-51 Segner D and Ibe D (1995) Properties of superelastic wires and their relevance to orthodontic treatment European Journal of Orthodontics 17: 395-402 Sims A P T, Waters N E, Birnie D J and Pethybridge R J (1993) A comparison of the forces required to produce tooth movement in vitro using two self-ligating brackets and a preadjusted bracket employing two types of ligation European Journal of Orthodontics 15: 377-385 Tonner RIM and Waters NE (1994) The characteristics of superelastic Ni-Ti wires in three point bending. Part 1: The effect of temperature The characteristics of superelastic Ni-Ti wires in three point bending. Part 2: intra-batch variation European Journal of Orthodontics: 16: 409-419 and 421-425 Verstrynge A, Van Humbeeck J and Willems G (2006) In-vitro evaluation of the material characteristics of stainless steel and beta-titanium orthodontic wires American Journal of Orthodontics and Dentofacial Orthopaedics 130: 460-470 Waters NE (1992) Superelastic nickel titanium wires British Journal of Orthodontics 19: 319-322 West AE, Jones ML and Newcombe RG (1995) Multiflex versus superelastic: a randomised clinical trial of the tooth alignment ability of initial archwires American Journal of Orthodontics and Dentofacial Orthopaedics 108: 464-471 Weilland F (2003) Constant versus dissipating forces in orthodontics: the effect on initial tooth movement and root resorption European Journal of Orthodontics 25: 335-342 Zinelis S, Eliades T, Pandis N, Eliades G, Bourauel C (2007) Why do nickel-titanium archwires fracture intraorally? Fractographic analysis and failure mechanism of in-vivo fractured wires American Journal of Orthodontics and Dentofacial Orthopaedics 132: 84-89

Useful related references not referred to in this chapter Lu KH (1964) Analysis of dental arch symmetry (abstract) Journal of Dental Research 43: 780

ADVANCED PASSIVE SELF-LIGATION CASE SET-UP EXCELLENCE IN ORTHODONTICS 2012

Chapter

9

Advanced case set-up and the first four visits David Birnie

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Introduction The way a case is set up is both an extension of the diagnostic process and the start of the finishing process. It is therefore crucially important to get this part of treatment as right as possible in order to ensure a high quality result is obtained in the minimum amount of time. Much has changed in this arena in the last 18 to 24 months and this chapter reflects current thought.

Simultaneous or sequential mechanics?

Traditionally, orthodontic treatment has been done in a sequential fashion similar to the following stages:

• • • • •

alignment and derotation levelling and overbite reduction torque control and overjet reduction extraction space closure finishing

Sequential mechanics is predicated on most significant group tooth movement being done in ‘working’ archwires – normally stainless steel 0.019” x 0.025”. The problems of tooth control with conventionally ligated appliances means the early use of space opening, space closing or buccal segment correction mechanics is rare.

Secure ligation means that the above five stages can occur to a large extent simultaneously; the trick is to match the strength of any space opening mechanics (coil spring), space closing mechanics (power chain) or buccal segment correction mechanics (inter maxillary elastics) to the rigidity of the archwire so as not to over-power the archwire.

Initial treatment planning versus case management techniques All orthodontic treatments need a detailed initial treatment plan; this is derived from clinical observation and measurement, x-rays and cephalometric analysis, photographs and study models. Plans however do not always follow intentions – they may become off-plan. Case management techniques are the methods used to bring an off-plan initial orthodontic treatment plan back on plan. This follows the Plan, Do, Check, Adjust (PDCA) cycle originally described by Walter Shewart of Bell Laboratories and later popularised by Edward Deming. For orthodontic treatment, the cycle is like this and repeated until the end of treatment: Plan Do Check Adjust

initial treatment plan or plan for next visit execute plan (eg: change archwire, start elastics, etc) at next visit, read what changes have taken place react by changing mechanics or making other mechanics

This cycle is visit to visit case management; the key to efficient and effective orthodontic treatment is to ensure that visit to visit case management follows the overall plan without deviation, error or rework. Easy to say but difficult to do …!

Pitts 6-5-4-6 approach Tom Pitts has described an approach to the early stages of treatment which helps structure the decisions necessary to optimise the effect of early treatment mechanics. This approach is based on he sue of passive selfligation but it provides a useful structure for any type of appliance system. This includes:

• • •

six decisions that should be made at the start of treatment five aesthetic and five occlusal features which should be ‘read’ at each visit the fourth visit – photos, panoramic radiograph and repositioning appointment

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•

169

six aspects to focus on during finishing

Six decisions to be made at the start of treatment These are:

• • • • • •

bracket system and archwire progression tooth recontouring bracket position torque selection disarticulation strategy early elastics

Bracket system and archwire progression Clinicians should use the bracket system they are familiar with and which meets their patient’s preferences. Some bracket systems have less functionality than others; in general, metal brackets have most functionality (eg: auxiliary vertical and horizontal slots) but aesthetic brackets may be preferred by the patient.

Tooth recontouring Look carefully to see if any tooth reshaping is necessary. Very pointed upper canines may make it difficult to produce a final buccal segment relationship that has no intercuspal ‘black space’. Tooth reshaping may need to be done in two stages; once before the start of treatment and again when alignment has been achieved. Tooth reshaping may be subtractive or additive.

Subtractive tooth reshaping This involves reducing tooth structure. Pitts (2009) suggests that most upper canines require reshaping in order to reduce the height of their cusps and thus ensure a better finish by extruding the broader are of the labial face of the canine and thus allowing to fit together with the lower arch with less ‘black space’. Adjustment of the lateral incisors and the upper first premolars may also be necessary at this time. It is sensible to be fairly bold in adjusting the canine shape but less so with the other teeth; more tooth material can be removed at a later stage if necessary but not replaced. If reducing an incisal edge, bear in mind the effect of this on the width/height ratio of the incisor crowns (normally 80%, range 65% to 85%).

Additive tooth reshaping This can range from repair of a fractured incisor corner to building up a peg-shaped or diminutive tooth. There is no reason why the temporary build-up cannot be done by the orthodontist using a flowable restorative composite. For problems of tooth width, space will need to be made to allow the additional width to be added.

Diminutive lateral incisors are best positioned so that of the additional width to be added, one third is added mesially and two thirds distally; this generally provides the best anterior aesthetics.

It is suggested that gross adjustments of tooth shape are done at the start of treatment or as soon as tooth position will allow while minor tooth reshaping is done at the end of treatment to finalise and enhance the finish.

Bracket positioning Careful attention to bracket positioning can significantly affect tooth position. Pitts bracketing is preferred; for reduced overbites, brackets are placed more gingivally while for deeper overbites, brackets are place on the FA point. Bracket positioning is becoming individualised to each patient rather than using the same bracket positioning scheme (eg: FA point) all the time.

Pitts (2009) suggests more gingival positioning of brackets using a line through the mesio-distal contact point line as a guide.

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• plan using the maxillary canine and position the incisal tiewings on the mesio-distal contact point line with the bracket on the maximum contour of the tooth (usually just anterior to the FACC). The bracket therefore is positioned more gingivally and more anteriorly than is normal • the lateral incisor bracket is positioned 0.25 mm more gingivally and the central incisor bracket 0.5 mm more gingivally. Where incisors are rotated, consider positioning brackets towards the edge of the tooth most displaced from the arch to ensure full rotational correction • place the maxillary premolar brackets on the mesio-distal contact point line ensuring that the brackets are on the maximum height of the buccal surface contour Figure 9.1: The mesio-distal contact point line is used as a guide.

• the maxillary first molar is placed on The line of the brackets should progressively diverge towards the anterior the mesio-distal contact point line with buccal creating a wedge effect groove on the pad matching the buccal groove on the tooth; the maxillary second molar is similarly positioned but 1.5 mm occlusal to the mesiodistal contact point line.

This bracket positioning creates a wire plane which rises as it progresses anteriorly and provides the upper limb of the wedge effect. A cautionary note is the quality of the enamel is poorer close to the amelo-cemental junction and particular care should be taken in debonding.

Mandibular brackets and tubes follow a similar logic.

• •

•

again, key off the maxillary canine and position the incisal tiewings on the mesio-distal contact point line with the bracket on the maximum contour of the tooth (usually just anterior to the FACC).

The bracket therefore is positioned more gingivally and more anteriorly than is normal for the mandibular incisors, place the bracket parallel to the long axis of the crown with the incisal tie-wings on the mesio-distal contact line. For anterior open bites place both maxillary and mandibular incisor brackets approximately 1.5 more gingivally and for deep bites cases, place the brackets approximately 1.5 mm more incisally. For patients with open bites, it often helps to leave some curve of Spee. for mandibular premolars, place the bracket parallel to the long axis of the tooth and 0.5 mm gingival to the mesio-distal contact point line

for the maxillary molars, position the buccal groove of the molar tube over the buccal groove of the tooth and place the occlusal edge of the bracket molar pads 0.5 mm gingivally to the mesio-distal contact point line. Unlike in the maxilla, both first and second molar tubes have the same vertical positioning in the mandible.

Torque selection The concept of selective torques is not new however their selection and use has become increasingly refined (see Thomas 2009). It is helpful to think about:

• • •

what is the inclination of the teeth now? what inclination do the teeth need to be at the end of treatment? what will happen to the inclination of the teeth during treatment?

ADVANCED PASSIVE SELF-LIGATION CASE SET-UP EXCELLENCE IN ORTHODONTICS 2012

• • •

171

o in deciding this, consider what would happen if you treated the case with round wires only will the natural changes that occur during treatment help or hinder your inclination goal? o remember that in extraction cases, teeth tend to detorque both in the labial and buccal segments as a consequence of the arch becoming shorter what effect will play between the archwire and the bracket slot have? Will it help or prevent achievement of the final tooth position?

What effect will your mechanics have (eg: class 2 elastics will tend to retrocline the upper anterior teeth

This then allows selection of the most appropriate torques to achieve the treatment goal. As an example, nonextraction class 2 division ii cases often undergo significant inclination change as a result of tooth tipping and therefore often do not require upper incisor brackets with significant positive torque. In addition, the same tooth on the contralateral side of the mouth may require a bracket with different inclination characteristics.

While preadjusted brackets have previously been referred to as high and low torque brackets, there is now a move to rename them positive and negative torque brackets reflecting their ability to increase (positive) or decrease (negative) inclination.

Maxilla Positive Standard Negative Mandible Positive Standard Negative Table 9.1:

1 DQ +22º +15º +2º 1 and 2 DQ -3º -11º

2 DQ +13º +6º -5º 3 DQ +13º +7º 0º

3 DQ +11º +7º -9º 4 DQ -5º -12º

4 and 5 DQ

6 SL

7 Ti

-11º

-18º

-27º

5 DQ

6 SL

7 Ti

-17º

-28º

-10º

Selective torques for Damon Q brackets

Methods of applying torque are as follows:

• • • • • •

selective torques inverting brackets semi-customised selective torques (non standard application of selective torques) bending torque in the wire o manually o SET (superelastic torqued) archwires torquing auxiliary fully customised appliance (Insignia, Incognito)

Disarticulation strategy Disarticulation is a key part of the early stages of treatment and can be applied anteriorly or posteriorly. It can be used to protect or develop incisor display or smile arcs.

•

anterior disarticulation is used in patients with low facial heights, deep overbites and where the exposure of the upper incisors is not to be reduced. In conjunction with early elastics, it allows extrusion of the posterior buccal segments. Anterior disarticulation is achieved using anterior bite turbos (ramps); the preferred material for these is Dentsply Triad Gel which is VLS (visible light cure) flowable acrylic material available in four shades (colourless, pink, red and blue). OrthoArch Mini Molds are used to shape the material prior to placement; it is possible to use composite adhesive but this is not recommended where teeth in the opposing arch contact the ramps as the filler can cause tooth abrasion. The Triad Gel is much softer and will not damage opposing teeth. The ramps

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Figure 9.2: The OrthoArch Mini Mold set; the most commonly used components are the ramp. the pad and the button

can be placed on upper central incisors, upper lateral incisors or upper canines if the patient has a significant incisal overjet • anterior disarticulation can be used in class 3 cases to aid correction of a class 3 incisor relationship. In these cases, the turbos are placed behind the lower incisors.

• posterior disarticulation is used where it is not desired to increase lower facial height but to maintain or reduce it. This applies to cases with anterior open bites and some crossbite cases. Use Mini Molds again but use the molar pad instead of the turbo. The pads should be placed on the mesio-palatal cusps of the upper first and second molars and the pads equilibrated to ensure and even contact. In anterior open bite cases, the patient should be given clenching exercises to try and achieve posterior intrusion and to strengthen the masticatory muscles; the effectiveness of these exercises is uncertain but at worst will simply make no difference.

The other Mini Mold that is commonly used is the lingual button; composite is best used for this as there is no opposing tooth contact and the Triad Gel is too liquid to reliably fill the more complex mould.

Early elastics Disarticulation allows the opportunity to use early elastics to effect vertical and antero-posterior changes in the occlusion free from resistance to movement that occurs from interdigitation. In deciding how elastics should be used, the following factors should be taken into account:

• • • •

the size and material of archwire being used the size and strength of the elastics the direction of pull of the elastics or their wear pattern how long the elastics should be worn each day the presence and location of bite ramps or pads Much of the development of these concepts has come from Tom Pitts, Stuart Frost and Jeff Kozlowski.

Early archwires are very light and the elastic force needs to be matched to these so as not to overpower them.

Initial elastics are therefore 2 oz.

Light

Medium

Medium/heavy

Heavy

Extra heavy

2 oz/60g

3 oz/85g

4 oz/100g

5 oz/130g

6 oz/170g

3/16”

Quail

Otter

Rabbit

Kangaroo

Impala

1/4"

Owl

Seal

Fox

Bear

Ram

5/16”

Parrot

Dolphin

Penguin

Zebra

Moose

Table 9.2: Intraoral elastic sizes and strengths commonly used in orthodontics. The names of the elastics are those used by Ormco but the table can be repopulated to cover other manufacturer’s ranges

For example the protocol for a class 2 deep bite case would be as follows:

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Wire

Elastic size

Elastic pattern

Duration

Disclusion

0.014” CuNiTi

Quail 3/16” 2 oz

Short class 2 L6-U4

Fulltime

Anterior ramps

0.018” CuNiTi

Quail 3/16” 2 oz

Short class 2 L6-U4

Fulltime

Anterior ramps

0.014” x 0.025” CuNiTi

Quail 3/16” 2 oz

Short class 2 L6-U4

Fulltime

Anterior ramps (Add to ramps as required)

0.018” x 0.025” CuNiTi

Parrot 5/16” 2 oz

Class 2 Reverse V L6-U3-L4

Correct to edge-to edge and hold for 3 months; then night times only

Progressively reduce ramps as overbite is controlled

0.019” x 0.025” SS

Kangaroo 3/16” 5 oz Impala 3/16” 6 oz

Full class 2 L6-hook on upper archwire

Full time if still class 2

Remove ramps

For a class 1 open bite, the protocol would be as follows: Wire

Elastic size

Elastic pattern

Duration

Disclusion

0.014” CuNiTi

Parrot 5/16” 2 oz

Rainbow LR2-UR1-UL1-LL2

Fulltime

Posterior pads and muscle exercises

0.018” CuNiTi

Parrot 5/16” 2 oz

Rainbow LR2-UR1-UL1-LL2

Fulltime

Posterior pads and muscle exercises

0.014” x 0.025” CuNiTi

Parrot 5/16” 2 oz

Rainbow LR2-UR1-UL1-LL2

Fulltime

Posterior pads and muscle exercises

0.018” x 0.025” CuNiTi

Dolphin 5/16” 3 oz or Parrot 5/16” 2 oz

Rainbow LR3-UR1-UL1-LL3

Fulltime if bite still open Correct to normal overbite and hold for 3 months; then night times only

Progressively reduce pads as overbite is reduces but continue muscle exercises

Dolphin 5/16” 3 oz or Parrot 5/16” 2 oz

Rainbow Lower R hook-UR1-UL1Lower L hook

Fulltime as required Correct to normal overbite and hold for 3 months; then night times only

Remove pads but continue muscle exercises

0.019” x 0.025” SS 0.017” x 0.025” TMA when corrected

Elastic patterns • full class 2 • • • • • • • •

o from lower first or second molar to hook on upper archwire full class 3 o from upper first or second molar to hook on lower archwire short class 2 o from lower first molar to upper first premolar or o from lower second premolar to upper canine short class 3 o from upper first molar to lower first premolar or o from upper second premolar to lower canine class 2 reverse V o from lower first molar to upper canine to lower first premolar class 3 reverse V o from upper first molar to lower canine to upper first premolar rainbow o from lower right lateral incisor to upper right central incisor to upper left central incisor to lower left lateral incisor reverse rainbow (for class 3 cases) o from upper right lateral incisor to lower right central incisor to lower left central incisor to upper left lateral incisor posterior cross elastics o as required but may involve multiple teeth; apply to all teeth in crossbite

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• •

o can combine with a class 2 or class 3 component canine V o from lower first premolar to upper canine to lower canine posterior V o from upper first molar to lower first premolar to upper archwire hook

In general, use 2 oz elastics on round CuNiTi wires, 4 oz elastics on rectangular CuNiTi and 6 oz elastics on stainless steel or TMA.

Developing a bonding plan The six decisions above constitute the bonding plan. The bonding plan is best developed from careful clinical observation, digital photographs, radiographs and study models if available.

Torque selection for anterior brackets should be done prior to bonding.

Five aesthetic features to check before Appointment 4 • • • • •

smile arc development buccal corridors gingival display changes incisor axial inclination canine and buccal segment axial inclination

Five occlusal features to check before Appointment 4 • • • • •

bracket height and alignment levelling and overbite correction antero-posterior correction transverse development arch coordination and interdigitation

Appointment 4 - photo/pan/repo appointment About four weeks after placement of the 0.018” x 0.025” archwire, schedule a bracket repositioning appointment with a new orthopantomogram (may not be necessary) and some up to date digital photographs of the occlusion.

Use this appointment to review torque selection as well as first and second order bracket position. In addition, review need for further tooth reshaping. This represents the end of the first stage of finishing.

Six features to finish • • • • • •

check CR=CO check full correction achieved check interdigitation and arch coordination final adjustment of tooth shape and size gingival shape adjustment finishing elastics required?

Myofunctional therapy The forces that move teeth can either come from:

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• • •

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the archwires elastics the muscles (lips, cheeks, tongue, masticatory, respiratory)

While there is a wealth of information about archwires, and to a lesser extent about elastics, much less seems to be written about the effect of muscles although orthodontists routinely harness their effects through the use of functional appliances. The influence of muscles plays a significant role in the aetiology and treatment of anterior open bites. Soft tissues are difficult to analyse, difficult to treat and difficult to monitor during treatment and myofunctional therapy is often seen as a fringe or alternative therapy by mainstream orthodontics. It is a poorly researched and understood field where measurement and compliance are difficult and success is variable.

Nevertheless, it is perhaps worth revisiting.

However, Etsuko Kondo’s book, Muscle Wins! Treatment in Clinical Orthodontics is worth diligent study. It focuses on the ‘functional recovery of abnormal tongue, perioral muscle, chewing and cervical muscle activities, as well as respiration, in correcting malocclusion’. In the paper by Kondo and Aoba (2000), two cases are presented, successfully treated by myofunctional therapy and orthodontics, which many orthodontists would believe are only manageable by orthognathic surgery.

Nasal respiration The importance of nasal respiration for the proper development of the lower face has been commented on. The effects of nasal restriction and therefore a change to oral breathing have been suggested as underdevelopment of the maxilla in the transverse and sagittal planes as well as an increase in lower facial height.

Yoga exercises can be used to help patients change to oral respiration. The subject should be either lying down or sitting and should inhale and exhale deeply and regularly using nasal respiration; the ratio of the time spent in inhalation and exhalation should be 1:2. Starting off with a minimum inhalation time of four seconds, this can be built up to an inhalation time of 16 seconds in adults. Once this has been mastered, a retention phase can be added; the ratios now become 1 (inhale): hold breath (4): exhale (2) – so for a 4 second inhale, retention is 16 seconds and exhalation 8 seconds.

Tongue thrusts

Alexander (1999) has described a simple series of exercises can be taught to patients with a tongue thrust.

The first stage is to position the tongue in the palate so that it is just about to produce a “click.” This position can is used as a reference to the proper tongue position when the patient swallows. The tongue is then held in this position and the tip of the tongue forced upwards. This retrains the tongue muscles and should be done in sets of 10, three times a day. Etsuko Kondo has described a similar exercise where patients are asked to flatten chewing gum into the vault of the palate.

The second exercise is called the “3-S’s”: slurp, squeeze, and swallow. The patient is asked to collect saliva, which is the slurp; bring the teeth together and activate muscles of closure, the squeeze; and lastly, with the tongue in the click position, the patient swallows. It is suggested that molar pads are fitted to the first and second molars when using the squeeze exercise.

Huang et al (1990) have demonstrated the effectiveness of tongue spurs in controlling tongue thrusts and hence closing anterior open bites. This has a small sample but those that were treated had a positive success rate which was maintained at least one year after appliance removal. We have tried tongue cribs and there is no doubt that they work but:

• • •

not all patients find them comfortable they require the use of molar bands at a time when most cases are fully bonded if myofunctional therapy was as effective, then this would be the preferred method of treatment

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Ortho Technologyâ&#x20AC;&#x2122;s Tongue Tamers (McRae EJ 2010) are a neat bondable solution to tongue spurs and eliminate the need for molar bands.

Summary There is a lack of both reliable clinical anecdote and research in this area. At the moment, success may be achieved but we are never quite sure why, nor are we able to predict in which patients it may occur. Nevertheless it shows promise which is worth further investigation regardless of how difficult that may be. It may that we need to determine what intervention, in what circumstances, produces a successful outcome.

References Alexander CD (1999) Open bite, dental alveolar protrusion, Class I malocclusion: A successful treatment result American Journal of Orthodontics and Dentofacial Orthopaedics 116: 494-500 Huang GJ, Roberto Justus R, Kennedy DB, and Kokich VG (1990) Stability of anterior openbite treated with crib therapy The Angle Orthodontist 60: 17-24 Kondo, E (2008) Muscle Wins! Treatment in Clinical Orthodontics Seoul, DaehanNarae Publishing Inc Available from www.musclewins.com Kondo E and Aoba TJ (2000) Nonsurgical and nonextraction treatment of skeletal Class III open bite: its long-term stability American Journal of Orthodontics and Dentofacial Orthopaedics 117: 267-287 Kozlowski J (2008) Honing Damon System mechanics for the ultimate in efficiency and excellence Clinical Impressions 16: 24-28 Downloaded from http://www.ormco.com/index/ormco-education-clinical-impressions Accessed 21 January 2012 McRae EJ (2010) Bondable lingual tongue spurs to treat anterior open bite Master's Theses (2009 -). Paper 25. http://epublications.marquette.edu/theses_open/25 Accessed 21 January 2012 Pitts TR (2009) Begin with the end in mind: bracket placement and early elastics protocols for smile arc protection Clinical Impressions 17: 4-15 Downloaded from http://www.ormco.com/index/ormco-education-clinical-impressions Accessed 21 January 2012 Thomas WW (2009) Variable torque for optimum inclination Clinical Impressions 17: 21-29 Downloaded from http://www.ormco.com/index/ormco-education-clinical-impressions Accessed 21 January 2012

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Chapter

177

10 The development of preadjusted appliance systems David Birnie

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Introduction The development of appliances is subject to the following pressures:

• • • •

•

health and safety concerns o cross infection control o allergy/toxicity concerns by the public a recognition of biological variability and hence the inappropriateness of a single prescription for all malocclusions limitations of existing appliances and orthodontist’s wish for greater sophistication patient preference for inconspicuous appliances o miniaturisation o aesthetic brackets o lingual appliances downward pressure on o manufacturing costs by manufacturer and specialty o treatment costs by patient

Health and safety Cross infection control Puncture injuries are possible from:

• •

the tails of wire ligatures the use of an explorer to remove elastomeric ligatures

Allergy and toxicity

Orthodontists have assumed that orthodontics treatment is safe and that brackets, wires and adhesives do not cause cancer or birth defects. Fifteen years ago, the State of California passed Proposition 65, the Safe Drinking Water and Toxic Enforcement Act (Turpin 2001). The Governor of California must publish a list of chemicals known to cause cancer, birth defects and other reproductive harm; this list includes nickel, nickel compounds and chromium. The California Dental Association recommended that dental offices display the following: Warning: Restorative materials such as composite and amalgam fillings, crowns, orthodontic appliances such as brackets and wires, and other materials used in dental treatment contain chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.

Concern about nickel sensitivity therefore intensifies; it is known that atoms from materials within body tissues or body cavities can redistribute themselves into the body tissues. Nickel is the most common contact allergen in women and nickel hypersensitivity has an increasing prevalence. Fortunately, nickel sensitivity is significantly more difficult to develop across mucosa than skin and so many patients who are sensitive to nickel on their skin can wear orthodontic appliances without difficulty (Kerosuo et al 1995). Nickel allergy is more common in girls (30%) than in boys (3%) and in adolescents with pierced ears (31%) than those without ear piercing (2%).

Orthodontic treatment does not appear to increase the risk of nickel sensitisation (Kerosuo et al 1996, Janson et al 1998). The German Bundesgesundheitsamt has made recommendations against the use of nickel containing steels in orthodontics and consequently many German manufacturers now produce nickel-free brackets and archwires. Hence, stainless steel alloys such as Remanium and Noninium have been produced which have only tiny proportions of nickel (less than 0.2%) (Matasa 1995).

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14

179

12

12

10

Mg of nickel in saline

10

% of nickel

8 6 4 2

8

6

4

2

0 316L

Figure 10.1:

305

302

PH 17-7

SAF 2205

PH 17-4 Cr-Co

Nickel content of bracket alloys

Ni-Free

Ti

0 NiTi wire

Bracket

Molar band

Headgear

Figure 10.2: Nickel release from orthodontic components after 14 days in saline (from Grimsdottir et al 1992)

Low nickel stainless steels are manufactured by adding either cobalt or manganese. The percentage of nickel in various alloys is shown in the Figure 10.1. Nickel release, however, is not proportional to the nickel content of the alloy but to the nature of the alloy itself.

In an effort to circumvent this problem, Dentaurum and Ormco have produced titanium brackets, and other manufacturers such as TP, cobalt chromium brackets. It was thought that one of the problems with titanium might be that it has a high coefficient in sliding due to galling and fretting. Kusy et al (1998) have compared the coefficients of friction with titanium and stainless steel brackets against beta-titanium, nickel-titanium and stainless steel archwires concluding that the frictional characteristics of titanium and stainless steel brackets are similar in the passive configuration. This result is surprising and due to the surface chemistry of the two alloys.

Both titanium and stainless steel form oxide layers on their surface which facilitate sliding. A more detailed discussion of the differences between stainless steel and titanium is given later in this chapter.

TP Orthodontics has produced a bracket made of cobalt chromium (ASTM F-75, Cast Cr-Co-Mb alloy for surgical implant applications). This is reported in a Technical Brief (1997) available from the TP website.

3M/Unitek have challenged Proposition 65 in respect of its intraoral metal orthodontic products and obtained a successful resolution in that the Court deemed that the amount of chemicals released intraorally was not sufficient for disclosure under Proposition 65.

Grimsdottir et al (1992) studied the release of nickel from various orthodontic components left in saline for fourteen days and the results are shown in Figure 10.2. Despite the high content of nickel (up to 50%) of nickel in nickel titanium archwires, no nickel release takes place. This is probably due to the highly corrosive nature of titanium which binds extensively to nickel preventing its release. In addition, archwires are subject to extensive cold working which again inhibits corrosion release.

Rahilly and Price (2003) provide an excellent review article of nickel allergy and alternatives for use in patients with nickel allergy.

Nickel sensitivity is usually tested for by using a cutaneous sensitivity (patch) test of 5% nickel sulphate in a petroleum jelly substrate. Results are read after 2 to 3 days. Marigo et al (2003) described the development of an in vitro cell proliferation assay for testing for the presence of nickel antigen. Exposure to nickel castings for more than 24 months resulted in lower levels of cell proliferation suggesting that the response might be modulated by the development of tolerance. Nickel sensitive patients demonstrated a type 2 immune response and a lack of type 1 immunity (interferon Îł).

In summary, the issue of nickel sensitivity is not a significant one in healthcare terms although a very, very small proportion of patients will have a sensitivity to nickel that affects treatment. Against this background is a political debate which probably has insignificant merit in healthcare terms.

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Bracket materials and manufacture Stainless steel For most orthodontic patients, appliances continue to be made from stainless steel but as Bob Dylan said “The times they are a’changin”. Concern about nickel sensitivity as exemplified by California’s Proposition 65 has prompted exploration of alternative bracket materials as discussed in the previous section.

The design specifications that Andrews required in the Straight-Wire Appliance originally necessitated the use of a cast bracket – a labour-intensive, costly and by today’s standards an inaccurate method of bracket manufacture.

In its time, it was a revolutionary step forward from the drawn and milled bracket.

The manufacture of stainless steel brackets Cast stainless steel is rather softer than cold drawn and milled stainless steel as shown in Table 10.1.

Fully Softened Yield Strength

A comparison of the hardness of a cold drawn and milled edgewise bracket, a standard pattern StraightWire Appliance bracket and an Attract bracket is also given in the same Table 10.1.

Cold Worked

240-300

700-800

170-200

300-350

(MPA) Hardness (VPN)

An interesting review of direct bonding metallic brackets is given by Matasa (1992). The Straight-Wire appliance is now used by 71.6% of American Table 10.1: Properties of stainless steel and bracket hardness orthodontists and 17-20% of the brackets received by Orthocycle in 1987-89 were made by “A” Company.

Brackets are made from austenitic stainless steel in classes 303, 304, 316 and 317 of the AISI (American Iron and Steel Institute). As the number increases, more alloying metals are added to the iron and the carbon content is lowered. The addition of the letter L shows a further reduction in carbon content. Steels with lower AISI numbers are soft, easy to mill but have low corrosion resistance. AISI 316L steel is considered too hard to be milled. In “Phoenix Without Ashes”, the house magazine of Orthocycle, “A” Company brackets (standard, Attract and MiniTwin) demonstrated the lowest corrosion rates.

SWA

VDMH

229±18

Attract

251±22

Cold drawn

290±26

Milling is too expensive and prone to human error although the Unitek Dynalok bracket was a milled one-piece bracket and was a rather clever piece of engineering. There are clear advantages in making a one-piece bracket and this becomes feasible with the use of casting, sintering and metal injection moulding. Sintering is the partial welding of metal powders below their melting point while metal injection moulding uses other additives (lubricants, thermopolymers, etc.). Thus the moulds have to be larger than the finished product and require considerable skill in their design. The resulting brackets are however more accurate and homogeneous and have high corrosion resistance.

Flores et al (1994) provide further information in a study on bracket deformation. They concluded that brackets made out of 17-4 PH (precipitation hardened) (“A” Company MiniTwin) and 303S (“A” Company Regular Twin and Attract) stainless steels, were best for orthodontic use with the former steel being significantly stronger. The greatest effect in relation to bracket deformation was stainless steel type and regular twin brackets generally had the highest resistance to deformation. As slot torque increased so brackets deformed with less force.

The Tru Straight-Wire bracket is made from 17-4 PH steel and is metal injection moulded (MIM). The market will be increasingly dominated by metal injection moulded brackets because:

• • •

they offer more accurate bracket manufacture the manufacturing process is cheaper MIM brackets have less frictional resistance between bracket and archwire

Vaughan et al (1995) have shown that the use of sintered brackets can reduce frictional resistance by 40% to 45%.

This is supported by an interesting paper by Ogata et al (1996) which looks at the effect of vertical deflection on

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the frictional resistance of cast and sintered brackets. The bracket types tested include conventional edgewise designs, friction-free (but not self-ligating) edgewise designs and TP Tip-Edge brackets.

Retention of brackets Pad size MacColl et al (1998) looked at the relationship between bond strength and pad size with both microetched and conventional bases. There was no difference in shear bond strength for pads between 6.82 mm2 and 12.35 mm2 in size; a pad of 2.38 mm2 Pad surface design Bracket bases are designed in one of three ways to provide adequate retention:

• • •

a mesh particles adhered to the bracket base (spheres, rods or similar) grooves or undercuts placed in the surface of the base (Unitek 3M Dynalok brackets) Secondary surface enhancements

Secondary surface enhancements may be used to:

• • •

increase bond strength create a uniform bond strength between bracket bases of different materials and different sizes allow the use of a single bonding material for all bracket types irrespective of which material they are manufactured from

These secondary surface enhancements may be:

• • •

surface roughening through ion bombardment or other etching processes flame spray coating of particles on the primary retention surface deposition of a chemically activatable material (such as SiO) on the primary retention surface

MacColl et al (1998) showed no difference in shear bond strength between a manufacturer-applied microetching process (grit blasting) and sandblasting in the surgery with a Danville Engineering sandblaster.

Optimesh XRT increases bond strength through a thermal spraying process probably involving initial etching with argon ion bombardment and subsequent deposition of a 2 micron layer of 316 alloy which is then sintered to improve adhesion of the powder. It results in an increase in bond strength of approximately 35% compared with a 100 x 100 stainless steel mesh base.

Cobalt chromium A detailed exposition on a cobalt chromium bracket is given on the technical papers section of TP Orthodontics’ website by Devanathan and Chudzynski (1997). The driver for the production of this bracket has been the issue of nickel sensitivity; however, cobalt and chromium are still far from inert in terms of their performance as implants or explants. Cobalt chromium brackets contain about 0.5% nickel compared with 4% for PH 17-4 stainless steel and 12% for 316L stainless steel. Atomic absorption spectroscopy shows that the release of nickel from a cobalt chromium bracket is 0.02% mg/l compared with 0.3% mg/l for a stainless steel bracket. In addition, cobalt chromium is harder than stainless steel (Rockwell hardness of 35 against 30 for 316 SS). This suggests that cobalt chromium brackets may have less friction than stainless steel brackets.

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Titanium

Titanium brackets are manufactured by Dentaurum (Rematitan) and SDS Ormco/A Company. (Titanium Orthos 2 or TO2). Commercially pure titanium (cp Ti) is the most passive metal available for implants and explants and so is worth considering for bracket manufacture. The disadvantage of titanium is that although it is covered by a passive layer of titanium dioxide or rutile, it is subject to galling and fretting if this oxide layer breaks down because of the inherent softness of titanium. This softness is the reason that titanium alloys usually have a matt finish – it is extremely difficult to produce a high polish on a soft material. An excellent review of titanium as a bracket material is given by Kusy et al (1998). Some concerns have been expressed about the potentially corrosive effects of fluoride toothpastes on titanium because of their low pH; Harzer et al (2001) showed that minor pitting and corrosion can be seen on titanium brackets exposed to acidic fluoride containing toothpastes but that this is not likely to affect their clinical performance during the average orthodontic treatment time.

The composition of titanium brackets Titanium is covered with a thin passive surface layer of titanium dioxide called rutile. The typical composition of titanium brackets and rutile is as shown in Table 10.2.

The passive oxide layer of rutile has the following composition as determined by electron spectroscopy for chemical analysis (ESCA) (Kusy et al 1998). The rutile layer is extremely thin (200Å - 300Å thick) but is extremely hard and durable. The high percentage of hydrocarbons and the lack of titanium in the surface layer suggest an organic or even polymer like surface according to Kusy et al (1998).

Kapur et al (1999b) showed that titanium brackets demonstrated superior dimensional stability to stainless steel brackets and delivered higher forces at 15° and 30° of torque; titanium delivered less force at 45° and this finding was interpreted as meaning that the titanium brackets were more reactive and therefore delivered the force over a longer period of time.

Dentaurum Rematitan brackets are machined and the retentive base pads produced by laser treatment. Titanium Orthos 2 brackets use 6-4 titanium for the bracket (similar to 17-4 PH stainless steel) and cp Ti for the bracket pad (similar to 316 stainless steel which is commonly used for stainless steel bracket bases. 6-4 titanium is alloyed with aluminium to improve its physical properties.

Titanium brackets have a matt grey appearance and this reflects their surface texture which is measured as optical RMS roughness (σo,a). Typical values for brackets and archwires are shown in Table 10.3.

This (perhaps) raises the question as to whether titanium brackets might perhaps retain more plaque (Harzer et al 2001).

Titanium bracket Rutile Carbon

0.05%

42.0%

Fluorine

0.0%

2.3%

Hydrogen

0.06%

0.0%

Iron

0.30%

0.0%

Nitrogen

0.35%

1.5%

Oxygen

0.35%

40.1%

Titanium

98.98%

14.1%

Table 10.2:

Typical composition of titanium brackets and rutile Brackets

Stainless steel

0.19 μm

Titanium

0.32 μm

Archwires 0.06 μm

Chromium cobalt

0.20 μm

β -titanium

0.22 μm

Nickel titanium

0.32 μm

Table 10.3: Optical RMS roughness of titanium and stainless steel brackets and archwires.

In addition, cp Ti shows 60% greater wetability than 316 stainless steel with acrylic based adhesives suggesting that bond strength may be improved with titanium brackets.

The tribology of titanium brackets Tribology is the study of friction and lubricants.

Kusy’s study of titanium in the passive configuration (Kusy et al 1998) and in the active configuration (Kusy and O’Grady 2000) showed that:

• stainless steel and titanium have similar static and dynamic frictional coefficients (μs and μk) in active and passive configurations • stainless steel couples generate less frictional force than nickel titanium and β– titanium couples respectively. β–titanium

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183

performs worst of all archwire alloys regardless of bracket type the passive surface layer (rutile) does not break down as force or angulation increases in wet conditions, titanium displays a slight adhesive effect binding is comparable for all couples tested titanium brackets are a suitable substitute for stainless steel brackets Titanium

Stainless steel

μs

μk

μs

μk

0.018” x 0.022”

92.6

124.4

66.9

101.6

0.018” x 0.025”

59.2

76.9

27.0

34.6

0.021” x 0.025”

35.2

87.1

162.0

216.4

Table 10.4: Static and dynamic frictional characteristics of stainless steel and titanium brackets with stainless steel archwires (from Kapur et al 1999a)

Kapur et al (1999a) had slightly different findings in that they found that titanium brackets performed better than stainless steel as archwire size increased. Differing results were found by Michelberger et al (2000). This study used a rather different design where a single surface contact was established between an archwire and bracket material and attempted to measure dynamic friction; this study did not, however, use the model

of drawing an archwire through an arch wire slot.

In summary, the balance of evidence suggests that titanium performs in a similar manner to stainless steel and in terms of friction is a suitable alternative material for bracket manufacture.

Aesthetic brackets The appearance of fixed orthodontic appliances has always been of particular concern to many patients. The development of appliances, which would combine both acceptable aesthetics for the patient and adequate technical performance for the orthodontist, has remained an elusive goal. Three methods of achieving these criteria have been attempted:

• • •

altering the appearance of or reducing the size of stainless steel brackets repositioning the appliance on to the lingual surfaces of the teeth changing the material from which brackets are made.

Early attempts to coat metal brackets with a tooth coloured coating were unsuccessful due to failure of the coating to adhere and to its poor translucence. There has recently been a firm trend towards the development of smaller stainless steel brackets but although these generally provide the technical performance required by the orthodontist, they offer a worthwhile but necessarily limited aesthetic advantage over conventionally sized appliances.

Modern aesthetic brackets are made of:

• •

•

resin o polycarbonate o polyurethane hybrids of resin and o ceramic o glass o glass fibre o metal o any combination of the above ceramic o polycrystalline alumina o monocrystalline alumina

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Early attempts to produce brackets of different materials included the use of polycarbonate. These brackets, while aesthetically satisfactory in the early stages of treatment, deteriorated in appearance with time and were insufficiently strong to withstand long treatments or transmit torque.

Ceramic, fibreglass and metal reinforced resin brackets More recently, ceramic, fibreglass, metal and ceramic and metal reinforced resin brackets have become available and while these are more durable than polycarbonate brackets, their ability to maintain their integrity over long treatments remains suspect. Their performance is however significantly better than polycarbonate brackets. The ceramic, fibreglass and metal reinforcement enhances the brackets ability to transmit torque by increasing its stiffness.

The performance of these brackets continues to improve and they probably have the potential to challenge ceramic brackets with further development. Nevertheless, their performance currently is below that of metal or ceramic brackets because of the flexibility of the resin component of the bracket. Harzer et al (2004) compared the ability of the Forestadent mini-Mono bracket, the Forestadent Brilliant bracket (a homogeneous polyoxymethylene bracket) and the Dentaurum Elegance bracket (a polycarbonate bracket with a metal slot to improve torque transmission) in a laboratory experiment. This showed that the metal bracket achieved the highest torque moments and was considerably more effective than both polycarbonate brackets. The Forestadent Brilliant bracket was the least effective at torque transmission and the Dentaurum Elegance bracket performed between the two but closer to the Forestadent Brilliance bracket.

Eliades et al (2004) tested the hardness of resin brackets (Dentaurum Brilliant, Forestadent Align, Leone and American Orthodontics Silicon) in vitro and in vivo. There was no difference between the as received state and the in vitro aging. However, in vivo, the polycarbonate brackets showed a significant reduction in hardness due to intra-oral aging factors such as fatigue, abrasion, temperature fluctuation, pH fluctuation and moisture ingress as well as polycarbonateâ&#x20AC;&#x2122;s intrinsic low modulus of elasticity.

Semi-aesthetic brackets Where other materials such as glass fibre, ceramic or metal are used to reinforce resin-based brackets, the reinforcement is usually (almost) invisible when the bracket is placed on a tooth and an archwire tied in.

Ormcoâ&#x20AC;&#x2122;s Damon 3 bracket represented a new class of bracket which is best described as a semi-aesthetic bracket.

In this bracket, the bracket base and bracket body is made of reinforced resin and the bracket slot and self-ligating mechanism is made of MIM-med metal. D3 brackets are shown in Figures 10.3 and 10.4. At the time of their introduction, these brackets underwent significant structural problems including separation of the resin and metal parts of the bracket and stress fractures of the upper incisor resin tie-wings; mechanical redesign and

Figures 10.3 and 10.4:

Ormco Damon 3 semi-aesthetic hybrid brackets

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reinforcement has now solved these problems.

Aging Although resin-based materials have improved considerably and continue to improve, they are not suitable for all patients for an entire treatment. The resin tiewings may be subject to wear and this may require replacement of brackets during treatment. Brackets are subject to modification of their structural properties due to biofilm adsorption (Eliades and Bourael 2005). This adsorption may affect brackets differently depending on their:

• • • •

porosity sorption susceptibility to corrosion biodegradability

Ceramics In late 1986, the first brackets made of ceramic materials became available and by the time that the 87th Annual Session of the American Association of Orthodontists was held in Montreal in May 1987, almost all major orthodontic manufacturers had either announced, or were about to announce ranges of ceramic brackets. This offered the possibility of a major advance in aesthetic orthodontics.

Ceramics are materials which are first shaped and then hardened by heat. This includes clays, glasses, some precious stones and metallic oxides. The ceramic material used in almost all orthodontic brackets is alumina, either in its polycrystalline or monocrystalline form. The advantages of using alumina for orthodontic brackets is that its appearance is very good, its chemical resistance is excellent, and it is both hard and, in certain respects, very strong. The disadvantages are that it lacks ductility, and is difficult and expensive to manufacture.

Ceramic brackets come in a variety of edgewise morphologies including true Siamese, semi-Siamese, solid and Lewis/Lang designs. Many brackets are made by specialist ceramic manufacturers and sold under proprietary names by manufacturers of orthodontic products or orthodontic supply companies. Some brackets from different manufacturers may therefore be almost identical products.

Monocrystalline (MCA) versus polycrystalline alumina (PCA) brackets Since 1987, both monocrystalline and polycrystalline ceramic brackets have been available and varied arguments put forward in favour of one or other material. Monocrystalline brackets are machined from long extrusions of synthetic sapphire with subsequent treatment to 'anneal' the surface and therefore reduce sites of stress concentration; smooth contours can be achieved by using a ‘tumbling’ process. Polycrystalline alumina brackets on the other hand are made by injection moulding submicron sized particles of alumina suspended in a resin, sintering them to fuse the alumina and finally machining the bracket as necessary to produce the finished article.

The physical properties of the raw materials (as opposed to brackets) compared with stainless steel are given in Table 10.5.

The figures for hardness show that both monocrystalline and polycrystalline alumina are significantly harder than stainless steel and that for tensile strength monocrystalline alumina is much stronger than polycrystalline alumina, which in turn is significantly stronger than steel. This is reflected in the fact that the only true Siamese brackets made from a ceramic material have been made from monocrystalline alumina.

Property MCA PCA Stainless Steel Hardness (Rockwell)

97.5

82.5

5-35

Tensile strength (psi x 1000)

260

55

30-40

Fracture toughness (MPa√M)

2-4.5

3-5

80-95

Table 10.5: Comparison of hardness, tensile strength and fracture toughness of monocrystalline alumina, polycrystalline alumina and stainless steel

The principle changes in the design of brackets has related to three areas:

•

bond strength

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• • •

bracket strength, especially when subjected to torque forces and in relation to tie wing strength frictional resistance debonding Bond strength

Ceramic brackets produced higher bond strengths than metal brackets. Metal brackets tended to fail at the bracket adhesive interface whilst ceramic brackets failed more commonly at the enamel resin interface.

Most companies have now moved to a mechanical method of bracket base retention in order to provide more predictable bond and debonding strengths. Wang et al (1997) revisited the bond strengths of a range brackets using a chemically coated base and a mechanical interlock. Brackets with a chemically coated base had higher bond strengths than metal and ceramic brackets with a mechanical interlock. Higher bond strengths showed that the debonding interface was at the enamel-resin interface and with lower bond strengths, at the resin-bracket interface. Higher bond strengths were found to produce some enamel fractures and detachments.

Bishara et al (1993) have shown that considerable variability occurs between chemically bonded, chemical/mechanically bonded and mechanically bonded brackets, different adhesives and different types of enamel conditioners. In addition, different etch times affect the bond strength with no etching and five second etches giving significantly reduced bond strengths (Olsen et al 1996).

Ormco’s Ice bracket has a bracket base coated with a monolayer of hollow evenly-sized zirconia balls – see Figure 10.5 and Figure 10.6. These are attached to the bracket base by a combination of chemical adhesive and fusion generated by heat during the manufacturing process.

Chen et al (2007) compared the debonding forces and failure modes of ceramic rackets in a simulated clinical environment. The authors compared 3M Unitek Clarity, Ormco Inspire and Ormco Inspire Ice which were debonded by hand and using a universal testing machine. Most brackets failed at the adhesive-bracket interface.

All three types of brackets showed cohesive failures; by hand, the cohesive failure rate was 70% Inspire, 20% Inspire Ice and 10% Clarity; by machine, the cohesive failure rate was 75% Inspire, 30% Inspire Ice, and 25% Clarity.

The cohesive fractures of Inspire and Inspire Ice occurred at the occlusal aspect of the base whereas those for Clarity occurred at the junction of the tiewings and the body and at the slot. The mean debonding forces for Inspire, Inspire Ice, and Clarity brackets were 25.72 ± 11.98, 17.92 ± 5.03, and 76.89 ± 23.47 N, respectively and no enamel damage was detected for any of the brackets. Note the reduction in debonding force for the Inspire Ice which was attributed to the reduction of zirconia balls on one edge of the bracket compared with Inspire.

Figure 10.5: SEM picture of evenly sized zirconia balls on the base of an Ice bracket; note the small ‘neck’ securing the ball to the base of the bracket thus providing undercuts for the retention of the adhesive

Figure 10.6: zirconia balls.

SEM of base of Ice bracket evenly coated with

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187

Reported problems with ceramic brackets

• • • • •

tooth abrasion bracket breakage loss of tooth control increased archwire friction debonding difficulty/damage Bracket strength

One of the early debates relating to ceramic brackets was that of monocrystalline alumina versus polycrystalline alumina. Patent restrictions meant that there would be only one brand of monocrystalline alumina bracket. The promised theoretical advantages of Starfire were slow to materialise; the technical design of the bracket which was almost identical to a metal bracket meant that certain aspects of treatment mechanics required no change when switching from metal to ceramic brackets. The Ormco/“A” Company Inspire bracket replaced Starfire in 1999.

Scott (1988) has pointed out that the tensile strength of ceramics is very dependent on the surface condition of the ceramic and this can make tests on bulk samples misleading and irrelevant. In addition, an important physical property related to the behaviour of ceramics is fracture toughness, the ability of a material to resist fracture. This is determined by stressing the material by impact and measuring the size of crack produced. The units of measurement are metres pascals per square root metre. It can be seen that in this mode of testing, both types of alumina perform poorly compared with stainless steel and this reflects their lack of ductility.

Johnson et al (2005) investigated the tiewing strength of several makes of ceramic bracket including 3M Unitek Clarity, American Orthodontics Virage, Dentaurum Fascination, GAC Mystique, Ormco Inspire, Rocky Mountain Luxi II and TP Orthodontics InVu. The results are shown in Figure 10.7 and show the progress made in the design and manufacture of ceramic brackets over the last decade. The tiewing of the Inspire bracket did not fracture at all under the test conditions and the authors consequently eliminated it from the study. The authors went on to conclude that semi-twin designs (Virage, Fascination and Mystique) had stronger tiewings than true twins (Clarity, Luxi II, InVu and Inspire) although this may have not been the case had the Inspire bracket been included.

Tooth abrasion

MPa

Ceramic brackets are much harder than enamel and rapidly cause wear if occlusal interferences are present. The American Association of Orthodontists carried out a survey in 1988 of members experience with ceramic brackets.

As a result of the survey, the President of the American 250 Association of Orthodontists, Dr John Lindquist, suggested that 200 both health and safety concerns existed on the part of the 150 orthodontic specialty regarding ceramic brackets and prudent 100 practitioners might wish to discuss the potential risks at an informed 50 consent meeting with the patient and/or parent (Lindquist 1989). The 0 results were again summarised in Clarity Virage Fascination Luxi II InVu Mystique Inspire the next AAO bulletin supplement Figure 10.7: The in vitro tiewing strength of ceramic brackets; note that the Ormco (7:4 Winter 1989). Of the 21% who Inspire bracket did not fracture at all but that the value given is the failure value of the steel ligature at that time reported seeing (from Johnson et al 2005). True twin brackets are coloured blue but include Inspire which did not enamel damage, 59% of that break and semi-twin brackets are coloured plum. damage was caused by abrasion.

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

The first report of this cause of damage had only recently appeared (by Professor Scott in 1988) and this problem is now entirely avoidable by careful selection of cases, bracket location and treatment mechanics. Ceramic brackets should only be placed on lower teeth in cases where the overbite is at no stage increased. If such brackets are to be placed on the lower incisors in a deep bite case, then the initial use of an upper bite plane, bite turbos, molar bite ramps or selective sectional mechanics to fully reduce the overbite in the early stages of treatment are highly advisable. Sometimes, the simple expedient of placing lower bonds at a more gingival level suffices. Placement of ceramic brackets on lower posterior teeth would rarely seem sensible. A better solution is to use ceramic-metal reinforced resin where contact between enamel and a ceramic bracket is likely and aesthetic brackets are necessary.

Bracket breakage The low fracture toughness leads to a higher rate of bracket breakage than with stainless steel brackets.

Anecdotally reported breakage rates vary widely. Odegaard (1989) reported three breakages in 500 brackets (Transcend) used throughout treatment. Interestingly, his in vitro tests showed that the force required to break a ceramic bracket was equal to that required to deform a metal bracket. One of the course presenters (NH) has found a clinical breakage rate of 12 in 340 brackets (mainly Starfire brackets). Only four of these brackets required replacement since the fully Siamese bracket morphology of Starfire brackets leads to one of the four wings fracturing and the remaining wings frequently provide adequate control if treatment is due to finish before too long. This contrasts with semi-Siamese or single brackets which almost always require replacement. Fracture rates have declined as manufacturers improve their production processes. For example, the introduction of the second generation of Starfire brackets in 1989 was claimed by the manufacturers to more than halve the fracture rate in clinical use, (to less than 4%) principally as a result of the heat treatment reducing sites of surface stress concentration. Winchester (1991) found lower breakage rates in vitro with more recently developed brackets.

Increasing production control will probably also result in less variability in reported breakage rates.

Ligation with ceramic brackets Meanwhile, several precautions should be taken to minimise bracket breakage. External trauma to and scratching of the brackets during archwire changes must be avoided. Ligatures and the ligating instruments are the main potential culprits. Careful ligation is necessary and elastomeric rings or Teflon coated ligatures (both conventional and Kobayashi) are recommended to prevent tie wing fracture. Monocrystalline ceramic brackets have a true Siamese configuration which allows the use of figure of eight elastomeric ligation methods as used for metal brackets whereas most polycrystalline brackets have a semi-Siamese tiewing design which is a significant drawback. Semi-Siamese tiewing designs may also make it difficult to place both elastomeric chain and ligating modules on the same bracket because of the reduced depth of the tiewing. The loss of tooth control so noticeable with some of the narrower single ceramic brackets is attributable to this difficulty in obtaining effective ligation on such brackets.

Archwires and ceramic brackets The risk of excessive forces when placing or removing rectangular archwires which almost completely fill the slot can be reduced by using a more resilient wire (e.g.: nickel titanium or TMA) before proceeding to the stainless steel wire or as a full size finishing wire or as a substitute for a stainless steel wire.

Placement of additional torque in archwires may cause tiewing fracture on insertion with ceramic brackets. In addition to the use of large size lower modulus wires as recommended above, consideration should be given to increasing the amount of torque by inverting the bracket where appropriate (such as on a lateral incisor that was originally palatally positioned).

Contact sports and ceramic brackets Patients who participate in contact sports which involve a high risk of injury to the face and teeth are less suitable for ceramic brackets. All patients wearing ceramic brackets should be advised to wear a mouthguard when participating in contact sports.

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189

Orthognathic surgery with ceramic brackets During orthognathic surgery, there is clearly a potential for instrumentation to cause bracket fracture. The transparency/translucency and radiolucency of ceramic brackets makes fragments of bracket hard to locate at operation and during recovery when the cough reflex is suppressed. The use of these brackets in such patients must therefore be considered very carefully.

However, given a careful surgeon and an anaesthetist aware of the problems we would not preclude the use of ceramic brackets in cases requiring orthognathic surgery.

Friction and ceramic brackets The problem of friction and ceramic brackets is well known. Angolkar et al (1990) demonstrated that:

• • •

rectangular wires produce more friction than round wires nickel titanium and beta titanium archwires produce more friction than stainless steel or cobalt chromium wires ceramic brackets generate significantly more frictional resistance than stainless steel brackets.

Saunders and Kusy (1994) have looked at the surface topography and frictional characteristics of ceramic brackets.

It was concluded that:

• • • •

monocrystalline brackets (MCA) have a smoother slot finish than polycrystalline brackets (PCA) the frictional characteristics of MCA and PCA are comparable archwire material has more effect on friction than bracket material multiple tests demonstrate polishing and smearing of PCA slots

Bazakidou et al (1997) evaluated friction in several types of aesthetic bracket and a metal bracket to serve as a baseline. The brackets used are shown in Table 10.6. The lowest frictional resistance for both slot sizes was produced by the GAC bracket without a metal slot liner. There was no distinct trend between composite brackets with and without a metal slot liner and the frictional resistance with wire ligation was approximately three times more variable than that with elastomeric ligation.

Injection moulded polycrystalline ceramic brackets have been developed (Class One Orthodontics) which claim to have a smoother slot finish thus reducing friction. More importantly, 3M Unitek have introduced a ceramic bracket (Clarity) with a metal slot insert which is designed to solve the problem of increased frictional resistance between archwire and bracket slot. The effectiveness of this innovation is supported by Nishio et al (2004) who found that the least friction was generated by all metal brackets followed by ceramic brackets with a metal slot and then ceramic brackets with a ceramic slot.

A further refinement has been the insertion of a silica layer in the slot area to improve both frictional characteristics and aesthetics. Cha et al (2007) tested four different types of ceramic bracket against a control stainless steel bracket and determined that the ceramic bracket with a silica coating in the slot generated the least frictional resistance of all the Bracket Type 0.018” slot 0.022” slot ceramic brackets and sometimes metal Unitek Miniature Twin less than the stainless steel polycrystalline ceramic RMO Signature bracket. The increase in frictional monocrystalline ceramic ACO Starfire resistance as the angulation composite/metal slot Ormco Spirit between bracket and archwire was composite/metal slot GAC Elan increased in 5˚ increments up to composite/no metal slot GAC 15˚ was commendably low.

AO Silkon

Table 10.6:

composite/metal slot

Brackets used in the study by Bazakidou 1997

The increased frictional resistance

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

is also in part due to the hardness of the ceramic causing gouging of the relatively softer wire surface.

It is likely that further progress in this area will be made by attention to the engineering of the bracket slot.

Clinically, it is suggested that:

• • • • •

ceramic brackets are not used on premolar teeth where sliding mechanics are used if the patient has a wide smile and ceramic brackets are placed on the premolars, then space closure with loops may be helpful use stainless steel wire rather than a nickel-titanium wire for space closure use round rather than rectangular wire in the labial segment if there is difficulty in closing space changing to a new archwire may also reduce friction if the previous wire has become gouged and space closure has halted

Interestingly, a paper by Ireland et al (1991) supported the view that in the buccal segments, the choice of wire and the method of ligation had much more effect on friction than did the use of ceramic or metal brackets.

Indeed, in tests on a single bracket, friction was higher in metal brackets. Frictional forces in sliding mechanics are clearly complex and hard to model comprehensively.

Reicheneder et al (2007) have compared the frictional characteristics of two self-ligating aesthetic brackets (Ultradent Opal, a glass-filled, nickel-free, polycrystalline, self-ligating aesthetic bracket and the Gestenco Oyster bracket, a fibreglass-reinforced composite bracket) with four conventionally ligated aesthetic brackets: 3M Unitek Transcend, Ormco Inspire, GAC Allure and Gestenco Image. The self-ligating brackets had significantly lower friction than the conventionally ligated brackets for 0.0175” x 0.025” and 0.019” x 0.025” stainless steel archwires.

The Opal bracket had the lowest frictional resistance of all bracket archwire combinations but simulated aging of 9-10 month and 18-20 month duration narrowed this bracket’s advantage.

Self-ligating ceramic brackets now include 3M Unitek Clarity SL, GAC In-Ovation C and Ormco Damon Clear.

Debonding ceramic brackets Removal of ceramic brackets has been an area of significant concern. The lack of ductility means that there is no scope for breaking the bond by flexure of the bracket. This flexure has been shown to contribute to the lower bond strength that exists between metal bracket bases and composite than between composite and tooth when bonding is achieved without moisture contamination. With ceramic brackets, the relative bond strengths are easily reversed and bond failure at the enamel-composite interface with the necessarily higher level of debonding force has caused instances of enamel loss. It is sensible to avoid using ceramic brackets or to use a very careful debonding technique on structurally compromised teeth. In the AAO survey previously referred to, 36% of those who had noticed tooth damage at any stage had seen enamel flaking at debonding. This was in 1988 and it is probable that manufacturers initially overestimated the bond strength required to retain the bracket throughout treatment and did not take account of the differences necessary in debonding technique between ductile metal and brittle ceramic brackets. The progressive development of ceramic brackets and bonding techniques means that this is now a rare complication.

The following methods of debonding ceramic brackets have been described:

• • • • • •

conventional debonding pliers ceramic bracket specific debonding pliers air rotor ultrasonic scaler electrothermal debracketing laser-aided debonding

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

•

191

collapsible brackets with a designed ‘fault line’

Debonding has become much easier than in the late 1980s; however it still remains more of a challenge than debonding conventional Siamese metal brackets. Operators will learn about their particular combination of adhesive and bracket. The most important feature of debonding ceramic brackets is maintaining the integrity of the enamel surface. Kitahara-Céia et al (2008) have shown that ceramic brackets with mechanical retention or polymer base retention perform better in this respect than ceramic brackets that utilise chemical retention.

However, 3M/Unitek Clarity brackets are designed to collapse on debonding. Debonding forces are similar to other ceramic brackets and in 50% of tests on the 3M/Unitek Clarity bracket, one half of the bracket only debonded while the other half was left on the tooth; this was usually easy to remove however (Bishara et al 1997).

Theodorakopolou et al (2004) compared the debonding characteristics of Ormco Inspire and 3M Unitek Clarity brackets. They found that the shear bond strengths (using Transbond XT as the adhesive) when tested in an Instron machine were 20.3 ± 8 MPa and 21.7 ± 5.2 MPa. This is a relatively high figure for an in vivo shear bond strength. An additional sample of the same brackets were debonded using the manufacturer’s recommended technique and using the manufacturers recommended pliers. Over 90% of the brackets of both types debonded at the bracket-adhesive interface. No enamel fractures were observed using the manufacturers recommended technique. The clear recommendation is therefore to follow the manufacturer’s instructions!

In 2004, 3M Unitek introduced the APC-Plus Clarity bracket. This bracket has a colour sensitive adhesive which is sensitive to the degree of cure being pink when uncured and turning clear when completely cured. StaribratovaReister and Jost-Brinkmann (2004) examined the effect of APC-Plus adhesives on bonding and debonding time.

Two operators required substantially more time for the bonding of APC-Plus Clarity brackets compared with APC Clarity brackets and no difference was found in the time required to remove residual adhesive on debonding between the two brackets.

In Ormco’s Ice bracket, the area of the bracket base closest to the gingival margin has less retention to allow a failure zone in the adhesive to propagate as the bracket is debonded by rotating it occlusally.

Pattern Bracket and buccal tube assemblies normally come in either standard, or mini/micro versions. The trend is for mini/micro brackets to predominate consistent with bracket design that can produce adequate tooth control.

Morphology Morphology is the configuration of the bracket.

Brackets

Siamese Most brackets are available in a Siamese design and this morphology is recommended when using conventional brackets.

Offset gingival pad brackets These brackets were originally described by Swartz and were an Ormco innovation (Swartz 1994). Bonding premolars is traditionally difficult because of:

• • • •

the short clinical crown enamel abnormalities in the gingival third of the crown may still be covered with amorphic follicle may have more aprismatic enamel

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

• •

an enamel rod direction that is more divergent from perpendicular and thus less retentive of resin tags the tendency for dislodgement due to masticatory forces

Upper and lower premolar brackets have been increasingly available with a larger occlusally extended bonding base and a gingival bracket offset to:

• • • •

improve bond strength by increasing the pad size utilise more of the coronal enamel for retention make it easier to position these brackets on the FA point reduce gingival impingement

A randomised controlled trial has been carried out by Tidy and Coley-Smith (1998) which shows that gingival offset brackets have a risk of bond failure which is five times less than with conventional brackets. This corresponds to the more anecdotal improvement suggested by Swartz (1994). The advent of adhesion enhancers and improved bonding techniques have made this development largely superfluous.

Single wing We do not use single wing brackets except in extremely rare circumstances and then primarily for other reasons (see Attract brackets).

Alexander Signature brackets Wick Alexander uses single wing brackets on canines and bicuspids in the Alexander discipline.

Attract Brackets Attract brackets are a single wing bracket in which the mesiodistal width has been reduced but an attempt made to maintain rotational control by extending the bracket channel beyond the tiewings. The brackets are radiussed to make them more comfortable. This may make them more suitable for treating certain types of patients where trauma from the appliance must be kept to a minimum such as those patients with epidermolysis bullosa. The brackets are poor at controlling rotations on severely malposed teeth and offer few advantages over Tru StraightWire or Mini-Twin brackets.

Self-ligating brackets A more extensive and detailed discussion of self-ligating brackets can be found in the chapter on Self-ligating Brackets: Theory and Practice. However, Fleming et al (2009b) compared treatment with a self-ligating bracket system (3M Unitek SmartClip) and conventional preadjusted edgewise brackets (3M Unitek Victory). The archwire sequence used was 0.016-in round, 0.017 × 0.025-in rectangular, 0.019 × 0.025-in rectangular martensitic active nickel-titanium archwires, and 0.019 × 0.025-in stainless steel archwires. There was little difference overall in the pattern of arch alignment and leveling related to the 2 preadjusted appliances. However, there was a statistically greater increase in intermolar width in the group treated with the self-ligating appliance, although the difference was only 0.91 mm. In an earlier paper, Fleming et al (2009a), the authors found no difference in the efficiency of tooth alignment in patients with mild lower incisor irregularity for the same two appliance groups.

Pavoni et al (2011) compared the effects of self-ligating brackets (TIME 3) and aligners (Invisalign) and demonstrated that fixed appliance treatment with self-ligating appliances produced better outcomes than aligner treatment and greater archform development and posterior expansion than aligners. The inclusion criteria for the study was mild crowding (mean 4.4 ± 0.8 mm in class 1 cases. The treatment times for the two groups were not different. Suggested reasons for the poorer performance of aligners were compliance and their inability to manipulate teeth in three dimensions.

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193

Damon brackets Damon 2 System (D2) Damon 2 System (Damon 1998) brackets are self-ligating brackets and are dealt with in a separate chapter. They are a much-improved version of the Damon SL bracket with a much-improved internal slide which does not open spontaneously and does not break during treatment. The bracket has been continually refined and is now sufficiently reliable for use as a single bracket system within an orthodontic practice or department.

Damon 3 (D3), Damon 3MX and Damon Q Damon 3 brackets were introduced in the latter part of 2004. They are a part composite and part metal bracket; the slot and slide are metal injection moulded and the base and the upper tiewing (gingival in the upper arch and occlusal in the lower arch) are made of composite with a resin rich outer layer. An all metal version of D3 (D3MX) was introduced in mid 2005. An updated version of Damon 3 MX was introduced in 2009 and is called Damon Q. Vertical slots A variety of vertical slot brackets is available. Unfortunately there is no standardisation of vertical slot size which goes 0.018" x 0.018" (Mini-Twin), through 0.020" x 0.020" (“T” slot brackets) to 0.0185" x 0.046" (BroussardMinnesota Integrated brackets).

Vertical slots may be used for:

• • • • •

partial ligation uprighting springs rotation springs locking pins or hooks tying teeth together

Although vertical slots are useful, pressure to keep bracket profile as low as possible means that they are became uncommon but re now making a come-back. The Damon Q appliance has both a vertical slot and an auxiliary horizontal slot.

Power arms Cast integral hooks are often available on molars and extraction series premolars and canines but are increasingly being replaced by replaceable drop-in hooks.

Hooks are recommended on upper and lower first and second molars.

Canines and premolars are used without hooks although hooks have been available since the introduction of the appliance. Originally designed as power arms these were clumsy, prone to damage and a trap for plaque and food debris. An L-shaped hook followed which has now been replaced by a short vertical ball ended hook.

Attempting to move teeth along the archwire using integral hooks often results in a loss of rotational control of the tooth being moved. Hooks are useful for short intermaxillary elastics that are sometimes used to fully intercuspate the occlusion at the end of treatment but the disadvantages of the presence of any type of hook on premolars and canines outweigh their advantages during what is a very small part of the duration of treatment.

Buccal tube assemblies

Convertible brackets Convertible brackets were normally used on all first molars although with the introduction of superelastic archwires the need for these is now questionable. However, with the advent of nickel titanium wires, the need for convertible brackets has been eliminated and we stopped using them because of their tendency to spontaneously

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

convert when conversion was not desired. Self-ligating first molar tubes are now available and these facilitate the placement of stainless steel working archwires and torque adjustments on second molars; these are strongly recommended although it takes a little time to get used to working with them.

Hooks Cast integral hooks are used on all molars.

Tubes Double or triple tubes are available on first molar bands according to personal preference. The EOT tube is gingivally placed on double tubes and occlusally placed on triple tubes. There has in the past been some criticism of the first molar/second molar contact point relationship. The anatomy of the lower first molar band has now been changed by adjusting the position of the dominant buccal groove. This is termed “mesial to mesial” positioning of the buccal tube compared with the standard “indent to indent” positioning. Molars are now routinely bonded and so only single tubes are required.

Molar tubes Molar tubes are not convertible and therefore have no tiewings although they have a hook. This considerably reduces their profile and reduces the risk of occlusal interference. In addition, the mesial entrance to the tube is belled to make it easier to insert the archwire. The new titanium tubes made by Ormco are very low profile indeed and available for both first and second molars.

M/P TUBES Second molars use single tubes. Ormco’s M/P bondable tube for second molars is useful where the tooth is only partly erupted. The tube is designed to fit on the mesiobuccal corner of the tooth only.

Slot size Height Most appliances are available with slot heights of 0.022" and 0.018". The use of an 0.022" slot is strongly recommended because:

• • •

this gives lighter forces in the early stages of treatment by providing more freedom between archwire and bracket slot in the early stages of treatment sliding mechanics requires the use of a stiff archwire during the sliding phase coordination of archwires is more easily achieved with heavier archwires

An interesting debate has recently sprung up about whether orthodontics needs two different slot heights (Rubin 2001); this has been linked with a suggestion to metricate bracket and archwire sizes (Peck 2001). We strongly support the use of the 0.022 slot for the reasons stated above and at the moment believe there is little need to metricate bracket sizes and archwires.

Depth

Slot depth is normally 0.028" but the bioprogressive version of the appliance has an increased slot depth of 0.030".

This variant however is not easily available. The 0.028" slot depth is recommended. The Damon System brackets (D2, D3 and D3MX) have an 0.027" slot depth to improve rotational control with working archwires.

Incisor bracket sets Andrews (1989) described different incisor bracket sets for use in differing skeletal patterns. These differed from one another in the amount of torque in the brackets but not in any other respect. The Set A bracket set, designed for Class 2 skeletal patterns had less palatal root torque in the upper incisors and more labial crown torque in the lower incisors to facilitate the establishment of a normal incisor relationship whereas Set C for Class 3 skeletal

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

Tooth

Set A

Set S

Set C

U1

2

U2

-2

3

8

L1

4

-1

-6

L2

4

-1

-6

Table 10.7:

7

12

Minimum

Translation (mm) 0-2

Medium

3-4

+3

+4

+5

Maximum

>5

+4

+6

+6

Table 10.8:

Tip

Distal Rotation +2

+2

Upper Molar Torque +4

Posterior bracket sets

Incisor Bracket Sets Tooth Upper incisors Lower incisors Posterior Brackets Upper Arch Canines

Set Set C Set S Tip T-1

Offset T-2

Premolars

T-1

T-1

Molars Lower Arch Canines

T-4

T-2

T-1

T-1

Premolars

T-2

T-2

Molars

T-2

T-2

Table 10.9:

patterns had the reverse. Set S was for Class 1 malocclusions. Details of the incisor bracket sets are given in Table 10.7.

Translation (extraction) series brackets

Incisor bracket sets

Set

195

Origins and details of Roth prescription

Translation brackets were introduced by Andrews (1989) to compensate for the unwanted tooth movements that occurred during closure of extraction spaces. These posterior bracket sets (i.e.: molars, premolars and canines) had increased tip and antirotation according to how much translation of the tooth was expected.

Minimum (T1), moderate (T2) and maximum (T3) bracket sets are available. T4 brackets are molar brackets without the five degrees of tip in the standard prescription. The use of translation series brackets as described by Andrews is not recommended. Details of posterior bracket sets are given in Table 10.8.

The existence of incisor bracket sets and translation brackets shows that Andrews did not envisage a single appliance and prescription which would be suitable for all malocclusions.

Incisor sets and translation brackets Evolution of Roth prescription The introduction of incisor bracket sets and translation series posterior bracket sets greatly complicated inventory control for the Straight-Wire Appliance. In one of the parts of the JCO series of articles, Andrews (1976d) commented that Dr Roth found that a large percentage of his cases could be treated with Set C upper incisor brackets, Set S lower incisor brackets, minimum translation brackets in the upper posterior buccal segments and lower canines and maximum translation series brackets on the upper canines and lower posterior segments. This prescription thus became known as the Roth prescription. Some drift has taken place from the original Roth prescription as described by Andrews but its origins remain clear. The origins of the Roth prescription are as shown in Table 10.9.

The Roth prescription was at one time the most popular of all prescriptions particularly amongst younger orthodontists. The prescription was relaunched by Ormco/“A” Company as the Tru Straight-Wire system.

Some bracket features are easily identifiable – a Damon System 2 bracket or an Inspire! or Clarity bracket are instantly identifiable by their shape and morphology. Sometimes the bracket series may be more difficult to identify; while it is probably possible to tell stainless steel from titanium brackets, it would be much more difficult to tell stainless steel from cobalt chromium. The orthodontist also needs to know:

• • • •

what the bracket series is (Tru Straight-Wire, Orthos, MBT etc) which tooth type the bracket is for what prescription the bracket has how to orient the bracket on the tooth.

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

The easiest identification is the last feature. Brackets are invariably identified by a cast or painted dot on the distogingival tie wing. This dot may be used to identify the tooth type by making dots on different tooth types a different colour. Otherwise the bracket morphology can be used to identify tooth type (lateral incisors have thicker bases than central incisors).

The prescription the bracket has is often more difficult to determine; it can be identified by a cast letter between the tiewings (Straight-Wire Synthesis), the use of additional coloured dots but frequently less easily identifying features are used such as casting marks on the bracket base.

Bracket and buccal tube identification Prescriptions The term prescription describes the section of angulation, inclination and offset values used to treat a particular

Andrews

U1

U2

U3

U4

U5

U6

Tip

5

9

11

2

2

Torque

7

3

-7

-7

-7

Rotation

0

0

0

0

0

Roth

U1

Tip

U2

U3

-9

-9

-6

-6

-11

-17

-22

-30

-31

10

10

0

0

0

0

0

0

U6

U7

L1

0 L7 -1

12 17

8 10

-2 3

-7

-7 -7

-14 0

-14 0

-1

-1

-11

-17

-22

-30

-30

U1

0 U2

4 U3

2 U4

2 U5

14 U6

14 U7

0 L1

0 L2

2 L3

4 L4

4 L5

4 L6

4 L7

5

9

6

2

2

0

0

2

2

5

2

2

2

2

12 7 17

8 3 10

0 7

-7

-7

-18

-27

-1 -6

-1 -6

0 7

-17

-22

-28

-10

0 U2

0 U3

5

9

6

6 -5 13

7 -9 11

U1

0 U2

0 U4

15 2 22

2

0 U3

0 U5 2

0 U4

12 U6

0 U5

10 U7

0

12 U6

0 L1

0

0 L3

2

2

5

-3 -11

7 0 13

0 L1

0 L2

0 L4

-3 -11 10 U7

0 L2

2

0 L3

0 L5 2

0 L4

2 L6 2

0 L5

2 L7 2

2 L6

2 L7

4

8

8

0

0

0

0

0

0

3

2

2

0

0

17

10

-7

-7

-7

-14

-14

-6

-6

-6

-12

-17

-20

-10

0

Tip

0 U2

0 U3

0 U4

0 U5

10 U6

10 U7

0 L1

0 L2

0 L3

0 L4

0 L5

0 L6

0 L7

5

9

10

0

4

0

0

2

4

6

3

3

0

0

15

9

-3

-6

-8

-10

-10

-5 -10

-5 -10

-6

-7

-9

-10

-10

Variation

Table 10.10:

L6 -1

U1

Rotation

L5 0

Rotation

Torque

L4 -1

Tip

Tip

L3 7

0

Alexander

L2 2

Rotation

Torque

2

2

Tip

Orthos

L7 2

0

0

Torque

L6 2

0

U1

MBT Versatile +

L5 2

0

Rotation

Standard torque Negative Positive

L4 5

0

Tip

Damon Q

L3 2

13 9

0

Standard torque Lo-torque Hi torque

L2 2

9

Rotation Damon 3/3MX

U5

L1 0

5 Variation

Torque Super torque

U4

U7 0

U1

U2

U3

U4

U5

U6

U7

L1

L2

L3

L4

L5

L6

L7

5

8

10

0

0

0

0

2

3

6

0

0

-6

0

14

7

-3

-7

-7

-10

-10

-5

-5

-7

-11

-17

-22

-27

0

0

0

0

0

10

14

0

0

0

0

0

4

4

Andrews, Roth, Damon, MBT Versatile +, Orthos and Alexander prescriptions compared

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

197

malocclusion.

Prescriptions may be based on scientific study, such as the standard Andrew's prescription or Ormco’s Orthos appliance, or on a choice of variables which allows the treatment of a majority of cases. e.g.:

• • • •

Roth MBT Versatile + Damon Alexander

Prescriptions may also be individualised to a specific clinical situation (such as an instanding lateral incisor). e.g.:

• •

semi-custom appliances custom appliances such as the Ormco Insignia appliance and the 3M Unitek Incognito appliance developed by Dirk Weichmann.

Specific prescriptions

The in/out measurements for all prescriptions from the same manufacturer are normally the same.

In the following paragraphs and in Table 10.10, the Andrews, Roth, Bennett-McLaughlin, MBT Versatile +, Damon System, Alexander and Orthos prescriptions are compared.

Andrews, Roth and Damon prescriptions Andrews prescription The basis of current prescriptions is the Andrews and Roth prescriptions. Andrews has recently made minor changes to his prescription including the adoption of his original class 3 lower incisor set with -6 degrees of torque and abandoning the tip on the upper first and second molars. In addition, the torque in the lower first and second molars has been increased a little which is contrary to the trend seen in other prescriptions.

Roth prescription The Roth prescription uses Andrews original Set C (class 3) upper incisor set which gives more torque in the upper incisors and also buccal tube assemblies with increased torque on the upper molars. Since the prescription is extraction based, there is anti-tip and anti-rotation built into the buccal segment brackets. The torque between the lower first and second molars is equalised but still quite large. The canines have additional tip, which facilitates canine guidance. A Roth prescription variation is the super torque extraction brackets which have additional torque in the upper incisors. The Roth prescription now stands alone as the only prescription not using the class 3 lower incisor set either in the main prescription or as a variation.

It can be seen that the Roth prescription has the most tip on the upper canine in order to facilitate canine guidance. The Andrews prescription alone carries its tip back into the molar region and this can make correct positioning of the upper first molar difficult and this feature has been dropped by all other prescriptions. In the lower arch, the tip on the canines is again increased in the Roth prescription to facilitate canine guidance. The Roth prescription also has distal crown tip on the lower buccal segments as Roth believed his prescription would be more anchorage demanding. This slight distal tip simulates the Tweed anchorage setting procedure.

The Roth prescription has increased molar torque in the molar region to prevent dropping of the palatal cusps.

The canine has less torque than in the standard prescription because of the increased torque on the lateral incisor and because of his concern over reciprocal forces from the torque on the lateral incisor and thus prevent undue prominence of the upper canine root.

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

The supertorqued Mini-Twin brackets are designed by Roth for class 2 cases in which only the upper first premolars are extracted. In order to get the buccal segments a full unit class 2 and no more, additional torque is required on the upper incisors. This increased torque has now been adopted by many other prescriptions such as the MBT prescription.

The 0° offset upper first molar tubes are again designed to allow the rotated first molar to take up more arch length in upper first bicuspid extraction cases.

Tru Straight-Wire bracket system The Tru Straight-Wire bracket system consists of metal injection moulded brackets on a rectangular pad. The bracket system is guaranteed against inadvertent debonding when Reliance Phase II adhesive is used. The bracket system retains the standard mesiodistal bracket dimension on the lower incisors and slightly increases it on the upper lateral incisors. The upper incisor mesiodistal widths are slightly less. The occlusogingival bracket height is significantly smaller than for the standard size twin and slightly larger than MiniTwin brackets. In addition the Tru Straight-Wire system is cheaper than the Mini-Twin Roth prescription brackets.

Damon system The Damon prescription is similar to the Andrews prescription but with less tip on the canines and the option of increased upper incisor torque and the class 3 lower incisor set.

The MBT Versatile + prescriptions The MBT Versatile + (Bennett and McLaughlin 1997) prescription should be seen as an evolution of the BennettMcLaughlin prescription (Bennett and McLaughlin 1993). The Bennett-McLaughlin prescription follows the Andrews prescription closely but with increased incisor torque, the class 3 lower incisor set, no upper molar tip and reduced lower second molar torque. Both prescriptions use Roth’s super torque upper incisor brackets and Roth torque values on the upper molars. The MBT Versatile + prescription follows the trend to less and more progressive tip in the upper and lower arches.

degrees

The Orthos prescription The Orthos prescription has increased distal root tip on the second premolars to facilitate matching of the marginal ridges between the second premolars and first molars. There is increased torque on the upper incisors and less and more progressive torque in the lower buccal segments. The Orthos prescription also gives the option of -10° lower incisor brackets. It should be noted that a -5° bracket only just eliminates the third order play in a 0.019" x 0.025" archwire; a -10° 25 bracket would just start to give a little lingual crown torque 20 (remembering that not all the treatment built into the 15 bracket/archwire combination will 10 actually be transmitted to the tooth).

5 0 -5

U1 Inclination

U2 Inclination

System 80

Minnesota

Tracey

Level Arch

Root

Roth

Ricketts

Planche

Hilgers

Hasund

Gerety

Goumare

Damon

Cetlin

Creekmore

Bennett

Burstone

Alpern

Andrews

Alexander

-10

U3 Inclination

Figure 10.8: The variation in inclination for the upper central incisor, the upper lateral incisor and the upper canine between prescriptions

The Alexander prescription The Alexander prescription is unusual in having -6 degrees tip on the lower first molar.

This is designed to promote levelling and gain arch length.

Summary The Roth prescription has mesial rotation on both upper and lower canines to prevent unwanted

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

rotation into the extraction space.

Increased rotation on the first and second molars helps to control the rotational position of these teeth particularly when intramaxillary traction is being used.

12

10

8

6

4

2

0

Figure 10.9:

199

The variation in angulation for the upper canine between prescriptions

The range of options for bracket and buccal tubes presented by preadjusted edgewise appliances is confusing to the newcomer to the appliance. Users of the standard prescription appliance who routinely treat moderate to difficult malocclusions have found it difficult to obtain adequate incisor torque and upper molar control. Hence there has been increasing interest in some aspects of the Roth

prescription and increasingly in exceeding those values.

It is however probable that the Roth prescription confers few benefits on the premolars in the upper and lower arches and marginal benefit on the canines in each arch. Low profile micro-sized tubes are almost essential on both first and second molars.

The MBT Versatile+ prescription and the Orthos prescription reflect a trend towards prescriptions with less torque and less tip.

Recommended prescription

A single prescription is no longer recommended. It is better to select brackets with the appropriate torque for individual malocclusions and thus semi-customise appliances.

Variation in prescriptions Claude Matasa (1994) writing in “Phoenix Without Ashes” compares twenty different prescriptions from today’s preadjusted appliance systems (Figure 10.8). The inclination values of upper incisors varied by over 25°, the angulation of upper canines by 10° and the inclination of lower canines by 20°. This variability is similar to that seen in Andrews’ sample.

Problem

Solution

Lack of upper incisor torque

increased palatal root torque on upper incisor brackets

Proclination of lower incisors

increased lingual crown torque on lower incisor brackets

Maxillary posterior segments compromise cuspid rise

increased buccal root torque in upper molar tubes

Antero-posterior profile of lower incisor brackets interferences on rotated teeth and with opposing incisors

causes

lower profile lower incisor brackets achieved with rotation or compensation-in-slot technology

Uprighting lingually inclined mandibular posterior segments

reduced torque values in mandibular posterior segments

Lower second premolar bond failures due to occlusal interferences

gingivally offset brackets

Height discrepancy between second premolars and first molars

increased distal root angulation on second premolars

Maxillary first molar rotation

increased molar rotation (offset): increased prominence of second premolar base

Poor root paralleling

more progressive angulation in buccal segments

Non-Caucasian patients

race-specific prescriptions

Table 10.11:

List of problems with existing prescriptions and their solutions

200

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

In conclusion, therefore:

• • • • •

Andrews’ sample was highly variable it is difficult to recommend a believable average for most values current prescriptions are also highly variable although certain trends are discernible a single prescription cannot fit all malocclusions we should think of Straighter-Wire rather than Straight-Wire

Trends in prescription design

Despite much hard work, orthodontists still do not have the perfect appliance. Table 10.11 lists problems can be identified with current designs together with the steps being taken to put them right.

Some of the rationale behind these changes is given by Andreiko (1994).

Race-specific prescriptions Prescriptions for specific racial types are now beginning to appear on the market. Ormco offer the Orthos AP (Asian Prescription) appliance.

This differs from the standard Orthos prescription in the following respects:

• • • • •

reduced distal root angulation in the lower cuspid and incisor brackets increased distal root angulation on lower second premolars mesial rotation (offset) in lower first molar tube flatter upper incisor bracket bases with reduced prominence increased lower incisor proclination

GAC produces the OPA (Oriental Prescription Appliance).

Some of the rationale behind these changes is given by Andreiko (1994).

Ligation systems

grams

Ligation systems may be conventional tie wing ligation systems or self-ligating systems. There is considerable interest in self-ligating brackets because of their 140 advantages in cross infection control, low friction 120 sliding mechanics and economy of time (no chairside assistant required) and money (saves cost of ligatures).

100 Recent technical developments, such as the 80 Ormco/“A” Company Damon 2, Damon 3/3MX Systems and Damon Q, have considerably improved 60 the performance of the slide mechanisms and now 40 make these appliances a realistic proposition for everyday use. In the past years, interesting evidence 20 has begun to emerge in support of self-ligating 0 brackets.

Papers by Harradine (2001) and Eberting et 1.5 mm 3 mm 4.5 mm 6 mm al (2001) which compared treatment time and quality Simulated canine displacement Aqua CEL Mystique CEL Aqua Slide Mystique Neo-Clip of self-ligating brackets with preadjusted edgewise appliances showed significant reductions in overall Figure 10.10: The forces released to produce tooth movement treatment time, the number of treatment visits and with conventional elastomeric ligation and low friction aesthetic ligatures. improved or equal treatment results. These papers are Note that at deflections greater than 1.5 mm, the conventional ligatures discussed in more detail in the Self-ligating brackets – release so little force (< 1.0 g) that they do not show on the graph (from Camporesi et al 2007)

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

201

Theory and Practice chapter.

No doubt spurred by the competition from self-ligating brackets, innovations have taken place in the development of conventional elastomeric ligation systems. Camporesi et al (2007) examined the forces released (eg: available for tooth movement) with a 0.014” wire displaced to simulate a displaced canine with two different ceramic brackets (Leone Aqua and GAC Mystique) ligated with conventional elastomeric ligatures and two types of low-friction aesthetic ligatures Leone Slide and GAC Neo-Clip . The results are shown in Figure 10.10. At deflections up to 1.5 mm, there is little difference between the ligation methods but once the wire deflection reaches 3 mm, almost no force (< 1 g) is released by the wire to provide tooth movement using conventional elastomeric ligation.

Benefits of preadjusted edgewise appliances It perhaps remains astonishing that there is so little evidence to support the use of preadjusted edgewise appliances. Despite this, preadjusted edgewise appliances are the fixed appliances of choice for nearly all orthodontists. So where do preadjusted edgewise appliances stand in a world of evidence-based clinical practice?

There has certainly been lots of supposition about their supposed advantages:

• • • •

reduction in chairside time reduction in treatment time better and more consistent results fewer adverse effects

Rate of retraction per 3 weeks (mm)

In 1993, Kattner and Schneider compared the results 0.018" slot standard edgewise appliances and Roth prescription preadjusted edgewise appliances from two practitioners using the Ideal Tooth Relationship Index (ITRI) described by Haeger (1989). There was no difference 10 in the ITRI scores pre-treatment and no difference between the standard edgewise appliance and the Roth prescription preadjusted edgewise appliance after 7.5 treatment. There were significant differences between the results obtained by the two orthodontists however; the orthodontist who used a 0.0175" x 0.025" finishing wire as 5 opposed to 0.016" x 0.022") and whose treatment took 2 years 5 months (versus 1 year 11 months) had an almost 10% better ITRI score than the other.

2.5

0 Tip-Edge

SWA

Rocke (1994) has suggested the use of Tip-Edge brackets on canines to facilitate canine retraction with the StraightWire appliance.

5

This hypothesis has been tested by Lotzof et al (1996). On a small sample of 12 patients, where each served as their own control, the speed of, and anchorage loss related to canine retraction was compared for the TP Tip-Edge appliance and the Roth prescription “A” Company Straight-Wire bracket. This is in reality a very poor paper and generated a significant amount of correspondence in the American Journal of Orthodontics and Dentofacial Orthopaedics. The principal criticisms:

Rate of anchorage loss (mm)

4

3

2

1

0 Tip-Edge

SWA

Figure 10.11: Rates of retraction and anchorage loss for TipEdge and SWA brackets

• •

the sample size was small the force used to retract the Tip-Edge bracket was excessive

202

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

•

the tooth uprighted with the Tip-Edge bracket was never uprighted which would have consumed more anchorage

The rates of retraction and of anchorage loss for the Tip-Edge and SWA brackets are shown in the accompanying graphs.

Although Andrews (1979) suggested that a reduction in wire bending would reduce the adverse effects of orthodontic treatment, there has been little evidence to support this contention despite its logical premise.

Mavragani et al (2000) , from the University of Bergen, compared premolar extraction Class 2 division i cases treated with conventional 0.018" edgewise technique and 0.018" straight-wire technique (3M/Unitek New Bergen Technique). All cases had standardised intra-oral x-rays taken with the long cone paralleling technique. For the conventional edgewise technique, the mean root resorption for upper central incisors was 13.75% and for lateral incisors 11.9%; for the straight-wire technique, it was 7% for upper central incisors and 9% for lateral incisors. Only the difference in root resorption on the central incisors was significant (at the 5% level). The study concludes that the straight-wire appliance may offer more gentle and constant forces thus reducing the likelihood of root resorption. However, the mean overjet for the edgewise group was 8.06 mm and for the straight-wire group 6.11 mm.

In 2011, Moesi et al investigated whether changes in bracket prescription produced visually different occlusal results; they investigated the Roth and MBT prescriptions using the Incisor and Canine Aesthetic Torque and Tip (ICATT) score. This study has found that bracket prescription had no effect on the aesthetic judgements made by experienced orthodontists from the post-treatment study models of patients treated with premolar extractions and a fixed appliance system using either a Roth or a MBT prescription. In the majority of cases, the ability of the clinicians to determine which bracket prescription was used was no better than chance in the majority of cases.

This thought provoking study raises several interesting questions about the use of prescriptions in preadjusted fixed appliances and their effectiveness.

In 2009, Akhoundi et al investigated the effects of conventional edgewise and preadjusted edgewise appliances on occlusal balance contacts at the end of orthodontic treatment. The presence of balancing contacts was more frequent in the standard edgewise group although protrusive contacts were similar between the two groups.

However, the standard edgewise group tended to have group function whereas the group treated with the preadjusted edgewise appliance tended to have a mutually protected occlusion.

Fixed appliance use in the United Kingdom Banks et al (2010) carried a postal questionnaire study of fixed appliance use patterns in the UK in 2010. The researchers found that most orthodontists used an 0.022” slot with conventionally ligated preadjusted edgewise appliances; nickel titanium and stainless steel were the principal archwires used. Older orthodontists seemed to prefer banding molars, the Roth prescription and chemically cured bonding agents while younger orthodontists were more likely to bond molars, use light cured adhesives and the MBT prescription.

Limitations of existing appliances Current appliance systems are limited in their ability to:

• • • •

cope with biological variation have limited control of arch guided tooth movement due to their flexible ligation systems lack of flexibility in allowing use of auxiliaries frictional resistance

In addition, the trend to increased miniaturisation of brackets and the use of more flexible archwires brings into question the concept of standard angulations in bracket slots. The slot angulation should be a function of:

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

• • •

203

bracket width archwire flexibility applied load

This topic has been comprehensively discussed by Matasa (1996).

More sophisticated appliances “Smart” featured appliances Several appliances are beginning to incorporate “smart” features such as the spring clip action in the Strite Industries SPEED appliance and the variable slot geometry and progressive torque application of the TP Tip-Edge appliance.

Semi-custom appliances Semi-custom appliances are those which exceed the morphological and positional specification of a fully programmed appliance but which are not precisely designed and fabricated to the unique morphology and guidance needs of a specific patient.

These include the BEDDTIOT appliance (Hocevar 1985) and the use of mixed prescription Straight-Wire appliances where the mix of prescription has tried in part to customise the appliance to the patient.

In selecting a semi-custom prescription it is sensible to start with the standard prescription and decide what departures are necessary from this prescription. The only parameter that varies in the many variants is inclination.

Generally, err on the side of overcorrection; so if bringing a tooth out from the palate or correcting retroclined upper incisors, choose a bracket with a higher inclination to try and achieve a measure of over-correction.

Custom appliances Custom appliances are appliances designed and fabricated to match precisely the unique morphology and guidance needs of a specific patient. Creekmore and Kunik (1993) have sought to overcome the limitations of current preadjusted appliance systems by developing the Slot Machine which allowed brackets to be placed on the teeth at predetermined angulations and inclinations prior to indirect bonding.

Custom appliances can be divided into two classes:

• •

appliances which have custom prescription but a standard base and pad appliances which have both a custom prescription and a custom base and pad

Appliances with custom prescriptions but standard base and pad Andreiko (1994) describes the development of the Ormco Elan system - a custom appliance derived from the patient’s skeletal and dental characteristics. This will incorporate not only custom brackets and buccal tube assemblies but also customised archwires. The appliance has now been renamed the Ormco Insignia appliance and was launched in 2004. It is a pioneer in an area which will at some stage become the standard for fixed orthodontic appliances. It has different degrees of customisation according to bracket system (eg: a ceramic bracket is more difficult to customise than a metal bracket because of different manufacturing techniques), a precision bracket positioning system/software, indirect bonding and customised archwires. Insignia is the basis of a digital platform which will support fully customised conventional appliances, ceramic brackets, self-ligating appliances and aligners (ClearGuide Express).

A fuller discussion on custom appliances is in the chapter on Customised Precision Prescription Appliances.

Appliances with custom prescriptions, base and pad Dirk Weichmann has also developed a fully customised custom lingual appliance called Incognito, now owned by 3M Unitek. One disadvantage of fully customised appliances is cost.

204

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

References Akhoundi MSA, Hashem A and Noroozi H (2009) Comparison of occlusal balance contacts in patients treated with standard edgewise and preadjusted straight-wire appliances World Journal of Orthodontics 10: 216â&#x20AC;&#x201C;219 Alexander RG (1986) The Alexander Discipline: Contemporary concepts and philosophies Glendora, Ormco Corporation Andreiko C (1994) JCO Interview: On the Elan and Orthos systems Journal of Clinical Orthodontics 28: 459-468 Andrews LF (1975) Accomplishing orthodontic treatment in six months with the straight-wire appliance In: Cook J T, ed. Transactions of the third International Orthodontic Congress: London, Staples Andrews LF (1976a) Straight-Wire appliance: origin, controversy, commentary Journal of Clinical Orthodontics 10: 99-114 Andrews LF (1976b) The straight-wire appliance: explained and compared Journal of Clinical Orthodontics 10: 174-195 Andrews LF (1976c) The straight-wire appliance: case histories: non-extraction Journal of Clinical Orthodontics 10: 282-304 Andrews LF (1976d) The straight-wire appliance: extraction brackets and classification of treatment Journal of Clinical Orthodontics 10: 360-379 Andrews LF (1976e) The straight-wire appliance: extraction series brackets Journal of Clinical Orthodontics 10: 425-441 Andrews LF (1976f) The straight-wire appliance: extraction series brackets (continued) Journal of Clinical Orthodontics 10: 507-529 Andrews LF (1976g) The straight-wire appliance: arch form, wire bending and an experiment Journal of Clinical Orthodontics 10: 581-588 Andrews LF (1979) The straight-wire appliance British Journal of Orthodontics 6: 125-143 Andrews LF (1989) Straight Wire The Concept and the Appliance San Diego, L A Wells Co. Andrews LF (1972) The six keys to normal occlusion American Journal of Orthodontics 62: 296-309 Angolkar PV, Kapila S, Duncanson MG and Nanda R S (1990) Evaluation of friction between ceramic brackets and orthodontic wires of four alloys American Journal of Orthodontics and Dentofacial Orthopaedics 98: 499-506 Banks PA, Elton V, Jones Y, Rice P, Derwent S and Odondi L (2010) The use of fixed appliances in the UK: a survey of specialist orthodontists Journal of Orthodontics 37: 43-55 Bazakidou E, Nanda RS, Duncanson MG and Sinha P (1997) Evaluation of frictional resistance in aesthetic brackets American Journal of Orthodontics and Dentofacial Orthopaedics 112: 138-144

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

Bennett JC and McLaughlin RP (1993) Orthodontic treatment mechanics and the preadjusted appliance London, Wolfe Medical Publishing Bennett JC and McLaughlin RP (1997) Orthodontic management of the dentition with the preadjusted appliance Oxford, Isis Medical Media Bishara SE, Fehr FE and Jakobsen JR (1993) A comparative study of the debonding strengths of different ceramic brackets, enamel conditioners, and adhesives American Journal of Orthodontics and Dentofacial Orthopaedics 104: 170-179 Bishara SE, Olsen ME and Von Wald L (1997) Evaluation of debonding characteristics of a new collapsible ceramic bracket American Journal of Orthodontics and Dentofacial Orthopaedics 112: 552- 559 Camporesi M, Baccetti T, Franchi L (2007) Forces released by esthetic preadjusted appliances with low-friction and conventional elastomeric ligatures American Journal of Orthodontics & Dentofacial Orthopaedics 131: 772-775 Cha J-Y, Kim K-S and Hwang C-J (2007) Friction of conventional and silica-insert ceramic brackets in various bracket-wire combinations Angle Orthodontist 77: 100-107 Chen H-Y, Su M-Z, Chang H-FF, Chen Y-J, Lan W-H, Lin C-P (2007) Effects of different debonding techniques on the debonding forces and failure modes of ceramic brackets in simulated clinical set-ups American Journal of Orthodontics & Dentofacial Orthopaedics 132: 680-686 Creekmore TD and Kunik RL (1993) Straight-Wire: the next generation American Journal of Orthodontics and Dentofacial Orthopaedics 104: 8-20 Damon DH (1998) The rationale, evolution and clinical application of the self-ligating bracket Clinical Orthodontics and Research 1: 52-61 Devanathan D and Chudzynski J (1997) [On-line] Technical evaluation of a new orthodontic bracket TP Laboratories Technical Brief http://www.nu-edgebrackets.com/pdf/WP_Nu-edge.pdf Accessed: 23 January 2010 Eberting JJ, Straja SR and Tuncay OC (2001) Treatment time, outcome and patient satisfaction of Damon and conventional brackets Clinical Orthodontics and Research 4: 228-234 Eliades T, Gioka C, Zinelis S, Eliades G and Makou M (2004) Plastic brackets: hardness and associated clinical implications World Journal of Orthodontics 5: 62-66 Eliades T and Bourael C (2005) Intraoral aging of orthodontic materials: the picture we miss and its clinical relevance American Journal of Orthodontics and Dentofacial Orthopaedics 127: 403-412 Fleming PS, DiBiase AT, Sarri G and Lee RT (2009a) Efficiency of mandibular arch alignment with 2 preadjusted edgewise appliances American Journal of Orthodontics and Dentofacial Orthopaedics 135: 597-602 Fleming PS, DiBiase AT, Sarri G and Lee RT (2009b) Comparison of mandibular arch changes during alignment and leveling with 2 preadjusted edgewise appliances American Journal of Orthodontics and Dentofacial Orthopaedics 136: 340-347 Flores DA, Choi LK, Caruso JM, Tomlinson JL, Scott GE and Jeiroudi MT (1994) Deformation of metal brackets: a comparative study Angle Orthodontist 64: 283-290 Grimsdottir MR, Gjerdet NR, Hensten-Pettersen A (1992) Composition in vitro corrosion of orthodontic appliances American Journal of Orthodontics and Dentofacial Orthopaedics 101: 525-532 Haeger RS (1989) A static occlusal analysis based on ideal inter-arch and intra-arch relationships. [Master's Thesis] Chicago: University of Illinois at Chicago

205

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THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

Harradine NWT (2001) Self-ligating brackets and treatment efficiency Clinical Orthodontics and Research 4: 220-227 Harzer W, Schröter A, Gedrange T and Muschter F (2001) Sensitivity of titanium brackets to the corrosive influence of fluoride-containing toothpaste and tea Angle Orthodontist 71: 318-323 Harzer W, Bourauel C and Gmyrek H (2004) Torque capacity of metal and polycarbonate brackets with and without a metal slot European Journal of Orthodontics 26: 435-441 Hocevar RA (1985) Begg-edgewise diagnosis determined totally individualised orthodontic technique: foundations, description, and rationale American Journal of Orthodontics and Dentofacial Orthopaedics 88: 31-46 Ireland AJ, Sherriff M and MacDonald F et al (1991) Effect of bracket and wire composition on frictional forces European Journal of Orthodontics 13: 322-328 Janson GRP, Dainesi EA, Consolaro A, Woodside DG and de Freitas MR (1998) Nickel hypersensitivity before during and after orthodontic therapy American Journal of Orthodontics and Dentofacial Orthopaedics 113: 655-660 Johnson G, Walker MP and Kula K (2005) Fracture strength of ceramic bracket tie wings subjected to tension Angle Orthodontist 75: 95-100 Kapur R, Sinha PR and Nanda RS (1999a) Comparison of frictional resistance in titanium and stainless steel brackets American Journal of Orthodontics and Dentofacial Orthopaedics 116: 271-274 Kapur R, Sinha PR and Nanda RS (1999b) Comparison of load transmission and bracket deformation between titanium and stainless steel brackets American Journal of Orthodontics and Dentofacial Orthopaedics 116: 275-278 Kattner PF and Schneider BJ (1993) Comparison of Roth appliance and standard edgewise appliance treatment results American Journal of Orthodontics and Dentofacial Orthopaedics 103: 24-32 Kerosuo H, Moe G and Kleven E (1995) In vitro release of nickel and chromium from different types of simulated orthodontic appliances Angle Orthodontist 65: 111-116 Kerusuo H, Kullaa A, Kerusuo E, Kanerva L and Hensten-Pettersen A (1996) Nickel allergy in adolescents in relation to orthodontic treatment and piercing of ears American Journal of Orthodontics and Dentofacial Orthopaedics 109: 148-154 Kitahara-Céia FMF, Mucha JN and Marques dos Santos PA (2008) Assessment of enamel damage after removal of ceramic brackets American Journal of Orthodontics & Dentofacial Orthopedics

134:548 -555

Kusy RP and O’Grady PW (2000) Evaluation of titanium brackets for orthodontic treatment: Part II: The active configuration American Journal of Orthodontics and Dentofacial Orthopaedics 118: 675-684 Kusy RP, Whitley JQ, Ambrose WW and Newman JG (1998) Evaluation of titanium brackets for orthodontic treatment: Part I: The passive configuration American Journal of Orthodontics and Dentofacial Orthopaedics 114: 558-572 Lotzof LP, Fine HA and Cisnernos GJ (1996) Canine retraction: a comparison of two preadjusted bracket systems American Journal of Orthodontics and Dentofacial Orthopaedics 110: 191-196 Lindquist JT (1989) Letter to members gives results of AAO survey on ceramic brackets The Bulletin 7: 3 MacColl GA, Roussow PE, Titley KC and Yamin C (1998) The relationship between bond strength and orthodontic bracket base surface area with conventional and microetched foil-bases American Journal of Orthodontics and Dentofacial Orthopaedics 113: 276-281

THE DEVELOPMENT OF PREADJUSTED APPLIANCE SYSTEMS EXCELLENCE IN ORTHODONTICS 2012

Marigo M, Nouer DF, Genelhu MCS, Malaquias LCC, Pizziolo VR, Costa ASV, Martins-Filho OA and Alves-Oliveira LF (2003) Evaluation of immunologic profile in patients with nickel sensitivity due to use of fixed orthodontic appliances American Journal of Orthodontics and Dentofacial Orthopaedics 124: 46-52 Matasa CG (1992) Direct bonding metallic brackets: where are they heading?

American Journal of Orthodontics and Dentofacial Orthopaedics 102: 552-560 Matasa CG (1994) Preadjusted appliances: one shoe fits all (2) Phoenix without Ashes 7: 1-4 Matasa CG (1995) Trends: good bye Ni; welcome Co, Mn The Orthodontic Materials Insider 8: 4: 1-6 Matasa CG (1996) Bracket angulation as a function of its length in the canine distal movement American Journal of Orthodontics and Dentofacial Orthopaedics 110: 178-184 Mavragani M, Vergari A, Selliseth NJ, Bøe OE and Wisth PJ (2000) A radiographic comparison of apical root resorption after orthodontic treatment with a standard edgewise and a straight-wire edgewise technique European Journal of Orthodontics 22: 665-674 Michelberger DJ, Eadie RL, Faulkner MG, Glover KE, Prasad NG and Major PW (2000) The friction and wear patterns of orthodontic brackets and archwires in the dry state American Journal of Orthodontics and Dentofacial Orthopaedics 118: 662-674 Moesi B, Dyer F and Benson P (2011) Roth versus MBT: does bracket prescription have an effect on the subjective outcome of pre-adjusted edgewise treatment?

European Journal of Orthodontics Advance Access doi: 10.1093/ejo/cjr126 Nishio C, da Motta AFJ, Elias CN, and Mucha JN (2004) In vitro evaluation of frictional forces between archwires and ceramic brackets American Journal of Orthodontics and Dentofacial Orthopaedics 125: 56-64 Odegaard J (1989) Debonding ceramic brackets.

Journal of Clinical Orthodontics 23: 632-635 Ogata RH, Nanda RS, Duncanson MG, Sinha PK and Currier GF (1996) Frictional resistances in stainless steel bracket-wire combinations with effects of vertical deflections American Journal of Orthodontics and Dentofacial Orthopaedics 109: 535-542 Olsen ME, Bishara SE, Boyer DB and Jakobsen JR (1996) Effect of varying etching times on the bond strength of ceramic brackets American Journal of Orthodontics and Dentofacial Orthopaedics 109: 403-409 Pavoni C, Lione R, Laganà G and Cozza P (2011) Self-ligating versus Invisalign: analysis of dento-alveolar effects Annali di Stomatologia 2: 23-27 Peck S (2001) Orthodontic slot size: it’s time to retool Angle Orthodontist 71: 329-330 Rahilly G and Price N (2003) Nickel allergy and orthodontics Journal of Orthodontics 30: 171-174 Reicheneder CA, Baumert U, Gedrange T, Proff P, Faltermeier , and Muessig D (2007) Frictional properties of aesthetic brackets European Journal of Orthodontics 29: 359-365 Rocke RT (1994) Employing Tip-Edge brackets on canines to simplify straight-wire mechanics American Journal of Orthodontics and Dentofacial Orthopaedics 106: 341-350 Rubin RM (2001) Re: A plea for agreement Angle Orthodontist 71: 156

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Saunders and Kusy (1994) Surface topography and frictional characteristics of ceramic brackets American Journal of Orthodontics and Dentofacial Orthopaedics 106: 76-87 Scott G (1988) Fracture toughness and surface cracks - the key to understanding ceramic brackets Angle Orthodontist 58: 5-8 Staribratovaâ&#x20AC;&#x201C;Reister K and Jost-Brinkmann P-G (2004) Bonding and debonding characteristics of APC-Plus Clarity compared to APC Clarity brackets World Journal of Orthodontics 5: 312-316 Swartz ML (1994) Successful second bicuspid bonding Journal of Clinical Orthodontics 28: 208-209 Theodorakopolou LP, Sadowsky PL, Jacobsen A and Lacefield W (2004) Evaluation of the debonding characteristics of 2 ceramic brackets: An in vitro study American Journal of Orthodontics and Dentofacial Orthopaedics 125: 329-336 Tidy DC and Coley-Smith A (1998) Gingival offset premolar brackets - a randomised clinical trial Paper presented at the Golden Jubilee Symposium at the Royal College of Surgeons of Edinburgh Turpin DL (2001) Editorial: California proposition may help patients in search of better oral health American Journal of Orthodontics and Dentofacial Orthopaedics 120: 97-98 Vaughan JL, Duncanson MG, Nanda RS and Currier GF (1995) Relative kinetic frictional forces between sintered stainless steel brackets and orthodontic wires American Journal of Orthodontics and Dentofacial Orthopaedics 107: 20-27 Wang WN, Meng CL and Tarng TH (1997) Bond strength: a comparison between chemical coated and mechanical interlock bases of ceramic and metal brackets.

American Journal of Orthodontics and Dentofacial Orthopaedics 111: 374-81 Winchester L J (1991) Bond strengths of five different ceramic brackets: an in vitro study European Journal of Orthodontics 13: 293-305

Useful related references not referred to in this chapter Balut N, Klapper L, Sandrik J and Bowman D (1992) Variations in bracket placement in the preadjusted appliance American Journal of Orthodontics and Dentofacial Orthopaedics 102: 62-67 Roth RH (1972) Gnathologic concepts and orthodontic treatment goals In: Jarabak JR and Fizzell JA, Technique and treatment with light-Wire edgewise appliances: St Louis, The CV Mosby Company Roth RH (1976) Five year clinical evaluation of the Andrews Straight-Wire Appliance Journal of Clinical Orthodontics 10: 836-850 Roth RH (1981) Functional occlusion for the orthodontist: Part 1 Journal of Clinical Orthodontics 15: 32-40 Roth RH (1981) Functional occlusion for the orthodontist: Part 3 Journal of Clinical Orthodontics 15: 174-198 Roth RH (1985) Treatment Mechanics for the Straight-Wire appliance In: Graber TM and Swain BF eds. Orthodontics: Current Principles and Techniques: St Louis, The CV Mosby Company Roth RH (1987) The Straight-Wire Appliance 17 years later Journal of Clinical Orthodontics 21: 632-642

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Roth RH and Gordon WW (1981) Functional occlusion for the orthodontist: Part 4 Journal of Clinical Orthodontics 15: 246-266 Roth RH and Rolfs DA (1981) Functional occlusion for the orthodontist: Part 2 Journal of Clinical Orthodontics 15: 100-123 Swain BF (1986) Straight wire design strategies: five year evaluation of the Roth modification of the Andrews Straight-Wire Appliance In: Graber LW ed. Orthodontics State of the Art Essence of the Science: St Louis, The CV Mosby Company

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Chapter

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11 Self-ligating brackets: theory and practice Nigel Harradine and David Birnie

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Introduction Self-ligating brackets have an inbuilt metal labial face which can be opened and closed. These brackets incorporating their own ligation system have existed for a surprisingly long time in orthodontics - the Russell Lock edgewise attachment being described by Stolzenberg in 1935 – but they have made a major impact in orthodontics only in the last decade. There is no doubt that they add a new dimension to orthodontic treatment and it can be argued that they are more than just a bracket system facilitating tooth movements that are difficult to achieve with conventional appliances. It is worth trying to think about the other benefits that current selfligating brackets may offer and some of these concepts are encapsulated in an article by Alan Pollard (2003).

Many designs of self-ligating bracket have been patented, although only a minority have become commercially available.

New designs continue to appear, with at least twenty four new brackets since 2000 (Table 11.1). This rapidly accelerating activity is in spite of the fact that until recently, self-ligating brackets had never attracted more than a small percentage of bracket sales. All manufacturers have come to appreciate the capabilities of these brackets.

Bracket

Year

Russell Lock

1935

Ormco Edgelok

1972

Forestadent Mobil-Lock

1980

Orec SPEED

1980

“A” Company Activa

1986

Adenta Time

1994

“A” Company Damon SL

1996

Ormco TwinLock

1998

Ormco/”A” Co Damon 2

2000

Gestenco Oyster

2001

GAC In-Ovation

2002

GAC In-Ovation R

2002

Adenta Evolution LT

2002

Ultradent Opal

2004

Ormco Damon 3

2004

3M Unitek SmartClip

2004

Ormco Damon MX

2005

Class One/Ortho Organisers Carrière LX Forestadent Quick

2005

Lancer Praxis Glide

2006

GAC System-C

2006

GAC In-Ovation L

2006

Ultradent OPAL metal

2006

Forestadent Quick

2006

Lancer Praxis Glide

2006

GAC In-Ovation C

2006

3M Unitek Clarity SL

2007

American Orthodontics Vision LP

2007

Dentaurum Discovery SLB

2007

Ortho Technology Lotus

2008

Ormco Damon Q

2009

Ormco Damon Clear Aesthetic

2010

Ormco Nexus

2011

Table 11.1:

Self-ligating bracket designs

2006

We have a fairly wide range of experience with different selfligating brackets since 1982, having in the past treated a considerable number of cases with Speed brackets, a few with Mobil-Lock brackets, a large number with Activa brackets from 1986 to 1995, Damon SL brackets from 1995 to 2000 and TwinLock brackets on a few cases. We treated many cases with Damon SL brackets which had tie-wings and a selfligation slide and superseded Activa in 1996. Damon 2 brackets were a substantial further development of this concept. Damon MX brackets have a new slide mechanism and the successor Damon Q brackets are due for release as we go to press. In-Ovation is another well-known bracket which was previously known as Interactwin and Sigma before their commercial release in 2000. They have tie-wings but have an active self-ligation clip. The 3M Unitek SmartClip bracket has wire-retaining spring clips added to either side of a conventional bracket and is a passive self-ligating design. The relative merits of active and passive clips or slides will be discussed later in this chapter. Aesthetic self-ligating brackets have also appeared. Oyster and Opal brackets are made of composite polymers whilst Clarity SL, In-Ovation C and Damon 3 are semi-aesthetic brackets. Damon Clear is a ceramic bracket with a ceramic slide. Other manufactures such as Forestadent (the Philippe bracket) and Adenta have produced lingual self-ligating brackets. Adenta LT brackets are a lingual version of the Time bracket.

We have used fifteen of the designs in Table 11.1 which is not an exhaustive list, new brackets having continued to appear with great frequency in recent years. In the light of these experiences and against the background of this explosion of self-ligating designs, this chapter looks first at the requirements of an ideal bracket ligation system and the extent to which the current self-ligating brackets meet these requirements.

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Properties of an ideal ligation system Orthodontists have become so used to accepting that tie-wing brackets are the way that ligation is performed, that it is worthwhile considering a list of ideal properties of any ligation system. This puts in perspective any assessment of the benefits and difficulties with current self-ligating systems. Archwire ligation should:

• • • • • •

be secure and robust ensure full bracket engagement of the archwire exhibit low friction between bracket and archwire be quick and easy to use assist good oral hygiene be comfortable for the patient

Conventional wire and elastomeric ligatures in relation to the requirements for an ideal ligation system Secure robust ligation

It is highly desirable that once ligated, the system is very resistant to inadvertent loss of ligation. Wire ligatures are good in this respect, whilst elastomeric ligatures are much less good, especially if left for too long without being renewed. The force decay of elastomerics has been well documented (Taloumis et al 1997). A paper by Eliades and Bourauel (2005) discusses the underlying reasons for this loss of mechanical properties and its clinical significance, whilst Crawford et al (2010) thoughtfully quantified the in vivo loss of elastomeric ligating force.

Full bracket engagement

It is a large advantage if the archwire can be fully engaged in the bracket slot and then maintained there with certainty. Wire ligatures essentially meet this requirement if tied with care. Elastomerics are again worse in this respect since they may on occasion exert insufficient force to fully engage even a flexible wire and the subsequent degradation of their elastic performance may cause a significant further loss of full engagement as the elastomeric stretches. Twin brackets with the ability to ‘figure of 8’ the elastomerics are a significant help in this respect but certainly not a complete answer.

Quick and easy to use This is a major weak point of wire ligatures and the principal reason for the enormous decline in their use. Maijer and Smith (1990), and Shivapuja and Berger (1994) have shown that wire ligation is very slow compared to elastomerics. In the latter study, the use of wire ligatures added almost 12 minutes to the time needed to remove and replace two archwires. This is the largest and very understandable reason why so few wire ligatures are now used.

Low friction

Wire ligatures are again better than elastomerics; producing 30%-50% of the friction forces in the study by Shivapuja and Berger (1994) but the forces still reach undesirable levels relative to the force levels considered ideal for tooth movement. Khambay et al (2004) also found that stainless steel ligatures produced lower frictional forces than elastomerics. Interestingly, the polymeric-coated SuperSlick ligatures (TP Orthodontics Inc. Indiana) which were designed to reduce friction, produced more friction than more conventional elastomerics. Also, the force normal to the archwire produced by a wire ligature is very variable (Iwasaki et al 2003) even after training in a standardised method of ligature tying. This force has also been shown to be more variable for elastomeric ligatures than for passive self-ligation (Thorstenson and Kusy 2001). When initially placed, an elastomeric in a ‘figure of 8’ configuration increases the friction by a further 70-220%. compared to the ‘O’ configuration (Sims et al 1993) .

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Easy attachment of elastic chain

Some self-ligating brackets such as Opal and SPEED dispensed with tie-wings. This makes attachment of elastic chain and if desired, elastomeric ligatures somewhat less convenient. Most of the recently developed self-ligating brackets have tie-wings, although some of these offer rather reduced undercut, the manufacturers giving greater priority to reduction in overall bracket size. Placement of elastomeric chain behind the archwire avoids ant problem of retention of the chain and minimises friction from the chain.

Assists good oral hygiene

Elastomerics accumulate plaque more than do tie-wires and fluoride releasing elastomerics have yet to reach reliably robust performance levels by way of compensation. The ends of wire ligatures are however an additional obstacle to oral hygiene. An interesting paper by Turkkahraman et al (2005) compared elastomerics and wire ligatures with respect to various measures of plaque quality and quantity, gingival index, probing depth and bleeding on probing. The bacteriology results slightly favoured wire ligation, but not to a significant extent, but the important sign of bleeding on probing was substantially higher with elastomeric ligation.

Comfortable for the patient

Elastomerics are good in this respect, but wire ligatures require careful tucking in of the ends to avoid soft tissue trauma and even then can occasionally be displaced between appointments and cause discomfort.

Summary: What are the disadvantages of conventional ligation?

• failure to provide and to maintain full archwire engagement • high friction • for elastomerics, the force (and therefore tooth control) decays and they are sometimes lost • potential impediment to oral hygiene • wire ligation is a very slow process Wire ties are secure, robust, enable full, partial or distant ligation and have lower friction than elastomerics. Their large drawback is the time required for ligation. Elastomerics are quick but less good in every other respect.

Neither method is ideal and both are inferior to a molar tube assembly which is universally adopted as the ‘ligation’ of choice on posterior teeth. It is easy to find examples of the deficiencies of conventional ligation, but clinicians have become accustomed to tolerating these shortcomings.

Proposed core advantages of self-ligating brackets In the last two decades, a consensus has emerged on the potential core advantages of self-ligation. These advantages apply in principle to all self-ligating brackets although the different makes vary in their ability to deliver these advantages consistently in practice. The proposed core advantages can be summarised as:

• • • •

more certain full archwire engagement lower friction between bracket and archwire less chairside assistance faster archwire removal and ligation

Secure, full archwire engagement Full engagement is a feature of self-ligation because, if a clip or slide is functioning properly, it is either fully shut or it is not. Unintentional partial engagement is not possible. There is no problem of decay of the ligature as with elastic ligatures. However, security of ligation will depend on the clip/slide being robust and not inadvertently opening. Until recently, this requirement for security of performance was not fully met by any self-ligation designs, but several current brackets have mechanisms which deliver this advantage and the consequent enhanced control of tooth position. Secure, full archwire engagement maximises the potential long range of action of modern low modulus wires and minimises the need to regain control of teeth where full engagement is

SELF-LIGATING BRACKETS: THEORY AND PRACTICE EXCELLENCE IN ORTHODONTICS 2012

2.5

lost during treatment. In a recent splitmouth study (Mezomo 2011), of canine retraction on 0.018” stainless steel wires, self-ligating brackets were found to give better rotational control of the canine than conventionally ligated brackets. 80% of canines rotated more than 10 degrees with conventional brackets, as opposed to 33% with Smartclip brackets over the 12 week period.

2

1.5 newtons

215

1

0.5

Low friction This aspect has received much debate and some good investigation. Very low friction A Co Damon SL Adenta Time TP TipEdge A Co Std when drawing wires through well-aligned brackets has been clearly demonstrated Figure 11.1: Data from Thomas et al (1998) showing typically very low friction and quantified many studies e.g. Sims et al for self-ligating brackets compared to conventional ligation (1993, 1994), Berger (1990) and Shivapuja and Berger (1994) for both Activa and Speed brackets and indeed Edgelok. Voudouris (1997) reported greatly reduced friction with Sigma and Interactwin prototypes and with Damon brackets. The friction is dramatically lower than for elastomeric rings with conventional brackets and seems to be an inherent characteristic of self-ligating brackets. Thomas et al (1998) confirmed extremely low friction with Damon brackets compared to both conventional preadjusted and also Tip-Edge brackets. Kapur et al (1998) found that with NiTi wires the friction per bracket was 41 g with MiniTwin and conventional ligation and 15 gm with Damon brackets whilst with stainless steel wires, these values were 61 gm and only 3.6 gm respectively. Pizzoni et al (1998) have reported that Damon brackets showed lower friction than Speed which in turn had less friction than conventional brackets stating that: “In the case of rectangular wires, the Damon bracket was significantly better than any of the other brackets and should be preferred if sliding mechanics is the technique of choice”. Meling et al (1997), examining the effect of friction on wire stiffness concluded that each elastomeric placed in an ‘O’ configuration produces an average of 50 gm of frictional force. This figure is supported by Khambay et al (2004) using a method which gave zero friction for Damon 2 brackets and found mean frictional forces ranging between 43 and 98 gm (0.43 and 0.98 cN) for various elastomeric/archwire combinations.

0

0.014 NiTi

0.0175 TF

0.016x0.022 SS

0.016x0.022 NiTi

0.019x0.025 SS

The crucial question is how relevant these clear results are to the in vivo situation. The obvious next requirement was to investigate resistance to sliding with active archwires and this has also been extensively investigated.

Resistance to sliding - friction in vivo and with active wires

The equation RS = FR + BI + NO is now widely appreciated within orthodontics, but needs to be investigated in ways which are clinically realistic. RS = the total resistance to sliding in a given situation.

FR = classical friction. This is the resistance to relative movement between two surfaces. It depends on the materials and the normal (at right angles to the surface) force between the surfaces. Thus rubber materials have higher friction than metal. This explains why cars have rubber tyres and why trains cannot climb or descend steep slopes. In orthodontic context, the normal force is the force of ligation, hence figure of eight elastomerics have higher friction than those in an ‘O’ configuration.

Angulation (degrees)

Damon SL

0 3.5 6.0

0 0 80

Conventional Bracket 34 55 140

Table 11.2: Resistance to sliding (RS). for different bracket angulations with a 0.018/0.025 archwire. Forces in cN. The difference is 60 gm at 6 degrees of angulation Thorstenson and Kusy (2001)

BI = binding is the resistance to sliding when edges or corners of a material are in contact with the opposing surface. This applies in all active archwires in a bracket slot and is directly proportional to the angle of contact.

NO = notching and refers to the effect on RS of

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damage to one of the surfaces. Some ceramic brackets have in the past been shown to cause such notching if the angle of contact was high. It is probably not a significant factor in most clinical situations.

Several earlier studies e.g. Read-Ward et al (1997), Loftus et al (1999) demonstrated that laboratory studies involving active archwires found a reduced difference in RS between self-ligating and conventional brackets than studies with passive archwires where FR was the only contributor to RS. This is to be expected because ligation force is only one contributor to RS. Three good studies by Thorstenson and Kusy have investigated aspects of this topic. Thorstenson and Kusy (2001) examined the effects of varying active tip (angulation) on the resistance to sliding. They also found that angulation beyond the angle at which the archwire first contacts the diagonally opposite corners of the bracket slot causes a similar rise in resistance to sliding of both self-ligated (Damon SL) and conventional brackets.

However, at all degrees of tip, the Damon brackets produced significantly less resistance to sliding (Table 11.2). At a realistic angulation of 6 degrees for an 0.018" x 0.025" stainless steel wire, the difference is 60 gm per bracket which is very probably of clinical significance. The second paper (2002a) compared different self-ligating brackets for resistance to sliding with active angulations. It quantifies a little more closely the lower resistance to sliding with passive self-ligation and points out that low resistance to tooth movement can lead to unanticipated movement as is mentioned later in this chapter. The third paper (2002b), examined the same factors with wires of different sizes and in the dry state. The increase in friction when larger wires deflect the clips in active selfligating brackets is quantified and the scanning electron micrographs of the different brackets show very clearly the relationship between small and large wires and active clips and passive slides. A study by Matarese et al (2008) is yet another to show that irregularity of the teeth does not prevent self-ligating brackets (Damon2 in this instance) from producing significantly less resistance to sliding.

The relative clinical importance of classical friction and binding

The views expressed on this important point vary widely, even when the same research is being quoted. For example, Brauchli et al (2011) quote data from Thorstenson and Kusy (2001) to the effect that for an 0.018” x 0.025” wire, “with angulations of 7° between the archwire and slot, more than 94% of the RS is caused by binding”. This has been taken to imply that the contribution to RS from the lowered friction with self-ligation is irrelevant.

Whenever archwire activation causes binding. In fact, it is of course the very low friction with self-ligating brackets that makes any binding component such a high percentage of the overall RS. If the friction is zero, the binding component will constitute 100% of the RS. The other way of accurately describing the same data is as we have done in the preceding paragraph – “At a realistic angulation of 6 degrees for an 0.018" x 0.025" stainless steel wire, the difference is 60 gm per bracket which is very probably of clinical significance”. Pliska et al (2011) have also investigated the relationship between tipping moments and RS. They too found that at high levels of tip, any reduction in friction is drowned by the high binding, but at lower levels, a potentially significant reduction in RS was seen as expressed in grams for force. In their words, “At the higher moment levels (4000 g-mm), no significant reduction in RS was found between conventional (CL) and self-ligating(SL) brackets on both SS and NT archwires. At lower levels of applied moment (2000 g-mm), reductions in RS of 18% (42.7g) and 18% (38.5 g) were found between the CL bracket and the best performing SL bracket on NT and SS, respectively.” Some enthusiasts and severe sceptics about the benefits of self-ligation can both be justifiably accused of selective quoting from research to suit their point of view. Our intention is to thoughtfully and accurately scrutinise and report results in the context of best clinical relevance.

One study (Reznikov 2010) appears in its summary to contradict these findings of Thorstenson and Kusy and Matarese, although the actual figures in their tables show much lower RS values for self-ligating brackets. They attribute their conclusion that self-ligation in fact causes higher RS, to the lack of deformability in a metal labial slot face compared to an elastomeric. Their experimental setup examines the effect of a very small (e.g. 0.15 mm) lingual displacement of a tooth on an 0.018” x 0.025” stainless steel wire. The lingually displaced tooth was not permitted to rotate or move labially into a passive alignment. Extremely high RS values (349-641 cN) were recorded for this tiny archwire displacement. The reader is left wondering how we ever move teeth along a wire if such high resistance forces are so easily generated. We suspect that this setup fails to realistically model the clinical situation. All laboratory studies need careful scrutiny of the likely realism of their modelling of the in vivo

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situation. Most such studies will only aim to model part of the full clinical picture. Brauchli et al (2011) clearly demonstrate how sensitive the results of such studies are to the specifics of the experimental setup e.g. in one of their setups, SPEED brackets counter-intuitively exhibited lower RS when there was binding than when there was no binding. Further complexity when modelling clinical variables is revealed in the study by Heo and Baek (2011). They found different relative levels of reduction in friction with different self-ligating brackets with different archwire alloys and with deflections in different planes of space. For example, when comparing Cu NiTi and austentic NiTi, Damon-Q and Damon-3Mx produced significantly lower RS with Cu NiTi whereas Clarity-SL produced lower RS with austentic NiTi. It should however be noted from this study that typical levels of RS with a tooth displaced vertically by 3 mm from its neighbours ranged from 400-500cN for self-ligating brackets but were 2700 cN with a conventional bracket (3700 cN with austenitic NiTi). This size of difference would seem to be of potential clinical significance.

Systematic reviews of RS and self-ligation A systematic review of this question by Ehsani et al (2009) concludes that the case is proven for lower RS with self-ligation with round wires, but not for the larger rectangular wires or with active archwires where more evidence is still required. An interesting facet of the study selection for this review is that two seminal papers by Thorstenson and Kusy referred to above were not mentioned. The characteristic strengths and limitations of a systematic review are probably illustrated in that they tend to weigh papers of differing quality equally and conclude that no conclusions can yet be drawn. Whilst there is still ample scope for more and better studies of this potentially complex field, we feel that current evidence and extensive clinical experience supports the view that resistance to sliding is lowered to a clinically significant extent with self-ligation, but that this remains a view with inconclusive experimental support.

Studies of net aligning force Net aligning force is the other side of the resistance-to-sliding coin and is an equally important way of exploring and expressing RS. Until recently this has been inadequately appreciated and investigated. Almost all studies had measured the force resisting an archwire sliding along a wire. Three recent and excellent papers have explored this the converse â&#x20AC;&#x201C; namely the net aligning force remaining in an archwire in spite of the resistance to sliding - when a tooth is significantly misaligned. Baccetti et al (2009) measured this in relation to vertical displacement of a tooth. The rather novel and well-considered difference from many studies is that their Instron machine did not measure the force required to pull an archwire through the brackets, but measured the residual net aligning force on the misplaced tooth. They found that at low levels of misalignment there was little difference between ligation methods, but beyond a 3mm vertical misalignment, with conventional ligation the aligning force available was very substantially reduced by conventional ligation. At 6 mm displacement there was no remaining aligning force with conventional ligation but 40 to 120 gm remaining for self-ligating brackets. An interesting point is that a similar effect was found with Synergy low-friction ligatures, but of course the paper by Matasa (2001) has described how elastomerics when held away from the archwire achieve this low friction at the cost of lower control. This paper by Baccetti is typical of the trend towards better in vitro methodology in this area of investigation.

The same team (Franchi et al 2009) used the same methodology with a buccally displaced canine with essentially the same findings. At 4.5 mm of buccal displacement, the net force delivered using conventional brackets had dropped to zero whilst 120 gm of force remained with the passive self-ligating and low friction brackets. It should be noted that in both of these directions of tooth displacement â&#x20AC;&#x201C; vertical and buccal - the interaction which provides the alignment is entirely with the walls of the bracket slot and the ligation component need have no interaction with the archwire at all. The friction force between the ligature and the archwire is responsible for negating the desired tooth-aligning force. The reader should consider what tooth movement is likely to arise from the forces stored in the archwire if it is initially unable to move the canine. This question will occur later in this chapter when considering the work of Badawi and potential qualitative differences in tooth movement.

This inverse relationship between friction and residual effective force was also investigated by Peterson et al (2009) who measured the residual forces available to align a lingually placed canine tooth. They found that the

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friction from an elastomeric ligature significantly reduced (“eats up”) the force available for alignment by approximately 50%. An additional finding was that if the elastomerics were artificially aged, their frictional force was reduced to an extent that the residual force was not substantially less than with a self-ligating bracket (the active In-Ovation R). However, we should remember that such a relaxed elastic will correspondingly diminish the control of the archwire, especially if the tooth is lingually placed or rotated. Interestingly, these laboratory results were very similar to an in vivo study by Crawford et al (2010) who also found that the substantial weakening of the elastomerics in vivo was directly related to a reduction in friction. Interestingly the authors comment that “the results of our in situ study concur with those of the best outcomes from the laboratory studies, although the variability was greater and increased the longer the material was in the mouth”. Well-designed in vitro studies may indeed give a good indication of in vivo conditions.

Key point: Brackets which generate less friction should move teeth with a lower applied force but can correspondingly produce higher net forces on the tooth if too thick or stiff wires are used during alignment.

Friction in vivo – occlusal and masticatory forces A further factor has been investigated in studies by Braun et al (1999) and O’Reilly et al (1999) who found that various vibrations and displacements of a test jig (to mimic intra-oral masticatory forces) can substantially reduce the friction with conventional ligation. This is a valid line of enquiry and an interesting finding, but the question then arises as to how accurately these laboratory studies mimic intra-oral masticatory ‘jiggling’ forces. The full interpretation of laboratory friction studies is clearly difficult and the in vivo situation will show substantial variation. An study by Iwasaki et al (2003) employed an intra-oral device to produce a combination of tipping and ligation forces and measured the effect of chewing gum on the resulting resistance to sliding. They concluded, “these results refute the hypothesis that masticatory forces consistently and predictably decrease friction”. This conclusion is probably a bit too firm to be fully justified.

Clinically, the low friction is very evident from the need with self-ligation to place a stop on all archwires to prevent the strong tendency for the archwire to slide through the brackets and traumatize the mucosa distally.

Measurement of the variables which influence in-vivo friction will remain a challenge, but progress is being made.

Meanwhile, the balance of the current evidence from studies and from clinical experience is that self-ligation provides very significant reduction in friction in all dimensions of tooth movement.

Clinical significance of low friction Friction must be overcome for the majority of tooth movements to occur. Such movements include levelling, bucco-lingual alignment, rotation, correction of angulation, opening of space and any space closure with sliding mechanics. Frictional forces arising from the method of ligation are one source of the resistance to this relative movement between archwire and bracket. Correspondingly higher forces must therefore be applied to overcome this resistance and this has two related potential effects which inhibit tooth movement. Firstly, the net effective force is much harder to assess and is more likely to be undesirably higher than levels best suited to create the optimal histological response. Secondly, the binding forces are higher both between bracket and wire and also at the contacts between irregular adjacent teeth. These binding forces also inhibit the required relative movement between bracket and wire. Only a few tooth movements such as space closure with closing loops placed in the space, expansion of a well-aligned arch, and torque (inclination) changes are not influenced by a low-friction method of ligation. At the same time, it must be remembered that with any given archwire, the net force on a tooth will be higher of the friction is lower. Smaller, softer archwires will therefore be indicated in many situations with self-ligating brackets. This point was well made by Matarese et al (2008) “it appears that the significant reduction of friction we found when testing self-ligating brackets against conventional ones allows the mechanical characteristics of the wires to be exploited more efficiently. This suggests that, when practitioners use self-ligating brackets, these should be coupled with wires that generate lower levels of force to avoid overloading the periodontal tissues.”

Key point: Low friction with self-ligation is for certain. Low resistance to sliding in clinical practice seems probable from the

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best available data. More research will improve our knowledge of how much this reduces resistance to sliding in real clinical situations.

Secure ligation and low friction as a combination of properties

Other bracket types - most notably Begg brackets - have low friction by virtue of an extremely loose fit between a round archwire and a very narrow bracket, but this is at the cost of making full control of tooth position correspondingly more difficult. Some brackets with an edgewise slot have incorporated shoulders to distance the elastomeric from the archwire and thus reduce friction, but this type of design also produces reduced friction at the expense of reduced control, since the shoulders which hold the ligature away from the archwire increase the slot depth and reduce the tension in the elastomeric. This reduces the control of rotations or of labiolingual tooth position. Elastomeric rings cannot provide and sustain sufficient force to maintain the archwire fully in the slot without also pressing actively on the archwire to an extent which increases friction.

Comparison with a molar tube This comparison is helpful in this context, since such an attachment is in essence a passive self-ligating bracket with the slide permanently closed. If a convertible molar tube is converted to a bracket by removal of the slot cap or straps, an elastomeric or even a wire ligature can prove very ineffective at preventing rotation of the tooth if it is moved along the wire or used as a source of intermaxillary traction. These ligation methods simultaneously increase friction while attempting to retain full archwire engagement. The challenge of simultaneously combining low friction and good control was very nicely illustrated in an article by Matasa (2001), who investigated ‘low friction’ conventional brackets. He showed that all steps to reduce friction in the design of such brackets involved distancing the elastomeric from the archwire with reduced tooth control. The investigation into three such ‘low friction’ bracket types by Thorstenson and Kusy (2003) also found no evidence that bumps in the floor of the archwire slots reduced resistance to sliding. With tie-wing brackets and conventional ligation, an improvement in friction is usually at the cost of deterioration in control. The combination of very low friction and very secure full archwire engagement in an edgewise-type slot is currently only possible with self-ligating brackets (or with molar tubes!) and is likely to be the most beneficial core feature of such brackets. This combination enables a tooth to be slid along an archwire with lower and more predictable net forces and yet under complete control with almost none of the undesirable rotation of the tooth resulting from a deformable mode of ligation such as an elastomeric.

Possible anchorage consequences of low friction and secure full archwire engagement This combination of properties could possibly conserve anchorage for three reasons:

•

• •

with low friction, the net tooth-moving forces can be more predictably low and the reciprocal forces correspondingly smaller. A study by Yee et al (2009) measured canine retraction and anchorage loss with a light (50 gm) and heavy (300 gm) forces. The percentage of anchorage loss was significantly but not dramatically higher (62%) with the heavy force than with the light force (55%). lower applied forces may facilitate release of binding forces between wire and bracket, enhancing sliding of brackets along a wire. individual teeth - for example canines - can be retracted separately along an archwire and thus potentially reduce the overall anchorage demands by reduction of the root area of teeth to be moved at any one time, but with none of the potential disadvantages of other methods of separate canine retraction with conventional brackets e.g. loss of rotational control. Following such separate canine retraction, the low friction of self-ligating brackets then permits the sensible use of sliding mechanics to retract incisors even though there will now be a minimum of three brackets distal to the remaining space through which archwire sliding must occur. This applies equally to preservation of anterior anchorage in hypodontia cases.

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Alignment of severely irregular teeth

One situation in which the combination of low friction and secure full engagement should prove particularly useful is in the alignment of very irregular teeth and especially the resolution of severe rotations where the capacity of the wire to slide through the brackets of the rotated and adjacent teeth significantly facilitates derotation. This relationship between friction and derotation has been described and quantified by Koenig and Burstone (1989) and the potential adverse forces shown to be very large. Low friction should therefore permit rapid alignment and more certain space closure, whilst the secure bracket engagement permits full engagement with severely displaced teeth and full control whilst sliding teeth along an archwire. Modern, low modulus wires substantially enhance our ability to harness these benefits. These effects were specifically explored ex vivo by Matarese et al (2008). It is this feature which gives the strong clinical impression that the alignment of crowded teeth with self-ligating brackets but without extractions is facilitated if this is the desired treatment goal. However, it must be remembered that faster alignment has not been found in a number of studies.

Less chairside assistance and faster ligation/ archwire removal The original motive when developing the earlier self-ligating brackets was to speed the process of ligation. For example a paper by Maijer and Smith (1990) demonstrated a fourfold reduction in ligation time with Speed brackets compared to wire ligation of conventional brackets. Shivapuja and Berger (1994) have shown similar results but also that the speed advantages compared to elastomeric ligation are less dramatic (approximately one minute per set of archwires). Voudouris (1997) has also reported a fourfold reduction in archwire removal/ ligation time with prototype Interactwin brackets. A study by Harradine (2001) found statistically significant but clinically much more modest savings in ligation/re-ligation time with Damon SL - an average of 24 seconds per archwire removal and replacement. It should however be remembered that archwire 'ligation' using self-ligating brackets does not require a chairside assistant to speed the process, since self-ligating brackets require no passing of elastomeric or wire ligatures to the operator during ligation. Turnbull and Birnie (2007) investigated the difference in time taken to open and close brackets for different archwire groups with Orthos and Damon 2 brackets. The authors found time savings slightly greater than those of Harradine with Damon 2 brackets being 1 second per bracket for opening brackets and 2 seconds per bracket for closing brackets. It was twice as quick to close Damon 2 brackets as to ligate Orthos brackets. For both bracket systems, the time taken to ligate and unligate archwires decreased with increasing archwire size (and correspondingly better tooth alignment) as shown in Figure 11.2.

It is very probable that more recent bracket types such as the Damon 3MX or Damon Q would show much greater savings in time for archwire changes because the mechanism is so easy and rapid even for a novice. Interestingly, no studies with these brackets have emerged â&#x20AC;&#x201C; probably because the speed and ease of the more modern brackets is now taken as read.

10

Factors which have hindered the adoption of self-ligation

9 8 7

seconds

6 5 4 3 2 1 0 1 Damon open

2

Wire group

Orthos open

3 Damon close

4 Ortho close

Figure 11.2: Opening and closing times per bracket for Damon 2 and Orthos brackets for various archwire groups (from Turnbull and Birnie 2007)

It is interesting and instructive to consider why in spite of the potential advantages, selfligation has for so long and until so recently been a small part of orthodontics. In part this has been the result of imperfections in bracket performance. These imperfections have varied with different bracket designs and can be illustrated by examples from Table 11.1. We have used fifteen of the types in that table.

In our opinion, an ideal self-ligating bracket should deliver the core advantages already

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discussed and in addition should:

• • • • • • • • •

be very easy to open and close with low forces applied to the teeth during these procedures and with all archwire sizes and materials never open inadvertently, allowing loss of tooth control have a ligating mechanism that never jams or breaks or distorts or changes in its performance through the treatment period have a positively-held open clip/slide position, so that the clip or slide does not obstruct the view of the bracket slot or the actual placement of the archwire be tolerant of a reasonable excess of composite material without obstructing the clip/slide mechanism permit easy attachment and removal of all the usual auxiliary components of an appliance such as elastomeric chain, undertie ligatures, laceback ligatures without interfering with the self-ligating clip/slide permit easy placement and removal of hooks/posts and possibly other auxiliaries on the brackets.

With the security of self-ligation, the use of elastics directly to a bracket is much more frequently appropriate than with conventional ligation have a suitably narrow mesiodistal dimension to take advantage of the secure archwire engagement and permit large inter-bracket spans. have the performance expected of all orthodontic brackets in terms of bond strength and smoothness of contour

Reasons for the previous slow adoption of self-ligation:

• •

•

many brackets have been less than satisfactory in several of these requirements. Only more recently have advances in design and manufacture got close to producing a self-ligating bracket which meets all the requirements listed above. an inherent conservatism amongst orthodontists who tended to stick with the equipment and ideas given to then during their initial training. They learn skills which lessen the deficiencies of this equipment and way of thinking and then stick in their comfort zone. This is part of human nature.

Without thoughtful and innovative clinicians pushing for better products, manufacturers tend also to be conservative and fail to invest time, thought and resources into developing better products.

Happily, the field of self-ligation has produced several such clinicians to whom we are all indebted. the third factor limiting the rate of previous progress has been a lack of widespread appreciation of what low friction, secure archwire engagement and light forces can achieve. The potential of this combination of qualities was always apparent to most of the minority who used self-ligation even with earlier, less satisfactory bracket types.

A discussion of the essential features of some types of self-ligating bracket will serve to summarise the problems and the progress in bracket design.

Ormco Damon system Damon SL brackets

These self-ligating brackets (Figure 11.3) became available in 1996. They had a slide which moved vertically on the labial surface of an otherwise fairly conventional twin tie-wing bracket. These brackets were a major step forward, but suffered two irritating problems - the slides inadvertently opened and were prone to breakage. The study by NH (2001) quantified these problems. In 25 consecutive cases in treatment for more than one year, 31 slides broke and 11 inadvertently opened between visits. This compared with 15 broken and lost elastomeric ligatures in 25 consecutive cases treated with conventional brackets. Slide breakage was due to work hardening of the slide corners.

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Figure 11.3: (1996)

The Damon SL bracket

Figure 11.4: (2000)

The Damon 2 bracket

Figure 11.5: The Damon 3 bracket (2004). Slide opening is with a tool which engages the labial aperture. Slide closing is by finger pressure

Damon 2 System brackets (D2) The imperfections in the Damon SL led to the development of Damon 2 System brackets (Figure 11.4) which placed the slide within the shelter of the tiewings. Combined with the metal injection moulding manufacture, which permits closer tolerances, these developments almost completely eliminated inadvertent slide opening or slide breakage and made the ligation robust and secure. The improvements also permitted a much narrower bracket with the consequent advantages of a larger inter-bracket span. However, the brackets were not immediately and consistently easy to open and this aspect of functionality is important to the new user. Also, it was possible for the slide to be in a half-open position, hindering archwire removal or placement.

Damon 3 brackets (D3) These brackets (Figure 11.5) featured three major changes from previous Damon brackets.

• • •

a tooth-coloured composite resin base and upper tie-wing which reduces the visual impact of the bracket a completely new vertically-placed chair-shaped spring clip behind the slide. a rhomboidal shape of the bracket and slide which facilitates bracket siting

The ease of use of the slide mechanism was a huge improvement over previous versions of the Damon bracket, but early production examples suffered significant three very significant problems relating to the resin

Figure 11.6: (2005). Slide closed

The Damon 3MX bracket

Figure 11.7: (2005). Slide open

The Damon 3MX bracket

Figure 11.8: The Damon 3MX bracket (2005). Bracket ID in slot base

SELF-LIGATING BRACKETS: THEORY AND PRACTICE EXCELLENCE IN ORTHODONTICS 2012

Figure 11.9: Drop-in hooks for Damon 3MX brackets; Damon Q brackets use a slightly different shoulderless design

Figure 11.10: Q brackets

223

Drop-in hooks in place for Damon 3MX and Damon

component and the security of its junction to the metal component. These problems were largely overcome but they illustrate the considerable technical demands in manufacturing an ideal bracket.

Damon 3MX brackets These brackets (Figures 11.6, 11.7 and 11.8) were all-metal and had essentially the same slide mechanism as D3 with further refinements. They had a vertical slot behind the archwire slot into which prefabricated click-in auxiliary hooks can be added to any bracket as required (Figures 11.9 and 11.10) and removed when no longer needed. The main irritation with these brackets proved to be their susceptibility of the slide mechanism to becoming jammed with calculus build-up in some patients. This must have been a major factor in their replacement by Damon Q.

Damon Q brackets

These are the latest version of the Damon system (Figures 11.11 to 11.13) and illustrate the continued refinement of self-ligating bracket designs.

For example, the slide mechanism is designed to be even easier, more secure and more comfortable for the patient when opened and closed and immune to the effects of calculus accumulation. A clever feature is the reciprocal nature of the opening forces which leaves almost no net force on the tooth and the slide is opened. The brackets are also smaller in all dimensions than their predecessors and space has been found for a horizontal as well as a vertical auxiliary slot.

Figure 11.11: Ormco Damon Q bracket with gate closed; note horizontal auxiliary slot in upper tiewing; there is also a vertical slot

Figure 11.12: Ormco Damon Q bracket with gate open

Figure 11.13: The SpinTek tool with its opening and closing ends. The opening end is rotated to produce forces which are almost entirely borne by the bracket, not by the tooth. The closing end incorporates an archwire-location element with the same function as the Cool Tool

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Aesthetic self-ligating brackets

Figure 11.14: Ormco Damon Clear aesthetic brackets in the upper labial segment and Damon Q brackets in the lower arch and upper premolars.

Aesthetic self-ligating brackets have appeared on the market as manufacturing and material technology improves. GAC’s In-Ovation C is a polycrystalline bracket with a rhodium plated metal clip; a debonding guide is available as a podcast. Ormco have recently introduced the Damon Clear aesthetic bracket – a polycrystalline bracket with a ceramic slide (see Figure 11.14). Ceramic brackets are likely to need more progressive archwire sequences than metal brackets to prevent bracket damage. TMA archwires are probably more sensible for active torque than are stainless steel wires.

GAC In-Ovation brackets • these popular brackets are extremely easy to close inadvertently before the archwire is in position and the downward direction of closure makes this more likely in the lower arch.

• the security of closure of the flexible clip can be overcome by some rectangular nickelFigure 11.15: The Figure 11.16: The more titanium wires, which can cause spontaneous GAC In-Ovation bracket recent Opin R version of the GAC opening of the clip. This applies more to the In-Ovation bracket permits narrower R versions of the bracket with their opening of the clip using a probe narrower slides. in the labial notch • when using wire-ligature underties to maintain space closure or lacebacks across extraction spaces, the spring clips are a nuisance in competing for the space behind the tie-wing.

In-Ovation brackets have an active clip and this aspect is discussed in a later section of this chapter

3M Unitek SmartClip brackets This bracket which became available in 2004 is a conventional bracket with additional nickel-titanium spring clips mesial and distal to the tie-wings (Figure 11.17). It is a passive self-ligation system with a distinctive clip mechanism. The following points are pertinent.

• • •

the insertion of small diameter archwires is easy. removal of archwires with the special tool needs a little practice but is easy with small diameter wires the spring clip has to cope with providing easy insertion and also no inadvertent loss of ligation for both small flexible and large stiff archwires. This is a very testing requirement. Other spring clips (such as on SPEED brackets) with their vertical action have a rigid bracket component to assist the spring in resisting loss of ligation. The spring on the SmartClip has to cover the wide range of requirements for different wire sizes with one shape and stiffness of spring unaided by a rigid component.

• with early brackets, removal of larger, stiffer wires meant overcoming an advertised 2 kilograms of force per bracket with a labially directed force. This force seemed high to the operator and to the patient

Figure 11.17:

3M Unitek SmartClip bracket

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•

•

225

and recently the manufacturers have responded by introducing a more flexible clip. This should permit easier removal of thicker archwires, but may make spontaneous loss of archwire engagement more frequent – time will tell. Many operators advise avoiding all stainless steel wires with these brackets due to the force and discomfort associated with archwire insertion and especially removal. This factor may be related to the findings reported by O’Dwyer at the British Orthodontic Conference 2008 that archwire changes were on average 48 seconds slower with SmartClip than with conventional ligation. Fleming et al (2009) also found substantially greater pain associated with archwire changes with SmartClip when compared with conventional ligation even in the early alignment phase. More recently the use of two 0.014” wires in the one slot has been recommended as a good way of minimising these difficulties. the effective width of the bracket is wider than for most other self-ligating brackets which have taken advantage of the more secure, full ligation of self-ligating brackets to reduce bracket width, thus lowering forces with no loss of tooth control. The wider SmartClip brackets reduce the interbracket span and would be expected to provide higher forces. This bracket has recently become available as a ceramic bracket with the same metal spring clips (Clarity SL).

At the British Orthodontic Conference 2008, Sidhu and Sherriff reported significantly higher friction resistance for Smartclip brackets with almost all archwires when compared with Damon MX.

Active clip or passive slide?

This is an issue which has attracted heated debate (Matasa 1996), (Rinchuse 2007). It is therefore worth a detailed consideration.

In Table 11.1, SPEED, In-Ovation, Nexus and Quick brackets are examples of brackets which have a sliding spring clip, which encroaches on the slot from the labial aspect, potentially placing an active force on the archwire. Time brackets have a similar clip but for closure it rotates round a tie-wing rather than slides into place. These three brackets all have potentially active clips. In contrast, Damon brackets have a slide which opens and closes vertically and creates a passive labial surface to the slot with no intention or ability to invade the slot and store force by deflection of a metal clip. Smartclip, Praxis Glide, Carrière LX, Vision LP and Lotus are also passive systems.

An active clip can store some of the applied force in the clip as well as in the wire. The intended benefit is that in general terms a given wire will have its range of labiolingual action extended and produce more alignment than would a passive slide with the same wire. This needs more detailed consideration. It is perhaps helpful to think of the situation with three different wire sizes.

•

with thin aligning wires smaller then 0.018" diameter The potentially active clip will be passive and irrelevant unless the tooth (or part of the tooth if it is rotated) is sufficiently lingually placed in relation to a neighbouring tooth that the wire touches the clip. In that situation, a higher total force will usually be applied to the tooth in comparison to a passive clip. Even if there is no significant clip deflection there is still a force on the wire which would not exist with a passive clip because the active clip effectively reduces the slot depth from 0.027" (the depth of a Damon slot) to approximately 0.018", either immediately - if the clip is not deflected - or as the wire goes passive if it is deflected. This additional force is unlikely to be detrimental with modern low modulus wires but should be borne in mind. For teeth which were initially placed lingual to their neighbours, the active clip can bring the tooth more labially (up to a maximum of 0.027 - 0.018 = 0.009 inches) with a given wire. These figures are slightly complicated by the fact that the active clip does not reduce the slot depth to the same extent over the whole height of the slot - the clip on Speed, Time and In-Ovation brackets impinges into the slot more at the gingival end than at the occlusal. This is well visualised in the illustrations in Thorstenson and Kusy (2002b). This asymmetry would make a difference with small diameter wires depending on the relative vertical positions if neighbouring teeth. The effect of having an active clip at this early stage of treatment can be thought of as having a potentially shallower bracket slot. This will frequently produce higher forces with a given wire but a potential maximum extra 0.009" of labial movement of some teeth for a given small diameter wire. This figure is approximate for the reasons

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•

•

given above. Pandis et al (2010) found no difference in the rate of alignment when comparing the passive Damon MX with the active In-Ovation R brackets. for wires > 0.018" diameter The active clip will place a continuous lingual force on the wire even when the wire has gone passive. On teeth which are in whole or in part lingual to a neighbouring tooth, the active clip will again bring the tooth (or part of the tooth if rotated) slightly more labial than would have been the case with a passive clip at 0.027" slot depth. The maximum difference will be the difference between the labiolingual dimension of the wire and 0.027". For a typical 0.016" x 0.022" intermediate wire, this would give a maximum difference of 0.005". 0.016" x 0.025" or 0.014” x 0.025” nickel titanium wires are recommended as the intermediate aligning wire for Damon and this wire reduces this potential difference to 0.002". Lingually placed teeth would have a slightly higher initial force with an active clip and wires of this intermediate size. With an active clip, an active lingually-directed force will remain on the wire even when it is passive with thick rectangular wires An active clip will probably make a labiolingual difference in tooth position of 0.002" or less which is very small. An active places a lingually directed force on the wire in all circumstances which results in a higher friction and resistance to sliding. The relative merits regarding torque effectiveness are discussed below.

Torque effectiveness and active vs. passive brackets The suggestion that the lingually-directed force on a rectangular wire from an active clip (or from a conventional ligature) will cause additional torque from an undersized wire is interesting. Figure 11.18 shows that the clip places a diagonally directed lingual force on the wire. However, the need for an active clip to invade the slot reduces the available depth of one side of the slot, which increases the slop angle of play and so reduces this moment arm of the torquing mechanism. SPEED brackets have more recently addressed this problem on upper incisors by extending the gingival walls of the slot either side of the clip as “torquing rails”. This should indeed restore the torquing effectiveness, but at the cost of torquing forces a reduced mesiodistal width of the clip and therefore potentially reduced rotational control in a bracket which is already narrow. In-Ovation brackets have a small central portion of the slot wall which is at the full slot depth and provides full torquing capacity on that section.

The other potential source of torque is the bucco-lingual interaction between the base of the slot and the labial clip or slide. This topic has recently been investigated with a variety of methodologies. Firstly, a study by Badawi et al (2008) addressed the question whether the archwire contact with the labial active clip contributes to torque effectiveness. With their methodology, the lingually directed force from an active clip did indeed contribute to torquing capacity. They expressed this as a reduction of the ‘slop’ angle (play) at which sufficient force is generated to influence third order tooth position. However, Huang et al (2009) explored the same issue not by direct measurement but by using finite element modelling and they found very opposite results for torque effectiveness. They found that although SPEED brackets did indeed have the smallest play, the force at this angle was far too small to provide effective torque and the torque moment only got to therapeutic levels at a much higher angle than for the passive Damon brackets. The torque effectiveness of conventionally ligated Discovery brackets with either elastic or stainless steel ligatures was very comparable to the behaviour of the Damon. This paper therefore suggests that the couple between the gingival and buccal slot walls is more important than any effect from the active clip. More work has been published from the team in Alberta using the same technology as Badawi (2008) but the investigators had thought Figure 11.18: Diagram of a SPEED bracket with conventional and bevelled rectangular wires, both showing further about the most appropriate methodology and the best the reduced gingival slot wall depth and consequent statistical analysis and interpretation of the data. In this study reduction in torquing ability from the upper and lower which focused on torque forces with different wire alloys bracket walls in one direction. Torque rails on some stainless steel, TMA and nickel-titanium – (Archambault et al brackets are designed to address this issue.

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2010), - they concluded that the reduced slop angle with an active clip ( 5 degrees less) did not in fact produce a clinically significant difference in torque forces. Exploring this in more detail (Major et al 2011) they again concluded that from a clinical perspective the torque plays were essentially identical for Damon Q, In-Ovation R and SPEED brackets. The torque plays for these three bracket types were 11.3°, 11.9°, and 10.8°, respectively.

These conclusions therefore support the finite element analysis work by Huang et al.

Still further work by the team from Alberta (Major et al 2011b) has reinforced the conclusion that the delivery of torquing forces is very similar for Damon, Speed and In-Ovation brackets. They found that all brackets had torque play between approximately −12° and 10.5°. Incidentally, this means that to correct or prevent retroclination of an upper central incisor to an angle of 110 degrees to the maxillary plane through torque application (as opposed to just tipping the tooth labially), no torque force at all will typically be applied to an upper central incisor by the inbuilt torque with an 0.019” x 0.025” wire with a prescription less than 18 degrees and effective levels of torque force would require a few more degrees that that. These calculations of required torque inclination may in fact be conservative. Brauchli et al (Angle on-line ahead of print 2012) found that the range of ‘slop’ (zero torquing force) was larger - from minus 15 to plus degrees for a number of brackets. Pertinent to this section, they too found no difference in the torque performance of passive and active self-ligating brackets. By measuring brackets with the clip open and shut, they found that the contribution to torque from the active clip was 1Nmm which is a small percentage of the torquing force thought to be clinically effective.

The use of selective incisor torque prescriptions (see chapter on Development of preadjusted appliance systems) is also important in relation to torque effectiveness. For example, Damon brackets have high, standard and low torque prescriptions for the upper incisors and these values have been further refined (with the high-torque value increased) for Damon Q brackets. Lastly, it should be noted that a ‘real-world’ clinical study by (Pandis et al 2006) found no lack of incisor torque control with passive Damon brackets Key point: Active and passive self-ligating brackets do not inherently differ in their ability to apply torquing forces. An active clip contributes little to torquing force. Play or ‘slop’ in the torque dimension is greater than frequently appreciated and should influence our choices of prescription accordingly.

Data on force levels with active and passive self-ligation

At several international meetings since 2007 including the AAO annual session 2010, research data has been presented by Hisham Badawi and the team at the University of Alberta. This data was derived in real time from multi-axis force transducers on a whole arch set-up of any desired arrangement of the teeth. The details and robustness of this methodology have since been described (Badawi 2009). Also in this paper, studies compared the magnitude and directions of forces generated with the same wires in the same malocclusions but with different brackets. One study compared the forces generated with active and passive self-ligating brackets when a 0.014” nickel titanium wire was placed in a lower arch with lingually placed lateral incisors which were then moved labially in response to the forces in the wire. The resulting friction and binding produced a labially directed force on the central incisors which was reduced by between 73% and 82% when Damon 3MX brackets with their passive slide were used instead of In-Ovation brackets with an active clip. These results agree with those of Baccetti et al (2009) and (Franchi et al 2009) which also demonstrate the effects of elastomeric ligature friction in preventing the wire sliding distally through brackets on teeth adjacent to the irregular teeth. In this instance, the resistance to sliding resulting from an active clip greatly increased the force proclining the lower central incisors as the lingually placed laterals moved. This research is at an early stage, but much more high-quality data can be anticipated from this source.

Aging of spring clips

Finally, there are the questions of robustness, security of ligation and ease of use. Is a clip, which is designed to flex, more prone to breakage or permanent deformation or to inadvertent opening or closing? This question has not yet been thoroughly investigated, but one pertinent piece of work has been conducted by Pandis et al (2007) who retrieved spring clips from SPEED and In-Ovation R brackets following a course of treatment and compared the stiffness and range of action of these spring clips with unused spring clips. The two types of bracket had spring clips of very different initial stiffness and the In-Ovation clips lost an average of 50% of their stiffness during

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the treatment, whilst the SPEED clips had very little change in their performance. This change in properties is sufficient that it may well have biomechanical consequences of clinical significance.

Active or passive – conclusions • alignment:

•

• •

in theory, it is probable that with an active clip, initial alignment is more complete for a wire of given size to an extent which is potentially clinically useful. However, with modern low modulus wires it is possible to subsequently insert thicker wires into a bracket with a passive slide and arrive at the working archwire size after the same number of visits – ie: to store all the force in the wire rather than dividing it between wire and clip. friction: overall, an active clip will generate higher forces and higher friction. The increased clearance between a given wire and a passive slide will generate lower forces and may facilitate dissipation of binding forces and the ability of teeth to push each other aside as they align. It may also lead to qualitative differences in the direction and amount of tooth movement (see below) but this is yet to be established. robustness and ease of use: in any specific bracket these factors are frequently related to the type of clip or slide. torque control: there is good evidence that the presence of an active clip does not contribute significantly to torque control.

The question of active clip or passive slide has been challenging to quantify. It is yet to be convincingly demonstrated that it is the most fundamental aspect of self-ligation, but the lower force levels achieved with passive self-ligation for a given archwire are now being measured and may prove to be clinically significant. This issue may also be related, through associated design features, to other factors such as security of ligation or ease of use. It is hoped that this section of the chapter usefully informs a consideration of the claims made in this context.

More efficient treatment with self-ligation?

The papers discussed earlier have demonstrated a worthwhile saving in chairside time with self-ligation. In addition to this factor, there is a strong clinical impression that the combination of low friction and secure engagement enables more rapid and high-quality treatment. Several studies have investigated this suggestion. At least three studies (Harradine 2001), (Eberting et al 2001), (Tagawa 2006), found that self-ligation with earlier versions of Damon brackets was quicker, with less visits and good or better final alignment and occlusion than with conventional appliances used by the same operator/s. These were consecutive case series. A recent retrospective study by Vajaria et al (2011) also found a reduction of two months in treatment time. Several other (but not all) presented but unpublished consecutive case series have also found more efficient treatment with self-ligation, whilst Ong (2010) compared alignment, arch widths and spontaneous extraction space closure after 20 weeks of treatment in a retrospective study and found no difference in these parameters between Damon MX and conventional brackets. More recently, Ollivere (2012) published the results of two studies of consecutively treated premolar extraction cases and in both instances, found no significant difference in treatment time with his switch to active self-ligation and changes in treatment protocol. This thoughtful paper is to be applauded for the documentation of the effects of changes in personal practice. Ollivere rightly speculates on the factors other than the brackets which may influence treatment efficiency. One conclusion that may drawn here is that extending appointment intervals to 10 weeks for all stages of treatment – which was advocated by some clinicians a few years ago – is counterproductive in its effects on efficiency. We would regard that default length of treatment interval as taking too far the good idea of light forces being left to work out their activation.

All the currently published random controlled trials (Miles 2005), (Miles et al 2006), (Pandis et al 2007b), (Scott et al 2008), (Fleming et al 2009), (Fleming 2009b), (Fleming et al 2010) have not found any overall benefit in the alignment phase, although Pandis et al found that mild crowding was eliminated 2.7 times more rapidly with

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Damon 2 than with conventional brackets. Only one of these studies has to date reported data for the whole of the treatment period.

Another study by Miles (2007), found no improvement in the rate of en masse space closure with SmartClip selfligating brackets, although at that stage of the treatment, this would be expected because there was no relative movement between the archwire and the self-ligating brackets which were all mesial to the remaining spaces.

Two recent prospective split mouth studies (Burrow 2010) and (Mezomo 2011) of the rate of canine retraction on 0.018” stainless steel wires have also failed to find faster retraction with self-ligation, in fact Burrow found that with conventional brackets, the rate averaged 0.17 mm per month faster than with Damon 3 or Smartclip. The better rotational control with self-ligating brackets in the study by Mezomo has already been noted. This factor was not measured by Burrow.

Two recent systematic reviews (Fleming and Johal 2010) and Chen et al (2010), have concluded that there is insufficient evidence to support the view that treatment with self-ligating brackets is more or less efficient than with conventional ligation. Interestingly, the standard of evidence required by some authors for a systematic review can be gauged by the exclusion by Fleming and Johal of two arch alignment RCTs by Miles from their systematic review on the grounds of a high risk of bias.

Possible reasons for differences between findings in treatment efficiency studies

In some retrospective studies: • the groups may not be adequately matched for type and complexity.

• some other factor may have been confounding the results e.g. a different policy on extractions, archwire sequence or appointment interval with the different brackets • the casemix may have been unusual e.g. more complex cases than average.

In the random controlled studies which have almost all failed to find a difference in treatment efficiency: • only one (Fleming et al 2010) has yet reported on completed cases. Potential differences in treatment efficiency may be partially related to archwire control in the later stages of treatment. It is likely that additional time and archwire changes are required to regain the rotational tooth control where it has been lost with conventional elastomeric ligation.

• the study on closure of extraction spaces primarily involved the archwire sliding only through molar tubes in both groups.

• factors such as casemix, appointment interval, archwire sequence may not have optimized for the self-ligating brackets, but have been chosen to be identical regardless of bracket type.

• random controlled trials of orthodontic appliance systems are susceptible to the involvement of clinicians who are unfamiliar with one of the appliances. This may be a factor in these studies.

• the ‘nickel-titanium’ dilemma. This name refers to the fact that it is almost universally accepted that nickel-titanium wires are superior for tooth alignment when compared to their stainless steel predecessors. However, none of the studies which investigated that hypothesis ever demonstrated its truth – possibly due to design features in those studies. Similarly, none of the relevant studies ever demonstrated that straight-wire appliances were superior to plain edgewise, but the former are overwhelmingly preferred for reasons which are regarded by clinicians as being self-evident and in no need of the highest order of scientific proof.

Key point: It seems very probable that self-ligation does not confer a blanket advantage in treatment efficiency and that factors such as appointment interval, archwire sequence and case mix are also significant.

Further studies are in progress with a variety of bracket types and this is a rapidly moving field of enquiry.

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Is treatment less painful with self-ligation?

There have been a number of studies investigating the hypothesis that self-ligation produces less patient discomfort than conventional brackets and ligation. Tagawa (2006) in a case series found a substantial reduction in reported pain with Damon SL brackets. Miles (2006) in a split mouth study found lower pain levels with Damon 2 brackets during the alignment phase, although opening the brackets was more uncomfortable than removing elastomerics. This latter finding may have been related to unfamiliarity with the Damon 2 which was less immediately user-friendly than other and subsequent self-ligating brackets. Pringle et al (2009) in an RCT found significantly less pain during the initial 7 days of treatment with Damon 3 brackets when compared with elastomerics tied in an ‘O’ configuration. We can hypothesise that tying teeth with a figure-of-eight elastomeric might increase this pain difference.

However other authors (Scott et al 2008b) found no difference between Damon 3 and Synthesis in the first week of treatment and one study (Fleming 2009c), found no difference in pain levels comparing SmartClip and conventional brackets and also that the actual process of archwire changes with SmartClip brackets was significantly more uncomfortable than with conventional ligation. The distinctive mode of action of Smartclip brackets has been noted above. The systematic review by (Fleming and Johal 2010) concluded that the balance of evidence from the three publiched RCTs on this topic just favoured a reduction of pain with self-ligation.

A very interesting paper by Yamaguchi et al (2009) examined the question via a different measure of pain. They measured the level of the neuropeptidase substance P in gingival crevicular fluid. This substance is a marker of the inflammation and associated pain resulting from orthodontic forces. They found that treatment with Damon brackets significantly lowered the levels of this marker of pain and inflammation when compared with conventional ligation at 24 hours after archwire placement.

The hypothesis that self-ligation may be less painful is based on the assumption that forces on the teeth will be lower. Whilst it is very probable that lower applied forces will be more effective with self-ligation because less force will be lost through friction, lower forces are most certainly not inevitable and are particularly sensitive to the choice of archwire. Force levels have been discussed in this chapter.

Qualitative differences in tooth movement with self-ligation?

A number of verbal case reports and lecture presentations have in recent years proposed additional clinical benefits deriving from the combination of core advantages discussed above. Essentially, these reflect the belief that self-ligation – and particularly passive self-ligation – enables tooth-moving forces to be sufficiently light that forces from the soft tissues can compete with them. For example it has been proposed that the lips can restrain labial movement of the incisors and that the alignment of crowded teeth on a non-extraction basis will result in more lateral arch expansion and less labial incisor movement than would be the case with heavier forces and higher resistance to sliding – the “lip bumper” concept. Further, it has been claimed that expansion brought about by such light forces is more likely to achieve an archform which is in balance with the tongue and cheeks and can establish a wider arch which will be relatively stable because of altered tongue position. These proposals chime with two more recent proposals which are not confined to advocates of self-ligation. Firstly that the buccal teeth are frequently lingually inclined and this demonstrates that the basal bone is wider than the soft tissue balance has permitted the teeth to reflect. It is then proposed that uprighting such teeth over basal bone is in line with previous principles applied to the incisors and can be expected to be followed by a favourable adaptation of the soft tissues. Secondly, attention and research has been focused on the aesthetics of the buccal corridors between the buccal teeth and the oral commissures. Some of this research (Moore et al 2005) supports the view that lay opinion finds a wider archform relative to the oral aperture to be more aesthetic. Lastly, tomographic radiographs have demonstrated very large dehiscences of buccal bone following rapid maxillary expansion (Garib et al 2006).

These proposed benefits could be summarized by saying that alignment of teeth with these low forces and low friction could provide: • wider arches which may be more aesthetic

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wider arches which have better periodontal health than those resulting from more rapid and forceful expansion wider arches which may be more stable less incisor proclination for a given amount of crowding less need for extractions easier class 2 correction through a ‘lip-bumper’ effect

Such hypotheses have inconclusive or no research support or are yet to be formally investigated, but research is increasing in these areas. The potential for measurement of these forces has been potentially advanced to a very substantial degree by the development by Dr Badawi and co-workers at the University of Alberta (Badawi 2009) of a force measurement system of impressive power, realism and versatility. As yet this system only aims to model some of the variables, but does increase our ability to investigate force distribution with different brackets and wires. Readers should also refer to two letters about this laboratory research tool and its funding (Katz 2010) and (Badawi and Major 2010) which help put such research into perspective and show the potential for unjustified rejection of research and its conclusions. More recent publications from this team (Fok et al 2011a) (Fok et al 2011b), show striking evidence that the distribution of forces throughout an arch may well be very different with passive self-ligating brackets. In the instance of a vertically displaced canine tooth, with self-ligating brackets the forces and moments are confined to that tooth and its immediate neighbours, whereas with conventional ligation, they spread throughout the arch and include significant forces in the bucco-lingual dimension. This is significant food for thought which cannot be dismissed out of hand as an ex vivo anomaly. However, it is absolutely correct to say that the clinical consequences of these differences have yet to be scientifically demonstrated.

The “lip bumper” concept has been investigated in two studies. Fleming et al (2009b) in an RCT found very little difference between cases treated with conventional and self-ligation in terms of arch expansion or incisor proclination. More recently, Vajaria et al (2011) reported on a retrospective study of non extraction mildly crowded class I cases treated by one clinician who had used the archwires considered best suited to each bracket type.

Again, the results were very similar for both systems. There was approximately 2 mm greater upper molar and lower premolar expansion in the Damon group, but this may well be accounted for by the wider archform of the wires used in that group. The current evidence throws significant doubt on the “lip bumper” hypothesis, although there are plenty of individual cases where the application of light space-opening forces with the low RS of selfligation has resulted in surprisingly slight incisor proclination, so more investigation is justified.

It is fair to say that the clinical popularity of self-ligating systems and some of the claims on its behalf ran ahead of the evidence to firmly support all of the proposed advantages. In this it is not alone. Several other popular and very long-established orthodontic products such as straight-wire brackets and superelastic wires have never been convincingly demonstrated in clinical trials to hold advantages over their predecessor products, but are universally accepted as being hugely more effective. In the current climate it is likely that the evidence about these claims for self-ligation will shortly be more comprehensive than for superelastic wires.

Does self-ligation reduce the need for extractions?

A scrutiny of this claim benefits from some dissection of the indications for extraction which can be categorized as follows: • space for alignment of crowded teeth • profile improvement • interarch relationship o correction of overjet o correction of overbite Crowding: the combination of low friction and good archwire control which self-ligation provides would be expected to facilitate the alignment of crowded arches without extractions - if that is desired. This biomechanical reason for extraction should therefore be correspondingly reduced. It should however be recalled that in spite of the strong evidence for lower friction and good control, studies to date have not confirmed a generic increase in

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speed of alignment. Several case reports demonstrate that severe crowding can be accommodated without extraction if that is the desired goal in a specific instance.

Profile: If research confirms that self-ligation can align teeth with less incisor proclination and relatively more lateral expansion, then this would reduce the need for extractions to prevent or correct a profile which is too full. At present this remains an interesting and plausible hypothesis, but lacks support.

Interarch relationship: There is as yet no good evidence that self-ligation inherently reduces the potential role for extractions to reduce an overjet. It may however help prevent the creation of an unwanted overjet. With regard to establishing a positive overbite, it is equally possible that any reduction in incisor proclination for a given amount of tooth alignment would reduce the need for extractions to maintain a positive overbite, but there will always be cases where any such effect will be insufficient to eliminate the need for extractions.

Given the uncertainty about the ideas outlined above, self-ligation may appropriately lead to more therapeutic diagnosis in relation to extractions. If after arch alignment, extractions are judged to be necessary, little time may have been lost. If extractions prove not to be necessary, then this irreversible step will have been avoided.

Clinical tips when using self-ligating brackets These tips apply in varying degrees to all self-ligating brackets. Further clinical tips in the review article by NH

(2003).

Changing treatment mechanics It is useful to briefly list some of the ways that treatment can be changed to take advantage of the combination of low friction and full, secure bracket engagement.

Longer appointment intervals, but only for some stages of treatment The ability to ensure full and secure wire engagement of modern, low modulus wires makes an

extension of the interval between some appointments a logical step. Eight-week intervals are usually appropriate in the early stages if the irregularities are significant. This is a clear advantage for operator and patient. If the irregularities are mild, longer appointment intervals may simply prolong treatment.

More traction on lighter wires

The increased effectiveness of light forces and the decreased loss of control combine to enable more mesiodistal tooth movement to be sensible on lighter, more flexible wires. Compressed coil springs to move teeth apart can appropriately be placed from the first visit in many instances. Similarly light intermaxillary elastics are more appropriate at an early stage of treatment because they will probably be more effective and produce fewer undesirable side effects than would be the case with the necessarily heavier forces and conventional ligation.

Key point: The greater effectiveness (residual net force) of lighter applied forces reduces the traditional adverse side effects of traction to lighter wires.

Separate movement of individual teeth and parallel processing

The control of rotation during traction on an individual tooth makes this option much more attractive when required. This can conserve anchorage in a variety of situations without a penalty in loss of tooth control or disproportionate lengthening of the treatment. These mechanical features make it sensible in some malocclusions to separately retract canines to a class 1 relationship whilst simultaneously reducing the overbite.

By the time the overbite reduction permits upper incisor retraction, the canines are already class 1 but in good rotational control and the case is further advanced with anchorage conserved.

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Squeezing teeth into alignment

Crowded teeth seem to align more effectively, although this has not been demonstrated in random prospective trials. If the clinician wishes to align crowded teeth without making space with extractions, these brackets may facilitate the alignment and cause less incisor proclination than might be anticipated. Some clinicians, for example Dwight Damon, have exploited this capacity to an impressive extent, but in selected cases.

Bracket placement and bond-up Bracket placement is critical to the success of any treatment with any bracket. It is felt that normally, both maxillary and mandibular Figure 11.19: TP Traction Hook used to bring arches should be bonded at the same time and that bonding upper lateral incisor gently towards the line of the arch should include second molar to second molar in each arch, while space opening is occurring. The low friction because that is time-efficient. It is routinely possible to take records facilitates space opening. (photographs and study models), bond second molar to second molar in each arch and place upper and lower archwires in 60 minutes.

For teeth that are well displaced from the archwire or where there is insufficient space to place a bracket in an ideal position, it is helpful to use a TP Traction Hook 224-011 to gain some early control of these teeth with low friction as shown in Figure 11.19; this can be used to either tie the tooth to the archwire with Power Tube (normally with a space opening coil spring) or to pass through the archwire through the lumen of the traction hook to facilitate early alignment of the tooth. For rotated teeth, it is useful to offset the traction hook so that it is on the part of the crown furthest from the line of the arch to gain some spontaneous derotation. Damon Q brackets, In-Ovation and Speed brackets are amongst those which have a horizontal auxiliary slot which permits a low-friction application of piggyback archwires for ectopic teeth.

Opening and closing There are three components to handling archwires with self-ligation – locating the archwire in the slot, closing the slide or clip and opening the slide or clip.

Vision

In order to close and open the slides or clips easily, it is necessary to be able to see clearly whether the archwire is fully seated in the slot or not. Most problems in closing the slides or clips are due to failure to fully locate the archwire in the slot. It is strongly recommended that operators work under mild magnification (1.5 to 3 times) in order to visualise the relationship between the archwire and the slot. Magnifying loupes do not need to be expensive or elaborate. We have experience of Donegan Optical Company’s OptiVisor (extremely practical but not very elegant! Guide price £40.00), the Edroy Products Opticaid (practical, fits existing glasses, guide price £25.00) and NuView’s Voroscope MXL (variety of magnification and excellent light source, approximately £400.00). The Voroscope now comes with an LED light which extends the (rechargeable) battery life considerably and has a slightly bluish white light.

The best solution is custom loupes with an integral headlight such as those made by Orascoptic. These ensure optimal vision and posture.

They are extremely light and comfortable to wear. The Zeon portable headlight gives both excellent illumination and battery life.

Locating the archwire in the slot Figure 11.20: Orascoptic loupes with Discovery LED headlamp; the orange filter prevents composite setting prior to bracket positioning

With self-ligating brackets it is much more important to fully engage the wire before clip closure rather than attempt to close the clip and simultaneously engage the wire (with SmartClip brackets, this

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separation of engagement and closure is not possible). There are three reasons why an archwire does not seat in the slot:

•

there is something in the slot preventing the archwire

seating

• the archwire is not sufficiently deflected (but can be) to seat fully in the slot • the archwire cannot be deflected (too stiff) to seat fully in the slot Plaque or food debris in the slot can be sufficient to prevent the archwire seating fully in the slot; it is suggested that at each visit after the removal of the archwires, patients are given a disposable prepasted toothbrush (e.g.: Plak Smacker Pre-Pasted Disposable) to clean their teeth with before the new archwire is placed. This both emphasises the importance of good oral hygiene and ensures that the slots are brushed clean.

If this is not possible, then blowing out the slots and tubes with a 3-in-1 syringe will achieve the same effect.

Occasionally, some calcified material will be found in the slot and this needs to be removed by the orthodontist.

Figure 11.21: The Cool Tool is akin to a torquing key and facilitates archwire engagement when necessary.

Key Point: If you cannot see that the archwire is fully seated in the slot then the clip or slide will not close; either remove any debris from the archwire slot, deflect the archwire further or choose a less stiff archwire

Tools

If the wire is passive labiolingually, a tool is not required. Finger pressure is often sufficient to engage early aligning wires. However, if archwire engagement and clip/slide closure is difficult for a particular tooth, several practical tools and techniques are worth knowing.

•

•

for all bracket types, the wire can be held into the slot with a variety of tools or instruments. Simple tools such as a ligature tucker often suffice. However, these only push on one side of the bracket and may fail to fully engage the wire across the whole width of the slot. The Cool Tool (Figure 11.21) is excellent and pushes on both sides of the bracket. whereas engagement of an irregular tooth with an elastomeric ligature can involve considerable pulling on the tooth, with a self-ligating bracket, a pushing force is required. Reduction of a pulling force on the tooth when placing an elastomeric is difficult, but it is easy to reduce the net push on the tooth when engaging a wire in a self-ligating bracket by opposing that push with a lingually placed thumb.

Key Point: If the wire needs significant pressure to engage, use a labiolingual “squeeze technique”. As you push from the labial (e.g. with a Cool Tool or Damon Q SpinTek tool), also push the tooth from the lingual/palatal with a thumb of the same hand. The net force on the tooth is greatly reduced and the wire is fully engaged more easily and comfortably

• • • •

if the tooth is very rotated and one end of the slot is too close to the adjacent tooth for an instrument to be used to seat the wire, dental floss or a ligature wire looped over the archwire can be very helpful in fully engaging the wire on that side another occasionally useful manoeuvre on a very rotated or displaced tooth with any self-ligating bracket, is to first close the clip or slide and then thread the aligning wire through the closed bracket before engaging the other brackets i.e.: to first convert it to a ‘molar’ tube! once the wire is fully engaged, many brackets such as In-Ovation brackets, Damon 3MX and Q brackets and Speed brackets can be closed with a finger Time brackets are opened with a probe or other fairly sharp instrument such as a Mitchell’s trimmer using the hole in the clip. Speed brackets and In-Ovation R brackets can be opened by vertical

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pressure on the tail of the clip behind the bracket (eg: with a Mitchell’s trimmer) or can be opened via the hole/notch in the labial surface of the clip (e.g. with a probe).

Archwires Biting out Initial placement When placing the initial archwires, do not include the second molars. The patient will frequently bite an 0.014" archwire out of the second molar tubes; it is better to terminate the archwires at the first molars for the first visit and then pick up the second molars on the first nickel titanium rectangular archwires (0.018” or 0.014" x 0.025" or 0.016" x 0.025").

Long unsupported spans

• • • •

use tie-backs with flexible wires over extraction sites to lessen the effects of occlusal forces on unprotected spans of wire or defer spanning the extraction space until a thicker (e.g. 014” x 025” wire use small tubes bonded to deciduous teeth to reduce the length of the span support the wire with lengths of hard tubing just shorter than the unsupported space to allow for tooth movement do not place wire across unsupported span until alignment has taken place; this will then allow a thicker wire to be placed across the span

Prevention of ‘swivelling’ Low friction increases wire displacement. Ironically, the problems of wire displacement resulting from low friction are perhaps the most convincing and immediate clinical evidence that the low friction found in laboratory studies is readily apparent in vivo. Even with very irregular teeth, the very low friction with self-ligating brackets, especially in bracket systems that use a passive slide, enables aligning archwires to slip through the brackets and an archwire end to protrude. This is clearly a potential nuisance. Steps to prevent this can include:

•

•

• • •

small sections of stainless steel tube crimped onto the archwire. This is quick, easy, versatile and recommended. 0.5 mm soft tubing (approx. 0.020" internal diameter) is a good size for smaller diameter wires. With larger wires, 0.7 mm tubing is required, but a crimp-on hook may be a better option since it is harder to crimp normal resilient tubing securely onto the flat surface of a rectangular wire. Stops are usually placed in the anterior region and should be placed anterior to the crowding – one stop is sufficient in the lower arch, but two are advisable with the larger interbracket spans of the upper labial segment with one placed either side of a bracket. It is recommended that the stop is not placed on a significantly active part of the archwire. This would diminish the range of action of the wire where it is most needed. Such soft stops can be purchased from several manufacturers or cut in-house from a length of tube.

Damon archwires are available with small sections of soft steel tube already loaded and temporarily fixed in the midline by wax. These stops can be moved to the desired position and crimped. This is very convenient indeed. One stop is needed in the lower arch and two in the upper where the interbrackets spans are longer. placing a crimpable split stop on the archwire. Two sizes are available – 0.016" and 0.022" and are available from manufacturers such as 3M Unitek and Orec SPEED. flowable composite (e.g. Kerr Revolution 2) can be bonded to the archwire. The archwire must be dry. This method is not entirely reliable and not recommended. thorough turning in the ends of flexible archwires. An interesting innovation in this respect is the Bendistal plier described by Khouri (1998). This is designed to place an effective distal end bend in a superelastic wire without the need for over-bending which can be difficult and uncomfortable and also risks the loss of a bonded molar tube. However, it is a nuisance to need additional specialist pliers for this role.

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• •

selective locking of individual brackets to the archwire with elastomerics can be helpful in those designs which have a full conventional tie-wing assembly but is not completely effective. small V-shaped notches in the midline of flexible wires can also limit the scope for wire swivelling.

These are commercially available or can be bent into nickel-titanium wires with triple beak pliers.

Pre-notched wires are usually more expensive. Sometimes in the lower arch the notches are too large for the available inter-bracket span. Also, some notches can creep into the adjacent bracket and cause irregularity of that tooth. For these reasons, this particular method is not personally recommended

Clinical tip: place anti-swivel stops anterior to the crowding and not in an inter-bracket space where the wire needs to be significantly active

Archwire sequence Archwire sequencing is a little different with self-ligating brackets principally because of their excellent control between bracket and archwire. Because the ligation is secure and the RS is lower, one can confidently leave the early archwire to work out fully and so treatment intervals of 8-10 weeks are suggested in the early stages of treatment where teeth are significantly irregular. For patients with very irregular teeth, it may be necessary to continue the initial archwire for more than one visit; the emphasis is on light forces and giving the archwires the time to fully express their potential aligning capacity. This advice has been taken too far by some who have continued with lengthy intervals between appointments throughout treatment which only serves to lengthen treatment. It is important to remember that lower friction means higher net forces and thinner/softer wires are indicated in the alignment phase.

With passive self-ligating brackets, it is important to fill the labio-lingual dimension of the bracket slot before proceeding to a rectangular stainless steel archwire e.g. to use a 0.014” x 0.025” nickel titanium rather than a 0.016” x 0.022”. This need arises from the inherent need to fully engage a wire with self-ligation which is not an enforced discipline with conventional ligation.

The primary archwire sequence with passive brackets is as follows:

• • • •

0.014" nickel titanium superelastic (or 0.013”/0.012” in very irregular arches) 0.014" x 0.025" nickel titanium superelastic 0.018" x 0.025" nickel titanium superelastic 0.019" x 0.025" stainless steel

Where teeth are significantly displaced from the archwire and there is insufficient space to accommodate them in the dental arch, space should be made using an open nickel titanium coil spring. The coil spring should be approximately one bracket width wider than the space in which it is going to fit for normal interbracket spans. At the same time, a narrow attachment, such as a TP Traction Hook, should be bonded to the displaced tooth and gently tied on to the archwire with elastic thread (e.g.: PowerTube) or wire ligature. This limits proclination of the teeth during space opening by placing a lingual or palatal restraining force on the arch wire and speeds up the alignment process. Once sufficient space is available and the displaced tooth is close to the line of the arch, an initial aligning archwire can be placed through the traction hook to bring the displaced tooth into the arch prior to replacing the traction hook with a self-ligating bracket. Once tooth alignment has been achieved, a continuous wire ligature can be used to prevent space opening up in the labial segments.

Secondary archwires and wires are as follows:

• •

0.018” nickel titanium superelastic o this archwire is useful in cases with substantial residual irregularity or compromised periodontium as the next archwire step from the initial 0.014" nickel titanium superelastic 0.016" x 0.025" nickel titanium superelastic

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this archwire is useful in cases with little irregularity as the next archwire step from the initial 0.014" nickel titanium superelastic 0.016" x 0.025" stainless steel o can be useful for extensive sliding of individual teeth in hypodontia cases. Gives low friction with useful rigidity 0.019" x 0.025" RCOS (reverse curve of Spee) nickel titanium superelastic o used for managing deep overbites in both the upper and lower arches 0.017" x 0.025" TMA o useful for finishing bends where torque adjustments are not required 0.019" x 0.025" TMA o very useful for individual tooth movements at the end of treatment where archwire bends are required, especially for inclination (torque) adjustments. Consider using low friction variants if space closure required on this archwire o

• • • •

Distal ends

There is no need to turn down the distal ends of the archwires as the wires are already stopped by the crimpable stop. (An exception is for sectional archwires where a straight wire-end can be traumatic). In addition, turning down archwires distal to second molars is a frequent source of soft tissue trauma. Archwires should be cut flush with the distal end of the tube on the terminal molar. We experience no debonding of molar tubes when using distal end cutters and this may be partially due to taking care that the plane of the distal end cutters is the same as the archwire plane i.e.: the plane of the archwire bisects the joint of the distal end cutters. This prevents torquing forces being placed on the wire at the moment of cutting. In the upper arch, this necessitates lifting one's elbow up considerably to align the distal end cutters with the plane of the archwire.

When cutting stainless steel archwires prior to insertion in the mouth, cut the wire at an angle to provide a tapered end for insertion into the first and second molar tubes. In extreme cases or where the archwire has been distorted by blunt distal-end cutters, gentle reduction of the terminal portion of the wire with a green stone may facilitate insertion into the molar tubes.

Archform We recommend using the same preformed archwires for upper and lower arches. The upper archwire will effectively be larger because it is more anterior than the lower. The Damon archform usually provides slight expansion in the premolar and molar regions compared to some other archforms but not in the intercanine region. Customisation of archform should take place when stainless steel archwires are placed.

Elastics Drop in hooks enable a secure, frictionless method of attaching elastics both in the early stages of alignment and also to settle in the occlusion in the final phases of treatment Damon Q brackets permit the instant placement of a ball-ended hook on any tooth. Many self-ligating brackets permit the fabrication of a hook for insertion into an auxiliary slot. Possible configurations of finishing elastics are shown in Figures 11.22 to 11.27.

Debonding Self-ligating brackets are often more rigid than conventional twin brackets because of the engineering requirements of the body of the bracket and the need to provide a rigid housing for the clip or door. This means that at debonding, bracket removal may not occur by failure of the bracket adhesive interface by deformation of the bracket but by direct failure of the bracket adhesive interface, cohesive failure of the adhesive, direct failure of the adhesive enamel interface or a combination of any of these.

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The risk of enamel fracture has always been present with stainless steel and ceramic brackets, particularly in teeth where the integrity of the crown is compromised. The risk of enamel fracture is potentially increased by:

â&#x20AC;˘ â&#x20AC;˘

brackets with a rigid, non-deformable body structure the higher bond strengths delivered by adhesion enhancers and improved adhesives (3M Unitek have recently issued a warning that 3M Adper Prompt L-Pop Self Etch is unsuitable for orthodontic use because of the high bond strengths generated)

We have experienced no problems removing self-ligating brackets. The best way to debond most brackets is by squeezing under the tiewings with a conventional debonding plier applying no torsion or peel component to the force. The bracket usually distorts and debonds without placing undue force on the tooth, but with lower incisors, patience whilst squeezing is sometimes required. Molar tubes have no tiewings and are not easily distorted. Some torsion force may therefore be required to remove molar bonds. Happily, these teeth are sufficiently large that this does not cause discomfort.

Retention Retention is no different when using self-ligation. We use upper and lower clear overlay retainers worn at nights in the vast majority of cases. For extra security, we may use a bonded upper lateral to lateral retainer and a bonded lower canine to canine retainer. The upper retainer is made from 0.016" x 0.022" Reliance Hilgers Bond-a-Braid which is a flat braided archwire or Reliance Ortho FlexTech. This is placed with the flat surface on the cingulae of the upper incisors. In the lower arch, either a 0.025" single strand stainless steel wire is bonded to the lingual surface of the lower canines only with the ends of the retainer being sandblasted to aid retention, or a multistrand wire is bonded to all lower anteriors.

See also the chapter on Stability and Retention

Reflection Currently available self-ligating brackets offer the very valuable combination of extremely low resistance to sliding and secure full bracket engagement and deliver much of the potential advantages of this type of bracket. The secure archwire engagement may be the under-appreciated component of this combination.

Figure 11.22: Class 2 elastics; cutting distal to the lower first molars speeds up the rate of correction

Figure 11.23: Class 3 elastics; cutting distal to the upper first molars speeds up the rate of correction

Figure 11.24: Posterior V elastics are used to develop interdigitation in the buccal segments

Figure 11.25: An anterior trapezoidal elastics is used to close down anterior open bites

Figure 11.26: A Kobayashi ligature or Damon drop-in hook placed on one of the lower central incisor brackets makes it more comfortable to wear an anterior cross elastic

Figure 11.27: Triangular elastics or Schudy elastics can be used to develop buccal segment interdigitation in the last few weeks of treatment

SELF-LIGATING BRACKETS: THEORY AND PRACTICE EXCELLENCE IN ORTHODONTICS 2012

239

Some recent bracket types have excellent handling characteristics for opening and closing the slide. These developments offer worthwhile reductions in chairside times and the possibility of a significant reduction in average treatment time in some cases. An additional area of development has been the introduction of more aesthetic self-ligating brackets. Whilst further refinements are desirable and further studies essential, current brackets are able to deliver measurable benefit with excellent robustness and ease of use.

It is probably true to say that if the self-ligating appliance is used in exactly the same way as conventionally-ligated brackets have been, then the orthodontist will not get the best out of them. The combination of minimal friction, low forces and extended time between some adjustment visits allows tooth movements to occur which can be argued are technically not possible with conventional bracket systems. The orthodontist is technically able to more easily treat cases without extraction. A trend to more non-extraction treatment has clear benefits but also potential disadvantages if inappropriately applied:

• • • •

damage to the periodontium in the form of bony dehiscences and gingival recession increased potential for relapse profiles which are too full difficulty achieving a positive overbite if incisors are proclined

These potential problems mean that thoughtful treatment planning and monitoring of progress are essential and that a universal formula for all patients is not possible with any bracket system however good.

We are enormously enthusiastic about this high technology development in orthodontics. Not all of the hypotheses about potential advantages of these brackets are likely to be correct, but that should not deflect us from taking advantage of the undoubted strong points of self-ligation. We have used self-ligating brackets for many years, and since the mid 1990s they have been the mainstay of our clinical practice.

References Archambault A, Major TW, Carey JP, Heo G, Hisham Badawi H and Major PW (2010) A comparison of torque expression between stainless steel, titanium molybdenum alloy, and copper nickel titanium wires in metallic self-ligating brackets Angle Orthodontist 80:884-9 Baccetti T, Franchi L, Camporesi M, Defraia E and Barabato E (2009) Forces produced by different nonconventional bracket or ligature systems during alignment of apically displaced teeth Angle Orthodontist 79:533-539 Brauchli, Senn C and Wichelhaus A (2011) Active and passive self-ligation—a myth?

The Angle Orthodontist 81: 312-318 Brauchli, Senn C and Wichelhaus A (Angle on-line ahead of print 2012) Active and passive self-ligation—a myth? Part 1 torque control The Angle Orthodontist doi: http://dx.doi.org/10.2319/062011-673.1 Burrow SJ (2010) Canine retraction rate with self-ligating brackets vs conventional edgewise brackets The Angle Orthodontist 80: 626-633 Franchi L, Bacetti T, Camporesi M and Giuntini Z (2009) Forces released by nonconventional bracket or ligature systems during alignment of buccally displaced teeth American Journal of Orthodontics and Dentofacial Orthopaedics 136: 316.e1-6 Badawi H, Toogood RW, Carey JPR, Heo G and Major PW (2008) Torque expression of self-ligating brackets American Journal of Orthodontics and Dentofacial Orthopedics 133: 721-728 Badawi H, Toogood RW, Carey JPR, Heo G and Major PW (2009) Three-dimensional orthodontic force measurements American Journal of Orthodontics and Dentofacial Orthopaedics136: 518-528

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Badawi HI and Major PW (2010) Authors response to letter from MI Katz American Journal of Orthodontics and Dentofacial Orthopaedics137: 444-446 Berger JL (1990) The influence of the SPEED bracketâ&#x20AC;&#x2122;s self-ligating design on force levels in tooth movement: a comparative in vitro study American Journal of Orthodontics and Dentofacial Orthopaedics 97: 219-28 Berger JL (1994) The SPEED appliance: A 14 year update on this unique self-ligating orthodontic mechanism American Journal of Orthodontics and Dentofacial Orthopaedics 105: 217-223 Braun S, Bluestein M, Moore BK and Benson G (1999) Friction in perspective American Journal of Orthodontics and Dentofacial Orthopaedics 115: 619-27 Crawford NL, McCarthy C, Murphy T and Benson PE (2010) Physical properties of conventional and super slick elastomeric ligatures after intraoral use The Angle Orthodontist 8: 175-181 Chen SS-H, Greenlee MG, Kim JE, Smith CL and Huang GJ (2010) Systematic review of self-ligating brackets American Journal of Orthodontics and Dentofacial Orthopaedics 137: 726.e1-726.e18 Damon DH (1998) The rationale, evolution and clinical application of the self-ligating bracket Clinical Orthodontics and Research 1: 52-61 Damon DH (1998) The Damon low friction bracket: a biologically compatible straight-wire system Journal of Clinical Orthodontics 32:670-80 Damon 2 Videoconference DVD Damon System: The Workbook (only available to participants on Damon Courses) Eberting JJ, Straja SR, and Tuncay OC (2001) Treatment time, outcome and patient satisfaction comparisons of Damon and conventional brackets Clinical Orthodontics and Research 4: 228-234 Ehsani S, Mandich M-A, El-Bialy TH and Flores-Mir C (2009) Frictional resistance in self-ligating orthodontic brackets and conventionally ligated brackets Angle Orthodontist 79: 592-601 Eliades T and Bourauel C (2005) Intraoral aging of orthodontic materials: the picture we miss and its clinical relevance American Journal of Orthodontics and Dentofacial Orthopaedics 127: 403-12 Fleming PS, Di Biase AT, Sarri G and Lee RT (2009c) Pain experience during initial alignment with a self-ligating and a conventional fixed orthodontic appliance system Angle orthodontist 79: 46-50 Fleming PS, DiBiase AT, Sarri G and Lee RT (2009) Efficiency of mandibular arch alignment with two preadjusted edgewise appliances American Journal of Orthodontics and Dentofacial Orthopaedics135: 597-602 Fleming PS, DiBiase AT, Sarri G and Lee RT (2009b) Comparison of mandibular arch changes during alignment and levelling with two preadjusted edgewise appliances American Journal of Orthodontics and Dentofacial Orthopaedics 136: 340-347 Fleming PS and Johal A ( 2010) Self-ligating brackets in orthodontics â&#x20AC;&#x201C; a systematic review Angle Orthodontist 80:575-584 Fok J, Toogood RW, Badawi H, Carey JP and Major PW (2011a) Analysis of maxillary arch force/couple systems for a simulated high canine malocclusion: Part 1. Passive ligation.

The Angle Orthodontist 81: 953-959 Fok J, Toogood RW, Badawi H, Carey JP and Major PW (2011b) Analysis of maxillary arch force/couple systems for a simulated high canine malocclusion: Part 1. Passive ligation.

The Angle Orthodontist 81: 960-965

SELF-LIGATING BRACKETS: THEORY AND PRACTICE EXCELLENCE IN ORTHODONTICS 2012

Garib DG, Henriques JF, Janson G, de Freitas MR and Fernandes AY (2006) Periodontal effects of rapid maxillary expansion with tooth-tissue-borne and tooth-borne expanders: a computed tomography evaluation American Journal of Orthodontics and Dentofacial Orthopaedics 129:749-58 Hain M, Dhopatkar A and Rock P (2006) A comparison of different ligation methods on friction American Journal of Orthodontics and Dentofacial Orthopaedics 130: 666-670 Harradine NWT (2001) Self-ligating brackets and treatment efficiency Clinical Orthodontics and Research 4: 220-227 Harradine NWT (2003) Self-ligating brackets: where are we now?

Journal of Orthodontics 30: 262-273 Harradine NWT and Birnie DJ (1996) The clinical use of Activa self-ligating brackets American Journal of Orthodontics and Dentofacial Orthopaedics 109: 319-28 Heo W and Baek SH (2011) Friction properties according to vertical and horizontal tooth displacement and bracket type during initial leveling and alignment The Angle Orthodontist 81: 653-661 Huang Y, Keilig L, Rahimi A, Reimann S, Eliades T, Jager A and Bourauel C (2009) Numeric modelling of torque capabilities of self-ligating and conventional brackets American Journal of Orthodontics and Dentofacial Orthopaedics 136: 638-643 Iwasaki LR, Beatty MW, Randall CJ and Nickel JC (2003) Clinical ligation forces and intraoral friction during sliding on a stainless steel archwire American Journal of Orthodontics and Dentofacial Orthopaedics 123: 408-415 Katz MI (2010) Appearances count when industry underwrites research American Journal of Orthodontics and Dentofacial Orthopaedics 137: 3-4 Khambay B, Millett D and McHugh S (2004) Evaluation of methods of archwire ligation on frictional resistance European Journal of Orthodontics 26: 327-332 Kapur R, Sinha PK and Nanda RS (1998) Frictional resistance of the Damon SL bracket Journal of Clinical Orthodontics 32: 485-489 Khouri SA (1998) The Bendistal pliers: A solution for distal end bending of superelastic wires American Journal of Orthodontics and Dentofacial Orthopaedics 114: 675-6 Koenig HA and Burstone CJ (1989) Force systems from an ideal arch â&#x20AC;&#x201C; large deflection considerations Angle Orthodontist 59:11-16 Loftus BP, Ă&#x201A;rtun J, Nicholls JI, Alonzo TA, and Stoner JA (1999) Evaluation of friction during sliding tooth movement in various bracket-archwire combinations.

American Journal of Orthodontics and Dentofacial Orthopaedics 116: 336-45 Mah E, Bagby M, Ngan P and Durkee M (2003) Investigation of frictional resistance on orthodontic brackets when subjected to variable moments American Journal of Orthodontics and Dentofacial Orthopaedics 123: (abstract) A1 Major TW, Carey JP, Nobes DS, Heo G and Major PW (2011) Mechanical effects of third order movement in self-ligated brackets by the measurement of torque expression American Journal of Orthodontics and Dentofacial Orthopaedics 139:e31-44 Major TW, Carey JP, Nobes DS, Heo G and Major PW (2011b) Measurement of plastic and elastic deformation due to third-order torque in self-ligated orthodontic brackets American Journal of Orthodontics and Dentofacial Orthopaedics 140: :326-339 Maijer R and Smith DC (1990) Time saving with self-ligating brackets Journal of Clinical Orthodontics 24: 29-31

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Matarese G, Nucera R, Militi A, Mazza M, Portelli M, Festa F and Cordasco G (2008) Evaluation of frictional forces during dental alignment: An experimental model with 3 nonleveled brackets American Journal of Orthodontics and Dentofacial Orthopaedics 133: 708-715 Matasa CG (1996) Self-engaging brackets: passive vs. active.

The Orthodontic Materials Insider 9: 5-11 Matasa CG (2001) Brackets’ shape influences friction The Orthodontic Materials Insider 13: 2-5 Meling TR, Ødegaard J, Holthe K, and Segner D (1997) The effect of friction on the bending stiffness of orthodontic beams: A theoretical and in vitro study.

American Journal of Orthodontics and Dentofacial Orthopaedics 112: 41-49 Miles PG, Weyant RJ and Rustveld L (2006) A clinical trial of Damon 2 vs conventional twin brackets during initial alignment Angle Orthodontist 76: 480-485 Miles PG (2005) SmartClip versus conventional twin brackets for initial alignment: is there a difference?

Australian Orthodontics Journal 21: 123-127 Miles PG (2007) Self-ligating versus conventional twin brackets during en-masse space closure with sliding mechanics American Journal of Orthodontics and Dentofacial Orthopaedics132::223-5 Moore T, Southard K, Casko JS, Qian F and Southard TE (2005) Buccal corridors and smile aesthetics American Journal of Orthodontics and Dentofacial Orthopaedics127:208-13 Mezomo M, de Lima ES, Macedo de Menezes L, Weissheimer A and Allgayer S (2011) Maxillary canine retraction with self-ligating and conventional brackets The Angle Orthodontist 81: 292-7 Ollivere P (2012) Treatment efficiency of self-ligating brackets Orthodontic Update 5:15-19 Ong E, McCallum H, Griffin MP and Ho C (2010) Efficiency of self-ligating vs. conventionally ligated brackets during initial alignment American Journal of Orthodontics and Dentofacial Orthopaedics 138: e1-e7 O’Reilly D, Dowling PA, Lagerstrom L and Swartz ML (1999) An ex-vivo investigation into the effect of bracket displacement on resistance to sliding British Journal of Orthodontics 26: 219-227 Pandis N, Bourauel C and Eliades T (2007) Changes in the stiffness of the ligating mechanism in retrieved active self-ligating brackets American Journal of Orthodontics and Dentofacial Orthopaedics 132:834-7.

Pandis N, Polychronopoulou A, and Eliades T (2007b) Self-ligation vs. conventional brackets in the treatment of mandibular crowding: A prospective clinical trial of treatment duration and dental effects American Journal of Orthodontics and Dentofacial Orthopaedics 132:208-15 Pandis N, Strigou S and Eliades T (2006) Maxillary incisor torque with conventional and self-ligating brackets: a prospective clinical trial Orthodontics and Craniofacial Research 9:193-198 Pandis N, Polychonopolou A and Eliades T (2010) Active or passive self-ligating brackets? A randomised controlled trial of comparative efficiency in resolving maxillary anterior crowding in adolescents American Journal of Orthodontics and Dentofacial Orthopaedics 131: 12.e1-12.e6 Peterson A, Rosenstein S, Kim KB and Israel H (2009) Force decay of elastomerics ligatures: Influence on unloading force compared to self-ligation Angle Orthodontist 79: 934-938 Pizzoni L, Raunholt G and Melsen B (1998) Frictional forces related to self-ligating brackets.

European Journal of Orthodontics 20: 283-291

SELF-LIGATING BRACKETS: THEORY AND PRACTICE EXCELLENCE IN ORTHODONTICS 2012

Pliska BT, Beyer JP and Larson BE (2011) A comparison of resistance to sliding of self-ligating brackets under an increasing applied moment The Angle Orthodontist 81: 794-799 Pollard AP (2003) Capturing the essence of the Damon approach Clinical Impressions 12 (2): 4-12 Pringle AM, Petrie A, Cunningham SJ and McKnight M (2009) Prospective randomized clinical trial to compare pain levels associated with 2 orthodontic fixed bracket systems American Journal of Orthodontics and Dentofacial Orthopaedics 136:160-167 Read-Ward GE Jones SP, and Davies EH (1997) A comparison of self-ligating and conventional orthodontic bracket systems British Journal of Orthodontics 24: 309-317 Reznikov N, Har-Zion G, Barkana I, Abed Y and Redlich M. (2010) Measurement of friction forces between stainless steel wires and "reduced-friction" self-ligating brackets.

American Journal of Orthodontics and Dentofacial Orthopedics 138: 330-8 Rinchuse DJ and Miles PG (2007) Self-ligating brackets: Present and future American Journal of Orthodontics and Dentofacial Orthopaedics 132: 216-222 Scott P, DiBiase AT, Sherriff M and Cobourne MT (2008) Alignment efficiency of Damon3 self-ligating and conventional orthodontic bracket systems: A randomized clinical trial American Journal of Orthodontics and Dentofacial Orthopedics 134: 470.el-470.e8 Scott P, Sherriff M, Di Biase AT and Cobourne MT (2008b) Perception of discomfort during initial orthodontic tooth alignment using a self-ligating or conventional bracket system: a randomized clinical trial European Journal of Orthodontics 30: 227 - 232 Shivapuja PK and Berger J (1994) A comparative study of conventional ligation and self-ligation bracket systems American Journal of Orthodontics and Dentofacial Orthopaedics 106: 472-480 Sims APT, Waters NE, Birnie DJ and Pethybridge RJ (1993) A comparison of the forces required to produce tooth movement in vitro using two self-ligating brackets and a preadjusted bracket employing two types of ligation European Journal of Orthodontics: 15: 377-385 Sims APT, Waters NE, and Birnie DJ (1994) A comparison of the forces required to produce tooth movement ex vivo through three types of preadjusted brackets when subjected to determined tip or torque values British Journal of Orthodontics 21: 367-373 Stolzenberg J (1935) The Russell attachment and its improved advantages International Journal Orthodontics and Dentistry in Children 21: 837-840 Tagawa D (2006) The Damon system vs. conventional appliances: a comparative study.

Clinical Impressions 15:4-9 Taloumis LJ, Smith TM, Hondrum SO and Lorton L (1997) Force decay and deformation of orthodontic elastomeric ligatures American Journal of Orthodontics and Dentofacial Orthopaedics 111: 1-11 Thomas S, Birnie DJ and Sherriff M (1998) A comparative in vitro study of the frictional characteristics of two types of self ligating brackets and two types of preadjusted edgewise brackets tied with elastomeric ligatures European Journal of Orthodontics 20: 589-596 Thorstenson BS and Kusy RP (2001) Resistance to sliding of self-ligating brackets versus conventional stainless steel twin brackets with second-order angulation in the dry and wet (saliva) states American Journal of Orthodontics and Dentofacial Orthopaedics 120: 361-70 Thorstenson BS and Kusy RP (2002a) Comparison of resistance to sliding between different self-ligating brackets with second-order angulation in the dry and saliva states American Journal of Orthodontics and Dentofacial Orthopaedics 121: 472-782

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Thorstenson BS and Kusy RP (2002b) Effect of archwire size and material on the resistance to sliding of self-ligating brackets with second-order angulation in the dry state American Journal of Orthodontics and Dentofacial Orthopaedics 122: 295-305 Thorstenson BS and Kusy RP (2003) Effects of ligation type and method on the resistance to sliding of novel orthodontic brackets with second-order angulation in the wet and dry state Angle Orthodontist 73: 418-430 Turkkahraman H, Sayin MO, Bozkurt FY, Yetkin Z. Kaya S and Suleyman O (2005) Archwire ligation techniques, microbial colonization, and periodontal status in orthodontically treated cases Angle Orthodontist 75: 231-236 Turnbull NR and Birnie DJ (2007) Treatment efficiency of conventional versus self-ligating brackets: the effects of archwire size & material.

American Journal of Orthodontics and Dentofacial Orthopaedics 131: 395-399 Vajaria R, BeGole E, Kusnoto B, Galang MT and Obrez A (2011) Evaluation of incisor position and dental transverse dimensional changes using the Damon system The Angle Orthodontist 81: 647-652 Voudouris JC (1997) Interactive edgewise mechanisms: Form and function comparison with conventional edgewise brackets American Journal of Orthodontics and Dentofacial Orthopaedics 111: 119-40 Wildman AJ (1972) Round table - the Edgelok bracket Journal of Clinical Orthodontics 6: 613-23 Wildman AJ (1998) The Wildman TwinLock bracket Clinical Impressions published by Ormco Corporation 7 (2): 2-5 Yamaguchi M, Takizawa T, Nakajima R, Imamura R and Kasai K (2009) The Damon System and release of substance P In gingival crevicular fluid during orthodontic tooth movement in adults World Journal of Orthodontics 10:141-146 Yee JA, Turk T, Elekdag-Turk S, Cheng L and Darendeliler A (2009) Rate of tooth movement under heavy and light continuous orthodontic forces American Journal of Orthodontics and Dentofacial Orthopaedics 136:150.e1-150.e9

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Chapter

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12 Customised precision prescription appliances David Birnie

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Note that some of the hyperlinks in this chapter are to files, such as pdfs, which may take some time to download – please be patient!

Introduction The promise of fixed appliance systems that are fully customised to individual patient’s needs has been elusive but several technology breakthroughs in the past decades have brought these closer to every day clinical practice.

The power, speed, low cost and portability of modern computers has made substantial computing power readily available while digital design and manufacturing techniques are now transferable into orthodontic practice.

Customised precision prescription appliances or orthodontic treatment can be delivered by either:

• • • • • •

customising or individualising brackets to the patient’s tooth morphology and planned treatment needs customising the bracket-tooth surface composite/resin interface to the patient’s tooth morphology and planned treatment needs customising the archwires to the patient’s tooth morphology and planned treatment needs using selected prescriptions to semi-customise the appliance a combination of the above aligners

All patients seek value from their orthodontic treatment; value is defined as meeting the patient’s needs (always from the customer’s viewpoint) at a specified time and a specified price. Value is delivered through a value stream or the process(es) required to commission and deliver the value desired by the patient. Key goals in any business enterprise are shown Table 12.1 and these apply just as much to orthodontics as any other business. Although clinicians believe they do good quality clinical work, they often find it hard to define quality in a measurable way.

Quality can be defined as doing the right thing, to the right person, at the right time, first time – and all of those criteria are measurable. While cost, morale and safety are perhaps self-explanatory, lead time refers to the end-to end process time. Precision prescription orthodontic treatment has to offer advantages against these criteria and this chapter explores how it works and whether it delivers on its promise.

Levin (2006) has suggested eight questions which should be asked before adopting a new technology and these are summarised below and mapped to the business fundamentals in Figure 12.1.

•

will the technology improve the quality of patient care? o quality • will the technology reduce costs? o cost • will the technology generate new revenue? o cost • will the technology provide a return on investment? o cost • is the technology easy to use? o morale • can the technology be integrated with current practice Patient Staff technologies? o morale Quality Cost • will the technology increase efficiency?

Morale o lead time Lead time Safety • will the technology improve safety? o safety Table 12.1: The five The market for this type of technique is expanding rapidly and a list of some of the business fundamentals showing the direction each parameter should providers are given in Table 12.2. move in for both patients and staff

CUSTOMISED PRECISION PRESCRIPTION APPLIANCES EXCELLENCE IN ORTHODONTICS 2012

Manufacturer

Product

Type of appliance

Method of data acquisition PVS impressions

Customisation brackets

3M Unitek

Incognito

lingual

Align Technologies

Invisalign

aligner

PVS impressions

aligner(s)

Cadent

OrthoCAD IQ

labial

PVS impressions

Selective prescriptions

ePlan and ePlacement

labial

Orametrix

SureSmile

Ormco

Insignia

Geodigm

archwires

Itero intraoral scanner 5 day alginate impression

None – but set-up based on simulated end of treatment tooth positions

labial

Orascan intraoral scanner

archwires

labial

PVS impressions

brackets (full or semi depending on type) archwires

Table 12.2:

247

Relevant technologies Several technologies have come together to allow increased customisation of appliances to a individual patient’s requirements.

These are:

Digital imaging Digital imaging of photographs and radiographs now makes it easy to transmit or upload patient data to sites that are geographically distant.

In addition, the advent of intra-oral scanners promise the elimination of impression taking.

Some providers of precision prescription orthodontic appliances

Computer modelling Computer modelling, design and manufacturing programmes provide an unprecedented ability to visualise, manipulate and test treatment outcomes. The end results from these programmes can then be used to construct customised appliances and precision bracket placement systems.

Robotics Robotics are now being introduced to carry out precision archwire fabrication for nickel titanium, titanium molybdenum and stainless steel archwires.

High technology materials and manufacturing technique Metal injection moulding and nickel titanium archwires are two examples of high technology materials and manufacturing technology which facilitate customised appliances through high precision, economical use of materials and minimal finishing requirements.

Techniques Records

Digital photographs Digital photographs are required for some techniques. Normally eight photographs are required:

• • • • • • • •

full face with lips at rest full face with lips apart (say ‘Emma’) to see smile line profile with lips at rest centre occlusion right buccal occlusion left buccal occlusion upper occlusal lower occlusal

Digital radiographs More sophisticated techniques require the use of digital radiographs and OPG and lateral cephalometric images are requested.

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Representation of teeth

Impressions

The commonest way of recording the teeth in the mouth is by the use of impressions. It is important to use a rigid disposable tray so that the impression does not distort due to the tray flexing. Good quality trays are the President Impression Tray range manufactured by Coltene. The provider of the customised service may provide trays for use in taking impressions and may insist on their use with their particular technique eg: Align Technology ask users to use Align Technology trays to facilitate CT scanning. This may be because the impressions are scanned using an industrial CT scanner and the radiodensity of the trays is important. Both Align Technology and Cadent OrthoCAD provide their own design of trays.

In order to select the size of tray required to fit the patient, the bite registration is done first and then use to select the tray size as described in the Align Technology PVS Impressions Overview.

Our preferred materials come from Planet Smiles. Planet Smiles provides a full range of materials and accessories for 3D digital orthodontic applications and these are suitable for Ormco Insignia, Cadent OrthoCAD and Align Technology Invisalign techniques. The materials come in convenient single patient kits or can be bought in bulk at less cost.

Patient preparation Patient preparation requires three steps:

• • •

ask patient to remove any lip stick or lip balm as this will interfere with the setting of the polyvinyl siloxane impression materials ask the patient to brush their teeth using a preposted disposable toothbrush ask the patient to rinse with a mouthwash such as Listerine to get rid of any ropey saliva; although PVS impression materials are hydrophilic, they cannot displace saliva Operator preparation

Remember to ensure that both the operator and the assistant wear non-latex gloves as latex will prevent the PVS impression material from setting.

Bite registration Aligntech Institute have a short online instructional video on taking bite registrations for PVS impressions and further information is available on Aligntech Institute’s PVS Bite Technique Guide. Some bite registration materials are rigid which require undercuts to be blocked out; Planet Smiles Scan-Stuff bite registration material is sufficiently flexible not to require this and we have obtained good results with this material.

Impression technique We have used the technique described by Craig Andreiko on the Planet Smiles Scan-Stuff YouTube video. This is a two stage technique using a medium putty followed by a wash. A 0.75 mm foam tray liner is used in the putty impressions to create space for an even thickness of the wash and this is unique to Planet Smiles. Note the working and setting times for the putty and the wash and time the impression process appropriately. We have successfully used this technique for Insignia and OrthCAD IQ. Approximately 24 months ago, Planet Smiles introduced a putty/putty system called Passport. We now prefer to use Kerr Take 1 Advanced, a one-step PVS material. From experience, the Tray Fast set and the Wash Fast set provide the best combination with a working time of 1.5 minutes and a setting time of 2.5 minutes. We also use the Take 1 Advanced Bite Registration material.

Other techniques are described on the AlignTech website as follows:

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249

•

one step full putty arch with light body o pdf or video also available (open relevant section under PVS Impressions for video) • two step putty dam with medium body o pdf or video also available (open relevant section under PVS Impressions for video) • one step heavy body with light body o pdf or exe file also available (open relevant section under PVS Impressions for exe file) • two step heavy body with light body o pdf available Errors in impressions Impressions are prone to several errors; it is important to minimise these. Loupes are recommended for inspecting the impressions prior to sending them off to the service provider. Impressions should be systematically inspected as follows which is based on the recommendations given in Aligntech Institute’s PVS Bite Technique Guide and Cadent OrthoCAD’s IQ User Guide both of which provide valuable information on defects in impressions:

•

• • •

•

•

gingival margins o carefully follow the gingival margin all the way round both buccally and lingually. o all margins should be clearly defined o there should be at least two millimetres of impression material beyond the gingival margin all the way round the impression occlusal surfaces o all incisal edges and cusp tips should be clearly visible and sharply defined o the impression material should not have perforated through to the tray base molar area o the terminal molars should be fully visible in the impression material adhesion o the impression material should not have separated from the tray o the wash should blend seamlessly with the putty without delamination (maybe caused by using incompatible putty and wash materials) material appearance o there should be no folds, wrinkles or double imprints (caused by rocking or reseating the tray while the impression material is setting) o where there are small defects that require correction, do not be tempted to reline the impression; take a new one! o the impression material should have rolled over the edge of the tray increasing strength and retention tooth by tooth inspection o no parts of the tray should show through and there should be no very thin walls of impression material o all relevant anatomy should be present in the impression; the muscular folds and fraenal attachments should be clearly visible o the midline of the dental arch should normally coincide with the midline of the tray o there should be no voids or bubbles Cone beam CT

Three-dimensional diagnostic imaging using cone beam computed tomography (CBCT) is becoming a popular modality for both dental and orthodontic diagnostics. OraMetrix has undergone a three-year development project to integrate CBCT imaging with SureSmile digital decision support software and customized orthodontic treatment to transfer its benefits to orthodontic treatment outcomes. One advantage of this technique is that it brings distortion-free representation of the subsurface anatomy to SureSmile’s 3D virtual setup simulations.

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The use of CBCT involves the use of ionizing radiation but allows the incorporation of subsurface detail into the 3D data capture; however, if CBCT was a required component of the diagnostic process for a particular patient, its use to produce reconstruction of tooth anatomy would eliminate the use of impressions or an intra-oral scanner.

Kau et al (2010) investigated the difference between digital models derived from a Sirona Galileos CBCT using Anatomage InVivo Dental software and compared these with OrthoCAD models generated from dental impressions. They found that linear anatomical measurements were not significantly different between the two methods although resolution of dental anatomy was less good from CBCT than from digital models derived from impressions.

Intra-oral scanners Intra-oral scanners allow direct capture of tooth anatomy and eliminate the need for impressions. Several intraoral scanning systems are available or in advanced stages of development.

Cadent iTero™ The Cadent unit includes a computer, software, wand, and a built-in air compressor. The latter is used to send a stream of air over the lens to prevent fogging. The image is acquired using a strobe and color camera but the teeth do not have to be sprayed with any reflective powder. The probe can be placed directly on the teeth. The three-dimensional file is then processed and sent over the internet to Cadent’s facilities, where three dimensional virtual models can be created. These are then used to create an IQ set-up and downloaded to the orthodontists for approval. The obvious advantages are that there is no physical transport of impressions, no models to be poured or impressions to be analyzed. The orthodontist can immediately see the quality of the “impression,” and there is no concern about such issues as impression pulls or other distortions.

3M Lava™ COS 3M Espe acquired Brontes Technologies proprietary intra-oral scanning solution in late 2006 and have rebranded it Lava COS (Chairside Intra Oral Scanner). The Lava COS wand contains a highly complex optical system comprised of multiple lenses and blue LED cells. The system captures massive amounts of visual images in just seconds. Despite housing all of this technology, the wand weighs just 14 ounces and the wand tip is only 13.2 millimeters wide, maximizing manoeuvrability inside the mouth. This system, unlike other intra-oral scanners, uses a video stream to capture 20 3D data sets per second and then process and display these in real time.

DImensional Photonics International 3D DPI have an intra-oral scaner which uses accordion fringe interferometry (AFI). AFI offers many advantages over older "white light" scanners, which are likely to establish AFI as the dominant area scanning technology for multiple applications around the world. These advantages include, but are not limited to: lower sensitivity to ambient light variations and noise, very high accuracy, large projector depth of field, enhanced ability to scan shiny and translucent surfaces and the ability to scan without targets and photogrammetry systems. This system will be marketed by Ormco in late 2012.

Orametrix Orascanner™ The Orametrix Orascanner was prototyped by Orametrix and then redesigned by Stratos Product Development LLC to make it smaller, more comfortable and easier to use. The first intra-oral scanner on the market (Hajeer et al 2004), it revolutionised the technology by using active triangulation which meant that no fixed reference points were required. The scanner uses white light and the tip is heated to prevent fogging.

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D4D Technologies Intraoral Digitizer D4D Technologies Intraoral Digitizer (IOD) is a high speed laser intraoral scanner designed for use in restorative dentistry. Scans be either done directly or indirectly from an impression; the scanner uses a single laser point which is reflected off micro-mirrors oscillating at 200 cps.

Hint-ELs Directscan Hint-ELs are a German dental CAD/CAM company who have developed an intra-oral scanner called Directscan.

Again, designed for restorative rather than orthodontic use.

Densys3D Densys3d is an Israeli company whose technology has focused on the ease of acquisition of the image, fast processing time, accuracy, and ergonomic use by the dentist. The camera arm uses visible light and produces a small ASCII file enabling an open file architecture for easy integration to third party CAD/CAM machines. The optic head is small and has a depth of field of almost 3 cms. A 3D mouth ‘impression’ can be acquired in less than 90 seconds. The device was to enter clinical trials in 2007 but little further information is available from the company’s website.

There is little doubt that the acquisition of dental detail will in the future be obtained through intra-oral scanning; many products are now on the market although perhaps most of them have been designed for restorative dentistry rather than orthodontics. However, provided the equipment is capable of acquiring a whole arch scan, the technology is directly transferable to orthodontics. Many of these solutions use Geomagic’s Piano open architecture dental CAD/CAM software platform to convert scan data into 3D models.

Customised precision prescriptions Once the data has been recorded, information about the patient specific prescription will be required. This may be completed online but a printed copy is normally required to be sent with the PVS impressions to the service provider. The information required will be similar to the list below:

• • • • • • • • • • • • • • •

demographic details of patient orthodontist’s details preferred appliances selective torque values teeth to be bonded teeth to be extracted buccal segment relationship required at the end of treatment final overbite and overjet required at the end of treatment any spacing to be left planned tooth replacements or restorations planned interproximal reduction expansion or contraction of molar widths mesial or distal molar movement upper incisor edge alignment jig groupings or how trays are to be sectioned o for Insignia, the preferred jig groupings are 7654 321 123 4567 o for OrthoCAD, the trays are sectioned into quadrants, half arches or can be used as a full arch tray. The full arch tray is perfectly manageable with good moisture control.

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Constructing computer model from impressions

The computer model may be made from the impression by the following methods: CT scanning The impression can be scanned using and industrial CT scanner such as FlashCT. This means that no model needs to be cast but the radiodensity of the putty and the wash in the impression must be optimised to ensure the best possible image.

Surface scanning An excellent overview of 3D surface scanning in dentistry is given by Ireland et al (2008). Surface scanning may be contact or non-contact. Contact scanning is not used in these applications because the technique is too slow.

Methods for obtaining non contact surface scans are laser scanning and cone beam CT scans. OrthoCAD uses laser surface scanning to produce its digital models from poured plaster or stone models.

Destructive scanning Align Technology uses destructive scanning to make the computer model. The destructive scanner removes slices about 0.003 inch wide and a digital camera then takes a 2D scan after each slice. A computer stacks together around 300 of these digital images to create the 3D model.

Accuracy of computer models Definitions

Validity: validity refers to the degree to which a study accurately reflects or assesses the specific concept that the researcher is attempting to measure Reliability: reliability is the extent to which an experiment, test, or any measuring procedure yields the same result on repeated trials A number of studies have investigated the validity, accuracy and reliability of computerised dental models compared with conventional alternatives.

In 2002, Kusnoto and Evans confirmed that 3D laser scanning of dental study models and plaster facial models was sufficiently accurate to offer research potential.

Santoro et al (2003) investigated the reliability of the OrthoCAD system and plaster models. The measurements from the digital study models were slightly smaller but this difference was not significant. The authors concluded that digital models seem to be a clinically acceptable alternative to stone casts for the routine measurements used in orthodontic practice.

The validity of tooth size and arch width measurements for plaster and digital (OrthoCAD) models was evaluated

by Zilberman et al (2003) who concluded that:

• • •

measurement with digital calipers on plaster models produced the most accurate and reproducible results the OrthoCAD measurement tool showed high accuracy and reproducibility but was inferior to measurements done on plaster models with digital calipers digital calipers seem to be a more suitable instrument for scientific work. However, OrthoCAD's accuracy is clinically acceptable, and this or an equivalent 3D virtual model procedure would become the day-to-day standard for orthodontic use

Quimby et al (2004) compared measurements from 50 plaster models and 50 computerised models produced by OrthoCAD. Although small but statistically significant differences were found between the two systems, the

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authors concluded that these would not be clinically significant and that computer generated models were an acceptable alternative to plaster models.

In 2001, Tomassetti et al compared three different methods of calculating Bolton analyses with measurements taken from plaster study models with Vernier calipers. The methods used were QuickCeph Image Pro, HATS (Hamilton Arch Tooth System) and OrthoCAD. In terms of speed of use, QuickCeph was the quickest followed by HATS, OrthoCAD and Vernier calipers. Compared with the method using Vernier callipers, the HATS program had very similar results whereas OrthoCAD and QuickCeph were less well correlated. This may have been due to the difficulty in identifying landmarks with QuickCeph and OrthoCAD. Stevens et al (2006) compared Bolton analyses and PAR scores obtained from plaster models and Geodigm’s emodels. The authors concluded that no measurements associated with the Bolton analysis or the PAR score were clinically significantly different between the two systems and that digital models were a clinically acceptable replacement for plaster casts for the routine measurements made in most orthodontic practices; this was a similar result to that of Quimby et al (2004) but with a different digital model system. Stevens et al (2006) highlighted a number of limitations of digital models which were:

• • •

observing crossbites detail of midlines, occlusal anatomy and wear facets quantifying precise interdigitation

These concerns are likely to decrease with future software releases from all service suppliers. The authors expressed concern about the potential for distortion of alginate impressions during shipment or disinfection protocols.

Keating et al (2008) studied the accuracy and reproducibility of 3D optical scans of plaster models produced by a

Figure 12.1: Insignia allows comparison of photographs with digital occlusion to check accuracy and final occlusion as part of the Insignia Approval sequence

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Figure 12.2: Insignia jig groupings. The opaque jigs provide sufficient rigidity to allow clear space mesially and distally around the bracket to facilitate clean-up. Note also the excellent surface anatomy of the occlusal surface of the jig.

Figure 12.3: OrthoCAD transfer trays. The lower tray shows the hard outer shell tray from the outside occlusal surface. The upper tray shows the brackets in the soft inner tray with a thin layer of composite on each bracket pad to customise the appliance.

Minolta VIVID 900 non-contact laser scanner and the accuracy of physical replicas of the models reconstructed from the 3D data using a stereolithography rapid prototyping technique. The study concluded that:

• • • •

the use of using a hand held Vernier caliper to measure plaster study models was reliable and reproducible. the Minolta VIVID 900 was a reliable device for capturing the surface detail of plaster study models three-dimensionally in a digital the measurement of the captured ‘on-screen’ 3D digital surface models was reproducible the measurement of 3D digital surface models and plaster models of the same dentitions showed good agreement

However, the detail and accuracy of physical models reconstructed from digital data using the standard stereolithography techniques described may not be sufficient for certain applications; alternative methods of rapid prototyping may offer a more accurate method of model reconstruction from digital data.

Rangel et al (2008) have described a method of integrating three digital data sets: a digital dental cast, a digital 3D photograph of the patient with the teeth visible, and a digital 3D photograph of the patient with the teeth in occlusion such that it is technically possible to make a 3D data set of a patient's face, with the dentition positioned in the anatomically correct position in this 3D picture.

Leifert et al (2009) compared arch length measurements on conventional and OrthoCAD models and found no difference between the two methods in the mandible but significant although not clinically significant differences in the maxillary arch (mean differences 0.33 mm in he mandible and 0.44 mm in the maxillary arch). This was attributed to greater variability in the inclination of the upper incisors making it more difficult to accurately assess landmarks. It was concluded that both methods were satisfactory methods of assessing arch length discrepancy.

The use for digital study models in outcome scoring such as the ABO Objective Grading System (ABO OGS) seems to demonstrate systematic differences between conventional and digital study models (Costalos et al 2005, Okunami et al 2007 and Hildebrand et al 2008). In general, scores from digital models give higher ABO OGS scores than conventional models. Further development is likely to eliminate these differences.

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Pauls (2010) has demonstrated that using start of treatment and end of treatment study models which were digitalized using a 3D scanner, the final results following lingual orthodontic treatment using individualized brackets correlate satisfactorily with the therapeutic set-ups.

Overall, computerised methods are found to be perfectly satisfactory for clinical use and will continue to improve with hardware and software development.

Transport and communication PVS impressions must be transported to the service provider and this is usually done by courier such as Fedex or DHL; the service provider may or may not pay for shipping but will provide packaging, checklists and any necessary documentation. The orthodontist will usually be notified:

• • • •

when the impressions have been received by the service provider when the set-up is ready for approval when the set-up has been approved by the orthodontists and released to manufacture when the precision prescription appliance has been shipped

Turn-around time varies from two to four weeks according to manufacturer.

Approving the prescription All service providers will have slightly different methods of doing this but the broad principles are the same. For conventional labial appliances, the orthodontist selects preferences which represent the commonest types of appliance that they use; if more than one type of appliance is used (eg: metal for some cases and ceramic brackets for others), then multiple preferences can be selected.

The jig grouping (Insignia) should be selected; the preferred grouping is [7654] [321] [123] [4567]. Ensure that the jig grouping does not include teeth where the path of removal of the jig is significantly different. For OrthoCAD, the choice is where the trays are sectioned; this seems to work best if they are sectioned in the midline giving four separate bonding trays, one for each quadrant.

• • • • • •

in addition, end-of-treatment preferences may be selected such as: is bracket height to be at height of greatest contour, more gingival or more occlusal? in the buccal segments, is marginal ridge alignment to be obtained or alignment of cusp heights? are cases always to be treated to class 1 even if this means leaving spacing? should the upper lateral incisors be 0.5 mm higher than the central incisors or level with them? should the patient’s photographs be used to determine the smile arc? Is the orthodontist prepared to accept a slightly class buccal segment relationship or increased overbite in order to increase incisor show? are rotations to be over corrected or not? should the upper and lower canine brackets be placed more mesially to avoid canine offset bends?

Approving the set-up involves the following stages:

• • • •

check start of treatment digital models and occlusion for accuracy (and with intra-oral photographs if available) review post-treatment set-up from all angles and take note of any comments from service provider; note alterations to be made in set-up review mandibular occlusal view and adjust any tooth rotations as required review mandibular dentition from labial, occlusal and lingual views and adjust tooth heights, tooth angulation and tooth inclination as required. It is helpful to refer to the OPG and cephalogram at this stage

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• • • • • • •

review maxillary occlusal view and adjust any tooth rotations as required review maxillary dentition from labial, occlusal and lingual views and adjust tooth heights, tooth angulation and tooth inclination as required. It is helpful to refer to the OPG and cephalogram at this stage using the clipping tool, work round the arch checking each tooth contact and adjust as necessary check occlusion with digital set-up in occlusion for accuracy of end of treatment position check occlusion with digital set-up in occlusion for bracket interferences and adjust as required using wire plane tool add any special comments to the Notes field submit set-up electronically and approve for manufacture

Other additional features may be available in the software such as:

• • • • • • • •

display treatment preferences display occlusograms show mandibular trough 2D and 3D measurement including intertooth widths and Bolton analyses morphing between pretreatment and post-treatment occlusions clipping interaction to show a section plane through the teeth and study cusp fossa relationships compare start and end of treatment occlusions using side by side comparison of digital models and setup, digital models and setup and photographs or overlays amount and location of interproximal reduction

Figure 12.4: Stage 2 (tooth positioning) of the OrthoCAD sequence for approving a set-up. The left hand window shows the end of treatment result using Damon Mx brackets; the right hand window shows the start of treatment malocclusion with the brackets in place. Note the IQ approver window below the View Control tool.

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Insignia currently offers fully customized set-up for conventional twin brackets and for Damon selfligating brackets. In the Custom SL appliance system, the gates in the lower arch open occlusally in order to position the horizontal hook slot gingivally. There is no vertical slot for a hook. Two types of hook are available; a 90 degree hook for brackets and a 180 degree hook for molars. The Custom SL molar tubes have a very shallow hook which works well for 2oz elastics but not for heavier ones. Further information is given by Sarver 2009.

Bonding Figure 12.5: The Kerr Optiview retractor has minimal bulk inside and outside the mouth and provides effective retraction back to the second molars

• •

The key to successful bonding is clean, dry and well etched teeth.

Cleaning the teeth ultrasonically scale all the teeth to ensure all calculus is removed. Even young patients have calculus build-up, particularly on the buccal surfaces of the upper molars and around the lower incisors prophy all the teeth with a pumice paste such as Reliance First & Final

Moisture control • provided there are no contraindications, give the patient 600 mcg of atropine sulphate to take one hour before the bond up • use a good cheek and lip retractor. The Kerr Optiview (see page 7 of this link) works very well (Figure 12.5); it comes in standard and small sizes although the standard size seems to work well for all patients • use a small and simple saliva ejector with a tongue deflector. Although we have tried the Nola Dry Field System, we have found it too bulky and over complicated • use Dri-angles tucked behind the inside buccal wings of the Optiview to keep the buccal segments dry of saliva; Dri-Angles can also be used as tongue retractors. A mirror placed inside the mouth and against the Dri-Angle provides additional retraction when bonding the upper second molars if required • air dry the buccal, occlusal and lingual surfaces of the teeth to be bonded until no hint of etchant or moisture remains after etching Etching

• • •

do not use a self-etching primer; use either a good quality gel such as Ultradent’s UltraEtch or a liquid etch etch the whole of the buccal surface of each tooth to be bonded etch for a full 30 seconds

Primer

• •

if the system being used has composite already on the bracket bases, moisten these with Ormco OrthoSolo and ‘roll off’ any excess with a microsponge cover the buccal segment of each tooth to be bonded with a coat of OrthoSolo; this should not be too thin or too thick

Adhesive • our preferred adhesive is 3M Unitek Transbond XT LR

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• •

we have tried 3M Unitek Transbond Supreme Light Cure LV but found this too low a viscosity to penetrate the foil mesh on the underside of the bonding pad try and seat the jig cleanly first time; do not move the jig around or the set of the adhesive will be disturbed

Placement technique • for Insignia, angle the jigs so that the bracket base is at about 30 to the tooth surface and then roll it down into place. Insignia jigs seat very precisely. Use a microsponge to clean any excess adhesive from the mesial, distal and gingival edges of the bracket. Ensure that firm pressure is applied both from the occlusal and the buccal to ensure close adaptation between bracket and tooth surface. For jigs in the molar region, it is easier to transfer them into place with tweezers • for OrthoCAD, the transfer tray has to be seated in an almost vertical direction and it is not possible to remove any excess adhesive from the mesial and distal surfaces of the brackets, only from the gingival edge Light curing • Insignia has opaque expanded foam jigs and so light curing is slightly tricky. Use the smallest tip possible in the curing light (eg: 8 mm oval or smaller if possible). Cure from the gingival, the mesial and distal where possible and also from the lingual. Complete the cure once the jigs have been removed • OrthoCAD has a two part tray with a hard outer shell and flexible inner liner that holds the brackets.

Cure each tooth through the outer hard tray and then remove it. Complete the cure by curing each tooth through the soft inner liner Jig or transfer tray removal • to remove Insignia jigs, grip the jig across the centre buccolingually with a pair of Weingart pliers and gently roll the jig off buccally • for OrthoCAD, the outer hard tray is easily removed using fingers. The inner tray is flexible and can be gently disengaged from each bracket in turn, working from mesial to distal, by gripping the edge of the tray close to the gingival edge of the bracket(s) and unpeeling it from each bracket

Final clean-up • check for any excess adhesive. This will be less with Insignia (largely confined to occlusal edge of •

bracket) than with OrthoCAD (may be on mesial, distal and occlusal surfaces of pad) remove any excess adhesive with a debonding bur

Archwire placement • Insignia provides five sets of customised archwires; these are marked at the midline and on the right hand side to ensure that they are fitted with the correct orientation

Summary Customised precision prescription appliances offer several potential advantages as follows. The extent to which they are translated into tangible benefits is as yet unclear.

•

the digital records eliminate the need for plaster models o while digital records do not yet quite have the precision of plaster models, advances in technology and the disadvantages of plaster study models in relation to manufacture, storage and retrieval mean that the future of traditional plaster models has to be in serious question.

Now that plaster models are rarely required for appliance construction, the combination of

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diagnostic summary, digital photographs and digital representations of the teeth and roots probably provide adequate information to determine the pre-treatment start point • reduced bonding and set-up time o the time taken for the first few set-ups is likely to be slightly longer than for a conventional bond-up. With experience, the time taken seems to be similar to conventional appliance placement • reduced stress of bond-up o customised precision prescription appliances are easier to place than conventional bond-ups • allows placement of brackets and appliances by less experienced personnel o customised precision prescription appliances allow placement of the appliances without the necessity for the skills associated with direct bonding. The task can therefore be delegated to less skilled staff if required • reduced treatment time o if bracket positioning is improved by the virtual set-up technique, then it might be surmised that treatment times might be shorter as a result of this • reduced cost o although the initial cost is higher, this may be recouped if less visits are required and treatment times are shorter Overall, we are impressed with our early experiences with this technique and are convinced it will become the preferred way of placing fixed appliances in the future. The learning curve in the early stages is steepish but perseverance makes orthodontics even more enjoyable! Well worth a try.

References Costalos PA, Sarraf K, Cangialosi TJ and Efstratiadis S (2005) Evaluation of the accuracy of digital model analysis for the American Board of Orthodontics objective grading system for dental casts American Journal of Orthodontics and Dentofacial Orthopaedics 128: 624–629 Leifert MF, Leifert MM, Efstratiadis SS and Cangialosi TJ (2009) Comparison of space analysis evaluations with digital models and plaster dental casts American Journal of Orthodontics and Dentofacial Orthopaedics : 16.e1-16.e4 136 Levin RP (2006) Eight tips for evaluating technology Inside Dentistry 2: issue 6 Available at http://www.insidedentistry.net/article.php?id=1871 Accessed 29 December 2008 Hajeer MY, Millett DT, Ayoub AF and Siebert JP (2004) Current Products and Practices: Applications of 3D imaging in orthodontics: Part II Journal of Orthodontics 31: 154-162 Hildebrand JC, Palomo JM, Palomo L, Sivik M and Hans M (2008) Evaluation of a software program for applying the American Board of Orthodontics objective grading system to digital casts American Journal of Orthodontics and Dentofacial Orthopaedics 133: 283–289 Ireland AJ, McNamara C, Clover MJ, House K, Wenger N, Barbour ME, Alemzadeh K, Zhang L and Sandy JR (2008) 3D surface imaging in dentistry – what we are looking at British Dental Journal 205: 387-392 Kau CH, Littlefield J, Rainy N, Nguyen JT and Creed B (2010) Evaluation of CBCT digital models and traditional models using the Little's Index Angle Orthodontist 80: 435-439 Keating AP, Knox J, Bibb R and Zhurov AI (2008) A comparison of plaster, digital and reconstructed study model accuracy Journal of Orthodontics 35: 191-201 Kusnoto B and Evans CA (2002) Reliability of a 3D surface laser scanner for orthodontic applications American Journal of Orthodontics and Dentofacial Orthopaedics 122: 342–348

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Okunami TR, Kusnoto B, BeGole E, Evans CA, Sadowsky C and Fadavi S (2007) Assessing the American Board of Orthodontics objective grading system: digital vs plaster dental casts American Journal of Orthodontics and Dentofacial Orthopaedics 131: 51–56 Pauls AG (2010) Therapeutic accuracy of individualized brackets in lingual orthodontics.

Journal of Orofacial Orthopaedics 71: 348-361 Quimby ML, Vig KW, Rashid RG and Firestone AR (2004) The accuracy and reliability of measurements made on computer-based digital models Angle Orthodontist 74: 298–303 Rangel FA, Maal TJJ, Bergé SJ, van Vlijmen OJC, Plooij JM, Schutyser F and Kuijpers-Jagtman AM (2008) Integration of digital dental casts in 3-dimensional facial photographs American Journal of Orthodontics and Dentofacial Orthopaedics 134: 820-826 Santoro M, Galkin S, Teredesai M, Nicolay OF and Cangialosi TJ (2003) Comparison of measurements made on digital and plaster models American Journal of Orthodontics and Dentofacial Orthopaedics 124: 101–105 Sarver DM (2009) An interview with an Insignia doctor American Journal of Orthodontics and Dentofacial Orthopaedics 136: 853-856 Stevens DR, Flores-Mir C, Nebbe B, Raboud DW, Heo G and Major PW (2006) Validity, reliability, and reproducibility of plaster vs digital study models: Comparison of peer assessment rating and Bolton analysis and their constituent measurements American Journal of Orthodontics and Dentofacial Orthopaedics 129: 794-803 Tomassetti JJ, Taloumis LJ, Denny JM and Fischer JR (2001) A comparison of 3 computerized Bolton tooth-size analyses with a commonly used method Angle Orthodontist 71: 351–357 Zilberman O, Huggare JA and Parikakis KA (2003) Evaluation of the validity of tooth size and arch width measurements using conventional and three-dimensional virtual orthodontic models Angle Orthodontist 73: 301–306

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Introduction Many factors can make a treatment difficult. An incorrect treatment plan, poor patient motivation, and markedly malaligned teeth can all cause difficulties and these topics are all discussed in relevant chapters of this book. A frequent difficulty is that of obtaining sufficient anchorage - particularly if a “six keys” occlusion is our goal.

Andrews' textbook documents the causes of failure to achieve a six keys' occlusion and many of the cases would require additional posterior anchorage to be finished to his suggested goals. The anchorage available within one arch is related to space in that arch and that space is frequently obtained by extractions. Anchorage other than from this source has, with most biomechanics, involved enlisting the co-operation of the patient. This chapter chiefly addresses the means by which the need for this co-operation can be minimised and how the patients' efforts can be put to best use. Reinforcing anterior anchorage - as in Class 3 or hypodontia cases - is discussed in the chapter on Managing Class 3 Malocclusions.

Sources of anchorage Anchorage can be obtained from intra-oral and extra-oral sources and we should not forget the possibility of favourable growth and the question of our ability to enhance it. This latter aspect is discussed in the chapter on Functional Appliances. It is sensible to firstly summarise the possibilities for maximising intra-oral anchorage.

Sources of intra-oral anchorage • root surface area •

As discussed below, this is a fundamental source of anchorage ? bony cortex In spite of previously widespread hope that this may prove source of anchorage, there seems little evidence that this is indeed the case. It is clearly not difficult to move teeth labially right through the cortex. Rebellato et al (1997) found that lingual arches did not prevent mesial migration of molars even when no intra-arch traction was applied. A study by Ellen, Schneider and Sellke (1998) found no enhancement of vertical or horizontal anchorage when using utility arches to set up cortical anchorage. These papers would also suggest that palatal arches would not be expected to add to posterior anchorage. A paper by Radkowski (2007) in fact reported slightly more anchorage loss when trans-palatal arches were used. Zablocki (2008) in a study of matched cases again found no vertical or mesio-distal anchorage effects from a palatal arch.

Key fact: There is no evidence that palatal arches reinforce mesio-distal anchorage.

• mucosa and underlying bone

This is the source of anchorage which is sought with Nance buttons, removable appliances and lingual flanges on functional appliances. It is hard to measure, but appliances which cover a larger area of mucosa would be expected to provide additional anchorage. These appliances can cause trauma to the palate as anchorage is lost. We do not use Nance buttons.

• occlusal interferences Some extraction patterns e.g. upper first and lower second premolars can create useful interlocking of the dentition and increase the root surface area resisting a loss of upper arch posterior anchorage. Conversely upper canines stuck mesial to lower canines can lose upper arch anchorage as can attempted reduction of an overjet in the presence of a complete overbite.

Clinical Tip: Occlusal interferences are often overlooked as a source of anchorage loss

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• implants and temporary anchorage devices (TADs)

These are a powerful source of intra-oral anchorage and are discussed in the chapter on Temporary Anchorage Devices in Orthodontics.

The differential force theory This theory states that within limits, the rate of tooth movement is related to the applied force per unit root surface area. i.e. within a certain range of force, a given force will result in less tooth movement if spread over a larger number of teeth. This concept is fundamental to orthodontic anchorage and is at the heart of all orthodontic treatment and treatment planning. It does however remain a theory which is far from fully proven, although there seems strong indirect evidence that the differential force theory has substance.

Maximising root surface area For example, the study by Saelens and De Smit (1998) showed a greater mesial movement of molars and a lesser amount of anterior crowding resolved when second premolars rather than first premolars were extracted. Other studies supporting this theory are discussed in the chapter on Diagnosis and Treatment Planning in the section on planning extractions. Maximising root area in the anchorage unit is therefore sensible when anchorage is at a premium. In addition to choosing more anterior extractions, root surface area in the anchorage unit can be increased relative to the root area of the teeth we wish to move by:

• • • •

including second molars separate retraction of canines correcting centrelines one tooth at a time semi-transverse forces eg: pushing rather than pulling canines distally

Practical considerations may lessen the applicability and effectiveness of any of these in a given situation, but they are all potentially useful sources of anchorage.

Evidence for the differential force theory A further complication is that the data on the relationship between force applied and tooth movement achieved has yet to confirm a clear picture of the relationship between the two. A study by Pilon et al (1996) in beagle dogs showed that the rate of tooth movement and the amount of anchorage loss were not significantly different for forces ranging from 50 g to 200 g. Some dogs had teeth that moved quickly and others moved slowly regardless of the force level. The rate of movement was highly correlated between the left and right sides for any dog and this suggests that inherent metabolic factors may be much more important than force level in determining the rate of movement of teeth - including those in an anchorage unit. Anecdotal clinical observation certainly suggests that human patients show similar variation in orthodontic response to applied force.

It might be concluded from a casual reading of this important paper that the differential force theory was in serious doubt in its entirety. However, tooth movement was still related to the root surface area - anchorage units moved less than the individual premolar teeth. The ratio of movement was not the same as the ratio between the root surface areas. The anchorage unit averaged ten times the root surface area of the premolar and yet moved an average of 25% of the premolar movement, not 10%. Root surface area definitely seems to matter i.e. there is some scientific support for the differential force theory, but we don’t yet know the exact extent of its influence and there are clearly other factors which are important.

A meta review by Ren et al (2003) referred to over 400 studies of relevance and it is clear that the details of the relationship between force applied and tooth movement remain insufficiently understood or documented.

Later work by this same team Von Bohl et al (2004), confirmed the poor correlation between force level and tooth movement or the degree of histological hyalinisation. This paper used an implant to cleverly compare different force level per unit root surface area with no complicating anchorage loss. The paper also has an excellent summary bibliography of force and pressure levels in previous studies. Numbers are necessarily small in studies using beagle dogs, but figure 4 in that paper does show data which suggest that for that dog, lower force

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favoured premolar movement whereas higher force favoured molar movement. This finding is supported by a more recent study by Yee et al (2009) who measured canine retraction and anchorage loss with a light (50 gm) and heavy (300 gm) forces over a 12 week period. The 300 gm force produced significantly more movement of both the canine and the anchorage unit and the percentage of anchorage loss was significantly higher (62%) with the heavy force than with the light force (55%). This supports the differential force theory.

Root surface area – summary • force level is only part of the explanation of rate of tooth movement • spreading the force over larger root area does reduce the rate of movement (and thus preserve anchorage)

Retracting six teeth at once In extraction cases where anchorage is not at a premium, clinicians traditionally retract the canines until there is sufficient space to align the incisors and then the complete labial segment of six teeth is retracted as a unit as opposed to fully retracting the canines to a class 1 relationship and then retracting the incisors. On theoretical grounds, retracting all six teeth simultaneously would be expected to increase anchorage demands and although this increase is not necessarily apparent clinically, there must be good reasons for choosing this theoretically more anchorage demanding plan. These reasons fall into two categories, namely, simplicity and control of canine rotation.

Simplicity and control: Sliding all six teeth as a unit along a stiff wire involves very simple archwire fabrication and activation when compared with three sectional archwires and closing loops. Also, the chances of trauma to the lips, cheeks and gingivae are very small and the obstacles to oral hygiene are minimised. This method also makes it easy to keep all teeth under control and at the end of space closure there is no need to align the teeth for a second time before finishing. These advantages must be weighed against the possible increase in anchorage required.

Self-ligating brackets and anchorage

The chapter Self-ligating brackets – theory and practice discusses in detail the potential benefits of using selfligating brackets such as SPEED, In-Ovation or Damon Q. One such benefit is the ability to slide a tooth along a wire with very low friction and with no loss of control. This previously unavailable combination reduces the potential disadvantages of separate retraction of canines. We would therefore expect anchorage preservation to be enhanced if these mechanics are used with self-ligating brackets. It has certainly been reported in a very interesting study by Rajcich and Sadowsky (1997), that retraction of canines with sliding mechanics when the molar is prevented from tipping or sliding mesially incurs impressively low anchorage loss. There are simpler ways of controlling molar tip and slide than the one they suggest which uses an auxiliary arch. A crimped stop or hook is one of them. This combination of a self-ligating bracket, a stopped archwire and separate canine retraction is worth close consideration for anchorage enhancement and is considered more fully in the chapter on Self-Ligating Brackets.

Tipping and uprighting teeth versus bodily movement

Appliances such as Begg and Tip-Edge deliberately allow extensive distal tipping of anterior teeth followed by a later phase in which the mesially tipped roots are moved distally. The differential force theory is frequently quoted in this context in support of the idea that this two-stage movement will consume less anchorage overall.

This is another inadequately researched area. There is no doubt that tipping a tooth requires less anchorage than bodily movement, because a given force is concentrated on only a small part of the root area whereas in the anchorage unit where the teeth are held upright, the same force is spread over the whole mesially-facing area of the roots and is thus much lower per unit area of root surface. What has not been adequately explored is whether tipping and subsequently uprighting a tooth consumes less anchorage than achieving the same result with more bodily movement. In that second phase, the force is still resisted by the same root area in the anchorage unit, but is now also spread over the majority of the root surface of teeth in which the apex is more mesially placed than at the start of treatment and must therefore move distally through a large arc.

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A study by Lotzof et al (1996) missed a potential opportunity to shed some light on this. Upper canine retraction was compared within the same patient with a Tip-Edge bracket on one canine and a Straight-Wire bracket on the other. The differences were not even close to being statistically significant, but suggested that with much larger sample size, the Tip-Edge bracket might have shown that using the flawed protocol chosen, 0.6 mm less anchorage loss over the approximately 11 week time required to retract the canines. Apart from the small sample size (12 cases) the major reservation about the study is that the tooth with the Tip-Edge bracket was, of course, allowed to tip distally but was not then uprighted. This negates any sensible comparison of rate of retraction or anchorage loss. It is easy to be critical and this study does reveal some of the practical difficulties in assessing the relative anchorage consumption of differing mechanics. More recently, a good study by Shpack et al (2008), found that bodily retraction of a canine consumes the same anchorage as tipping followed by uprighting and incidentally, bodily retraction was more rapid by an average of 38 days.

Measuring anchorage In all the discussion about anchorage and anchorage loss, the relative merits of the various means of assessing anchorage are rarely discussed. Assessment means comparison over time of tooth position relative to a non-tooth structure. The data is either cephalometric or from study models.

Cephalometric measures of anchorage • lower incisor anteroposterior position

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This is probably the most common method in clinical practice. A more labial position of the lower incisors at the end of tooth movement is conventionally considered to represent loss of anchorage.

Similarly, except in the treatment of bimaxillary proclination or in some class 3 cases, a more posterior position of lower incisors following treatment is considered to be unused intraoral posterior anchorage. Cephalometric measures such as Lower incisor to Nasion-Pogonion, or Lower incisor inclination to mandibular plane are used to assess this aspect of anchorage consumption/loss. The reference structures being used are the Nasion-Pogonion plane or the mandibular plane or - in the Steiner analysis - the line Nasion-B point. This is a simple and very useful tool, but does have its limitations. In particular, it gives no information about the quantity and sources of anchorage provided to move teeth distally, only about the anchorage consumed. pitchfork analysis This is a very well known form of superimposition on bony structures, described and popularised by Lysle Johnston (1985, 1996). This reference structure is essentially the maxilla and zygoma.

Johnston developed a comprehensive set of measures relative to a mean functional occlusal plane, which provide a measure of anteroposterior movement of upper and lower incisors and molars and the contributions of mandibular and maxillary growth. Whilst still not providing full quantification of the anchorage work done (no measurement of changes in incisor inclination or canine angulation), it provides an extremely useful summary of the contributors to anteroposterior achievements. superimposition on other cranial structures There are other well-known reference structures, for example, De Coster’s line in the cranial base and Bjork’s ‘stable’ structures in the maxilla and mandible. Each structure has its merits. A paper by Mannchen (2001) has pointed out some disadvantages in the pitchfork analysis. The criticisms are essentially twofold: Firstly, that the maxilla is not the best structure on which to superimpose, because rotational changes of the maxilla during treatment will effect the resolved anteroposterior components. Secondly, that the mean functional occlusal plane can also change and effect the measurements relative to it. Mannchen compared the results when the same cases were assessed using the pitchfork analysis and Bjork’s structures. He found a tendency for the pitchfork to estimate more skeletal and less dental change (approximately 1 mm) compared to using Bjork’s structures. All reference structures have disadvantages – both in principle and in terms of the practicalities of reliable identification and measurement of structures. In an individual case the veracity of cephalometric superimpositions on the best fit of various structures should be viewed with significant scepticism.

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Study model measurement

Over many years, there have been investigations of the suitability of the palatal rugae for superimposition of changes in maxillary teeth. There has been a recent resurgence of interest in this method, prompted by the developments in digital imaging which assist the recording, enhancing and measuring of the upper study models.

Hoggan and Sadowsky (2001) reviewed some of the previous papers and carried out a study which concluded that palatal rugae landmarks are as reliable as cephalometric structures for superimposition. However, it should be noted that the standard deviation of repeated measurements was 0.8 mm or more for several of the measures.

This would mean that a real difference of 1.6 mm is unlikely to be shown to be statistically significant. Indeed in the study, a difference of 1 mm between the cephalometric and study model measurements of the same parameter was not statistically significant. Of course, this also reflects on the relative unreliability of cephalometric measures of molar position. Ashmore et al (2002) have utilised different digitising techniques to measure molar movement in the vertical and anteroposterior directions and concluded that superimposition on the palatal rugae was sufficiently reliable to pursue as a method.

There is no ideal method of measuring anchorage loss and anchorage achieved, but cephalometrics provides information of great value for both scientific and clinical purposes. The use of palatal rugae needs further investigation, but with newer digital techniques and the advantage of good identification of tooth landmarks, it may prove to have a useful place.

'Fixed' class 2 traction Intermaxillary traction - Class 2 in the context of this chapter - is a traditional way of transferring anchorage from one arch to another. Such traction is frequently required in extraction cases where retroclination of the lower incisors is not required and methods which reduce or eliminate the need for patient co-operation in relation to Class 2 elastics are surely worth considering. Many appliances have been produced to try to meet this aim. Most have not proved popular for a variety of reasons. Most commonly the problems are:

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excessive breakage rates of the class 2 device excessive breakage of the archwires or loss of adjacent bonded attachments difficult to place o quickly o with the correct activation o in a position where occlusal forces do not lead to breakage or distortion and where trauma to the cheeks is unlikely special attachments are required (e.g. oval upper molar tubes with the Klapper spring)

Devices, which are rapidly placed, comfortable, robust and effective, are clearly a big technical challenge, but a form of class 2 traction which is effective and requires no active patient participation remains a very worthwhile objective.

Types of fixed class 2 traction • Saif spring • Alpern interarch coil spring • Jasper Jumpers • Eureka piston spring • Bite fixer • Klapper superspring • Forsus flat spring • Forsus FRD spring • TwinForce bite corrector • Sabbagh spring

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(Fixed functionals- e.g. Fliplock Herbst)

This list is not comprehensive, new designs emerging with regularity. Nickel-titanium springs which can withstand being tied in as class 2 'elastics' for several months were disappointing as a product because of breakage problems. Such springs were available under the name ‘Saif springs’ The Alpern spring is a sheathed coil spring.

All other fixed forms of intermaxillary traction employ compression of an elastic device rather than extension.

Curving pusher springs Several of the fixed calls 2 traction devices can be grouped together under this heading. When the patient closes in a retruded mandibular position, the spring is compressed and curves buccally into the sulcus. We tried Jasper Jumpers in the past on a significant number of cases and found their effectiveness severely compromised by a very high breakage rate. A more recent version involves a snapaway capability which is claimed to preserve the ‘Jumper’ for reassembly, but this perhaps just saves on ‘Jumpers’ rather than enhances treatment efficacy. A study

by Stucki and Ingervall (1998) reports a 9% breakage rate. Clinicians do report success however and this concept may prove its worth with more robust springs. Weiland et al (1997) have reported cephalometric changes with the Jasper Jumper which are typical of a tooth-borne functional-type appliance and overjet reduction in an average of six months, but no mention of breakages or other technical problems. A more recent development of this idea is the ‘Bite Fixer’. This has a coil spring which surrounds a flexible core rather than a central spring surrounded by a flexible cover (the Jasper Jumper design). We have tried these and met with success but they, or the archwires to which they are attached, are not immune from breakage. One challenge with this type of device is the need to build in a good range of action as the mouth opens by providing travelling space along a wire.

Forsus flat springs are leaf-like nickel-titanium springs. Other companies sell the same spring under different names. A prospective study by Karacy (2006) good and equal success with Forsus flat springs and Jasper jumpers with low breakage rates Tips when using Bite Fixers or other ‘curving pushers’ • if you have lower molar bands with double tubes, use them to place an auxiliary mandibular wire from the lower molar to the main archwire just distal to the lower canine. This increases the range of possible mandibular movement and prevents the need to remove a lower premolar bracket. The auxiliary wires are easy to fabricate. The additional investment in time, complexity and double tubes is reported to greatly increase patient comfort and certainly reduces breakage, but is likely to remain an unpopular additional complexity.

• if you have a self-ligating upper molar attachment such as the Damon, this eases the placement of such an auxiliary distal to the upper first molar.

• do not overactivate, especially at the first visit. This increases patient comfort. If the overjet is large, the device will be passive when the mandible is postured forward as far as the patient can achieve Piston-type pusher springs Eureka springs are compressed nickel-titanium springs in a piston arrangement. They are designed by John De Vincenzo and manufactured in San Luis Obispo, California. An excellent study by Stromeyer, Caruso and De Vincenzo (2002), measured the cephalometric effects in 50 consecutive cases which had failed to cooperate with conventional elastic class 2 traction. The appliance was successful in achieving class 1 canine and molar relationships in all cases in an average of 4 months (range 2 to 14 months). This compares with an average of 27 months of treatment prior to starting the Eureka springs because of non-compliance. The cephalometric changes were almost entirely dentoalveolar and of equal extent in upper and lower arches. The average age at the start of the Eureka spring stage was 16.0 years, reflecting the long previous treatment with no compliance. They are fairly technique-sensitive in terms of placement with correct activation and positioning, requiring a tieback ligature to be accurately placed.

A more recent version of this concept is the Sabbagh spring which can be used as a fixed functional or as a fixed class 2 traction device. The Forsus FRD is similar. The Twinforce bite corrector is also a linear piston device. As the name suggests, the TwinForce has two pistons containing two springs which give a longer range of action and therefore, it is hoped, a lower breakage rate.

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Clinical Tip: All these appliances attach on the buccal surfaces and therefore tend to place buccal crown torque on the teeth.

Palatal crown torque plus some contraction of the archwires may be needed to counteract this buccal flaring.

One factor shared by all the curving pusher springs and many but not all of the piston-type springs is the need for a headgear tube for the distal (maxillary) attachment. This has several disadvantages:

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one suspects that this would severely tax the bond strength of a molar bond and placing molar bands is an additional chore. adjusting the attachment to ensure that the curving pusher-type (in particular) easily bypasses the archwire tube can be tricky – especially if the headgear tube is gingival to the archwire tube.

Clinical Tip: Piston-type fixed class 2 traction devices tend to be more comfortable and have a longer range of action.

Fixed functional appliances These differ from fixed forms of class 2 traction only in that the force is stored in the muscles and ligaments rather than in the elasticity of a metal spring.

Types of fixed functional appliance:

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Herbst appliance MARA appliance Sabbagh appliance with spring element locked (Fixed twin-block) AdvanSync Molar-to-molar appliance developed by Terry Dischinger

The MARA (Mandibular Anterior Repositioning Appliance), popularised by James Eckhart, consists of two buccally placed wire ‘wedges’ attached to molar bands which interlock in a postured bite as do twin-blocks or the Dynamax. We have no personal experience of these. More recently we have employed fliplock Herbst appliances (made by TP Orthodontics) direct to rectangular tubing slid over the archwires. This promising approach is very similar in its practicalities to the piston-type class 2 traction devices, but attachment is significantly easier - see the chapter on Functional Appliances. Terry Dischinger’s molar-to-molar appliance – AdvanSync -has a short telescopic piston attached just to the upper and lower molars and is described in the chapter on Functional Appliances.

It is probable that one or two designs of fixed class 2 traction will emerge as robust, easy to attach, comfortable and effective and these will steadily grow in popularity. Our impression is that the linear piston-type devices or a non-elastic Herbst-type attachment will prove more robust and more comfortable than the devices which compress into a curve towards the cheek. A large factor in the robustness of this linear piston-type of device may come form the inherent extendibility and the lack of need for the end of the device to travel along an archwire or auxiliary wire.

Headgear Decline in our personal use of headgear We have steadily used less headgear over many years until we now never use it. Several reasons contribute to this trend. Some relate to a slight shift in average treatment goals and others to availability of better technology for class 2 correction and anchorage control.

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functional appliances which have better compliance fixed functionals

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more class 2 elastics being employed self-ligating brackets seem to reduce anchorage demands (not proven) and favour earlier use of lighter class 2 traction more lower incisor proclination accepted more arch expansion accepted TADs have revolutionised intra-oral anchorage possibilities

Direction of headgear pull

We favoured a direction of pull that is significantly above the occlusal plane in order to avoid a backwards rotation of the mandible and the need to chase the retreating target of the lower incisors to obtain overjet reduction.

The excellent review by Bowden (1978) of the effects of altering headgear geometry has more recently been supported and amplified by Yoshida et al (1995) who investigated the initial direction of movement within the periodontal membrane of upper first molars with headgear using magnetic sensors. These authors support the view that a short outer bow ending opposite the centre of resistance of the molar offers the best options. They highlight the disadvantages of too flexible an outer bow in inadvertently altering the intended direction of force and they again point out the drawbacks of a cervical pull. It is however worth noting that the comparative vertical effects of occipital and cervical headgear may not be entirely clear-cut in clinical practice. For example, the paper

by Burke and Jakobson (1992) revealed, as expected, substantial differences in upper molar extrusion, but no clear short or long term differences in measures of face height. O’Reilly et al (1993) show definite mandibular rotation from cervical headgear when compared to occipital pull. It would still seem sensible to avoid upper molar extrusion since this is only desirable in a class 3 case where autorotation of the mandible is being deliberately sought. Of course, the skeletal effects of headgear (see chapter on Functional Appliances) are not desirable in a class 3 case.

Clinical tip: Always pull from above the occlusal plane

Force level No single study of which we are aware has thoroughly investigated in a controlled manner the effects of differing force levels. Many different papers have however shown very similar effects from widely varying force levels. One irritation is that many papers do not make clear whether the forces quoted are total or per side. It seems probable that force level is less important than force duration in a situation where force application is inherently intermittent. (It has incidentally been shown that high forces if required are tolerated much better if delivered by occipital rather than by cervical traction – O’Reilly 1993).

Hours of wear If headgear is prescribed, we would favour using it only in bed at nights. Most, but not all, patients will co-operate sufficiently with headgear if asked only to wear it at night and several manoeuvres can be employed to lessen the problem of non-compliance. One of the simpler measures has emerged from a study by Cureton et al (1993a) who used concealed timers in the headgear of two groups of patients to show that the use of headgear calendars increased the wear by an average of 2.6 hours per day and also greatly increased the accuracy of the patients’ estimates of their hours of wear.

Clinical tip: If we use headgear, we should consider using headgear charts routinely A further study by Cureton (1993b) using the same covert timers revealed that even experienced clinicians are very inaccurate at assessing the actual hours of wear that their patients are achieving, although with greater experience, orthodontists become more sanguine about the hours achieved (rightly) and lower their estimates.

These covert timers were not sufficiently cheap or robust for routine use, but a much more modern inexpensive electronic device - the Affirm headgear traction module - became commercially available in the 1990s. A similar paper by Cole (2002), in a small number of patients (16) over a short period (8 weeks) also showed some marked

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lack of reliability in the recorded hours in a significant percentage of patients. Whist 69% wore headgear for >84% of the time recorded on their chart, 31% were at 58% or less. However, the RCT comparing palatal implants and headgear (Sandler et al 2008), reported very good levels of headgear compliance and success which rather surprised the authors.

Safety and headgear Although reports of injuries from headgear continue to be rare in the literature (eg: Booth-Mason and Birnie 1988, Chaushu, Chaushu and Weinberger 1997), this is a topic which demands our continued close interest if we use headgear. Samuels (1996) and Samuels et al (1996b) have published surveys of the reported injuries in many countries and have classified the reported incidents as follows:

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accidental disengagement when the child was playing whilst wearing the headgear incorrect handling by the child during the fitting or removal of the headgear deliberate disengagement of the headgear caused by another child unintentional disengagement or detachment of the headgear whilst the child was asleep

Efforts to reduce the chance of injury from the facebow continue to follow one of three strategies.

• prevention of release of the facebow from the molar tube • limiting the force required to release the traction force from the facebow and thus preventing elastic recoil injuries – catapult or slingshot injuries • limiting the potential for damage by blunting or shielding all the ends of an inadvertently released facebow.

Examples of the first strategy are the plastic safety straps (e.g. Masel type) and the customised facebow locks developed by Samuels et al (2000). Safety straps have to try to square the circle of being tight enough to allow insufficient movement for the bow to leave the tube whilst still being capable of insertion and comfortable wear.

In practice, this is usually achievable or at the worst, the facebow can be inadvertently removed from the tubes with the strap still attached, but the inner bow will remain in the mouth where the scope for serious, irreversible damage is extremely small and the range of possible labial movement of the bow in response to traction is too small to permit a ‘slingshot/catapult’ type of injury. Such safety straps are inexpensive, quick and easy to fix and to wear.

The customised facebow locks recommended by Samuels et al (2000) have become commercially available as Nitom headgears or they can be made ‘in-house’ by a laboratory adding to a chosen facebow. They are usually fairly easy to adjust and insert although with significantly rotated molars they can be awkward to place.

Adjustments to the length of the inner bow also require adjustments to the safety lock wire. In many ways these represent the most logical and potentially effective method to date. A paper describes the successful experience of a group of clinicians with these facebows (Samuels et al 2000). One comment is that even the short outer bows are inconveniently long unless used with a snapaway traction module.

Examples of the second strategy are the many snap-release headgears available of which some have better mechanical performance than others (Postlethwaite 1989, Stafford et al 1998), but all possibly suffer from the limits of their ambition which is solely to prevent one type of potential injury - the slingshot/catapult type.

Examples of the third approach are the previous Guardian facebow from Lancer, which is still available from GAC and the partially plastic bows made by Odontec. These are a sensible idea but significantly more demanding to insert than an orthodox bow or a Nitom bow (especially if the molars are rotated or instanding). We do not recommend this approach.

There is of course, no reason why more than one of these categories of safety measure cannot be simultaneously adopted. In addition, it is essential that suitable verbal and written instruction is always given about placing and

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removing the headgear and behaving appropriately when wearing headgear. The British Orthodontic Society has published guidelines on headgear safety and Samuels and Brezniak (2002), have published a review of this topic.

Distalising molars/assisting headgear Several devices have been described as means of assisting or replacing headgear in the distalising of molars. Most of these are described as non-compliance devices

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repelling magnets compressed coilspring distaliser of various types, both buccal and lingual.

Hilger’s Pendulum/Pendex appliance 'nudgers'

Repelling magnets • Several authors e.g. Gianelly (1989) , Bondemark et al (1994) and Bondemark (2000) have described

•

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this use of magnets for distalising molars. We have not tried them for several reasons: other strategies work well, the force is inherently high initially with an exponential (which is the opposite of the required pattern (obeying Coulomb’s Law)) and attaching headgear simultaneously is not easy which leaves the problems of reciprocal forces and anchorage loss.

Bondemark et al (1994) elegantly showed that superelastic coils are more effective than magnets in distalising molars and that this may well be associated with the much more constant forces applied by the superelastic coils. The appliances were reactivated every four weeks and the anchorage loss (no headgear was worn) was 50% of the 3 mm average distal movement in 6 months. This anchorage loss is a serious drawback to these methods of distalising molars without anchorage reinforcement and it must be assumed that in many such cases, the upper incisors will finish further forward than at the start of treatment or - if extractions are used - that the scope for upper incisor retraction is substantially reduced.

Everdi et al (1997) also reported on a comparison between nickel-titanium coilsprings and repelling magnets. Again, the coilsprings produced greater distalisation, in spite of the magnets being reactivated at weekly intervals (!) to overcome the exponential decay of magnetic force. The molar distalisation was accompanied by significant tipping (approximately 9 degrees) in both methods.

Anchorage loss was not even measured, but the photographs in the article show that the first premolar has moved mesially as much as the molar has moved distally from the second premolar.

This suggests that the anchorage loss was large.

Clinical tip: In the light of these papers, we remain firmly disinclined to try magnets or to recommend them as a means of distalising teeth

Distalising coil springs Gianelly (1998) and Gulati et al(1998) have separately reported on the use of compressed coilsprings to distalise molars with either fixed or removable Nance appliances to reinforce anchorage. Gianelly did not measure anchorage loss. Gulati found approximately 1 mm of mesial movement of all ten anterior teeth for every 2.8 mm of distal molar movement. The Wilson coilspring system also undoubtedly produces effective molar movement but the reciprocal forces have to be opposed by class 2 traction and the remarks above therefore apply.

The paper by Muse et al (1993) clearly shows that the class 2 traction to this appliance causes almost as much mesial lower molar movement as distalisation of the upper molar and the upper incisors are extruded by the class 2. If the co-operation with wearing the class 2 is not good then the upper incisors move labially instead. It is interesting to compare the changes obtained by Muse in four months with those described by Firouz et al (1992) using unassisted high-pull headgear instructed to be worn for 12 hours per day for six months. The rate of

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distalisation with headgear was 0.1 mm less per month than with the distalizing coils, but there was, of course, no anchorage loss with headgear alone and there was no distal tipping of the upper molars as with the coils.

Jones jig and distal jet There are several named versions of compressed coilspring devices including the distal jet (placed on the palatal), Keles slider (also on the palatal) Keles and Sayinsu (2000), Keles (2002) and Jones jig (buccally placed). They vary slightly in their ease of use and in the usual force levels. Jones jigs use an average of 75 gm. force (Brickman et al 2000) and distal jets 240 gm (Ngantung et al 2001). However, the results are similar. Data on anchorage loss for most of these appliances is shown in Table 13.1. A further paper by Papadopoulos et al (2004) measured anchorage loss with a modified Jones jig. They too found it to be very expensive for anchorage. The overjet increased by 64% and the premolars moved mesially by 185% of the molar distal movement ! The paper by Chiu et al (2005), comparing the distal jet and pendulum appliances (see below) found more distal movement and less anchorage loss in the distalisation phase with the pendulum.

Clinical conclusion: Coil springs used in this way do not therefore seem to confer benefit unless the labial movement of the lower incisors is part of the plan and class 2 elastics are worn to enable harnessing of the anchorage in the lower arch. As with all anchorage considerations, very gentle forces with little obstruction can be surprisingly effective. e.g. opening of space with coil springs and low friction self-ligating brackets.

Pendulum appliance This was described by Hilgers in 1992 and is analogous to a fixed â&#x20AC;&#x2DC;nudgerâ&#x20AC;&#x2122;. The TMA distalising finger springs are inserted into palatal sheaths on the molar bands. A relatively high force of 230 g per side is reported by Ghosh and Nanda (1996). As with the majority of these appliances, the anchorage loss was resisted by a Nance button bonded to the first premolars. The advantage of the design is that patient compliance with wearing the removable appliance is not required. In six months, an average of 3.4 mm distal movement was achieved, with substantial variability and distal molar tipping of 8 degrees. The anchorage Author Method Anchorage loss in mm. loss was an average of 2.6 mm or 0.75 (usually the premolar) per mm. gain mm for every 1 mm of distal movement of the molars. This is greater than the Gulati Coilsprings 0.4 0.25 mm and 0.35 mm anchorage loss Wilson coilsprings 0.8 Muse per mm distal movement reported by Pendulum 0.75 Ghosh Giannelly and by Bondemark using Byloff Pendex (tipping) 0.48 magnets. A pendulum appliance is Pendulum 0.32 Bussick clearly a technique which loses a great Pendex (bodily) 0.53 Byloff deal of anchorage and this may be Pendulum 0.69 / 0.48 / 0.41 Kinzinger et al related to the relatively high forces Gianelli Magnets 0.25 which are opposed by a relatively small Magnets 0.5 Itoh anchorage unit.

The oral hygiene Magnets and coils Not measured Everdi consequences of a Nance button in Magnets and coils 0.35 Bondemark place for six months should also be Bondemark (2000) Magnets and lingual coils 0.6 considered. The paper by Kinzinger et al Keles Coils 0.53 (2005) showed that less anchorage was Distal jet 1.2 (!)

Ngantung et al provided by deciduous molars than by Gianelli Coils and compressed loops Not measured premolars.

Runge

Jones jig

1.00 (!)

Haydar and Uner

Jones jig

1.2 (!!)

Hoggan and Sadowsky

Jones jig

0.8

Papadopoulos et al

Jones jig

1.85(!)

Mavropoulos et al

Jones jig

1.17(!)

Fortini et al

Screws

0.4

Ferro et al

Nudger + headgear

0.19

Table 13.1:

Anchorage loss with molar distalising appliances

The Pendex appliance This is a pendulum appliance with a midline expansion screw. Two papers

by Byloff and Darendeliler (1997) and Byloff et al (1997) have further quantified the effects with smaller activations producing a reported initial

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force of 200-250 g. Anchorage loss of the premolars was 0.5 mm for every 1 mm distal movement with a high average distal tipping of 14.5 degrees for the first molar. The second paper describes a pendulum appliance with uprighting bends in the springs which were used to upright the distally tipped molars in a second phase of activation. The overall rate of distal molar movement was slower , but the distal tipping was reduced to an average of 6 degrees. The penalty was a slightly higher percentage of anchorage loss - 0.54 mm for every 1 mm distal movement - and more transmission of this anchorage loss through from the premolars to the incisors. A paper by Bussick and McNamara (2000) with a large sample of 101 patients found an average mesial movement of the premolars which was 32% of the distal molar movement. A variation on this theme is the distaliser described

by Fortini et al (2004), which uses bilateral screws with a Nance button as the anchorage. This requires the compliance of the patient to turn the screws, but is cemented to molar and premolar bands. The average anchorage loss per mm of distal molar movement is shown in Table 13.1.

Anchorage loss with ‘non-compliance’ molar distalisers This review of these appliances has focused on the high level of anchorage loss. It should also be remembered that they only distalise two teeth (or four if the second molars are counted) whereas at least eight of the anterior teeth will have moved mesially by approximately the amounts indicated in the table above. Enthusiasts for these appliances refer to the benefit of palatal arches or Nance buttons in preventing subsequent mesial movement of the molars when intra-traction is subsequently applied to distalise the anterior teeth. This overlooks the fact that Nance buttons (or similar) failed to prevent anchorage loss in the initial molar distalisation phase. The paper by Chiu et al (2005), comparing the distal jet and pendulum appliances is unusual in looking at the outcomes, including anchorage loss, through the entire treatment and not just the initial distalisation phase. Jasper jumpers, Nance buttons and in some cases, headgear, were used to support anchorage during the postdistalisation phase.

In spite of this, the upper molars ended the treatment more mesially positioned than at the start and there was “significant flaring” of the incisors. It seems reasonable to contend that anchorage must be sought from outside the upper arch at some stage if a significant overall net gain in distal tooth movement is to be achieved. The longstanding theories of anchorage and the results from all the papers in Table 13.1 are still sufficient for us not to have included these devices in our practice to any significant extent. More recently, specific molar distalizing devices to use have been described (eg: Karaman et al 2002 with palatal implants and Kinzinger (2009) with miniscrews, to support a distal jet). This is a very different scenario, is likely to be successful from the aspect of anchorage loss and is discussed in the chapter on Temporary Anchorage Devices in Orthodontics.

‘Nudgers’ These are removable appliances with finger springs to aid distalisation of molars and we used to employ them frequently. They are intended to assist headgear by holding on during the day to the progress obtained at night.

Used without headgear, the remarks above on non-compliance molar distaliser apply equally to nudgers. Several well-known clinicians such as Ten Hoeve and Cetlin (1983) advocated such appliances. This appliance can lessen the required hours of headgear wear and it is also a very useful way to get differential movement in one quadrant when required. When we used more headgear, we found these appliances very valuable. As always, there are potential pitfalls. These are:

Potential problems with nudgers • excessive molar tipping which then needs uprighting • excessive anchorage loss with an increase in overjet • a false sense of security which is dispelled when the nudger is discarded and the headgear is insufficient on its own

Avoiding problems with nudgers

These problems can be very largely avoided if the following points are noted:

•

only activate the spring by 2 mm and make them out of wire no thicker than 0.7 mm and preferably 0.6 mm. If the headgear is not worn, then there should be virtually no detectable distal movement.

Headgear is the motive force and the springs should very largely only hold on to what the

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headgear achieves. This is a significantly different situation from the use of coils, finger springs or magnets described above. overcorrect the molar relationship if the molars look undesirably tipped, leave the nudger passive and raise the outer bow to upright the molars before discarding the nudger use gentle initial aligning wires so that the headgear does not have to combat a sudden heavy uprighting force if any tipping has occurred if concerned at the time of stopping the nudger, increase the headgear hours for one visit

These are all applications of the usual principals behind anchorage conservation. Ferro et al (2000) published a study of 110 patients treated with a nudger and cervical headgear. They advocated gentle activation (2-3 mm.) of the finger springs and found an average of 3.6 mm. distal movement of the molars compared to untreated controls with an average of 0.7 mm increase in overjet. The anchorage loss was therefore 19% of the distal movement. This anchorage loss is not negligible but is lower than any of the figures in the table above for noncompliance appliances and, of course, the headgear offers a plausible means of maintaining the distal position of the molars once retraction of the anterior teeth starts.

Indications for using a nudger with headgear added at nights • class 1 cases with class 2 molars • class 2 division ii cases where distal molar movement is required • adults needing distal movement • asymmetrical molar relationships These are all situations where the more powerful anchorage enhancing effects of functional appliances are less suitable, but the advent of TADS, particularly mini screws, has rendered headgear essentially obsolete.

Clinical tip: If you are using headgear to correct a class 2 molar relationship, a nudger is a very worthwhile addition. The separation of the occlusion is an additional benefit and nudgers are a useful means of achieving a differential left/right effect.

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References Ashmore JL, Kurland BF, King GJ, Wheeler TT, Ghafari J, and Ramsay DS (2002) A 3-dimensional analysis of molar movement during headgear treatment American Journal of Orthodontics and Dentofacial Orthopaedics 121:18-29 Bondemark, Kurol J and Bernhold M (1994) Repelling magnets versus superelastic nickel-titanium coils in simultaneous distal movement of maxillary first and second molars Angle Orthodontist 64: 189-198 Bondemark L (2000) A comparative analysis of distal maxillary molar movement produced by a new lingual intra-arch Ni-Ti coil appliance and a magnetic appliance European Journal of Orthodontics 22:683-95 Booth-Mason S and Birnie DJ (1988) Penetrating eye injury from orthodontic headgear - a case report European Journal of Orthodontics 10: 111-114 Bowden DEJ (1978) Theoretical considerations of headgear therapy: A literature review British Journal of Orthodontics 5: 145-152 Brickman CD, Sinha PK, and Nanda RS (2000) Evaluation of the Jones jig appliance for distal molar movement American Journal of Orthodontics and Dentofacial Orthopaedics 118:526-34 Burke M and Jacobson A (1992) Vertical changes in high-angle Class II, Division 1 patients treated with cervical or occipital pull headgear American Journal of Orthodontics and Dentofacial Orthopaedics 102: 501-508 Bussick TJ and MacNamara JA (2000) Dentoalveolar and skeletal changes associated with the pendulum appliance American Journal of Orthodontics and Dentofacial Orthopaedics 117: 333-43 Byloff FK and Darendeliler MA (1997a) Distal molar movement using the pendulum appliance. Part 1: Clinical and radiological evaluation.

The Angle Orthodontist 67: 249-260 Byloff FK, Darendeliler MA, Clar E, Darendeliler A (1997b) Distal molar movement using the pendulum appliance. Part 2: The effects of maxillary molar uprighting bends.

The Angle Orthodontist 67: 261-270 Cetlin NM and Ten-Hoeve A (1983) Nonextraction treatment.

Journal of Clinical Orthodontics 17: 396-413 Chaushu G, Chaushu and Weinberger T (1997) Infraorbital abscess from orthodontic headgear.

American Journal of Orthodontics and Dentofacial Orthopaedics 112: 364-367 Chiu PP, McNamara JA, Franchi L (2005) A comparison of two intraoral molar distalisation appliances: distal jet versus pendulum American Journal of Orthodontics and Dentofacial Orthopaedics 128: 353-65 Cole WA (2002) Accuracy of patient reporting as an indication of headgear compliance American Journal of Orthodontics and Dentofacial Orthopaedics 121: 419-23 Cureton SL, Regennitter FJ, and Yancey JM (1993a) The role of the headgear calendar in headgear compliance American Journal of Orthodontics and Dentofacial Orthopaedics 104; 387-394 Cureton SL, Regennitter FJ, and Yancey JM (1993b) Clinical versus quantitative assessment of headgear compliance American Journal of Orthodontics and Dentofacial Orthopaedics 104: 277-84 Ellen EK, Schneider BJ and Sellke T (1998) A comparative study of anchorage in bioprogressive versus standard edgewise treatment in Class II correction with intermaxillary elastic force American Journal of Orthodontics and Dentofacial Orthopaedics 114:430-6

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Everdi N, Koyuturk O and Kucukkeles N (1997) Nickel-titanium coil springs and repelling magnets: a comparison of two different intra-oral molar distalisation techniques.

British Journal of Orthodontics 24: 47-53 Ferro F, Monsurro A, Perillo L (2000) Sagittal and vertical changes after treatment of Class II Division I malocclusion according to the Cetlin method American Journal of Orthodontics and Dentofacial Orthopaedics 118: 150-8 Firouz M, Zernik J, Nanda R. Firouz M, Zernik J, and Nanda R (1992) Dental and orthopaedic effects of high-pull headgear in treatment of Class II, Division 1 malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 102: 197-205 Fortini A, Lupoli M, Giuntoli F, Franchi L (2004) Dentoskeletal effects induced by rapid molar distalisation with the first class appliance American Journal of Orthodontics and Dentofacial Orthopaedics 125:697-705 Ghosh J and Nanda RS (1996) Evaluation of an intraoral maxillary distalisation technique American Journal of Orthodontics and Dentofacial Orthopaedics 110: 639-46 Gianelly AA (1998) Distal movement of the maxillary molars American Journal of Orthodontics and Dentofacial Orthopaedics 114:66-72 Gianelly AA et al (1989) The use of magnets to move molars distally.

American Journal of Orthodontics and Dentofacial Orthopaedics 96: 161-167 Gulati S, Kharbanda OP and Parkash H (1998) Dental and skeletal changes after intraoral molar distalisation with sectional jig assembly American Journal of Orthodontics and Dentofacial Orthopaedics 114: 319-27 Haydar S and Uner O (2000) Comparison of Jones jig molar distalisation appliance with extraoral traction American Journal of Orthodontics and Dentofacial Orthopaedics 117:49-53 Hilgers JJ (1992) The pendulum appliance for class II non-compliance therapy.

Journal of Clinical Orthodontics 26: 706-14 Hoggan BR and Sadowsky C (2001) The use of palatal rugae for the assessment of anteroposterior tooth movements.

American Journal of Orthodontics and Dentofacial Orthopaedics 119: 482-8 Itoh T, Tokuda T, Kiyosue S, Hirose T, Matsumoto M and Chaconas SJ (1991) Molar distalisation with repelling magnets.

Journal of Clinical Orthodontics 25: 611-617 Johnston LE (1985) A comparative analysis of class II treatments In Vig PS and Ribbens KA (ed.) Science and clinical judgement in orthodontics Monograph 19 Craniofacial growth series University of Michigan Ann Arbor pp 103-148 Johnston LE (1996) Balancing the books on orthodontic treatment: an integrated analysis of change British Journal of Orthodontics 23: 93-102 Karacy S, Akin E, Olmez H, Gurton AH and Sagdic D (2006) Forsus nitinol flat spring and Jasper Jumper corrections of class II division 1 malocclusions Angle Orthodontist 76: 666-672 Karaman AI, Basciftci FA and Polat O (2002) Unilateral distal molar movement with an implant-supported distal jet appliance Angle Orthodontist 72:167-174 Kinzinger GSM, Gulden N, Yildizhan F, Diedrich PR (2009) Efficiency of a skeletonized distal jet appliance supported by miniscrew anchorage for noncompliance maxillary molar distalization American Journal of Orthodontics and Dentofacial Orthopaedics 136:578-586 Keles A and Sayinsu K (2000) A new approach in maxillary molar distalisation: Intraoral bodily distalizer American Journal of Orthodontics and Dentofacial Orthopaedics 117: 39-48

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Keles A (2002) Unilateral distalisation of a maxillary molar with sliding mechanics: a case report Journal of Orthodontics 29: 97-100 Kinzinger GSM, Gross U, Fritz UB and Diedrich PR (2005) Anchorage quality of deciduous molars versus premolars for molar distalisation with a pendulum appliance American Journal of Orthodontics and Dentofacial Orthopaedics 127:314-23 Lotzof LP, Fine HA and Cisneros GJ (1996) Canine retraction: A comparison of two preadjusted bracket systems.

American Journal of Orthodontics and Dentofacial Orthopaedics 110: 191-6 (Also see correspondence on this paper American Journal of Orthodontics and Dentofacial Orthopaedics March 1997 pp 14A-16A) Mannchen R (2002) A critical analysis of the pitchfork analysis European Journal of Orthodontics 121-122 Mavropoulos A, Karamouzos A, Kiliaridis S, and Papadopoulos MA (2005) Efficiency of non-compliance simultaneous first and second molar distalisation Angle Orthodontist 75:532-539 Muse DS, Fillman MJ, Emmerson WJ, and Mitchell RD. (1993) Molar and incisor changes with Wilson rapid molar distalisation American Journal of Orthodontics and Dentofacial Orthopaedics 104: 556-565 Ngantung V, Nanda RS, and Bowman SJ (2001) Posttreatment evaluation of the distal jet appliance American Journal of Orthodontics and Dentofacial Orthopaedics 120:178-85 O'Reilly MT, Nanda SK, and Close J. (1993) Cervical and oblique headgear: A comparison of treatment effects American Journal of Orthodontics and Dentofacial Orthopaedics 103: 504-509 Pilon JGM, Kuijpers-Jagtman AM and Maltha JC (1996) Magnitude of orthodontic forces and rate of bodily tooth movement. An experimental study American Journal of Orthodontics and Dentofacial Orthopaedics 110: 16-23 Papadopoulos MA, Mavropoulos A, Karamouzos A (2004) Cephalometric changes following simultaneous first and second maxillary molar distalisation using a non-compliance intraoral appliance Journal of Orofacial Orthopaedics 65(2): 123-36.

Postlethwaite K M (1989) The range and effectiveness of safety headgear products European Journal of Orthodontics 11: 228-234 Radkowski MJ (2007) The influence of the transpalatal arch on orthodontic anchorage Thesis abstract from St Louis University. American Journal of Orthodontics and Dentofacial Orthopaedics 132: 562 Rajcich M and Sadowsky C (1997) Efficacy of intra-arch mechanics using differential moments for achieving anchorage control in extraction cases American Journal of Orthodontics and Dentofacial Orthopaedics 112: 441-8 Rebellato J, Lindauer SJ, Rubenstein, LK, Isaacson RJ, Davidovitch M and Vroom K (1997) Lower arch perimeter preservation using the lingual arch American Journal of Orthodontics and Dentofacial Orthopaedics 112:449-456 Ren Y, Maltha JC, and Kuijpers-Jagtman A-M (2003) American Journal of Orthodontics and Dentofacial Orthopaedics Angle Orthodontist 13:86-92 Runge ME, Martin JT, and Bukai F (1999) Analysis of rapid maxillary molar distal movement without patient co-operation.

American Journal of Orthodontics and Dentofacial Orthopaedics 115: 153-157 Sandler J, Benson P, Doyle P, Majumder A, Oâ&#x20AC;&#x2122;Dwyer A, Speight P, Thiruvenkatachari B, Yinsley D (2008) Palatal implants are a good alternative to headgear: A randomized trial American Journal of Orthodontics and Dentofacial Orthopaedics 133: 51-57 Saelens NA and De Smit AA (1998) Therapeutic changes in extraction versus non-extraction orthodontic treatment European Journal of Orthodontics 20:225-230

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Samuels RH (1996) A review of orthodontic face-bow injuries and safety equipment American Journal of Orthodontics and Dentofacial Orthopaedics 110: 269-72 Samuels RH, Willner F, Knox J and Jones ML (1996) A national survey of orthodontic facebow injuries British Journal of Orthodontics 23: 11-20 Samuels RH, Oâ&#x20AC;&#x2122;Neill J, Bhavra G, Hills D, Thomas P, Hug H, Brown M, Haining C, Stern M, DiBiase A, Straw S and HoyenChung D (2000) A clinical evaluation of a locking orthodontic facebow American Journal of Orthodontics and Dentofacial Orthopaedics 117: 344-50 Samuels and Brezniak (2002), Orthodontic facebows: safety issues and current management Journal of Orthodontics 29: 101-107 Shpack N, Davidovitch M, Sarne O, Panayi N, Alexander D. Vardimo AD (2008) Duration and anchorage management of canine retraction with bodily versus tipping mechanics Angle Orthodontist: 78: 95â&#x20AC;&#x201C;100 Stafford GD, Caputo AA and Turley PK (1998) Characteristics of headgear release mechanisms: Safety implications Angle Orthodontist 68: 319-326 Stromeyer EL, Caruso JM, and De Vincenzo JP (2002) A cephalometric study of the class II correction effects of the Eureka spring.

Angle Orthodontist 72:203-210 Stucki N and Ingervall B (1998) The use of the Jasper Jumper for the correction of Class II malocclusion in the young permanent dentition European Journal of Orthodontics 20: 271-281 Von Bohl M, Maltha J, Von den Hoff H, and Kuipers-Jagtman AM (2004) Changes in periodontal ligament after experimental tooth movement using high and low continuous forces in Beagle dogs Angle Orthodontist 74:16-25 Weiland FJ, Ingervall B, Bantleon HP and Droacht H. (1997) Initial effects of treatment of class II malocclusion with Herren activator, activator-headgear combination, and Jasper Jumper.

American Journal of Orthodontics and Dentofacial Orthopaedics 112: 19-27 Yee JA, Turk T, Elekdag-Turk S, Cheng L, Darendeliler A (2009) Rate of tooth movement under heavy and light continuous orthodontic forces American Journal of Orthodontics and Dentofacial Orthopaedics 136:150.e1-150.e9 Yoshida N, Jost-Brinkmann PG, and Yamada Y (1995) Initial tooth movement under extraoral force and considerations for controlled molar movement Angle Orthodontist 65: 199-208 Zablocki HL, McNamara JA, Franchi L, Baccetti T (2008) Effect of the transpalatal arch during extraction treatment American Journal of Orthodontics and Dentofacial Orthopaedics 133: 852-860

Useful related references not referred to in this chapter Carano A, Testa M and Siciliana G (1996) The lingual distaliser system European Journal of Orthodontics 18: 445-448 McSherry PF and Bradley H (2000) Class II correction - Reducing patient compliance: A review of the available techniques Journal of Orthodontics 27: 219-227

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279

14 Temporary anchorage devices in orthodontics Nigel Harradine

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Introduction Temporary anchorage devices (TADs) have emerged as a major development in orthodontics in recent years.

Miniscrews appeared as the subject of encouraging research and case reports in the late 1990s. We have now been using them for several years, during which time they have become established as a very practicable part of orthodontics which is capable of dramatically expanding the scope of orthodontic treatment. Before considering miniscrews in some detail, it is helpful to review the development of the other types of TAD.

Conventional dental implants In 1945, Gainsforth and Higley first conceived the concept of skeletal orthodontic anchorage using vitallium ramal screws in dogs. This attempt failed, as did almost all implants of that era, chiefly because the metals used were not conducive to the later discovery of osseointegration through titanium. Inflammation around the vitallium screw led to loosening and loss. In the 1960s, Brånemark (1969) and colleagues introduced the concept of osseointegration, using pure titanium implants, defining osseointegration as 'living bone in direct contact with a loaded implant surface.’ From the outset, Brånemark (1977) was rigorous in reporting long-term rates for success and failure. However, few clinicians envisaged the use of titanium implants in orthodontics at that time. It was not until the 1980s, that several animal studies using titanium implants for orthodontics reported successful results. Roberts et al (1989) studied the effects of orthodontic force on titanium implants in rabbits and dogs with a large majority of the implants remaining stable after 13 weeks of continuous loading with 300 gm force.

Conventional osseointegrated implants, as used in restorative dentistry, have since become a standard part of multidisciplinary care involving orthodontics Vince Kokich (1996), but their convenient and appropriate use is limited to a minority of cases because they can only be placed in those positions in a dental arch where there is adequate bone, where orthodontic anchorage is needed and can be used, and where a subsequent implantsupported restoration is required. It should be noted that in 1985, Kokich et al reported a novel source of absolute anchorage when they deliberately induced ankylosis of a deciduous canine tooth which was then used to protract the maxilla in a patient with severe maxillary retrusion.

Key summary: Conventional dental implants are only occasionally the option of choice – where they will subsequently be needed for supporting a crown or bridge

Midpalatal implants A next step in adapting implant technology to orthodontics was the development of short but otherwise conventional dental implants to be placed in the midline of the palate. These are now a well-recognized and documented source of anchorage, but are still relatively expensive and complex. They need careful siting anteriorly in the palatal vault to ensure sufficient bone depth and no contact with the roots of adjacent teeth, and are therefore relatively inconveniently situated for a palatal arch to take advantage of them. These implants are typically 3–4mm in diameter and 6mm in length. Traditionally they have been left to osseointegrate before force application. Tinsley et al (2004) gives an excellent description of the typical current use of these implants and further practical tips can be found in two articles by Cousley and Parberry (2005) and Cousley (2005). The further results of a random controlled clinical trial involving such implants has more recently been published by Sandler et al (2008). A good recent prospective study of palatal miniscrews reported a success rate of 92% (Mannchen and Schatzle 2008) in which the implants were left to osseointegrate for an average of 13 weeks. Interestingly, a recent tomographic study (Gracco et al 2008), concluded that there is sufficient bone posteriorly in and near the palatal midline for insertion of miniscrews. This is frequently a much more convenient place for application of forces to a palatal TAD and shows the versatility of miniscrews.

Key summary: Conventional but short dental implants are successful in the palatal midline, but their substantial extra complexity and invasiveness makes miniscrews relatively more attractive.

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Onplants These are based on the impressive research of Block and Hoffman (1995). These authors used a subperiosteal titanium alloy disk, 2 mm thick and 10 mm wide, coated with hydroxyapatite. This disk-type onplant was inserted subperiosteally and left unloaded for four months to osseointegrate before uncovering and placement of attachments. The large potential advantage of this use of osseointegration is that there is no need for any bone depth, so the onplant can be placed in a much wider range of sites than a conventional implant. Two soft tissue surgical interventions are however still required. It is essentially true that after a further decade of development

by Nobel Biocare who developed the Branemark system, they have yet to emerge as a widely available, commercially marketed product and with the emergence of miniscrews, they may no longer have a significant potential place in orthodontics.

Miniplates These were reported by Umemori et al (1999) and Sherwood (2002), and have been championed by Hugo de Clerck from Belgium amongst others. These are usually T-shaped or L-shaped, with the long arm of the T or L emerging through the mucosa and providing the point of attachment for the traction force. The most common sites for placement are the zygomatic arch and the angle of the mandible. The advocated advantages are twofold: that the fixing screws are above the root apices and therefore much less of a risk to the tooth roots. Secondly, the force application can still be brought close to the occlusal plane and easily avoid unwanted intrusion. These are definite plus points. A minus point is that a flap needs to be raised for insertion and removal and some patients and a few surgeons prefer a general anaesthetic for these procedures. Also the extra space required may render impracticable some applications nearer the front of the mouth. Overall patient acceptability seems good (Cornelis et al 2008) and some impressive results can certainly be achieved. De Clerck has demonstrated consistent distal movement of upper buccal segments in non-growing patients (Cornelis, De Clerck 2007) with the advantage over miniscrews in that application that the teeth can be moved past the TAD, whereas a miniscrew placed between the teeth will need repositioning at some stage. Also impressive has been De Clerckâ&#x20AC;&#x2122;s demonstration of substantial protraction of the maxilla and zygomatic arch with 150 gm of elastic traction applied to miniplates. For intrusion of posterior teeth they seem to be a very reliable technique De Clerck et al (2008). Some authors have found slightly higher percentage success rate with minplates than with miniscrews (Kuroda 2007), but also significantly more discomfort associated with their insertion and the necessary flap being raised. A study of the actual surgical technique (Cornelis et al 2008) quantifies the length of the placement procedure (averages ranged from 15 to 30 minutes per plate) and the postoperative discomfort. Fifteen of 200 plates required premature removal. Probably because of the discomfort whilst the mucosal flaps heal, De Clerck recommends starting traction three weeks after the surgery. Cha et al (2011) used a two week interval before starting reverse pull headgear to their plates.

Bollard Plates in class III patients We have started to use Bollard miniplates in young class 3 patients as advocated by Hugo de Clerck with some very encouraging success but also with some teething problems. This technique consists of light class 3 elastics worn to miniplates and he describes it as bone-anchored maxillary protraction (BAMP). The technique is described and the effects quantified in a paper by Cervidanes et al (2010). In this analysis of consecutively treated cases, the Wits analysis showed an impressive average 6 mm improvement in the class III skeletal pattern. A more recent paper from the same team by Nguyen et al (2011) has impressively documented enhanced maxillary and zygomatic growth in 24 consecutively treated cases. The average maxillary enhancement is approximately 4 mm with a range from 1.5 to 8.5 mm for the maxilla. This paper is strongly recommended and includes all the essential practical details of the technique. Another paper from the same team ( De Clerck and Swennen 2011) reports on success rates in 25 consecutive class 3 patients treated with Bollard plates. They report a very high 97% success rate for the 100 plates. They attribute this success to a number of details of careful , gentle surgical technique and postoperative care. Our early experience has met with some promising success but two important points have emerged. Firstly it is vital that the orthodontist is present at surgery until the surgeon is fully familiar with the requirements in order to ensure the precise and correct placement of the plates. The hooks must emerge where the applied elastics will not impinge on the soft tissues. The prominence of the hooks must be precise â&#x20AC;&#x201C; too prominent and the buccal/labial mucosa is traumatised, too close to the bone and the gingivae prevent comfortable placement of elastics. Secondly, we have expereinced a surprising incidence of loose plates. These

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can firm up if the elastics are discontinued for six weeks. Retrospective analysis of our technique has revealed that some of our screws were 1.5mm and not the recommended 2.3 mm and this may have permitted relative movement between screw and plate and hence loosening of the plate. This perhaps illustrates the potential importance of seemingly small details of technique.

Key summary: Miniplates slowly grow in popularity in specific sites and applications. They will probably establish a permanent role in these areas where their strong points outweigh the need for a flap to be raised and frequently a general anaesthetic to p lace and remove.

Miniscrews Miniscrews emerged as a treatment technology from the search for a TAD which fulfilled the following requirements.

Figure 14.1: A self-drilling miniscrew (Ormco VectorTAS) showing the head, transmucosal collar and intraosseous threaded parts. This particular screw has an additional bonecutting groove for sites with dense bone

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• quick, easy and comfortable to insert in a wide variety of sites without damage to adjacent teeth • convenient for application of orthodontic forces by a variety of means and in a variety of directions • available for force application soon or immediately after

insertion easily removed following use no patient discomfort at insertion, during use or at removal

As long ago as 1983, Creekmore and Eklund reported a case in which a vitallium implant was placed just below the anterior nasal spine and used for anchorage. A light elastic thread was tied from the head of the screw to the archwire 10 days after placement of the implant to intrude the maxillary incisors. This early loading of an implant, without the usual wait for osseointegration, was to become a major feature of the later use of miniscrews. It was many years before a real emergence of a body of work on miniscrews and most of this originated in the Far East.

Kanomi described the use of titanium mini fixation screws in 1997. The problem of accommodating an implant in an intact arch is the subject of papers by authors such as Ohmae et al (2001), Park H-S et al (2001) and Bae and Park H-S (2002). The literature has seen a rapid increase in papers on microscrews – many of them case reports.

Typical examples are the three contiguous papers in the August 2004 edition of the Angle Orthodontist by authors from South Korea, Taiwan and Japan. The first paper is another by Professor Park and co-workers (Park et al 2004) and focuses on distal movement. The next article by Yao et al describes molar intrusion by a combination of microscrews and miniplates and the third by Kuroda et al also describes molar intrusion – in this case by unusually long microscrews. A very good summary of the essentials of miniscrews can be found in the edition of Seminars in Orthodontics edited by Jason Cope in March 2005. NH edited a recent textbook by well-known Korean pioneers of these TADs - Orthodontic Miniscrew Implants by Paik C-H, Park I-K, Woo YJ and Kim T-W (2009).

This book is very well illustrated and covers all aspects of technique and a wide range of clinical applications.

We initially used the Aarhus system, developed by Professor Birte Melsen and co-workers, and the Dentos AbsoAnchor system developed by Professors Jae-Hyun Sung, Hee-Moon Kyung and Hyo-Sang Park who have carried out foundation research in the placement and immediate loading of such screws. More recently, we have used the IMTEC system, the LOMAS Quattro system from Mondeal and the Ormco VectorTAS system. To date we have used miniscrews for intrusion of molars and incisors, retraction of molars and anterior teeth and protraction of posterior teeth. This clinical experience has coincided with rapidly emerging evidence on many aspects of success and difficulties with miniscrews and this has overlaid our own clinical experience of problems and successes. It is still early days for confident certainties with many aspects of the use of miniscrews, but the following sections summarise the current state of evidence and experience in a rapidly moving field.

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Miniscrew configuration

Miniscrews have been produced with intraosseous diameters between 1.0 mm and 2.0 mm – much narrower than the 4 mm of a standard dental implant. Miniscrews are usually described as having three major components, an intraosseous threaded part, a transmucosal collar and a head. Figure 14.1 is of a VectorTAD miniscrew which is representative of these aspects of the design.

The intraosseous threaded part of the screw typically ranges between 6 and 11 mm. This particular screw is one of the types which have asymmetric buttressed threads. This pattern of thread facilitates insertion and increases resistance to pullout forces.

Figure 14.2: A coilspring with a specifically designed eyelet to match the screw head and provide secure, compact retention of the spring (Ormco VectorTAS).

Above the threaded section is usually a smooth-surface transmucosal section referred to as a neck or collar. Some manufacturers supply miniscrews with a longer collar for use in sites such as the palate or retromolar areas where the gingiva is thicker.

Above the collar is the head which provides the means of attachment of force (elastics, wires and coilsprings). The collar is often separated from the head by a wider area which is designed to help prevent the mucosa from intruding on the head.

Variations in miniscrew head design Because the earliest screws were adapted from bone fixation screws, early research and development focussed on the best size and form of the intraosseous threaded part of the screw. Most miniscrews have converged in their design in this respect. However, for orthodontic anchorage, there are potentially important variations in the design of the screw head.

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there must be easy and secure attachment for elastic chain, nickel titanium coilsprings and wire ligatures. Most screws will not permit attachment of a conventional coilspring, the head being too large for the eyelet on the coilspring. Some types VectorTAS (Figure 14.2 and 14.3) and DB Infinitas have specifically designed eyelets to fit their screw heads. These are very good. There are coilsprings designed with a specialised but generic eyelet to fit almost all miniscrew heads (Figure 14.4). These eyelets are keyhole shaped and are good but significantly larger. Some screw heads inconveniently require a ligature for almost all secure attachments of coilspring. this first requirement for easy and secure attachments must not weaken the screws’ ability to withstand the torque forces during insertion and removal the ability to attach a section of archwire to the head is not a big asset. The line of force of any traction must pass directly through the axis of the screw. If a section of archwire is used to cantilever the force, this will rotate the screw within the bone, negating the cantilevered direction of force. If a section of archwire is used in conjunction with a TAD, it is usual to link it to another TAD in tandem to negate this cantilever effect. More commonly, traction rather than pushing forces are applied to a TAD. the head must be rounded and so less likely to irritate adjacent the adjacent cheeks or tongue. Too small a head can be a problem in this respect, whilst some designs which add roundness by a ‘healing cap’ are consequently too bulky.

Self-tapping, pre-drilling and self-drilling These terms can cause confusion. Many miniscrews are described as self-drilling or self-tapping. Confusion can arise because all of these terms do not have strictly consistent definitions in the literature, but the terms can be usefully clarified.

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pre-drilling some screws require a pilot hole to be drilled before insertion. This preliminary procedure is sensibly called pre-drilling. It is required for screws that are blunt at their tip and are thus not selfdrilling. The only potential confusion in terminology is when referring to the creation of a very small preliminary indentation in the cortex with a round bur or specialised initiator bur. This very limited ‘pre-drilling’ is sometimes referred to as ‘pilot drilling’. This can be advisable even with selfdrilling screws when the bone is dense or the intended path of insertion is very oblique to the bone surface. self-drilling as the paragraph above infers, these screws have a sharp, pointed end and need no preliminary drilling. Again, there is a potential subdivision of design which may cause confusion of terminology, because some such screws have an additional notch or groove at their tip which adds to the bonecutting capability. These self-drilling screws are sometimes referred to as self-cutting. This additional bone-cutting notch has previously been considered by some authors to increase the chance of fracture of the screw tip, but with current designs this is not a well-supported concern.

The additional cutting power is designed to ease screw insertion, particularly in areas of more dense bone in the jaws such as the retromolar area. self-tapping all current miniscrews are self-tapping. Whether or not they are self-drilling, they require no separate tapping of a thread. The potential confusion here is that some authors e.g. (Chen et al 2008), use the term self-tapping to be synonymous with screws which require pre-drilling. Selftapping is therefore not a helpful term in our view.

Pre-drilling or self-drilling?

Many early designs took their lead from conventional dental implants and required pre-drilling. There has since been a strong trend to self-drilling. In favour of self-drilling is:

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better primary stability (Kim et al 2005) better screw-bone contact after 6 months (Heidemann et al 2001) probable better overall success rate less chance of damage to tooth roots (Barros et al 2011) simpler, quicker and cheaper procedure (no specialised drills required)

Melsen (2005) briefly summarises most of these points. We use self-drilling screws. It is still advisable to make a preliminary cortical indent in a few cases where the bone is especially dense (most commonly the posterior mandible) and especially if the intended path of insertion is significantly oblique to the bony surface – this is a

Figure 14.3: Intrusive force application from the spring in Figure Figure 14.4: Generic coilspring with ‘keyhole’ eyelet fits over 14.2 – a 6 mm Ormco Vector TAS most miniscrew heads (Mondeal LOMAS Quattro miniscrew). The keyhole is inconveniently long

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situation where the screw is prone to slip up the cortical surface causing soft-tissue trauma. An alternative strategy to avoid this slipping is to by placing the screw at right angles to the bone surface and then altering to an oblique angle once the first ‘bite’ in the cortex has occurred. In more dense bone, it sometimes requires 10 or more turns of the screwdriver before an initial bite of the cortex is achieved, so patience can be required.

Success rate of miniscrews A core aspect of miniscrew success is their stable retention in the bone. Most studies report success rates between 80% and 96% e.g. Park H-S et al (2005). Lim (2009) reported 83% success (and this is the identical success rate as that which NH has to date achieved in all screws inserted). A useful summary table of studies is on page 250 in Orthodontic Miniscrew Implants by Paik C-H et al (2009). A systematic review by Reynders (2009) identified 19 studies of sufficient quality and the success rate was mainly in excess of 80%. Another review Crisman (2010) included 14 studies and reported an overall success rate of 84% in 1519 screws.

Key point: When looking at estimations of success, look at the definitions of success. e.g. how long must a screw be in place to be deemed successful? If the screw loosens but is still usable, this is usually but not always counted as a success.

Similarly, removal and immediate replacement of a loose screw is sometimes not counted as a failure.

Factors affecting stability of miniscrews Several factors have been proposed as influencing success (stability of the screw). Individual studies have found correlations between one of these factors and success, but it is important to note that the systematic review by Reynders (2009) found no statistically supported associations with any factor and sometimes contrary correlations in different studies. The main proposed factors affecting success are as follows:

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screw diameter (Miyawaki et al 2003) (Park et al 2006). A diameter less than 1.1 mm is associated with a higher failure rate. A diameter greater than about 1.6 mm seems to confer no advantage and clearly wider screws run an extra risk of contact with tooth roots. This consideration is now largely of historic interest because almost all screws are currently between 1.4 and 1.8 mm in maximum diameter. 2.0 mm screws are suitable for sites such as the zygomatic ridge or retromolar pad, where avoidance of roots is not an issue screw length this usually refers to the intraosseous, threaded part of the screw. This length does NOT seem to be a factor in stability if the screw is more than 5 mm long (intraosseous length) (Miyawaki et al 2003) (Park et al 2006), (Kuroda 2007). All manufacturers produce screws of different lengths and longer screws may be advocated if the mucosal thickness is greater e.g. in the palate for alveolar placement. Mortensen et al (2009) found that in Beagle dogs, 3mm was definitely too short, reducing the success rate from 100% to 66% over the 6 week period. We principally use 6mm and some 8 mm screws. peri-implant inflammation (Miyawaki et al 2003), (Park et al 2006). A study by Cheng (2004) found that nonkeratinized mucosa was a risk factor for miniscrew failure. This is a less consistent finding. Owens et al (2007) found no correlation between success and lack of peri-implant inflammation, but most authors report that inflammation is more likely if screws are placed in non-attached mucosa and advise placement in or very close to attached gingiva. This is probably correct, but leaves open the question as to whether the inflammation is a cause of failure. Ure et al (2011) found that in Beagle dogs, resistance to loosening and loss was much lower for screws placed in non-keratinised mucosa. high maxillo-mandibular planes angle and bone density a high MMA was reported as a factor in the mandible by (Miyawaki et al 2003) who attributed this to thinner cortical bone in such subjects, but (Kuroda 2007) found no such association with MMA. Park et al (2008) found generally higher bone density in the mandible than the maxilla the angle of insertion

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Zhao et al (2011) produced data which suggested that an intermediate angle of insertion relative to the bone surface (50-70 degrees) produced better osseointegration and somewhat higher pullout forces than insertion at right angles or obliquely. Their reasons for these differences are plausible, although the differences, though statistically significant, are not very large. This may prove to be a contributing factor and may influence our angle of insertion if there are no other complicating considerations. time of loading and initial loading force many studies eg (Costa et al 1988) have shown that immediate loading does not reduce the success rate. Whilst success has been reported with a wide range of initial loads, a consensus is emerging that initial forces should err on the side of being light and 200 gm is a frequently suggested maximum. Owens et al (2007) found a good rate of tooth movement of a single premolar in beagle dogs with very light forces (25 and 50 gm) and like many other studies found no difference in the success rate with immediate loading or delayed loading (26 days in that instance). We load all our miniscrews immediately and with a force less than approximately 150 gm. Some of our earlier failures may well have been partially due to applying too high a force with the elastic string which we were advised to use. When using elastic string it is impossible to have an accurate idea of the force being applied. We now use elastic chain or nickel-titanium coils. Cornelis et al (2007) systematically reviewed all the animal experiments relevant to timing and amount of loading and summarizes very nicely the limits of our current knowledge and the areas which need more investigation. Garfinkle et al (2008) found that immediate loading and loading delayed by 5 weeks both had an 80% success rate. This dropped to 60% in non-loaded control miniscrews in the same patients. Interestingly, they also quantified a significant learning curve effect on their success rate.

Chen (2009) in a study on Beagle dogs found that completely unloaded screws had a success rate of 75% compared with 90% for screws immediately loaded with a 200 gm force. Zhang et al (2010) have found increasing degrees of osseointegration in beagle dogs if the application of force was delayed for two and then 4 weeks post-insertion. However it is interesting that all their screws were successfully retained over 8 weeks of traction regardless of whether zero, two or four weeks of delay were used.

Clinical message: Immediate loading confers no disadvantage and may actually improve success rates. Overall, our current view is that the factors which influence successful stability of miniscrews remain uncertain iin the light of current evidence

Stability of successful miniscrews We have had a clinical impression that some miniscrews remain firm but nevertheless drift in response to the applied force. A study by Liu et al (2011) used superimposed CT scans to assess screw movement during retraction of the upper labial segment. They found a small (average 0.23 mm) bodily mesial movement of the miniscrews and rather surprisingly, slightly greater mesial movement of the upper molars which were not receiving any mesially directed orthodontic traction force. The authors recommend allowing for this modest drift if possible when siting miniscrews.

Miniscrew insertion technique

Our initial personal success rates were definitely lower than those in the literature in spite of having attended and hosted courses and masterclasses and followed the best advice. In retrospect, there was a steep learning curve in progress around the world and even the best pioneers did not fully appreciate the importance of several aspects of technique.

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pre-drilling or self-drilling: We initially used the pre-drilling method, believing this more likely to give better control of direction. Although good success has been reported with predrilling, this method is now known to be a potential source of: o o

heat necrosis of the bone in spite of intentions to use copious irrigation and slow handpiece speed. 500-800 rpm is commonly advocated disruption of the cortex from wobbling of the bur

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greater incidence of root contact { (Barros et al 2011) quotes studies to that effect}

We now therefore only use self-drilling screws and only occasionally make a small indent in the cortex with a drill if the cortex seems very dense and resistance to initial insertion seems high. This is more likely in the posterior mandible Park et al (2008). It is now documented that almost all the primary stability arises from the cortex. This would explain why screw length is less critical than might be thought and also why minimal disruption of the cortex during insertion is important. It is therefore important to ensure smooth ‘wobble-free’ use of the screwdriver and a slow turning of the screwdriver is also advised with good pauses to allow the cortex to expand rather than fracture. It is also important not to insert until the smooth collar starts engaging the cortex because this may immediately work to provide a loosening force. operator experience: the factors discussed above relate to operator experience and this has been proposed and investigated as a significant factor. In a study by Kim (2010) he reported that the operator who placed all the mid-palatal miniscrews increased his success rate from 75% over the first eighteen months to over 90% thereafter. Garfinkle et al (2008) also found a definite effect of operator experience. Whilst this association seems intuitive and probable, the formal review by Reynders (2009) could only conclude that at present, operator experience “probably reduces failure rate”. Operator experience again arises as a factor in the study by Cho et al (2010) on root perforation discussed below.

Damage to tooth roots This is clearly a potential hazard. We know of no reports of the clinical incidence of root impingement, but the typodont study by Cho et al (2010) reported a 21% incidence of root contact for inexperienced operators and 13 % for experienced operators. None of the root contacts were “serious” or caused root perforation. We have only knowingly experienced root contact on one occasion ourselves. Practical steps to minimise the chances of root contact are:

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use screws of 1.4 to 1.8 mm maximum thread diameter choose a favourable site. For example, in the maxilla, the inter-radicular space between the roots of the second premolar and first molar tends to be greater than that between the roots of the first and second molars although biomechanical considerations may dictate placement distal to the first molar. The more apical the site, the greater the inter-radicular space, but the need to keep the screws in or close to attached mucosa will limit apical position as may biomechanical considerations and patient soft tissue comfort. A good anatomical study has been published by Hu et al (2009) who reported that the safest interradicular site in the maxilla is between the second premolar and the first molar, from 6 to 8 mm from the cervical margin. The CT study by Fayad et al (2010) found that on average there is 1mm less mesio-distal space distal to the upper first molar than mesial to that tooth (approximately 2.5 mm vs. 3.5mm). These dimensions are in line with those reported by Martinelli et al (2010). However, for upper molar intrusion, we would firmly recommend placing the screws distal to the first molar because this is more effective at intruding the second molar which is crucial in that instance. The safest zone for placement of a miniscrew in the mandible was between the first and second molars, less than 5 mm from the cervical margin.

Fayad et al also found variations in cortical thickness at different sites and an increase with age and in males and this may also influence success rate. due to the conical shape of tooth roots, it is obvious that there is more space between them in the apical areas. Theoretically, the more apically the miniscrew is placed, the less is the risk of root damage. However, this is limited by the width of attached gingiva and the depth of the buccal vestibule, as well as by biomechanical considerations. Placing miniscrews at an angle to the bone surface puts the screw tip nearer the wider space between to root apices whilst keeping the screw head in the attached mucosa. However, a large angle between the screw head and the mucosa may hinder attachment of coil springs and elastic chain and a shorter screw at a smaller angle may be a better combination. consider placing screws in the palate. There is more space on the palatal side between posterior teeth and the palatal midline (which is a good site in adults – Kim(2010)) eliminates the question of

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root contact. However, the palate is less comfortable to anaesthetise, usually needs a contra-angle screwdriver and is more awkward to utilise biomechanically.

Align the adjacent teeth thoroughly before screw insertion. Err on the side of diverging the roots adjacent to the site of insertion. Upper first and second molars will tend to initially have convergent roots.

Clinical tip: Consider placing brackets to slightly diverge the roots adjacent to the intended insertion site.

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check root alignment radiographically before insertion use injected local anaesthetic sparingly (<1 cm of syringe content) or not at all. See the section below on anaesthesia after approximately 1/3 of the screw is in bone, stop turning screwdriver, hold it very lightly and recheck passive orientation. If not satisfactory, remove and re-insert in an adjacent position. The study by Cho et al (2010) revealed that on the right side of the mouth, the insertion tended to err in the direction of slanting too distally, contacts therefore arising in the tooth distal to the embrasure in both jaws. stop insertion if discomfort is reported by the patient or if an increase in resistance - “doubling” Hembree et al (2009) - occurs after the full diameter of the screw is engaged in bone. Remove and re-insert in an adjacent position. On the one occasion when we (NH) experienced root contact, this was immediately revealed by slight discomfort as the screw neared full insertion. This discomfort was mild and immediately stopped when the screw was screwed out by two turns. The screw was then inserted in a different site with no complications. check radiographically after insertion. Two views from different directions may be needed to give the best view; even then we cannot always be certain that a radiographic indication of root contact is a genuine finding. In the study by Hembree et al (2009) of intentional damage to the roots of Beagle teeth, 26% of cases which indicated damage radiographically were found to have not sustained damage.

Perhaps we should draw no comfort from the ironic fact that Hembree et al (2009) took all measures including stents and radiographs to ensure damage to the Beagle dog roots but failed to achieve damage in 26% of the screws inserted.

Consequences of root contact Clearly, it is wise to minimise root contact. However, the literature supports the view that impinging on cementum and dentine is followed by repair in most instances (Asscherickx et al 2005), showed almost total repair twelve weeks after removing screws from beagle dogs. (Melsen 2005), and (Roberts 1989) have also observed good root repair. Penetration of the pulp would be expected to more serious but should be much less likely. Of course, penetration of a root would also be expected to impede movement of that tooth if that is a movement that is intended. An experimental study on ten patients was encouraging that any damage shows rapid repair once the screw contact is removed (Kadioglu et al 2008).

Neurovascular damage In the palate, the greater palatine neurovascular bundle consists of a nerve, artery and vein that enter the oral cavity through the greater palatine foramen. The two greater palatine foramina are typically located medial to the third molars. The bluish colour of the vein and softer texture of the gingiva in this region provide clues to the location of the neurovascular bundle in the corner of the palatal vault. The artery is the component of the bundle which is closest to the teeth and this is on average 12 mm from the palatal margin of the buccal teeth. Palatal alveolar miniscrews should be therefore be sited less than 10mm from the cement enamel junction to avoid damaging the greater palatine neurovascular bundle or alternatively they should be sited in or near the midline.

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Maxillary sinus penetration It may not be feasible to place a buccal alveolar miniscrew implant if the floor of the maxillary sinus extends to the alveolar bone between the maxillary posterior teeth. Although minimal complications have been reported following maxillary sinus perforation during orthodontic screw placement, (Costa et al 1988) it may be wise to avoid this area in patients with marked pneumatization.

Other potential problems with miniscrews

Fracture of miniscrews This has been reported, but is now largely historical. Several papers (Chen et al 2008), indicate that smaller diameter screws are much more likely to fracture. (Park et al 2006), had a high fracture rate of 10% and all bar one of these was a small diameter (1.2mm) screw. Some designs have also been more prone to screw fracture by having a narrow neck which took the torque force during insertion. To reduce the risk of fracture with thinner screws (1.2 mm or less) these are often designed to require pre-drilling to reduce torque load on such thin screws during insertion. Some authors, eg: Jason Cope, have also reported that early self-drilling designs with a notch or groove to aid bone cutting could be prone to fracture at the tip during insertion. We have personally suffered no screw fracture and it is probable that the better, more recent designs plus a better, slower, smoother insertion technique have made this a very rare potential complication. (Barros et al 2011) analysed forces required to fracture screws ex vivo and recommend screws of diameter greater than 1.3 mm as being suitable for resistance to fracture with self-drilling insertion.

Anaesthesia for miniscrew placement Topical anaesthesia is of course indicated whether or not there is a subsequent needle infiltration. Some clinicians find that topical anaesthetic alone is sufficient in all buccal mucosal sites. This may be more likely to be sufficient if a combination of prilocaine 2.5% and lidocaine 2.5% is used (Oraqix). If needle infiltration is then used, the amount should be sparing for the reasons described above in the section on avoidance of root damage. On the thicker palatal mucosa, topical anaesthesia alone is unlikely to be sufficient and completely painless anaesthesia is therefore unlikely.

Miniscrew removal No problems have been reported in the literature or indeed experienced by ourselves. The miniscrews are simply unscrewed. Even though osseointegration would not be strongly anticipated with immediately-loaded miniscrews, there is some microscopic evidence of osseointegration from an animal study (Kim et al 2005). Zhang et al (2010) have shown increasing degrees of osseointegration in beagle dogs over the first few weeks following insertion. However, small-diameter miniscrews are easy to remove even in the event of some osseointegration as removal torque is proportional to the square of the screw diameter. Anaesthesia is not required (just reassurance to the patient that this is the case).

Medical contraindications or relative contraindications to miniscrew placement • generalised bone pathology: severe osteoporosis, intravenous or high dose biphosphonate • • • • • •

treatment local bone pathology: radionecrosis at risk for bacterial endocarditis immune deficiency bleeding disorder heavy smoking poor oral hygiene

Biomechanics with TADs It is very important to appreciate the biomechanical consequences of applying forces from a site at a distance from the occlusal plane. If the force is in a mesial and intruding direction, then the teeth will move in both of those directions. This can significantly derange the occlusal plane if left for a period of time. It can also increase the

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Figure 14.5: A long crimp-on hook (Ortho Organisers) enabling distal traction without incisor intrusion.

Figure 14.6: An Ormco Vector post enabling mesial sliding of the premolar with force parallel to the occlusal plane. These hooks or posts can be crimped or can slide along the archwire. However, the binding when used uncrimped as in this figure is extremely high and the coilspring here principally acts by moving the entire upper arch.

friction during sliding mechanics. It is essential to have long crimp-on hooks available to enable forces to applied from TADs parallel to the occlusal plane if that is required. (Figures 14.5 and 14.6).

Stability of molar intrusion In the past, molar intrusion through orthodontic force application proved almost impossible to achieve to a clinically significant extent. The introduction of TADs offered a clear opportunity for successful molar intrusion and they have been widely employed to that end in cases with anterior open bites. A natural question is the stability of this novel tooth movement. A recent paper by Baek et al (2010) measured molar intrusion and overbite during treatment of nine adults and for three years post-treatment. Upper molars were intruded using miniscrews with palatal arches to limit buccal flaring of the molars. Adults are an excellent group for such a study because the complications of cephalometrics in the presence of significant facial growth are avoided. They found a good treatment response and good overall stability. Only 23% of the molar intrusion and 17% of the overbite improvement relapsed. Most of that relapse occurred in the first year post treatment. This is an encouraging report as is the paper by Deguchi et al (2011) which compared orthodontic treatment for AOB with and without miniscrew assisted intrusion of molars. They found that miniscrews indeed succeeded in achieving molar intrusion and reduction in the MMA and linear face height with very little incisor extrusion. All of these changes were the opposite in the groups treated without miniscrews. Two years after treatment, the upper molar intrusion and almost all the overbite had remained stable, with relapse of the approximately 1 mm of mandibular molar intrusion.

NICE guidance and further reading In November 2007, the National Institute for Clinical Excellence issued guidance on Miniscrews, stating that there are no safety concerns which should deter clinicians from using this technique. This guidance approves of their use, provides references for the basis for their use and comments from the consulted clinicians.

The April 2007 AJO-DO supplement Number 4 supplement 1 is devoted to miniscrew-related topics and is a good concentrated source of articles. The systematic review by Cornelis et al (2007) referred to previously is part of this supplement.

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References Asscherickx K, Vannet BV, Wehrbein BV and Sabzevar MM (2005) Root repair after injury from mini-screw Clinical Oral Implantology Research 16: 575-578 Barros SE, Janson G, Chiqueto K, Garib DG, Janson M (2011) Effect of mini-implant diameter on fracture risk and self-drilling efficacy American Journal of Orthodontics and Dentofacial Orthopaedics 140:e181-e192 Bae S-M and Park H-S (2002) Clinical application of micro-implant anchorage Journal of Clinical Orthodontics 36: 298-302 Baek M-S, Choi Y-J, Yu H-S, Kwak J, Park Y-C (2010) Long-term stability of anterior open-bite treatment by intrusion of maxillary posterior teeth American Journal of Orthodontics and Dentofacial Orthopaedics 138: 396.e1-396.e9 Brånemark P I, Adell R, Breine U et al. (1969) Intra-osseous anchorage of dental prostheses. I. Experimental studies Scandinavian Journal of Plastic and Reconstructive Surgery 3: 81–100 Brånemark P I, Hansson B O, Adell R et al. (1977) Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period Scandinavian Journal of Plastic and Reconstructive Surgery Supplement 16: 1–132 Block MS, Hoffman DR (1995) A new device for absolute anchorage for orthodontics.

American Journal of Orthodontics and Dentofacial Orthopaedics 107: 251-258 Cevidanes L, Baccetti T, Franchi B, McNamara JA and De Clerck H (2010) Comparison of two protocols for maxillary protraction bone anchors versus face mask with rapid maxillary expansion Angle Orthodontist 80: 799-806 Cha B-K, Choi D-S, Ngan P, Jost-Brinkmann P-G, Kim S-M, Jang I-S (2011) Maxillary protraction with miniplates providing skeletal anchorage in a growing Class III patient American Journal of Orthodontics and Dentofacial Orthopaedics 139: 99-112 Chen Y, Shin H-I, Kyung H-M (2008) Biomechanical and histological comparison of self-drilling and self-tapping orthodontic microimplants in dogs American Journal of Orthodontics and Dentofacial Orthopaedics 133: 44-50 Chen Y, Kang ST, Bae S-M, Kyung H-M (2009) Clinical and histologic analysis of the stability of microimplants with immediate orthodontic loading in dogs American Journal of Orthodontics and Dentofacial Orthopaedics 136: 260-267 Cheng SJ, Tseng IY, Lee JJ, Kok SH (2004) A prospective study of the risk factors associated with failure of mini-implants used for orthodontic anchorage.

International journal of Oral Maxillofacial Implants 19: 100-106 Cho U-H, Yu W and Kyung H-M (2010) Root contact during drilling for microimplant placement.

Angle Orthodontist 80:130-136 Cope JB (2005) Temporary anchorage devices in orthodontics: paradigm shift Seminars in Orthodontics11: 3–9 Cornelis MA, Scheffler NR, De Clerck HJ, Tulloch JFC and Nyssen-Behets C (2007) Systematic review of the experimental base of temporary skeletal anchorage devices in orthodontics American Journal of Orthodontics and Dentofacial Orthopaedics 131supp 1: 52-58 Cornelis MA, De Clerck HJ (2007) Maxillary molar distalization with miniplates assessed on digital models: a prospective clinical trial American journal of Orthodontics and Dentofacial Orthopaedics 132: 373-377 Cornelis MA, Scheffler NR, Nyssen-Behets C, De Clerck HJ and Tulloch CT (2008) Patients’ and orthodontists’ perceptions of miniplates used for temporary skeletal anchorage: A prospective study American Journal of Orthodontics and Dentofacial Orthopaedics 133: 18-24 Cornelis MA, Scheffler NR, Mahy P, Siciliano S, De Clerck HJ and Tulloch JF (2008) Modified miniplates for temporary skeletal anchorage in orthodontics: placement and removal surgeries.

Journal of Oral Maxillofacial Surgery 66: 1439-1445

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Costa A, Raffainl M and Melsen B (1998) Miniscrews as orthodontic anchorage: a preliminary report International Journal of Adult Orthodontics and Orthognathic Surgery 13: 201–209 Cousley RRJ (2005) Critical aspects in the use of orthodontic palatal implants American Journal of Orthodontics and Dentofacial Orthopaedics 127: 723-729 Cousley R RJ and Parberry DJ (2005) Combined cephalometric and stent planning for palatal implants Journal of Orthodontics 32: 20-25 Creekmore T D, Eklund M K (1983) The possibility of skeletal anchorage Journal of Clinical Orthodontics 17: 266–269 Crisman AG, Bertl MH, Celar AG, Bantleon H-P and Burstone CJ (2010) Miniscrews in orthodontic treatment: Review and analysis of published clinical trials American Journal of Orthodontics and Dentofacial Orthopaedics 137:108-113 DB Infinitas Clinical Manual De Clerck HJ, Timmerman HM and Cornelis MA (2008) Biomechanics of skeletal anchorage. Part 3. Intrusion Journal of Clinical Orthodontics 42: 270-278 De Clerck EEG and Swennen GRJ (2011) Success rate of miniplate anchorage for bone anchored maxillary protraction.

Angle Orthodontist 81:1010-1013 Deguchi T, Kurosaka H, Oikawa H, Kuroda S, Takahashi I, Yamashiro T, Takano-Yamamoto T (2011) Comparison of orthodontic treatment outcomes in adults with skeletal open bite between conventional edgewise treatment and implant-anchored orthodontics American Journal of Orthodontics and Dentofacial Orthopaedics 139:S60-S68 Fayad MMS, Pazera P and Katsaros C (2010) Optimal sites for orthodontic mini-implant placement assessed by cone beam computed tomography Angle Orthodontist 80: 939-951 Gainsforth BL and Higley LB (1945) A study of orthodontic anchorage possibilities in basal bone American Journal of Orthodontics and Oral Surgery 31: 406–416 Garfinkle JS, Cunningham LL, Beeman CS, Kluemper GT, Hicks EP and Kim M-O (2008) Evaluation of orthodontic mini-implant anchorage in premolar extraction therapy in adolescents American Journal of Orthodontics and Dentofacial Orthopaedics 133: 642-653 Gracco A, Lombardo L, Cozzani M and Siciliani G (2008) Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement American Journal of Orthodontics and Dentofacial Orthopaedics 134: 361-369 Heidemann W, Terheyden H and Gerlach GL (2001) Analysis of the osseous/metal interface of drill free screws and self-tapping screws Journal of Craniomaxillofacial Surgery 29: 69-74 Hembree M, Buschang PH, Carrillo R, Spears R and Rossouw PE (2009) Effects of intentional damage of the roots and surrounding structures with miniscrew implants American Journal of Orthodontics and Dentofacial Orthopaedics 135:280.e1-280.e9 Herman R and Cope JB (2005) Miniscrew implants: IMTEC Mini Ortho Implants Seminars in Orthodontics11: 32–39 Hu K-S, Kang M-K, Kim T-W, Kim K-H, Kim H-J (2009) Relationships between Dental Roots and Surrounding Tissues for Orthodontic Miniscrew Installation Angle Orthodontist 79:37-45 Kadioglu O, Buyukyilmaz T, Zachrisson BU, Maine BG (2008) Contact Damage To Root Surfaces Of Premolars Touching Miniscrews During Orthodontic Treatment American Journal of Orthodontics and Dentofacial Orthopaedics 134:353-360

TEMPORARY ANCHORAGE DEVICES IN ORTHODONTICS EXCELLENCE IN ORTHODONTICS 2012

Kanomi R (1997) Mini implant for orthodontic anchorage Journal of Clinical Orthodontics 31: 763-767 Kim JW, Ahn SJ and Chang YI (2005) Histomorphometric and mechanical analyses of the drill-free screw as orthodontic anchorage American Journal of Orthodontics and Dentofacial Orthopaedics128: 190-4 Kim YK, Yang S-M, Kim S, Lee JY, Kim KE, Gianelly AA and Kyung S-H (2010) Midpalatal miniscrews for orthodontic anchorage: Factors affecting clinical success American Journal of Orthodontics and Dentofacial Orthopaedics 137:66-72 Kokich V G, Shapiro P A, Oswald R et al. (1985) Ankylosed teeth as abutments for maxillary protraction: a case report American Journal of Orthodontics 88: 303–307 Kokich VG (1996) Managing complex orthodontic problems: the use of implants for anchorage Seminars in Orthodontics 2: 153-160 Kuroda S, Katayama A and Takano-Yamamoto T (2004) Severe anterior open-bite case treated using titanium screw anchorage Angle Orthodontist 74: 558–567 Kuroda S, Sugawara Y, Deguchi T, Kyung H-M and Takano-Yamamoto T (2007) Clinical use of miniscrew implants as orthodontic anchorage: Success rates and postoperative discomfort American Journal of Orthodontics and Dentofacial Orthopaedics 131: 9-15 Kyung H-M, Park H-S, Bae S-M, Kwon O-W and Sung J-H (2004) Handbook for the Absoanchor Orthodontic Implant Taegu Korea, Dentos Inc Liu H, Lv T, Wang N-n, Zhao F, Wang K-l, Liu D-x (2011) Drift characteristics of miniscrews and molars for anchorage under orthodontic force: 3-dimensional computed tomography registration evaluation American Journal of Orthodontics and Dentofacial Orthopaedics 139: e83-e89 Mannchen R and Schazle M (2008) Success rate of palatal implants: a prospective longitudinal study Clinical Oral Implants Research 19: 665-669 Martinelli FL, Luiz RR, Faria M, Nojima LI (2010) Anatomic variability in alveolar sites for skeletal anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 138: 252el-259 Melsen B and Lang NP (2001) Biological reactions of alveolar bone to orthodontic loading of oral implants.

Clinical Oral Implants Research 12: 144-152 Melsen B (2005) Overview - Mini-Implants: Where are we?

Journal of Clinical Orthodontics 39: 539-547 Melsen B and Verna C (2005) Miniscrew implants: the Aarhus anchorage system Seminars in Orthodontics 11: 24–31 Miyawaki S, Koyama I, Inoue M, Mishima K, Sugahara T and Takano-Yamamoto T (2003) ,Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 124: 373-378 Mortensen MG, Buschang PH, Oliver DR, Kyung H-M and Behrents R (2009) Stability of immediately loaded 3- and 6-mm miniscrew implants in beagle dogs—a pilot study American Journal of Orthodontics and Dentofacial Orthopaedics 136:251-259 Nguyen T, Cevidanes L, Cornelis MA, Heymann G, de Paula LK and De Clerck H (2011) Three-dimensional assessment of maxillary changes associated with bone anchored maxillary protraction American Journal of Orthodontics and Dentofacial Orthopedics140: 790-798 NICE guidance on Mini/micro screw implantation for orthodontic anchorage (2007) IPG 238

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Ohmae M, Saito S, Morohashi T, Seki K, Qu H, Kanoni R, Yamasaki K, Okano T, Yamada S, and Shibasaki Y (2001) A clinical and histological evaluation of titanium mini-implants as anchors for orthodontic intrusion in the beagle dog American Journal of Orthodontics and Dentofacial Orthopaedics 119: 489-97 Owens SE, Buschang PH, Cope JB, Franco PF and Rossouw PE (2007) Experimental evaluation of tooth movement in the beagle dog with the mini-screw implant for orthodontic anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 132: 639-646 Paik CH, Woo YJ, Kim JS and Park JU (2002) Use of miniscrew for intermaxillary fixation of lingual-orthodontic surgery patients Journal of Clinical Orthodontics 36: 132-6 Paik C-H, Park I-K, Woo YJ, Kim T-W (2009) Orthodontic miniscrew implants. Clinical applications.

Consulting editor Harradine N Mosby Elsevier ISBN 978-0-7234-3402-3 Park H-S, Bae S-M et al (2001) Micro-implant anchorage for treatment of skeletal class 1 bialveolar protrusion Journal of Clinical Orthodontics 35: 417-422 Park H-S, Kwon T-G and Sung J-H (2004) Nonextraction treatment with microscrew implants The Angle Orthodontist 74: 539–549 Park H-S Lee S-K and Kwon O-W (2005) Group distal movement of teeth using microscrew implant anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 75: 602-609 Park H-S, Jeong S-H and Kwon O-W (2006) Factors affecting the clinical success of screw implants used as orthodontic anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 130: 18-25 Park H-S, Lee Y-J, Jeong S-H and Kwon T-G (2008) Density of the alveolar and basal bone s of the maxilla and the mandible American Journal of Orthodontics and Dentofacial Orthopaedics 133: 30-37 Park Y-C, Lee S-Y, Kim D-H and Jee S-H (2003) Intrusion of posterior teeth using mini-screw implants American Journal of Orthodontics and Dentofacial Orthopaedics 123: 690-694 Ren Y, Maltha JC, and Kuijpers-Jagtman A-M (2003) American Journal of Orthodontics and Dentofacial Orthopaedics Angle Orthodontist 13: 86-92 Reynders R, Ronchi L and Bipat S (2009) Mini-implants in orthodontics: A systematic review of the literature American Journal of Orthodontics and Dentofacial Orthopaedics 135: 564.e1-564.e19 Roberts WE, Helm FR, Marshall KJ and Gongloff RK (1989) Rigid endosseous implants for orthodontic and orthopedic anchorage Angle Orthodontist 59: 247–256 Sandler J, Benson P, Doyle P, Majumder A, O’Dwyer J, Speight P, Thiruvenkatachari B and Tinsley D (2008) Palatal implants are a good alternative to headgear: A randomised trial American Journal of Orthodontics and Dentofacial Orthopaedics 133: 51-57 Tinsley D, O’Dwyer JJ, Benson PE, Doyle PT and Sandler J (2004) Orthodontic palatal implants: clinical technique Journal of Orthodontics 31: 3-8 Umemori M, Sugawara J, Mitani H, Nagasaka N and Kawamura H (1999) Skeletal anchorage system for open-bite correction American Journal of Orthodontics and Dentofacial Orthopaedics 124: 373-378 Ure,DS,, Oliver D, Kim KB, Melo,AC, BuschangPH (2011) Stability changes of miniscrew implants over time The Angle Orthodontist 81: 994-1000 VectorTAS website

TEMPORARY ANCHORAGE DEVICES IN ORTHODONTICS EXCELLENCE IN ORTHODONTICS 2012

Yao C-CJ, Wu H-Y, Kok S-H, Chang H-FF and Chen Y-J (2004) Intrusion of the overerupted upper left first and second molars by mini-implants with partial-fixed orthodontic appliances: a case report Angle Orthodontist 74: 550â&#x20AC;&#x201C;557 Zhang L, Zhao Z, Lia Y, Wua J, Zheng L and Tang T (2010) Anatomic variability in alveolar sites for skeletal anchorage Angle Orthodontist 80: 354-360 Zhao L, Xu Z, Zhao Z, Yang Z, Zhang L, Li Jand Tang T (2011) Effect of placement angle on the stability of loaded titanium microscrews: A microcomputed tomographic and biomechanical analysis American Journal of Orthodontics and Dentofacial Orthopaedics 139: 628-635

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INTRAORAL AUXILIARIES EXCELLENCE IN ORTHODONTICS 2012

Chapter

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15 Intraoral auxiliaries David Birnie

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Introduction Although we have used many intraoral auxiliaries in the past, their use seems to be in significant decline. To some extent, the advent of fully bonded fixed appliances has made orthodontists think hard about whether they really require intraoral auxiliaries because of the absence of bands with palatal (lingual) stainless steel surfaces to which to weld or solder attachments. In addition, the increasing number of nonextraction cases does not make lacebacks as essential or anchorage targets as rigorous; routinely including second molars in appliances may increase antero-posterior anchorage and make transverse control and coordination more effective and finally some intraoral auxiliaries, such as the lip bumper, are of dubious effectiveness.

Lacebacks The use of lacebacks in Straight-Wire Appliance mechanics has been described by McLaughlin and Bennett (1989).

Lacebacks may be used for the following reasons: 100

• to control mesial movement of the canines during alignment and levelling. This prevents incisor extrusion during these stages of treatment.

• to retract canines in cases with labial segment crowding during alignment and levelling • protection of flexible archwires in extraction spaces • centreline correction by unilateral canine retraction in one or both arches.

degrees

80

60

40

20

0 SNA

SNB

ANB SNMP SNI 1-MP Control Experimental

OP-MP Can Ang

The effectiveness of lacebacks has been studied by Robinson (1989). The results of this study are shown in Figure 15.1.

100

degrees

80

60

40

20

0 SNA

SNB

ANB SNMP SNI 1-MP Control Experimental

OP-MP Can Ang

The results showed retroclination of the lower incisors and distalisation of the lower incisor tip in the experimental group but not the control. There was no significant change in canine angulation. The lower first molars in the experimental group moved forward more than in the control group but this was not statistically significant.

8 6 degrees or millimetres

The control and experimental groups were comparable at the outset. Both groups were composed of premolar extraction cases. The experimental group was given lacebacks and the control group was not. The mean time interval from T1 to T2 was 8.8 months for the control group and 8.0 months for the experimental group.

4 2 0 -2 -4 SNI

1-MP Control

Can Ang 1-Y (mm) Experimental

6-Y (mm)

Figure 15.1: Comparison of changes in control and experimental group between T1, T2 and T1 and T2. The changes in canine angulation and 1-Y point were non significant; all other changes were significant at the 0.001 level.

Similar results were shown by Usmani et al (2002) in a randomised clinical trial in relation to the use of lacebacks in the upper arch. The authors concluded that in the upper arch, canine lacebacks prevent approximately 1mm of upper incisor proclination and have minimal effect on mesial molar movement. These

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effects are independent of pretreatment canine angulation.

Irvine, Power and MacDonald (2004) confirmed our views on lacebacks in a randomised controlled trial on their effectiveness. They concluded that the lower incisors retroclined a similar amount in four premolar extraction cases with and without lacebacks and that lacebacks were mildly but significantly anchorage consuming.

Archwire stops With the increasing use of self-ligating brackets, maintaining the archwire in a symmetrical position in the arch becomes more difficult as there is much less friction to hold it in place. With the increasing tendency to bond second molars early on in treatment, turning down the archwire behind the second molars can cause significant discomfort. Crimpable stops can be used to prevent archwire ‘swivelling’. The stops should be placed in an interdental space anterior to where you want the tooth movement to occur; the stop needs to fill most of the inter dental space – use two stops either side of one tooth if necessary. The stops should be placed anterior to any crowding to allow the wire to move distally as the crowding resolves. Between premolar teeth in the upper arch and between the central incisors in the lower arch is often ideal.

Crimpable stops These are available from 3M Unitek in 0.016"/0.018" (536-610) and 0.022" (536-620) sizes; the stops are split so that they can be positioned over an archwire already in place. Perhaps even better are similar and slightly softer stops from GAC; these are individual compared with the prestamped 3M Unitek strip from which individual stops have to be cut off. The softer stops are easier to crimp on to larger archwire sizes. They are approximately 2 mm in length and should be placed in an interbracket space which is slightly larger than 2 mm but where there is no or minimal archwire deflection.

Ormco now supply copper nickel titanium archwires with two soft prefitted stops which are very easy to position and crimp. They are secured on to the archwire with a small amount of wax to prevent movement in transit and are the same price as the wires without the stops. Individual stops are also available and these are ideal for TMA or stainless steel wires.

Composite stops Composite stops are preferred as they are more effective and cheaper than crimpable stops! Dry the archwire where you want to place the stop, take a small amount of bonding adhesive and place it on the archwire and mould it into place with a micro sponge moistened with Ortho Solo.

Archwire hooks Hooks Soldered hooks have been preferred on the grounds of neatness and flexibility of positioning. The art of soldering is easily learned; presoldered electrodes and an electrode holder are useful practical tips that make life easier.

However, soldering takes a finite amount of time and requires additional equipment and has given way to the use of either pre-soldered hooks or crimpable hooks.

Presoldered archwires have the disadvantage of requiring significant stock. However they are the preferred method of using hooks because of their robustness.

Crimpable hooks were unsatisfactory as they either did not stay on the archwire or they slid along it. The design of these has now improved considerably. TP make a tungsten carbide coated universal split hook which requires special pliers to place. However, the hooks are expensive and still tend to slide. American Orthodontics makes a neater split hook (in left and right versions) which does not have the tungsten carbide coating.

Johal et al (1999) carried out a laboratory investigation into the force required to dislodge crimpable hooks. The crimping force was found to be about 18 kg. They found that the TP hooks required almost twice the dislodgement force (11.7 ± 7.8N) of the American Orthodontics hooks (6.22 ± 0.8N) – note the difference in the

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standard deviations! It is suggested that both hooks probably functionally satisfactorily in the clinical situation as the retraction force applied by clinicians did not exceed 3.54 N during space closure (Nattress et al 1997). A further paper by Johal et al (2001) looked at crimping TP hooks to 0.019" x 0.025" archwires and found that male operators used a higher crimping force than females and that hooks were more firmly crimped when attached out of the mouth.

We now use preposted archwires which have reliable hooks; we think that the attachment of the hook softens the archwire around the weld or soldering point a little but this is again the most reliable and cost effective solution.

Clinical use preposted archwires for 0.019” x 0.025” stainless steel wires

tip:

Several makes of bracket now offer drop-in hooks to vertical or horizontal slots in the bracket.

Torquing auxiliaries Although the use of auxiliaries attached to brackets (uprighting springs, rotation springs, SideWinders) are an integral part of the Begg and TipEdge techniques, their use, for obvious reasons has been rare in edgewise therapy. However, edgewise appliances are not ver efficient at delivering torque for reasons of mechanical efficiency and sometimes some additional assistance is required. The ART 1 auxiliary is shown in Figure 15.2 where it is being used to provide additional torque to the upper incisors. Lower (reverse) torquing auxiliaries are also available; the upper torquing auxiliary can be placed from the incisal to provide a reverse torquing auxiliary for the upper arch. The auxiliaries are extremely well made with annealed ends and are available in a kit with upper and lower ART auxiliaries in small, medium and large sizes.

Attachments It is often helpful to be able to add small temporary attachments to teeth such as buttons, tubes and bite pads.

Ortho Arch Company’s Mini-Molds 2 (Figure 15.3) are a set of reusable or disposable silicone moulds that can be used to shape composite into: Figure 15.2: An ART (Anterior Root Torquing) auxiliary being used to provide additional torque to upper incisors

• • • • • •

habit control spurs anterior bite ramps molar pads for disclusion wire bonder for instant fixed retainers button bonder for lingual buttons bracket bonder for making a simple single wing bracket • tube bonder for making a simple archwire tube.

Intra-oral auxiliaries Figure 15.3:

Ortho Arch Company Mini-Mold kit

Systems

1

Atlanta Orthodontics, 1247 Zonolite Road NE, Atlanta, GA 30306 USA

2

Ortho Arch Company, Inc., 1185 Tower Rd, Schaumburg, IL 60173

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The following systems are either in common use or of particular interest.

• •

soldered removable o 0.036" doubled wire o buccal tube 0.042" round (lip-bumper) o Wilson 3-D

The use of removable intra-oral auxiliaries is preferred.

Types of palatal attachment have been described by Cook (1987) and Cook and Watts (1988). Ideally a palatal or lingual attachment should:

• • • • • • •

be securely attached to the band allow easy insertion of the appliance securely lock the appliance in place allow easy removal of the appliance allow the interchange of different manufacturers’ appliances have a hook for a cross-elastic have minimum bulk

Attachments produced by Ormco/“A” Company, GAC and American Orthodontics for 0.036" doubled wire all fulfil these requirements.

Transpalatal bars Originally described by Robert Goshgarian in 1972, the biomechanical aspects of the transpalatal bar or Goshgarian arch have been analysed by Burstone and Koenig (1981) and Baldini and Luder (1982). An excellent description of the use of the transpalatal bar is given by Rebellato (1995) and also by Melsen (1994) and Ingervall et al (1995).

Horizontal Anchorage Transpalatal bars have been claimed to provide horizontal anchorage of approximately 1 mm per year Root (1986); however, we have doubts as to the effectiveness of transpalatal bars in this context and no longer use them.

Cetlin suggests that molar distalisation can be achieved by placing rotations in the transpalatal bar to produce a distal force on each molar alternately (McNamara 1993). Whilst this can be achievable, it is difficult to obtain routinely and transpalatal bars on upper second molars are difficult to manage for both patient and operator.

Vertical Anchorage Vertical control of upper molars by placing the bar 5-6 mm off the palatal mucosa with a large and mesially facing loop is said by Cetlin to prevent molar extrusion and perhaps intrude molars. There is no evidence to support this although a transpalatal bar probably helps to prevent the development of anterior open bites by torquing the roots of the upper molars buccally.

Wise et al (1994) have published a study on the use of TPBs in non-extraction cases. The design of TPB used an anterior facing loop 1-2 mm off the palate. This investigated the interesting and eyebrow raising hypothesis proposed by Terrell Root that:

• a TPB stops vertical descent of the upper first molars and hence vertical maxillary alveolar growth • this alveolar growth is equal to one third of the total vertical growth of the face • therefore, wearing a TPB stimulates a third additional mandibular length

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Size

Wire diameter

1

0.032"

2

0.036"

3

0.038"

The hypothesis was not supported and there were no significant differences between the control and the experimental groups.

Rotational control of upper first molars Lamons and Holmes (1961) have shown that mesial rotation of 0.044" 4 the upper first molars is present in many class 2 cases. Derotation Table 15.1: Ideal sizes of quadhelix appliance of the molars may produce 1-2 mm of arch length gain as the first molars rotate about their palatal roots. Thus a transpalatal arch may be used to gain arch length and to help to correct a class 2 molar relationship. Upper first molars can normally be rotated mesio-buccally until their buccal surfaces are almost parallel.

However, Dahlquist et al (1996) have showed that in only two thirds of cases does the rotated molar move distally.

These workers found that the median distal movement was 0.3 mm on the right and 0.5 mm on the left but that because many molars move mesially the average gain was zero space.

Torque control of upper first molars Transpalatal bars may be used to prevent buccal tipping of molars when intruding posterior buccal segments using TADs or bone plates with traction in the buccal sulcus.

Molar rotators Nickel titanium molar rotators have been available for some time. Our experience of these is limited; they are clearly good for severely rotated molars but are difficult to place and difficult to control. They offer the advantages of nickel titanium with the disadvantage that they are not adjustable and therefore have a fixed range of action and cannot be modified to apply torque.

Torque control of upper molars Transpalatal bars can be used to produce effective buccal root torque of upper first molars.

Upper arch expansion Small amounts of upper arch expansion (up to a millimetre or so) can be obtained with a transpalatal bar.

Ingervall et al (1995) have described the use of a statically determinate transpalatal bar to correct a unilateral crossbite. This works well; use a large round palatal tube on the side where expansion is desired, so that a conventional lingual lock can rotate in it.

Sometimes, aggressive rotation of the upper first molars will cause a buccal crossbite in the upper premolar region as the archwire is bowed buccally - a sure sign that things have been a little overdone.

Types of transpalatal bar Transpalatal bars may be obtained with a forward facing or backward facing loop. The forward facing loop allows a transpalatal bar to be placed on both upper first and second molars.

GAC Cetlin bars are preferred because they are more resilient than other makes. All intra-oral auxiliaries should be secured into their sheaths with an additional elastic ligature - elastic separating rings are better for this than ligating rings.

Quadhelix The quadhelix is a useful intermediate upper arch expansion device and has been extensively described and popularised by Ricketts (1979). The optimum force for orthopaedic expansion is estimated at 500 g.

The quadhelix is capable of producing intermolar expansion of about 5-6 mm with sutural opening (Bell et al 1981). A ratio of 6:1 for orthodontic: orthopaedic expansion has been reported (Frank and Engel 1982). Overexpansion of 2-3 mm is required to compensate for relapse. Achieved expansion should be retained with an upper removable appliance.

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Urbaniak et al (1988) showed that:

• • •

as quadhelix size increases, force decreases significantly as wire size increases force increases significantly alloy (stainless steel or Elgiloy) is not a significant factor in force levels

The ideal size of a quadhelix to produce 500g force with 8 mm activation was as shown in the Table 15.1.

Nickel titanium expanders Nickel titanium maxillary expanders are available. These work well but it is important to choose the size carefully to match the desired for intermolar width as overexpansion is an ever present hazard. Perhaps we wonder whether the additional cost is worthwhile over a conventional quadhelix.

Donoghue et al (2004) compared the effectiveness of the quadhelix and a nickel titanium expander and found both to be equally efficient but that the quadhelix appeared to deliver more controlled and predictable expansion. The discomfort from both appliances was similar. There was additional cost related to the use of the nickel titanium expander due to the need for multiple expanders where expansion greater than 6 mm was required.

Nance palatal arches

Nance palatal arches provide some additional upper arch anchorage – but there is no such thing as absolute anchorage! If excessive demands are placed on Nance palatal arches then they embed themselves in the palatal mucosa and can be difficult to remove. Use as large a palatal button as possible and gentle forces to eliminate this. Nance palatal arches are particularly useful in upper first molar extraction cases and can be modified to incorporate an anterior bite plane if required.

Lingual arch Lower lingual arches are valuable where space is critical and for lower centreline correction. The Rocky Mountain/Wilson 3-D type is used for the convenience of easy removal. However, in the upper arch attempts to use the 3-D system have been frustrated by frequent breakage.

Reballato et al (1997) looked at the effect of lower lingual arches in preserving mandibular arch perimeter. The study had small groups and used lower lingual arches made of 0.032" stainless steel which contacted the cingulae of the lower incisors. In the experimental group, lower molars stayed more upright, lower incisors proclined, and the total arch length stayed constant whereas in the control group it decreased by 2.54 mm.

Lip bumper The correction of mild crowding, very narrow mandibular arches or arch asymmetry can be helped with the use of a lip bumper. The use of lip bumpers is described by Ten Hoeve (1985). Ten Hoeve suggests rotating lower second and first molars until their lingual surfaces are parallel. The lip bumper can be placed hard against the lower incisors to prevent their proclination and more gingivally if molar uprighting is required.

Osborn et al (1991) have shown that lip bumpers produce an overall increase in arch circumference of approximately 4.1 mm (range 0.7 mm - 8.8 mm). Some increase in arch length occurred (1.2 mm due to proclination of the lower incisors (2.92 degrees increase in IMPA). Passive increases in interpremolar and intercanine width occurred of about 2.5 mm.

Lip bumpers are used to gain arch length in mild crowding cases (4-8 mm). Two types of lip bumper exist: the wire type and the shield type.

Wire type lip bumpers are adjusted to be 2-3 mm in front of the lower incisors at the gingival margin, 4 mm away from the buccal segments and 2 mm molar expansion.

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Shield type lip bumpers are adjusted so that the top of the shield is placed 2-3 mm in front of the lower incisors, approximately 7 mm below the incisal edge, with 4-5 mm expansion in both buccal segments and the molar region (Nevant et al 1991).

Hodge et al (1997) have investigated the forces produced by lip bumpers and concluded that shield type lip bumpers produced higher resting forces than wire lip bumpers and that greater force was produced when the lip bumper was 4 mm rather than 2 mm in front of the clinical crown and gingival rather than in the middle of the crown. The magnitude of the forces produced was in the range of 10-20 grams at the mandibular molars.

Lip bumpers are re-adjusted at 6-8 week intervals to the original specification and treatment normally lasts 1-1.5 years.

The therapeutic effects of lip bumpers are therefore:

• • • •

lower incisor proclination distal tipping of the lower first molar slight extrusion of the lower first molar increase in transverse width of the canines, premolars and molars.

Some patients find lip bumpers very hard to tolerate.

Werner et al (1994) have described changes resulting from the use of a lip bumper which involved:

• • • •

reduction in incisor irregularity lack of incisor flaring broadening of the lower dental arch appreciable stability two years post treatment.

Similar results have been obtained by Grossen and Ingervall (1995).

Davidovitch et al (1997) carried out a prospective study to study the effects of continuous lip bumper treatment on mild to moderate crowding cases in the mixed dentition over a six month period. A matched control group had no orthodontic intervention. Inclusion criteria for the trial were:

• • • •

white ethnicity 3 to 8 mm ALD presence of deciduous second molars class 2 division i malocclusion

The changes seen in the experimental group were significantly different to the control group in which increases in arch length, perimeter and width were seen. The average decrease in crowding was approximately 5 mm with a standard deviation of 1 mm. These changes were attributed as follows:

• 45-55% incisor proclination • 35-50% molar distalisation and tipping • 5-10% transverse increase in canine and premolar width Lip bumpers produce transverse expansion of the lower arch and proclination of the lower incisors. These changes, if produced by active fixed appliances, would be regarded as unstable. It is presumably hypothesised therefore that lip bumpers produce long term changes in the pressure produced by the lower lip which results in stable changes in the lower arch. Ingervall and Thüer (1998) have studied the effect of wire and shield type lip

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bumpers on lower lip pressures and compared this with groups treated with active and passive lingual arches.

There was little difference in performance between the two types of lip bumper which produced the changes expected of them. The pressures on the lower incisors from the lower lip varied according to whether they were measured at the midline (-1.0 g/cm2 to 32.8 g/cm2) or between the left lateral incisor and canine (-2.6 g/cm2 to 13.4 g/cm2). The pressure from the lower lip was unaffected by the period of treatment with the lip bumper but active proclination of the lower incisors resulted in an increase in pressure from the lower lip. However the amount of proclination produced in the active expansion group was twice that generated by the lip bumpers and so the two effects are not comparable.

Clinical conclusion: We no longer use lip bumpers. The hypothesis underlying their use (‘natural’ and therefore stable change) is flawed, patients often find them very uncomfortable and there are simpler ways of obtaining the same result.

Correction of posterior crossbite The correction of posterior crossbite can be carried out in several ways and at several different times. It is not usual to correct crossbites in the deciduous dentition as these are often self-correcting and not carried over into the permanent dentition.

Prevalence and aetiology The prevalence of a posterior crossbite in the primary and early mixed dentitions has been reported to be between 8 and 22 per cent (Macena et al 2009). The aetiology of posterior crossbite is uncertain but factors that have been implicated include:

• • • • •

heredity poor nasal respiration and hence lowered tongue posture as hypertrophic tonsils/adenoids non nutritive sucking habits such as pacifiers and digits cleft lip and palate intubation during infancy

a result of allergic rhinitis or

In Macena et al’s study (2009), 34.5% used a pacifier and 9% were digit suckers. Of those who used a pacifier, 12.8% had a posterior crossbite and of those who were digit suckers, 9% had a posterior crossbite. Thilander et al (1984) in a study on early interceptive treatment of posterior crossbite reported that 79.9% of patients with posterior crossbite had a functional shift.

Definition and description A posterior crossbite is an abnormal buccolingual relationship between opposing molars, premolars, or both, in centric occlusion. It can be caused by a malposition of individual or groups of posterior teeth (dental crossbites), a malposition of posterior teeth accompanied by a functional mandibular shift (functional crossbite), or transverse disharmonies of the maxilla and mandible (skeletal crossbite).

Unilateral posterior crossbites are usually a bilateral narrowness of the maxilla (rarely is the mandible too wide) and the need for maximum intercuspation creates the functional shift. Bilateral crossbites rarely have functional shifts as the increased narrowness of the maxillary arch provides occlusal stability.

Patients with unilateral posterior crossbites and a functional shift have an asymmetric pretreatment condylar position with the noncrossbite side condyle in an anterior and inferior position in the glenoid fossa. On the crossbite side, the condyle is forced upwards and backwards. There is also an asymmetric pretreatment molar and canine relationship with a more Class II relationship on the crossbite side and a less Class II relationship on the noncrossbite side, concomitant with a midline deviation toward the crossbite side (Hesse et al 1997).

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Treatment

Harrison and Ashby (2001) published a Cochrane Review of orthodontic treatment for posterior crossbites. The evidence suggested that removal of premature contacts of the baby teeth is effective in preventing a posterior crossbite from being perpetuated to the mixed dentition and adult teeth. When grinding alone is not effective, using an upper removable expansion plate to expand the top teeth will decrease the risk of a posterior crossbite from being perpetuated to the permanent dentition. In Thilander’s study (1984), only 27.7% of the corssbites corrected with grinding. When carrying out occlusal grinding, it is important to reshape the canines to provide guidance ramps to assist crossbite correction; this usually means reshaping the palatal surface of the upper canines and the buccal surfaces of the lower canines. Lindner (1989) claimed an 85% success rate is the difference between that mandibular intercanine width and the maxillary intercanine width was < 3.5mm.

Myers et al (1980) undertook a study to determine whether functional posterior crossbites in children influenced the position of the mandibular condyle and to assess the effect of crossbite correction on condylar position. Ten children from four to nine years of age with functional posterior crossbites were treated by maxillary expansion.

Standardised transcranial radiographs were taken prior to treatment and following crossbite correction.

Pretreatment radiographs were taken with the child’s teeth occluded in the crossbite relationship and post treatment radiographs were made with the teeth in centric occlusion. Prior to treatment, there were significant differences in the horizontal and vertical joint space measurements between the crossbite and non-crossbite sides with the condyle being displaced superiorly on the crossbite side and inferiorly on the non-crossbite side. There were no significant differences between the two sides following crossbite correction and thus the position of the condyles had normalised in the fossae.

In a systematic review of posterior crossbites and functional changes, Andrade et al (2009) found that altered muscle function associated with posterior crossbite could reduce the bite force in mixed dentition. According to EMG analysis, children with posterior crossbite had asymmetrical muscle function during chewing or clenching, that is, the anterior temporalis is more active and the masseter less active on the crossbite than on the noncrossbite side. It was also suggested that posterior crossbite may increase the probability of children developing signs and symptoms of TMD. In a study on mandibular asymmetry in adults with posterior crossbite, O’Byrn et al (1995) found that in adults with unilateral posterior crossbite, the mandible was “rotated” relatively posteriorly on the crossbite side relative to the cranial floor. Also, the molars were positioned relatively posterolaterally on the crossbite side. Because of a lack of demonstrable difference in both mandibular skeletal asymmetry and condylar position within the fossa between the two groups, it was assumed that the glenoid fossa through remodeling was also located relatively posteriorly on the crossbite side, since the mandible was “rotated” relatively posteriorly in relation to the cranial floor. The authors concluded that unilateral posterior crossbites in adults in the absence of a functional shift of the mandible should probably not be corrected by orthodontic tooth movement alone. This suggests that if a unilateral crossbite is left untreated, full or partial remodelling of the glenoid fossae takes place.

Huynh et al (2009) investigated treatment response and stability of slow maxillary expansion using Haas, hyrax, and quad-helix appliances in a retrospective study. There were no significant differences in stability or treatment response during correction of posterior crossbite at T2 (after crossbite correction) and T3 (at least two years post treatment) among the three types of expander used. Expansion increased intermolar width by 5 mm and tipped each molar by 2.3°. At least 2 years after expander removal, molar width decreased by 1.3 mm, and the molars uprighted by 6°. Compared with non-crossbite norms, posterior crossbite subjects had narrower intermolar width before treatment and greater width after expansion, and were slightly wider at least 2 years posttreatment. Both a younger age at T1 (starting treatment earlier) and retainer use resulted in statistically greater intermolar width at T3. For each year earlier that treatment started, the patients had 0.42 mm more expansion in the long T1 T2 T3 term; the retainer group maintained 0.98 mm more 8.1 9.2 13.2 Age (years) intermolar width in the long term, compared with the 42.1 47.2 45.8 Intermolar width (mm) non-retainer group at T3 and for each year longer 155.4 150.8 163.2 Intermolar angulation (degrees) than 2 years out of the appliance, the molar Table 15.2: Huynh et al’s data on slow maxillary expansion uprighted 0.54° more. The data is shown in Table

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15.2.

Crossbite correction can usually be achieved without intraoral auxiliaries using:

•

• •

archwires on their own o this works best when the second molars are not in crossbite but the first molars and some premolars are. Engaging the second molars in the archwire provides the anchorage to correct the crossbite. Maxillary crowding is a favourable indicator for successful crossbite correction (but do not extract) archwires and cross elastics with disclusion o a more powerful method that corrects most crossbites. Ensure that all the teeth in crossbite are connected to the elastic. Frequently works in a single visit hyperexpanded 0.016” x 0.025” archwires with elastics and disclusion o more powerful still but rarely needed

References Andrade AS, Gameiro GH, DeRossi M and Gavião MBD (2009) Posterior crossbite and functional changes: a systematic review Angle Orthodontist 79: 380-386 Baldini G and Luder HU (1982) Influence of arch shape on the transverse effects of transpalatal arches of the Goshgarian type during application of buccal root torque American Journal of Orthodontics and Dentofacial Orthopaedics 81: 202-208 Bell RA and LeCompte EJ (1981) The effects of maxillary expansion using a quad-helix appliance during the deciduous and mixed dentitions American Journal of Orthodontics and Dentofacial Orthopaedics 79: 152-161 Burstone CJ and Koenig HA (1981) Precision adjustment of the transpalatal lingual arch: computer arch form predetermination American Journal of Orthodontics and Dentofacial Orthopaedics 79: 115-133 Cook PA (1987) Methods of attachment for palatal arches: an evaluation British Journal of Orthodontics 14: 285-291 Cook PA and Watts G (1988) Improving palatal attachments European Journal of Orthodontics 10: 380-384 Dahlquist A, Gebauer U and Ingervall B (1996) The effect of a transpalatal arch for the correction of first molar rotation European Journal of Orthodontics 18: 257-267 Davidovitch M, McInnis D and Lindauer SJ (1997) The effects of lip bumper therapy in the mixed dentition American Journal of Orthodontics and Dentofacial Orthopaedics 111: 52-58 Donoghue VE, Marshman LAG and Winchester LJ (2004) A clinical comparison of the quadhelix appliance and the nickel titanium (tandem loop) palatal expander: a preliminary, prospective investigation European Journal of Orthodontics 26: 411-420 Frank SW and Engel GA (1982) The effects of maxillary quad-helix appliance expansion on cephalometric measurements in growing orthodontic patients American Journal of Orthodontics and Dentofacial Orthopaedics 81: 378-389 Grossen J and Ingervall B (1995) The effect of a lip bumper on lower dental arch dimensions and tooth positions European Journal of Orthodontics 17: 129-134

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Harrison J and Ashby D (2001) Orthodontic treatment for posterior crossbites Cochrane Database of Systematic Reviews 2001, Issue 1. Art. No.: CD000979. DOI: 10.1002/14651858.CD000979 Hesse K, Artun J, Joondeph JR and Kennedy DB (1997) Changes in condylar position and occlusion associated with maxillary expansion for correction of functional unilateral posterior crossbite American Journal of Orthodontics and Dentofacial Orthopaedics 111:410-418 Hodge JJ, Nanda RS Ghosh J and Smith D (1997) Forces produced by lip bumpers on mandibular molars American Journal of Orthodontics and Dentofacial Orthopaedics 111: 613-622 Huynh T, Kennedy DB, Joondeph DR, Bollen A-M (2009) Treatment response and stability of slow maxillary expansion using Haas, Hyrax, and quad-helix appliances: A retrospective study American Journal of Orthodontics and Dentofacial Orthopaedics 136: 331-339 Ingervall B and ThĂźer U (1998) No effect of lip bumper therapy on the pressure from the lower lip on the lower incisors European Journal of Orthodontics 525-534 Ingervall B, Gollner P, Gebauer U and Frohlich K (1995) A clinical investigation of the correction of unilateral first molar crossbite with a transpalatal arch American Journal of Orthodontics and Dentofacial Orthopaedics 107: 418-425 Irvine R, Power S and MacDonald F (2004) The effectiveness of laceback ligatures: a randomised controlled clinical trial Journal of Orthodontics 31: 303-311 Johal A, Harper CR and Sherriff M (1999) Properties of crimpable archwire hooks: a laboratory investigation European Journal of Orthodontics 21: 679-683 Johal A, Loh S and Heng JK (2001) A clinical investigation into the behaviour of crimpable archwire hooks Journal of Orthodontics 28: 203-205 Lamons FF and Holmes CW (1961) The problem of the rotated maxillary first permanent molar American Journal of Orthodontics 47: 246-272 Lindner A (1989) Longitudinal study on the effect of early interceptive treatment in 4-year-old children with unilateral cross-bite.

Scandinavian Journal of Dental Research 97: 432-438 Macena MCB, Katz CRT and Rosenblatt A (2009)Prevalence of a posterior crossbite and sucking habits in Brazilian children aged 18â&#x20AC;&#x201C;59 months European Journal of Orthodontics 31: 357-361 McLaughlin RP and Bennett JC (1989) The transition from standard edgewise to preadjusted edgewise appliance systems Journal of Clinical Orthodontics 23: 142-153 McNamara JA and Brudon WL (1993) Orthodontic and Orthopaedic Treatment in the Mixed Dentition Ann Arbor, Needham Press Melsen B, Bonetti G and Giunta D (1994) Statically determinate transpalatal arches Journal of Clinical Orthodontics 28: 602-606 Myers DR, Barenie JT, Bell RA and Williamson EH (1980) Condylar position in children with functional posterior crossbites: before and after crossbite correction Paediatric Dentistry 2: 190-194 Nattrass C, Ireland AJ and Sherriff M (1997) An investigation into the placement of force delivery systems and the initial forces applied by clinicians during space closure British Journal of Orthodontics 24: 127-131 Nevant CT, Buschang PH, Alexander RG, and Steffen JM (1991) Lip bumper therapy for gaining arch length American Journal of Orthodontics and Dentofacial Orthopaedics 100: 330-336

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O'Byrn BL, Sadowsky C, Schneider B and Begole EA (1995) An evaluation of mandibular symmetry in adults with unilateral posterior crossbite American Journal of Orthodontics and Dentofacial Orthopaedics 107: 394-400 Osborn WS, Nanda RS, Currier GF (1991) Mandibular arch perimeter changes with lip bumper treatment American Journal of Orthodontics and Dentofacial Orthopaedics 99: 527-532 Rebellato J (1995) Two couple orthodontic appliance systems: transpalatal arches Seminars in Orthodontics 1: 44-54 Rebellato J, Lindauer SJ, Rubenstein LK, Isaacson RJ, Davidovitch M and Vroom K (1997) Lower arch perimeter preservation using the lingual arch American Journal of Orthodontics and Dentofacial Orthopaedics 112: 449-456 Ricketts RM, Bench RW, Gugino CF, Hilgers JJ and Schulhof RJ (1979) Bioprogressive Therapy Denver, Rocky Mountain Orthodontics Robinson SN (1989) An evaluation of the changes in lower incisor position during the initial stages of clinical treatment using a preadjusted edgewise appliance MSc Thesis, University of London Root TL (1986) The Level Anchorage System In: Graber L W ed. Orthodontics State of the Art Essence of the Science: St Louis, The CV Mosby Company Ten Hoeve A (1985) Palatal bar and lip bumper in non-extraction treatment Journal of Clinical Orthodontics 19: 272-291 Thilander B, Wahlund S and Lennartsson B (1984) The effect of early interceptive treatment in children with posterior cross-bite European Journal of Orthodontics 6: 25-34 Urbaniak JA, Brantley WA, Pruhs RJ, Zussman RL, and Post AC (1988) Effects of appliance size, arch wire diameter, and alloy composition on the in vitro force delivery of the quad-helix appliance American Journal of Orthodontics and Dentofacial Orthopaedics 94: 311-316 Usmani T, Oâ&#x20AC;&#x2122;Brien KD, Worthington and Derwent S (2002) A randomised clinical trial to compare the effectiveness of canine lacebacks with reference to canine tip Journal of Orthodontics 29: 281-286 Werner SP, Shivapuja PK and Harris EF (1994) Skeletodental changes in the adolescent accruing from use of the lip bumper Angle Orthodontist 64: 13-22 Wise JB, Magness BM and Powers JM (1994) Maxillary molar vertical control with the use of transpalatal arches American Journal of Orthodontics and Dentofacial Orthopaedics 106: 403-408

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OPENING AND CLOSING SPACES; PROBLEMS AND SOLUTIONS EXCELLENCE IN ORTHODONTICS 2012

Chapter

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16 Opening and closing spaces; problems and solutions Nigel Harradine

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Closing spaces with sliding mechanics Spaces can be closed with energy stored in loops in the archwire, but much more commonly, the teeth are made to slide along the archwire by energy stored in elastics or wire coil springs. Our usual mechanics for closing substantial spaces – such as extraction spaces – is to use a 0.019” x 0.025” stainless steel archwire and place closing coil springs from a hook on the archwire to the hook on a molar bond. Sliding mechanics are the simplest to place, adjust and control, especially since pre-adjusted appliances facilitate sliding mechanics, because the level-slot line-up means that torque can stay passive as teeth move along the wire. The effectiveness of this method was investigated by NH who found that in 5% of visits where space closing with sliding mechanics was intended, none had occurred. This figure rose to 15% for adult patients. This is clearly a significant problem to address.

Possible causes of failure of spaces to close with sliding mechanics When spaces fail to close further between visits, it is important to search systematically for possible causes.

Excessive friction This should be the first suspected cause. Friction is an important factor in tooth movement and the discussion in the chapter on Self-ligating brackets: Theory and Practice is relevant to problems of space closure. Situations in which friction may be excessive during space closure include the following:

• • • • • • • •

active forces between bracket and wire (especially torque forces) generate large friction the end of the arch wire is inside the molar tube a bracket or tube may have distorted or been inadvertently crimped with distal-end cutters ceramic brackets produce more friction (Kusy et al 1990) sometimes excessive space-closing force plus vigorous curve of Spee produces a marked bowing of the wire and this in itself may produce such friction multiple brackets distal to the space to be closed will increase friction conventional ligation increase friction – especially with elastomeric modules and especially if they are in a figure-of-8 configuration to test for excessive friction, swivel the wire from side to side within the arch - with any elastomeric ligatures removed. After one visit with an 0.019" x 0.025" working archwire in place, it should be possible to do this over a 2-3 mm range without undue effort. It is noticeable that when a closing elastic or spring is lost, the archwire frequently (almost always with self-ligating brackets) swivels to the other side until further swivelling is prevented by the archwire hook. This indicates that the applied force in one quadrant is larger than that arising from friction right round the arch (which must be greater than that in a single buccal segment) and that in that case, there was certainly net residual space closing force after subtracting frictional forces. Frictional forces are subject to very complex influences in vivo and are correspondingly hard to model in vitro. Ireland et al (1991) and many others have found that elastomeric ligation is a large factor in friction generation in vitro.

(This supports the view that self-ligating brackets would produce much lower friction - see chapter on Self-ligating brackets: Theory and Practice, which includes several references on ligation and friction). Ireland’s figures suggest that frictional forces may be approximately 200 g in a buccal segment of three teeth with pure bodily movement being mimicked. This may be a guide to choosing active closing forces in such circumstances, although it is more common only to slide through two or less brackets and applied forces of less than 200 gm usually close spaces very effectively under these circumstances.

Ireland et al also found, as have many other workers, that nickel-titanium archwires produce higher frictional forces in vitro and are therefore less suitable for sliding mechanics. In this respect the more recently developed wires with ion beam implantation (discussed in the chapter on Archwires and Biomechanics) have been shown to substantially reduce the friction in vitro on nickel-titanium and TMA wires and may possibly come to be seen as a

OPENING AND CLOSING SPACES; PROBLEMS AND SOLUTIONS EXCELLENCE IN ORTHODONTICS 2012

Figure 16.1: Glass ionomer cement on the lower molars to disclude the teeth and facilitate space closure.

Hypodontia has produced an unorthodox â&#x20AC;&#x2DC;extractionâ&#x20AC;&#x2122; pattern and increased the need for cusps to pass each other

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significant advance. However, a clever split mouth study by Kula et al (1998) of exactly this question, failed to demonstrate a statistically significant increase in the rate of space closure on the side where the TMA wire was ion implanted. The average space closure was indeed faster on the side with ion implantation (1.2 mm vs. 0.9 mm) but the power of the study did not reveal statistical significance. Further such studies would be of interest.

We usually use stainless steel wires for the majority of extraction space closure, but particularly with self-ligating brackets where loss of ligation control is virtually non-existent and applied forces can be lower, we frequently slide individual teeth or aggregate spaces on nickel-titanium wires. Stainless steel wires do, of course, have the additional advantage of greater rigidity for resisting tooth-tipping moments.

Occlusal interferences This is probably an underestimated cause of problems. Lower canine brackets can impede upper canine tips when correcting a class 2 relationship. Canine brackets are frequently placed a little too gingival in relation to the other brackets, especially if the canines are more pointed than average. This not only produces a marginally Draculoid effect but increases the chance of interference. Ricketts-type utility arches and T-loop arches also slightly increase the potential for this problem, since they cause relative canine extrusion. Unorthodox extraction patterns (e.g. extraction of upper canines) may also cause this difficulty. It is possible that the higher occlusal forces in adults and in ClassII/2 patients may contribute to greater occlusal interference and a perceived greater frequency of spaces being reluctant to close in such patients. We have become increasingly convinced that taking steps to lessen the occlusal interlocking during treatment facilitates many desirable tooth movements including space closure (Figure 16.1).

Intra-alveolar causes Retained deciduous tooth fragments or apices of extracted permanent teeth can obstruct space closure to a surprising extent. Occasionally, they are only visible on intra-oral radiographs. A rare, but not-to-be-forgotten cause.

Roots too close?

Some cases where the last bit of closure required can suddenly prove very stubborn give rise to suspicion that the cause is a too-close proximity of tooth roots on either side of the space. DPT radiographs sometimes seem to show such an appearance - particularly in the upper arch where the canine angulation is greater. With the advent of pre-angulated brackets, this was a potential cause for concern. The angulation of the brackets on the crowns should be checked, but is usually found to appear correct in such instances, although the premolar brackets may, on close inspection, be incorrectly angulated. We use canine brackets with only 6 degrees of tip (see The Development of Pre-Adjusted Appliance Systems), so this potential problem is even less likely.

Waisting of the bone It is felt by some that atrophy of the alveolus following tooth loss some years previously may prevent space closure, but we have frequently been surprised how well spaces close in such circumstances. The experimental study by Lindskog-Stockland et al.(1993) in beagle dogs supports the view that mesio-distal orthodontic tooth movement into edentulous areas definitely occurs and causes no loss of periodontal support. Such space closure may however be slower than usual.

Idiopathic!

In many instances, no definite cause can be found. There may be an undetected excessive friction, but some spaces can prove reluctant to close even with mechanics that eliminate friction as a possibility. A few patients are just obstinately spacious and there is a clinical suspicion that adults are more prone to slow space closure than growing patients. Space closure in the cases measured by NH showed a significant correlation between the sides at a given visit and this leads to the suspicion that a further factor, or factors, common to both sides of an

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individual patient are significant in the amount of space closure at a given visit. The study by Pilon (1996), also referred to in the chapter on Anchorage, strongly supports the view that tooth movement varies markedly between individuals because of variation in inherent metabolic factors. We should therefore expect the rate of space closure to vary but we should look particularly closely at significant left/right differences in rate of space closure because this suggests a local and correctable cause of such a difference, such as an occlusal interference or a local cause of increased friction.

Suggested sequence for dealing with a failure of space closure with sliding mechanics It is important to search systematically. This section principally envisages the problem to be in the buccal segments.

• • •

check for causes as listed above and remove them as appropriate if no cause can be found, and especially if the wire seems hard to swivel, assume that the friction is too high take all sensible steps to lower friction have thinner wires through the brackets where sliding needs to occur- thinning the relevant part of the archwire frequently seems to help o if the overbite situation permits, remove almost all the curve of Spee o ensure that any elastomeric ligatures on the sliding teeth are in a plain “O” configuration on one tie-wing only consider propping the bite with glass ionomer cement on the lower molars increase the force for one visit. If space-closing coils are being used, the addition of elastomeric chain is often effective, providing an initial increase in force which then reduces to the level previously provided by the coil alone consider attaching the coilspring/elastics to the first molar, leaving the second molar out of space closure for a visit or two o

• • •

This combination of steps almost always solves the problem.

•

•

if the space is still not closing, further increase in force is not advisable, usually ineffective and may be counter-productive. Check again for friction and for occlusal interferences. Consider switching to closing loops as the means of space closure. This is occasionally necessary, especially where the spaces are unavoidably situated where friction is higher and occlusal interferences more likely e.g. missing upper canines if sliding through ceramic brackets (this usually applies to anterior spaces), change the archwire.

The archwire surface may have been roughened by the ceramic bracket material

Closing spaces with loops in the archwire Advantages • friction is not a factor except for the bracket(s) between the loop and the space o

it is undoubtedly sensible on occasions to virtually eliminate friction as a possible suspect by using loops even if the spaces still prove reluctant in that particular patient, demonstrating that friction was not a significant part of the problem

Disadvantages • fabrication or a range of prefabricated wires is necessary. Loops must not impinge on any mucosa •

and must be placed accurately between brackets loops are an added oral hygiene hazard in a frequently ill-brushed section of the arch

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• • •

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loops increase flexibility at a stage when rigid wires are an advantage small, single loops are good for arch rigidity, but mean high space-closing forces and a short range of action activation can be awkward. When turning up the archwire is hard to control the activation. Turning up the archwire makes subsequent removal for adjustment very unlikely. Soldering a traction hook distal to the loop is an added nuisance.

None of these factors is very large, but they all add up to a definite clinical irritation and a good reason for preferring sliding mechanics as a routine. One option to consider is the use of prefabricated beta-titanium wires with T-loops. The lower modulus gives a better range of action with the wire still being thick enough and stiff enough to give good control. As with all prefabricated wires, a range of sizes is required.

Clinical tip: We very rarely use loops for space closure. If the guidelines above are followed, sliding mechanics is almost always the best solution

Other armamentarium for reduction of friction Wonder wire

This dual diameter wire has a rectangular anterior segment to maintain torque control in that region but with buccal segments which are round in cross section (usually 0.018"). This very good idea did not proved clinically to be very worthwhile in our hands. The round wire buccal sections are too slim for good control of tip and torque and bite opening and the cases, which do not slide well with conventional rectangular wire, do not go consistently better with Wonder Wire. Additionally, there is the need to stock wires of different length of rectangular anterior segment to accommodate arches of different dimension. It may be that there is a good clinical niche for this wire with the appropriate bracket, mechanics and force level, but in spite of trying it on a significant number of cases, we have not adopted it as part of our regular practice. Such wires are now available with the buccal segment section being 0.016" x 0.022" . This would probably retain sufficient rigidity to adequately control overbite and buccal segment alignment whilst significantly reducing friction on those teeth which were sliding. A thicker finishing wire would then become more important.

Self-ligating brackets Clinical tip: If elastic chain is used to close multiple small spaces, then placing it behind the archwire will provide the spaceclosing force with out affecting the very low friction of the self-ligation mechanism. This position for the chain is slightly less convenient (the archwire must be removed to change the chain) and a rather greater obstacle to good plaque control, but worth remembering.

These brackets have extremely low friction and provide good control and are therefore very suitable for use with sliding mechanics. They are described more fully in the chapter Self-Ligating Brackets: Theory and Practice.

Sectional mechanics Separate sections of archwire are another means of eliminating friction. These have been particularly championed

by Burstone, and a paper by Choy et al (2002) describes a further sectional system for space closure using a TMA cantilever spring in the buccal sulcus. The forces of such a system are easy to calculate, but whether the control of the segments in all planes of space is reliable and the spring sufficiently robust and free from mucosal irritation are pertinent questions. This mechanism is undoubtedly an appropriate use of the modulus and formability of beta titanium and is worth scrutiny.

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Prevention is better than cure Extractions and space closure

Figure 16.2: Mild crowding unnecessarily treated with treated with extractions. This greatly prolonged the treatment and provided the opportunity for problems with space closure

If treatment goals can be achieved without extractions, then this removes space closure as a problem. Other goals such as class 2 correction or alignment of very crowded teeth may then be harder and slower in some cases, but eliminating the possibility of unpredictably slow space closure should be one of the factors influencing extractions decisions (Figure 16.2).

Clinical tip: Detect failure of space closure at an early stage. Always cut the emerging archwire as short as the distal-end cutters permit, so that at the next visit, wire which protrudes sufficiently to permit clipping is a definite indication of space closure. (First check that the wire has not just swivelled round to that side) Several of the measures outlined for investigation of a failure to slide can be routinely incorporated to prevent such failure arising. The following practical tips seem logical:

• •

• • •

do not attempt space closure on a thick wire which needs to become passive on the teeth which need to slide - especially in the third order (torque). Some activity of curve of Spee does not usually seem a problem ensure that the wire protrudes beyond the end of the molar tube. Cut the wire to final length after insertion or - if nervous of removing bonded molar tubes - cut the ends with the anterior section held in the bracket slots and the wire lying buccal to the molar tubes. Incidentally, we do not experience molar bonds debonding with the use of distal-end cutters. It is important to concentrate on keeping the pliers parallel to the plane of the archwire with no twisting motion, but a patient, progressive squeeze! do not apply heavy initial closing forces. These forces can rotate the molar tube against the wire by a “bowstring” effect and thus increase friction if the operator wishes to reduce sources of friction from the outset, self-ligating brackets especially passive self-ligation brackets offer very low friction consider early retraction of upper canines to a class 1 relationship. This prevents occlusal interference with lower canine brackets. This option is especially attractive with self-ligating brackets which permit easy sliding but control canine rotation. A functional appliance also corrects class 2 relationships and most designs provide occlusal separation during this correction

Nickel titanium space-closing coils These coils have grown in popularity. A study by Samuels et al (1993) compared the space closing effectiveness of Alastic modules and "150 g" nickel-titanium (NT) coil springs on 0.019" x 0.025" archwires. The principal findings were:

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• • •

315

the NT springs produced more rapid and more consistent movement the NT springs produced similar average rate of space closure to that found by NH using Morita power chain, but with more consistency the Alastic modules produced approx. 33% less movement per unit time (≈ 2 mm over 5 months).

A further study by Samuels et al (1998) again demonstrated that nickel titanium coils produce more consistent space closure than elastomeric modules. Also this study showed that ‘150 g’ coils produced significantly faster space closure than ‘100 g’ coils, but increasing the force to ‘200 g’ produced no further increase in rate of closure.

150 g coils are therefore recommended.

An excellent RCT by Dixon et al (2002), compared space closure with NT coils, elastic chain and ‘active ligatures’ (a single elastic module activated with a ligature). Once again, the NT coils produced more space closure per unit time. From their results, the time required to close a 6 mm extraction space would average 17 months with an active ligature, 10 months with elastic chain and 7.5 months with NT coil. The NT coils cost more, but can be left for longer periods and do not require changing during space closure. The study started with 12 patients in each group and was designed with power to detect as statistically significant a difference of 3 mm over a four-month period. The difference of 1.83 mm between active ligatures and NT coils was statistically significant, but not the 1 mm difference between elastic chain and coils. Many clinicians would feel that a difference of 1 mm in four months was of clinical significance and that a study should therefore if possible, be designed with sufficient power to detect such a difference as statistically significant. Large numbers are hard to obtain for many studies. As in all such studies, there was a wide range of rate of space closure. For example, the standard deviation of four-month space closure with NT coils was 2 mm.

Another paper (Nightingale and Jones 2003), compared elastomeric and NT coils in vivo. Several findings are of potential interest.

• • •

the force decay of elastomeric chain was less in this study than in some other studies. The brand of chain may matter. the authors confirmed the well-known capacity for large activations of NT coils to exceed the range of the superelastic plateau, but did find a convincing plateau once the activation was in the appropriate range. there was no good relationship between force level and space closure, with one patient having no space closure over the 10-week period.

However, one might well disagree with the conclusion that there is no clinical significance in a difference between 0.84 mm/month closure with elastic chain and 1.04 mm/month for NT coils. This difference of 0.2 mm/month may not sound much, but would equate to 11.4 weeks difference in the time required to close a 6 mm space.

Also, the practical difficulties of having a good-size, homogeneous sample and following patients for a good length of time are apparent and are acknowledged by the authors.

Variation in force from nickel titanium coils Interestingly, although mostly billed as superelastic and therefore of essentially constant force, the force varies significantly with increased activation length e.g. from 45 g to 155 g for “100 g” coils when stretched between 5 and 15 mm. Also, the consistency of heat treatment during manufacture appears to vary, because the force for a given stretch varies from coil to coil of the same ostensible force. Further, there is frequently no significant difference in force for individual coils of ostensibly different force levels (eg: 100 g, 150 g, 200 g). A study by Ryan (1995) found a wide range of forces from available nickel-titanium coils, but a fairly flat plateau of force over a 5 mm range from 4 to 9 mm extension. A study by Manhartsberger and Seidenbusch (1996) found similar variability and recommended that the ‘9 mm’ coils (3 mm of actual coilspring) should not be stretched by more than 9 mm if a fairly flat superelastic plateau is to be maintained. Maganzini et al (2010) tested 14 closed NiTi coil springs from American Orthodontics, GAC, G&H, Ormco and Rocky Mountain. The mean peak load at 12 mm extension varied between 474 grams and 147 grams and only six springs exhibited changes in mean unload force of 50 grams or

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less over a deactivation range of 9 mm to 3 mm. The authors concluded that nickel titanium closed coil springs varied greatly in the peak load forces generated during activation and generated inconsistent unload forces throughout deactivation. Although nickel titanium closed coil springs with physiologic peak load forces and constant deactivation forces might be desirable, most coils tested failed to exhibit these characteristics.

A comprehensive study by Tripolt, Burstone, Bantleon and Manschiebel (1999) looked at light, medium and heavy GAC coilsprings over a range of temperatures. Many of the findings are of interest. These coilsprings seemed less variable in their force generation for a given nominal force than in other studies. A fairly flat superelastic plateau was found between 7.5 and 2.5 mm of activation and over this range there was little difference in the force from the heavy and the medium coilsprings. Use of the hysteresis effect by initial extension beyond the desired active length is recommended and is easily achieved. Over a temperature range from 30 to 40 degrees Celsius the effect of temperature on force levels was measurable but relatively small.

Force degradation in nickel titanium springs This has been investigated in vitro by Angolkar et al (1992). Interestingly, force degradation from initial force values of between 150 and 160 g did occur even though there was no movement (ie: space closure) permitted in their in vitro study design. Force decay ranged from 8% to 17% of the original force over 28 days. However this is enormously less than the figures usually found for elastomeric chain and in clinical practice no loss of performance is detected over an entire space-closing period of several months. Of course, the force provided by the NT coil will decrease in vivo as the space closes, particularly if the coil has been greatly activated and is beyond the superelastic plateau on first insertion.

Force degradation in elastomeric chain Lu et al (1993) investigated several of the relevant variables. This is an interesting comparison with the study by Angolkar. Principal findings were:

• • • •

chains from different manufacturers varied very significantly the longer the stretch, the greater the rate of decay of force none of the chains produced a force > 180 g for more than three weeks (and several for less than one week) if the starting force was less than 400 g between 50% and 70% of the force had decayed by 21 days

Baty (1994) in a very comprehensive review of elastomeric chain concluded that most studies indicate a loss of 50% to 70% of the force in the first day with only 30% to 40% remaining at 3 weeks. He also reported that prestretching the chain in order to reduce the rapid decay in force only increased the residual force at 3 weeks by 5% - clinically insignificant.

A further factor - fluoride release from chains - was investigated by Storie et al (1994). They found that the fluoride-releasing chain was unable to deliver a satisfactory force level for more than one week compared to 3 weeks for the conventional chain used for comparison. Fluoride was however released at a potentially therapeutic level. This is a product that clearly requires further development.

Nickel-titanium space closing coilsprings in practice Current research and experience suggests that NT coils are indeed a significantly faster and a more reliable method of space closure than elastomerics, which should logically be reserved for the aggregation of multiple small spaces where coil spring is impractical. Coilsprings are similar to power chain with respect to oral hygiene and gingival impingement difficulties - neither give significant problems. If stretched across a long span (e.g. 25 mm), they can distort and breakage occasionally occurs, but these are not common problems. Longer spans require a ligature to be incorporated to limit the stretch and the coils can be purchased with ligatures attached if required. Extensive data have yet to be published on the clinical effects of varying the force level, Samuels et al (1998) being a notable exception. The existing evidence supports the view that force levels over a fairly wide range are effective but that a nominal ‘150 g’ coil usually works well.

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Material

Type

Stainless steel

open

Elgiloy

open

closed closed Nickel-titanium

preformed lengths open coil bunched coil

Table 16.1:

Types of space-closing coil spring Type

Sentalloy (light) strip Sentalloy (light) preformed

Force (g) 55 65

Masel NiTi heavy (0.015")

270

Masel NiTi medium (0.012")

160

Masel NiTi light (0.010") Elgiloy Dentaurum stainless steel

55 75 (2 mm compressed = 275 g)

Table 16.2: Average forces from open coil springs - 16 mm length compressed to 10 mm

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Practical tips with nickel titanium coilsprings:

• the literature suggests that a typical 9 mm spring (3 mm of actual spring) should not be activated by more than another 9 mm. Only one size (9mm) need be purchased, but for spans longer than 20 mm it may be more convenient to use 12 mm springs than extend the coil with a ligature • to prevent dislodgement of the springs, the molar hook should be bent closed and if a ligature is used this should be wrapped round the archwire hook to prevent a similar problem at the mesial end of the spring. Occasionally the simultaneous use of intramaxillary elastics to an archwire hook causes the spring to be dislodged and the answer is to use a ligature and wrap it right round the hook • springs from different manufacturers vary in the robustness of the junction between the actual coil and the loops by which it is attached to hooks on archwires and brackets

Opening spaces We strongly prefer to open spaces by pushing rather than by pulling. This preference has arisen largely because of the advent of much more efficient coil springs, but there are also some biomechanical reasons. Usually, we wish to open space at the front of the arch. If the space is opened by pulling from the molars, this directly threatens antero-posterior anchorage. If space-opening coil springs are placed in the labial segments, the forces are partially transverse and frequently reciprocal. The transverse forces are resisted by the archwire and place less mesial force on the molars. It is also easier to prevent rotation of the teeth being moved when using push coil rather than elastic chain. Lastly, coil spring retains its force with very little and in some cases, no clinically detectable decay of force between appointments. The anchorage considerations of these mechanics are considered further in the chapters on Self-ligation: Theory and Practice and Anchorage.

Open coils seem more sensible for opening space. The only historical reason for buying closed coil and stretching it open was to retain a closed portion at each end to minimise the chance of trauma to the lips and cheek.

Stainless steel coils suffer from the enormous disadvantage that they have to be made from relatively low tensile wire because the work hardening in fabrication of a coil would otherwise cause brittle fracture. This problem does not arise with Elgiloy coils, which can be fabricated whilst soft and then heat-treated. This greatly enhances their performance although the modulus of elasticity is essentially the same for the two alloys. This effect was measured by Boshart et al (1990), Elgiloy springs having in one example 44% more wire/unit length and producing 40% less force than comparable stainless steel springs. The difference is frequently very much larger than this with many commercial coil springs (e.g.: Table 16.2).

The figures in Table 16.2 - obtained by NH - are very similar to those subsequently published by von Fraunhofer (1993) who found forces ranging from 55-70 g for light Sentalloy open coil over the same 6 mm compression and 200 g for 1 mm compression of stainless steel coil.

Nickel titanium open coil springs Nickel-titanium coils can take advantage of the lower modulus to provide a lower, more constant force over a longer range. (NB: some `heavy' nickel titanium wires can perversely provide a very high force because of the very long range of action and high elastic limit). Nickel titanium wire also suffers no clinically detectable deformation or loss of performance over a long period in the mouth, although force degradation has been demonstrated by

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Angolkar (1992) for closed springs. These potential advantages compared to Elgiloy are however not noticeable in practice. Coils of a preformed length can sometimes be too short for a given gap. Also, the very low modulus of nickel titanium necessitates very open coils and some patients find such coils traumatic to the lips and cheek. Also of interest is the difficulty in demonstrating a transformation temperature of coils made ostensibly from the same superelastic wire as archwires from the same manufacturer.

Nickel-titanium open coilsprings manufactured by GAC and 3M were tested for various properties by Bourke et al (2010). In contrast to other investigators, they found that:

• • •

the representative measured forces tended to be 10% to 40% less than the labelled value. all springs showed poor superelasticity. over time, the maximum force tended to decrease but the average force for a given deflection remained fairly constant.

This is a good, recent paper. It highlights the difficulty in properly comparing the force delivery of different springs and of interpreting the advertised force. One message is that the extent of spring compression substantially influences the force delivered. These results send the same messages as did the study by Maganzini et al (2010) for closed coilsprings. A saving grace is that we have little robust data on the relationship between force levels and tooth movement, as was discussed in the chapter on Anchorage.

OPENING AND CLOSING SPACES; PROBLEMS AND SOLUTIONS EXCELLENCE IN ORTHODONTICS 2012

References Angolkar PV, Arnold JV, Nanda RS, and Duncanson MG Jr. (1992) Force degradation of closed coil springs: An in vitro evaluation.

American Journal of Orthodontics and Dentofacial Orthopaedics 102: 127-133 Baty DL, Storie DJ, von Fraunhofer JA. (1994) Synthetic elastomeric chains: A literature review American Journal of Orthodontics and Dentofacial Orthopaedics 105: 536-542 Boshart BF, Currier GF, Nanda RS, and Duncanson MG Jr. (1990) Load deflection rate measurements of activated open and close coil springs Angle Orthodontist 60: 27-32 Bourke A, Daskalogiannakis J, Tompson B, Watson P (2010) Force characteristics of nickel-titanium open-coil springs American Journal of Orthodontics and Dentofacial Orthopaedics 138: 142.e1-142.e7 Choy K, Pae EK, Kim KH, Park YC and Burstone CJ (2002) Controlled space closure with a statically determinate retraction system Angle Orthodontist 72: 191-198 Dixon V, Read MJF, O'Brien KD, Worthington HV, Mandall NA (2002) A randomised clinical trial to compare three methods of orthodontic space closure Journal of Orthodontics 29:31-36 Ireland AJ, Sherriff M, and McDonald F. 1991) Effect of bracket and wire composition on frictional forces.

European Journal of Orthodontics 13: 322-328 Kula K, Phillips C, Gilbaro A and Proffitt WR (1998) Effect of ion implantation of TMA archwires on the rate of orthodontic sliding space closure American Journal of Orthodontics and Dentofacial Orthopaedics 114: 577-81 Kusy RP and Whitley JQ (1990) Coefficients of friction for archwires in stainless steel and polycrystalline alumina brackets.

American Journal of Orthodontics 98: 300-312 Lindskog-Stokland B, Wennstrom JL, Nyman S, and Thilander B (1993) Orthodontic tooth movement into edentulous areas with reduced bone height. An experimental study in the dog.

European Journal of Orthodontics 15: 89-96 Lu TC, Wang WN, Tarng TH, and Chen JW. (1993) Force decay of elastomeric chain-A serial study. Part II American Journal of Orthodontics and Dentofacial Orthopaedics 104: 373-377 Maganzini AL, Wong AM and Ahmed MK (2010) Forces of various nickel titanium closed coil springs Angle Orthodontist 80: 182-187 Manhartsberger C and Seidenbusch W (1996) Force delivery of Ni-Ti coil springs American Journal of Orthodontics and Dentofacial Orthopaedics 109: 8-21 Nightingale C and Jones SP (2003) A clinical investigation of force delivery systems for orthodontic space closure Journal of Orthodontics 30:229-236 Pilon JGM, Kuijpers-Jagtman AM and Maltha JC (1996) Magnitude of orthodontic forces and rate of bodily tooth movement. An experimental study American Journal of Orthodontics and Dentofacial Orthopaedics 110: 16-23 Ryan A (1995) Superelastic nickel titanium coil springs British Journal of Orthodontics 22: 370-376 Samuels RH, Rudge SJ, and Mair LH (1993) A comparison of the rate of space closure using a nickel-titanium spring and an elastic module: A clinical study American Journal of Orthodontics and Dentofacial Orthopaedics 103: 464-467 Samuels RHA, Rudge SJ and Mair LH (1998) A clinical study of space closure with nickel titanium closed coil springs and an elastic module.

American Journal of Orthodontics and Dentofacial Orthopaedics 114: 73-9

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Storie DJ, Regennitter F, and von Fraunhofer JA (1994) Characteristics of a fluoride-releasing chain Angle Orthodontist: 64: 199-210 Tripolt H, Burstone CJ, Bantleon P and Manschiebel W (1999) Force characteristics of nickel-titanium tension coil springs American Journal of Orthodontics and Dentofacial Orthopaedics 115: 498-507 von Fraunhofer JA, Bonds PW and Johnson BE. (1993) Force generation by orthodontic coil springs Angle Orthodontist 63: 145-148

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Chapter

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17 Functional appliances Nigel Harradine

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Introduction We use functional appliances in a large proportion of class 2 division i cases and this is usually integrated with a fixed appliance phase. This chapter outlines the reasoning, based on clinical experience and the evidence in the literature, which guides our case selection, choice of appliance type, and treatment timing. Also, the features that are of particular relevance to subsequent fixed appliance treatment will be discussed including extraction decisions and the use of headgear. Functional appliances are also discussed in the chapter on Class 2 Division ii Malocclusions.

Indications for functional appliances in class 2 division i malocclusions `Classic' functional appliance cases Some cases can be treated to an extremely acceptable result with functional appliances alone. These cases have a mild class 2 skeletal pattern, proclined upper incisors and no anterior or premolar crowding. Few such cases are found in the British Isles. Leaving aside for now the possibility that functional appliances may offer a qualitatively different mode of correction in Class 2 cases, a functional appliance in these cases is offering the potential for longer hours of wear than headgear and thus faster or more certain correction.

Interceptive treatment

Functional appliances are frequently advocated for early treatment. This is partly because a growth-enhancing effect is felt by some to be more likely at a younger age, partly because early treatment with fixed appliances is clearly problematic before the permanent teeth have erupted and partly to reduce the overjet early and reduce the chances of incisal trauma. Evidence in relation to all these ideas is discussed in this chapter. An additional factor in some countries, where relations between orthodontists and general dental practitioners are characterised by a degree of suspicion and financial competition, is the scope for acquiring a patient before they go elsewhere.

Compromise treatment

Some cases are not suitable for fixed appliance treatment because of, for example, poor oral hygiene. A functional appliance can offer an acceptable degree of occlusal and facial improvement.

Anchorage reinforcement Functional appliances are also a traditional means of gaining anchorage at the start of a case requiring fixed appliances, turning a testing class II case into an easy class 1 case. They are extremely good at rapidly correcting class 2 molar relationships and we frequently use them for this purpose, preferring them to headgear, because of greater compliance and effectiveness. Headgear is discussed in the chapter on Anchorage, where the types of case, which are less suitable for functional appliances, are listed. In addition, if there were features of the case that might place them in one of the above categories, (eg: good arch alignment, doubtful oral hygiene, a patient still in the mixed dentition), then functional appliances would seem even more appropriate. Conversely, where molars are significantly less than a full unit class 2 and there is substantial irregularity requiring extensive fixed appliance alignment, the patient may be more appropriately treated with fixed appliances from the start. With the development of better fixed functional appliances, this potential issue is diminishing.

Mode of action of functional appliances The eternal speculation, assertion and investigation concerning this topic continue, although better and better evidence is now available and there can remain little debate as to the average and variability of the effects.

Functional appliances can correct class 2 relationships with great rapidity and with a mode of force application which is distinct and much less obvious than with other appliances. This prompted the thought over many years that a qualitatively different mode of action is at work.

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Many authors (e.g. the reviews by Mills (1978 and 1983)) found a 1-2 mm apparent average increase in mandibular growth during active treatment in addition to the larger dentoalveolar changes. The small mandibular growth increment found in many studies could well be real, although the possibility of slight mandibular posturing must be noted.

Condylar position and changes during treatment With appliances such as the twin block that are worn virtually full-time, or fixed functional appliances of the Herbst, MARA or AdvanSync type, the rate of correction is sometimes faster than can be accounted for without attributing some of the correction to a temporary though very convincing change in condylar position. This seems very probable in the earlier results published by Pancherz (1991) showing the very short term effects of Herbst treatment and then the partial relapse over the following year. However, more recent work by the same author shows that most of the relapse is due to a reversal of the incisor tipping in both jaws (but more in the lower incisors) and that the condyle does not on average change its position within the fossa. A careful MRI analysis on two slightly small groups (20 twin-blocks and 20 controls) by Chintakanon et al (2000), also found that the condyles were essentially unchanged by functional treatment in their concentricity within the fossa, although there was a hint in the statistics that after treatment the condyles remained slightly further forward than their initial position. An MRI study by Ruf and Pancherz (1998) showed no mean change in condylar position within the fossa. More recent studies by Pancherz and co-authors (Baltromejus et al 2002 and Pancherz and Fischer 2003) have employed the concept of “effective temporomandibular joint growth”. This term combines the effects on mandibular position of three potential factors: condylar growth, glenoid fossa displacement and condylar position within the fossa. These papers have concluded that even with this wider consideration of condylar changes, “the amount and direction of TMJ changes …. were effected favourably although only temporarily in an anterior direction

by Herbst appliances”.

Key point: Functional appliances do not change the position of the condyle in the fossa in a position of centric relation.

Prospective randomised clinical trials (RCTs) Investigators into the mode of action have sometimes been divided into those with enthusiasm but no controls and those with controls but no enthusiasm. This factor certainly muddies the evidence, as do the specific methodological drawbacks highlighted by Tulloch et al (1990). The importance of good controls is highlighted by her study (Tulloch et al 1997a), which showed that favourable, or highly favourable short-term mandibular growth was exhibited by 83% of functional appliance cases but also by 31% of the untreated controls. The prospective studies that she advocated are challenging to complete successfully, but provide by far the most valid control groups for any therapeutic intervention.

We both took part in the MRC-funded multicentre prospective studies which had the necessary skilful design, suitable funding and involved random assignment of class 2 division i cases to treatment or no treatment (for at least fifteen months). This RCT compared early treatment with a twin-block and no early treatment (O’Brien et al 2003b) and found exactly 1 mm of average additional horizontal mandibular growth. This was 14% of the average overjet correction. O’Brien et al (2003a) describes the skeletal and dental effects of Herbst and twin-block cases randomly assigned in a second RCT to each appliance in older patients in the permanent dentition. The skeletal pattern enhancement in these RCTs can be described as very modest. These cases have been followed in the longer term and the long-term results have now appeared in print (O’Brien et al 2009a) and are discussed below.

It is worth noting that as long ago as 1967, Jakobsson in one of the very few prospective studies of cases randomly assigned to functional appliances, or headgear or no treatment, found no average enhancement of mandibular growth. A more recent similar study by Nelson et al (1993) also failed to find any mandibular growth enhancement by Harvolds or Frankels. The well known prospective randomised studies currently in progress and based at the University of Northern Carolina (UNC) and reported by Tulloch et al (1997b and 1998) showed a small (0.6 degrees/year) enhancement of mandibular growth in the short term, but none in the longer term. The RCT reported by Ghafari (1998), in Philadelphia, compared Frankel treatment to headgear, but had no untreated controls. It reported a modest absolute (no untreated controls) improvement in ANB of 1.3 degrees with the Frankel appliance. The RCT reported by Keeling et al (1998), from Gainsville and Seattle found an average apical

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base relationship improvement (Johnston’s pitchfork analysis) of 0.8 mm. To date all the RCTs in this field have concluded that the average enhancement of mandibular growth is approximately 1 mm with a fairly large standard deviation.

Authors continue to use descriptive text to describe the skeletal effects of appliances, which do not seem to be fully justified by the figures. For example, Manfredi et al (2001) reports “The mandible underwent a remarkable forward positioning”. Their figures show that the increase in SNB was 0.25 degrees greater than the control group with 99% confidence limits from 0.03 to 0.53 degrees.

The personal viewpoint article by Meikle (2005), which questions the value of RCTs is interesting in various respects. He states that they often only confirm the results of retrospective studies, which is certainly the case in this particular instance, but the majority view would be that the absence of selection bias and the elimination of the effects of unknown variables inherent in the randomisation process adds substantially to the confidence that can be placed in the results of retrospective studies. Another criticism is that RCTS are expensive, which they certainly are, but if they are well-conducted, they may answer the question sufficiently well that further studies of the same question or a closely-related question are then no longer appropriate. A bigger dilemma of appropriate methodology arises when universal clinical opinion fails to gain support from RCTs. Such a situation exists with superelastic nickel-titanium wires where RCTs failed to show improved performance over multistrand stainless steel aligning wires. This has not prevented their universal adoption.

The loss of growth benefits with time There is also considerable evidence that long term growth enhancement of the mandible is very much less than the short-term effects. Wieslander (1993) has recently demonstrated very encouraging short-term growth enhancement, which in the long term almost disappeared. This has also been shown by De Vincenzo (1991), Pancherz and Hansen (1986) and Pancherz and Fackel (1990). In the 1991 article, DeVincenzo wrote “This study found highly significant increases in mandibular length still present 2 years after treatment, diminished but still significant gains after 3 years, and no significant difference after 4 years”. The longer-term results from the UNC study (Tulloch et al 1998) also support these data. The authors write “The preliminary data from this trial suggest that the skeletal effects of early treatment are not maintained.” Keeling et al (1998), concluded that both the Bionator and headgear treatment resulted in skeletal pattern improvement which was “maintained”, but as has been mentioned above, one year after active treatment, the average apical base relationship improvement was only 0.8 mm compared to the untreated controls. The long-term results of the groups in the RCT by Keeling et al have also been published (Dolce et al 2007) and they show no long-term differences in the effect on the skeletal pattern from functional appliance treatment when compared to fixed appliance treatment.

(O’Brien et al 2009a) presents the final long-term results of the RCT of early Twin-block treatment which we were part of. The conclusions agree with those of other RCTs. In the long term there were no differences of skeletal pattern between those who received early (average age 9 years) Twin-block treatment and those who had 1 course of treatment in adolescence.

Pancherz, Ruf and Kohlhas (1998) also found impressive short-term growth enhancement followed by subsequent reduced rate of growth. This fascinating paper revealed in excellently clear graphs that in the long term the antero-posterior change in pogonion was actually less than in Bolton study patients matched for age and sex, although the vertical chin growth was slightly greater in the patients treated with the Herbst appliance. SerbesisTsarudis and Pancherz (2008) again showed a temporary increase in mandibular growth with a Herbst appliance, but absolutely no growth enhancement over a 2.6 year period. The short-term average growth enhancement may usefully assist overjet and molar correction, but does not appear to result in a significant long-term increase in mandibular anterior growth. (Interestingly, a group in that study treated with Tip-Edge and class II elastics showed a reduction in forward mandibular growth compared to controls). A recent paper by Wigal et al (2011) specifically investigated stability of results with a Herbst appliance and found that the 2 mm average enhancement of mandibular growth diminished to 0.4 mm by the end of the subsequent fixed appliance phase.

Optimistic reports of short-term orthopaedic effect must be viewed in this light.

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Method of measurement

A less frequently appreciated factor is the importance of the method of measurement of the mandibular growth increment. Many studies measure changes in mandibular length condylion-gnathion (Co-Gn) and frequently report impressive short-term growth increments. However, the measures which are much more relevant facially and occlusally are those which relate to the component of growth in an antero-posterior direction - e.g. parallel to the occlusal plane or perpendicular to a vertical from Nasion or the angle SNB. Also, these latter three measures will automatically include any remodelling of the glenoid fossa or forward repositioning of the condyle within the fossa, so the difficulties of accurately measuring these two potential changes are avoided with no loss of information. All studies in which both Co-Gn and a more antero-posterior measurement are used (e.g.: McNamara et al 1985) confirm that the antero-posterior effect is significantly smaller than the increase in mandibular length.

For example, Mills and McCulloch (1998) studying short term effects of twin block appliances found an impressive average enhancement of total mandibular length of 4.2 mm. compared to controls, but B point only moved 2.1mm more anteriorly and SNB was enhanced only by an average 1.6 degrees. The follow-up paper on these patients (Mills and McCulloch 2000) reported further post-treatment growth in mandibular length of 2.0 mm per year in the twin block group and 2.4 mm per year in the control group. They reported that “most of the positive gain in mandibular size achieved during the active treatment was still present three years post-treatment”.

However, in antero-posterior terms, the mandibular enhancement of 2.1 mm shrank to 1.5 mm. after this further three years - worth having, but not a large enhancement. These measurements again suggest that short-term skeletal benefit subsequently diminishes, but an important point is that the method of expressing growth clearly matters. Interestingly, Meikle (2005), seems to argue the converse – namely that the increase in anteroposterior prominence of the mandible is less important than the growth rotation or precise site of remodelling which may have underlain the anteroposterior contribution of mandibular growth which can contribute to overjet reduction or a more prominent chin. Whilst the underlying mechanism of growth is surely important for basic research, from the clinical standpoint the overall effect is surely of greater clinical significance.

Maxillary growth Slightly surprisingly, both the study by Weislander (1993) and one by Pancherz and Margareta Anehus-Pancherz (1993) showed that maxillary growth restraint actually increased relative to controls after the end of active treatment. Many other studies have found short-term maxillary restraint although this is not a universal finding.

Nelson et al (1993) and Courtney et al (1996) both found no significant maxillary restraint, nor did Keeling et al (1998) with the Frankel appliance or the UNC study with a modified Bionator. Several studies have shown equal or greater maxillary restraint by headgear. Maxillary restraint is usually measured via A point which is of course partly influenced by tooth movement. The balance of evidence suggest that maxillary restraint is modest, but less prone to subsequent dilution compared to the mandibular response

Variability of response We have mainly considered mean responses and differences. This is sensible because there are no useful predictors of individual change of skeletal pattern, but the data does show a very wide range of response. This is frequently under-emphasised. Two papers by Tulloch (1997a and 1997b), show a very wide range of skeletal response. The unpredictability of growth and of growth enhancement must be remembered in each individual case. It may well account for some of our cases going particularly well and others struggling for class 2 correction.

This is a further topic discussed by Meikle (2005), who argues that the average change in a group of patients can obscure the possibility for a very favourable growth modification effect in an individual. While this is surely true, until we can identify the factors which may indicate a potentially greater than average beneficial effect in an individual, we can only prescribe these appliances with the anticipation of an average effect. We must also remember when embarking on treatment the exactly equal possibility of unfavourable results in relation to the mean.

Face height and the response to functional appliances As Tulloch points out, there is a widespread belief that children who grow vertically will respond less well to class 2 treatment, but this is not well documented or understood. The study by Ruf and Pancherz (1997) found no evidence to support this view. The “hyperdivergent” cases in fact showed 1 mm. better mandibular response than the “hypodivergent” cases although this was not statistically significant. This evidence suggests that ‘high angle’ cases are no reason to avoid functional appliances because of the potential effects on growth.

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Incremental advancement of functional appliances

Functional appliances which can be easily advanced incrementally have been advocated on various grounds

• • •

enhancement of mandibular growth less dento-alveolar effect because lower force levels are placed on the teeth better patient compliance

There is very little evidence to support the first of these hypotheses. The extremely fastidious and useful study by DeVincenzo and Winn (1989), showed that there was no difference between the effects produced by one 6 mm advancement and two sizes of smaller incremental advancements. Very small incremental advancements produced very similar but much slower cephalometric changes. A paper presented at the 2002 British orthodontic conference by Phil Banks reported on the neat advancement mechanism he had developed for incremental advancement of twin-blocks (Carmichael et al 1999). The study he reported revealed no differences between the effects of these appliances and conventional twin-blocks. A subsequent RCT compared the effects of twin-block treatment with a single advancement to an edge-to-edge bite and the incremental advancement (Banks et al 2004). This excellent paper by the developer of this particular incremental mechanism clearly showed no advantage for the incremental method in terms of process or outcome of the treatment.

Du, Hägg and Rabie (2002) reported on a study comparing step-by-step advancement of a Herbst appliance with maximal mandibular protrusion with a Herbst. Unfortunately, the comparison was rendered much less effective by the addition of headgear to the incremental group and not to the other group. The differences found between the groups (slightly more maxillary restraint and slight closing of the MMA in the incremental group) were very consistent with the previously reported effects of addition of headgear to a functional appliance. A more recent study from the same group (Hägg et al 2008) did find some modest enhancement of forward mandibular growth with stepwise advancement of Activators and Herbst appliances Two reports of a RCT study (Gill et al 2002 and Sharma et al 2002) compared the hard and soft tissue effects of a conventional twin-block with a single large advancement and a modified twin-block named the Mini block which incorporated progressive advancement and an incisor torquing spur. The only differences of significance were that the conventional Twin-block retroclined the upper incisors a little more and advanced hard and soft tissue Pogonion approximately 2mm more on average. Lower incisor proclination was very similar. Gill and Lee (2005), in a further report on a RCT comparing these two appliances, again found no difference in the effects on skeletal pattern. Neville Bass has developed, described and demonstrated the Dynamax appliance (Bass and Bass 2003), which has an inbuilt and relatively easy mechanism for incremental advancement. This appliance is discussed in more detail below.

Incremental advancement: Almost all the evidence finds no growth benefits from incremental advancement of functional appliances.

Summary of functional appliances and growth enhancement A recent systematic review and meta analysis of the effects of functional appliances on short-term mandibular growth (Marsico et al 2011) concluded that “skeletal changes were statistically significant, but unlikely to be clinically significant”. The average increase in total mandibular length was found to be 1.79mm and the increase in A-P prominence of the mandible is of course less than that and even less in the longer term. It is gratifying that the study of which we are co-authors was one of only three found to meet the required standards for inclusion in the meta analysis.

The clinical implications of the evidence concerning the effects of functional appliances on skeletal pattern currently seem to be as follows:

•

it is probable that an average 1-2 mm. of extra short-term mandibular growth can be obtained. This is clinically worthwhile, but it would not be sufficient to obviate orthognathic surgery in those cases deemed to require it before the start of treatment

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• •

• • • •

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the increasing evidence is that the long-term gain in mandibular growth is very small or nonexistent. an average 1-2 mm of long-term maxillary restraint seems possible, although many studies fail to find this. In contrast to the mandibular effect, there is some evidence that this does not relapse after active treatment, but may continue and even increase. Headgear may well be more effective for maxillary restraint. we should remember the large variability of growth - both with and without treatment Some uncertainty remains about the influence of the pubertal growth spurt on growth enhancement – see the section below we should employ the very large occlusal benefits of functional appliances in the knowledge that a large proportion of their effect is via upper incisor retroclination and distal movement of upper molars we must remember and measure the effects of reciprocal forces causing anchorage loss and specifically lower incisor labial movement

Timing of treatment This should depend on a consideration of factors relating to dental development, growth and possibly psychological development.

Dental factors

Since the teeth we wish to move are the permanent teeth, it follows that the best time to start in relation to dental development is when the permanent teeth have erupted - especially if a fixed appliance phase is to follow. A substantially earlier start because of other factors risks prolonging the treatment, since there will need to be a pause whilst teeth erupt. Also, treatment whilst deciduous teeth are being shed may pose minor problems of appliance retention or a delay in the shedding of deciduous teeth.

Dental trauma A definite potential advantage of starting treatment early is the reduced incidence of trauma to prominent upper incisors. It is however hard to weigh this against the other factors discussed here. Studies are often not clear on the degree of incisal trauma. We would feel differently about a small enamel chip and a lost incisor. On balance we feel that in general the other factors outweigh the potential reduction in dental trauma which starting at say the age of 9 years of age would confer. Perversely, O’Brien et al (2003b) found a trend to increased incisor trauma in those patients who had early reduction of overjet compared to the controls. Further data is required to better assess the risk ratios for specific degrees of damage in this respect.

Psychological factors Many papers have addressed this aspect but most have not shed convincing light on the best age for patient motivation for and ability to co-operate with orthodontic treatment. The paper by Tung and Kiyak (1998), is representative. However, some evidence is staring to emerge. O’Brien et al (2003c) reported on the psychosocial effects of early twin-block treatment and found a significant benefit from treatment in terms of increased selfconcept scores and reduced negative social experiences. O’Brien et al (2009b) showed that immediately after twin block treatment the profiles of children who had received early treatment were perceived to be more attractive by their peers than those of children who did not receive treatment.

Patient compliance and age However, the effect of age on patient compliance is of large clinical significance. The studies by O’Brien et al (2003a and 2003b) showed a significantly lower failure-to-finish rate in the younger patients when treated by the same operator with the same appliance. Similarly, the study by Banks et al (2004), found that patients younger than 12.3 years were three times more likely to complete functional treatment with twin-blocks. Patient compliance is discussed further below.

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Growth

The principal issue in this area is whether it is sensible to try to synchronise treatment with the pubertal growth spurt.

Pubertal growth spurt: - predictability An important point is that the growth spurt cannot be predicted with clinically useful accuracy. Even with longitudinal monitoring of stature, Sullivan (1983), has shown that our prediction will still be more than one year incorrect in 33% of cases. The pubertal spurt can be accurately charted once it in full swing, enabling good retrospective studies, if not clinical prediction.

Pubertal growth spurt: - amount The maxillae may grow 2-5 mm more per year at the peak of the spurt than in the year before the spurt, but the size of the spurt is again very unpredictable. Is this difference worth delaying the start of treatment for in someone who is ready from the psychological and dental development viewpoints? Also, the later growth spurts tend to be smaller. The average patient - whether male or female - will be in the very late mixed dentition or early permanent dentition when the growth spurt is at its peak.

Pubertal growth spurt: - influence on orthopaedic effects of treatment Tiziano Baccetti and others (e.g. Cozza et al 2006) have promoted the view that the potential for growth enhancement with functional appliances is significantly dependent on coinciding treatment with the pubertal growth spurt. They point out that all the RCTs in this field have inverstigated pre-pubertal patients and that an RCT on pubertal patients is needed. The difficulty with such a study is the ethical question of leaving patients of pubertal age untreated as a control group for the duration of a functional appliance treatment. A study by Baccetti et al (2000), did indeed report a larger orthopaedic effect in a group treated at or just after the onset of the pubertal growth spurt than in a group (average 10 years of age) before the pubertal spurt. However the differences were very small indeed - e.g. pogonion advanced 2.5 mm in the early group and 2.6 mm in the pubertal spurt group. Others have investigated this factor. Kopecky and Fishman (1993), using hand wrist radiographs showed that cervical headgear was more effective at retarding A point at the peak of pubertal growth than before or after. The difference was only small (1 mm average) between the earlier and peak growth groups but the older patients (up to 17 years) were on average 2 mm worse off than the peak growth group. Pancherz and Hägg (1985), found that somatic maturation did indeed have a significant effect on the mandibular skeletal and dental response, but Pancherz and Anehus-Pancherz (1993), found no such effect in relation to the maxilla.

Hansen, Pancherz and Hägg (1991), found that timing in relation to the growth spurt did not influence the longterm changes, but later treatment was associated with substantially greater stability. In a more recent paper comparing patients treated before and after peak pubertal growth rate, Konik, Pancherz and Hansen (1997), found the Herbst appliance to be equally effective at molar relationship and overjet correction in both groups. However, there was approximately 2 degrees more tipping of both upper and lower incisors in the ‘late’ group.

Omblus et al (1997), found very little difference in the response to the Bass appliance in relation to age and growth periods. Tulloch in the May 1997 paper also concluded that there was little to be gained from precisely timing early treatment to specific age/maturity markers. Ghafari et al (1998), concluded that treatment in late childhood was as effective as that in mid-childhood. It seems far from proven that coinciding treatment with the growth spurt is of significant benefit in terms of growth enhancement.

The distinction between total change in skeletal pattern during treatment and the enhancement of beneficial change This is an important distinction. The figures in table 17.1 are from the RCTs by O’Brien et al of which we were coauthors. They show that on average, total beneficial growth (natural plus any enhancement) is maximum if treatment is started at the middle of those three ages. It can reasonably 9.7 11.5 12.6 Age at start of treatment (yrs) be suggested that this is the most 2.5 4.2 2.5 Average improvement in class 2 skeletal pattern (mm) favourable time to treat a class 2 problem, thus changing the class 2 Table 17.1: Figures from O’Brien et al showing total average favourable growth (natural relationship whilst growth is at its + any enhancement) with differing ages at start of treatment

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most helpful. However it should be realised that the enhancement of growth by the functional appliance treatment was modest and was not shown to differ between these three ages.

Timing of treatment - summary • enhancement of growth is on average small and seems to be only marginally related to the •

•

•

pubertal growth spurt. However, it is probable that regardless of growth enhancement effect, treatment is assisted during periods of overall more rapid growth. dental factors are also important. We usually want to start treatment as soon as the eruption of the permanent teeth permits and this is in the late mixed dentition. When using functional appliances at the start of treatment this may be slightly earlier than with treatment using fixed appliances from the start. an earlier start than this in large class 2 discrepancies may be advantageous in terms of dental trauma and co-operation, although the former point has yet to be well supported, but it also has potential drawbacks: long treatment, loss of patient motivation and a slower growth rate. We therefore recommend resisting the temptation to start too early cooperation with functional appliances is better before 12.5 years of age (see below).

TADs and functionals: Temporary Anchorage Devices (TADs) have dramatically changed our perspective on anchorage in older Class II patients, but functional appliances remain our preferred source of anchorage in patients of the optimal age range

Is two-stage treatment a good strategy?

The phrase “two-stage treatment” means different things to different people. To some it simply means starting with one type of appliance (eg a functional) and progressing to another (eg fixed). However, the phrase is frequently taken to mean something significantly different – an early phase of treatment in the early or middle missed dentition and then some years later, a second course of treatment in the permanent dentition. In relation to this second meaning of the phrase, this extremely pertinent question has - as is frequently the case - been addressed in an investigation by Lysle Johnston (Livieratos and Johnston 1995). In two groups of non-extraction class 2 division i patients matched by discriminant analysis and all treated by one operator, they compared twostage treatment involving a Bionator followed by standard edgewise (using Tweed mechanics) with patients treated with edgewise, headgear and class 2 elastics alone. Both groups were, on average, cephalometrically indistinguishable at the end of treatment but the two-stage patients had been in treatment for an average of eighteen months longer with an average of 10 more appointments. The patients in the two-stage group averaged 10.4 years of age at the start of treatment and this lead to an average treatment time of four years. This timing is reflected in another paper by Gianelly (1995), which refers to two-phase treatments and takes for granted a substantial gap between the two treatment periods. Gianelly argues against such scheduling.

Tulloch et al (1998), reported similar findings in a progress report on the North Carolina RCT: no significant differences in the morphology of the final result and lengthy two-phase treatment. The final results from this excellent study have been published (Tulloch et al (2004). This paper clearly demonstrates that the definite early benefits of early functional or headgear treatment did not result in any shorter or simpler second phase treatment or any better final result. One interesting finding was that early functional treatment doubled the later rate of extractions in phase 2.

The final long-term results of the RCT of early Twin-block treatment which we were part of (O’Brien et al 2009a) enable a high-level comparison of early twin block treatment (average start age 9.7 years) with treatment started at an average 12 years of age (most of whom were also treated with a twin-block). The early start to treatment provided no long–term advantages in terms of skeletal pattern, self-esteem, or significant reduction in extraction rate. On the contrary, those who had the early start to treatment had more attendances, received treatment for longer times, had significantly poorer final dental occlusion and incurred substantially greater costs than those who started at age 12.

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Stage

Twin-block

Average duration (months)

Range of duration (months)

8

3-14

Nights-only twin-block

2

1-4

Fixed appliances

15

10-23

Total

25

18-33

Two-phase treatment with a long mid-treatment pause must be seriously questioned as a generally appropriate treatment for Class 2 division i cases and we would only recommend it in occasional cases.

A study of 204 patients by von Brennan and Pancherz (2002) also concluded that treatment in the permanent dentition was quicker and better. However, some opportunities to shed Table 17.2: Treatment durations of 120 consecutive detailed light on this were missed. The paper did not cases – Harradine and Gale 2000 differentiate between active treatment and any midtreatment pause. There was little detail about the relative severity of the cases treated at the various dental stages – for example the starting overjet or skeletal discrepancy. The age range was from 5 to 36 years.

The article by David Turpin the editor-in-chief of the American Journal of Orthodontics and Dentofacial Orthopaedics in the October issue 2007, hails the long-awaited Cochrane review into this subject which analyses the studies already mentioned in the chapter and finds scant evidence to support an early phase of treatment followed by a pause. This conclusion chimes with our interpretation of the data and the conclusion about treatment timing in the section above.

In all of these studies, the overall treatment times with functional and fixed appliance phases were significantly longer than in our personal experience - as illustrated in Table 17.2 by 120 consecutive cases from those in the study by Harradine and Gale (2000). These shorter treatment times reflect an older age at the start which permits fixed appliances to immediately follow the functional phase.

Key clinical point: Treatment with removable functional appliances followed by fixed appliances is only lengthy if started too soon.

Patient compliance with removable functional appliances The potential advantage of functionals - when compared with headgear - of full time wear and a possibly greater growth modification, is balanced by the possibility that the bulky functional appliance may prove less acceptable to the patient and that treatment may therefore fail. For example, Cohen (1981), found that 34% of patients made no progress with an historic Andresen appliance and a further 31% only partially reduced the overjet. Ghafari (1998), defined uncooperative children as those who refused to continue with treatment despite all efforts to retain them and found that 42% of girls and 24% of boys fell into that category with Frankel appliances. (This compared with 5% of girls and 25% of boys who did not co-operate with headgear). This is a major drawback with the Frankel appliance and largely explains its lack of popularity.

Failure rates with Twin-block appliances A study by NH and David Gale (2000), of 200 consecutively started twin block cases revealed 35 patients where the overjet failed to completely reduce to <4 mm - a rate of 17.5%. Approximately half of these 35 reduced the overjet to 4-6 mm and went uneventfully to a successful finish, leaving 9% who were in essence a complete failure, never reducing the overjet below 6 mm. Morris et al (1998), found an “overall discontinuation rate” of 14% with twinblocks which is probably comparable with the 9% failure to reduce the overjet to < 6 mm in the study by Harradine and Gale. Morris also found a significantly higher discontinuation rate of 28% with the Bass appliance.

A similar rate of failure with the Bass appliance was also reported by Malmgren et al (1987), whilst McDonagh et al (2001), again reported a failure rate with the Bass appliance (41%) which was twice that for twin-blocks (23%). The relatively high compliance rate in our hands with twin-blocks is the prime reason for making these appliances a popular choice, although the results of O’Brien et al (2003a) for older patients showed unusually high failure rates (34%) and only the result for younger patients (O’Brien 2003a) which was 19% was similar to our personal experience as quantified in the results of Harradine and Gale (2000). (Banks et al 2004), found a failure rate of 25% with twin-blocks in patients in the permanent dentition. Gill and Lee (2005), reported a failure rate of 14% with either twin-blocks or mini-block appliances.

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Clinical experience suggests that almost all failure with removable functional appliances is explained by failure to wear the appliance, although it should be noted that Tulloch et al (1998), found that the statistics in the UNC study support the view that co-operation explained little of the variation in treatment response. This may reflect the difficulties of measuring degrees of co-operation in a linear manner.

Headgear versus Bionator Wheeler et al (2002), compared success rates at correction of molar relationships (not overjet) between bionators and headgear at a relatively early age. 100% molar relationship correction was only achieved in 42% of the bionator group and in 62% with headgear. If <¼ unit class 2 was considered a success, the success rates went up to 83% with the bionator and 100 with headgear. The question of headgear compliance is considered in the chapter on Anchorage but the current trend to pessimism about the success rates with headgear are put into a useful perspective by this study. One-piece removable functional appliances are not well tolerated.

Patient cooperation and age The paper by Banks (2004), reported that patients with a start age of less than 12.3 years were three times more likely to complete functional treatment with twin-blocks. This is in line with the results in O’Brien et al (2003a and 2003b) which showed a significantly lower failure-to-finish rate in the younger patients when treated by the same operator with the same appliance.

We have a distinct clinical impression that patients for whom the twin-block necessarily gives a large anterior open bite because of the need to have blocks of sufficient height, are less likely to wear the appliance on grounds of poor facial appearance (the ‘goldfish’ look). One advantage of the Dynamax appliance is that the lock between the upper and lower appliances is lingual to the teeth and not between the occlusal surfaces. This permits a much lower occlusal separation, but as stated above, this comes at the cost of a high rate of appliance breakage. Most fixed functional appliances produce no significant occlusal separation, although occlusal disengagement is always possible as with all fixed appliances.

Choosing a functional appliance The factors to be considered when choosing between types of functional appliance should include the following:

• • • • • • •

does an appliance produce different skeletal effects? does an appliance produce different dental effects ? (e.g. less lower incisor tipping) does it work more rapidly? is it easier to make and repair? is it more robust? is it more easily tolerated? are concurrent headgear or expansion easily accomplished if required?

Author

Appliance

Proclination (degrees)

Hansen et al (1997)

Herbst

11

Pancherz et al (1989)

Herbst

8.9

Lund and Sandler (1998)

Twin-Block

7.9

Mills and McCulloch (1998)

Twin-Block

5.2

Harradine and Gale (2000)

Twin-Block

4.6

Ghafari et al (1998) Trenouth (2000) Cura and Sarac (1997) Table 17.1: appliances

Frankel 2

2.2

Twin-block

1.3

Bass/HG

0

Average lower incisor proclination with functional

The paper by Weiland and Bantleon (1995), shows the very wide ranges of reported orthopaedic vs. orthodontic ratios of effect with appliances of the same type. In view of this large variety of reported effects, we feel there is still no good evidence to discount the view of Johnston in 1986 that all functional appliances have a similar orthopaedic effect and the choice should be made on differences in dental effects (in particular the degree of upper and lower incisor tipping) and other factors in the list above. It should be noted however, that several studies hint at incisor

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tipping and skeletal response as being inversely related in the short term. For example, the paper by Vardiman et al (2001), found that although only 13.5 % of the reduction in overjet could be ascribed to mandibular growth, the mandibular skeletal reaction was significantly and inversely related to mesial movement of the mandibular dentition. Less lower incisor proclination gives more opportunity for skeletal improvement. This relates to the consideration later in this chapter on design of the lower half of the twin-block appliance

Twin-block type appliances These appliances were originally described by William Clark (1982 and 1988). We have been increasingly using other fixed mechanisms (the semi-fixed Dynamax, Flip-Lock Herbsts on archwires, AdvanSync) but as a removable functional appliance we currently continue to favour twin-block for several reasons.

• • • • • •

relatively well tolerated by the patient; Harradine and Gale (2000) and Morris et al (1998) robust and easy to repair fairly easy to advance compensatory expansion is easy concurrent headgear easy suitable for mixed or permanent dentition.

Problems with Twin-Block type appliances This list seems genuinely shorter than the list of advantages.

The lower appliance The unusual feature that makes twin-block type appliances so acceptable to patients is, we believe, the division of the appliance into two firmly retained halves. This greatly facilitates speech and a comfortable mandibular posture. However, this does require a lower appliance that fits well and is well retained. Lower teeth are not as well endowed with undercut for cribs as are uppers - particularly in a younger age group. Also, the shedding and associated mobility of deciduous teeth interfere more with a well-retained appliance than with those functional appliances that have a looser relationship with the teeth. The lingual arch of the semi-fixed Dynamax has a potential advantage in these respects.

Factors which reduce problems with the lower appliance.

• • • •

cribs on first premolars and first molars or double cribs on both premolars - wait until these teeth are there avoid treating in the presence of multiple loose deciduous teeth - wait a little or remove them have an excellent impression and technician lower incisor capping and /or ball-ended incisor clasps aid retention and stability.

Posterior open bite One of the few features that require specific consideration is the tendency to posterior open bite during treatment. This is not a big problem. The prime cause is the lack of ability in some cases of these appliances to open the bite at anything approaching the rate of overjet correction. This can be exacerbated by the extrusion of upper incisors that accompanies retroclination. The ‘basic’ twin-block appliance has no component that prevents this extrusion.

Solutions to posterior open bite

• • •

lower incisor capping and upper incisor capping or 'torquing ' spurs trimming /undermining the blocks a period of nights-only wear after overjet reduction

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â&#x20AC;˘ â&#x20AC;˘

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when overjet reduced, place URA with very steep anterior biteplane to reduce overbite and hold mandible and lower incisors forward subsequent fixed appliances

One intriguing thought arises from work showing by Lee and Proffit (1995), that nearly all human tooth eruption occurs between 8 pm and midnight. Should we get our patients to wear the twin block just in the mornings once the overjet is reduced and the remaining posterior open bite can usefully settle at night when teeth erupt?

Control of upper incisor movement It is frequently advantageous to design the appliances to minimise upper incisor retroclination and extrusion.

Minimising these movements reduces the temporary posterior open bite and the need for upper incisor torque with fixed appliances. Several other types of functional appliances have upper incisor capping and the Bass (1982), and Teuscher (1978) appliances are notable for their incisor torquing springs. Trenouth (2000) and Harradine and Gale (2000), found the same average retroclination (14 degrees) with a labial bow. Harradine and Gale demonstrated a clinically worthwhile effect in reducing upper incisor tipping (to an average of 7 degrees) and also modest (1 mm.) but definite reduction in upper incisor extrusion by incorporating torquing spurs on the upper incisors in place of a labial bow. There was no additional anchorage loss in terms of lower incisor labial movement in this study. A minor potential problem with some of these modifications is the median diastema that opens when a midline screw is used in conjunction with anterior Southend clasps. Torquing spurs which can slide distally over the central incisors during the expansion phase are therefore preferred if expansion is not carried out with a separate preliminary appliance. Gill and Lee (2005), reported a 3 degree reduction in upper incisor retroclination with incisor torquing spurs.

Interestingly, Mills and McCulloch (1998), reported very little retroclination with no labial wirework at all, but Illing et al (1998), also with no labial wirework, found an average of 9 degrees of retroclination. Results clearly vary for reasons not yet fully explained. We are using more appliances with no labial wirework. Sometimes the differential molar and incisor distal movement is a nuisance with this arrangement. However, if the labial segment is mildly crowded, leaving the upper incisors with no attachment can provide relative distal molar movement and gain useful space within the arch. A paper online ahead of print in the Angle Orthodontist (Naqoob et al) finds no significant difference in upper incisor retroclination (10 degree vs 7 degrees)with or without a labial bow.

Compliance may well be improved by an absence of upper labial wirework.

Currently favoured design features Various factors inevitably dictate variations in our favoured design e.g. very irregular teeth, missing or unerupted teeth or attempts to achieve different vertical or incisor torque effects but broadly we have favoured the following recipe.

â&#x20AC;˘

URA cribs on the upper first premolars and the upper first permanent molars. Midline screw, blocks.

The expansion could be done first as a separate pre-functional appliance phase, but we prefer to start treatment by attacking the anchorage problem as a priority with simultaneous expansion. The suggested design is intended to give good upper incisor control whilst minimising the appliance bulk and the potential for median diastema creation.

LRA double cribs on lower first and second premolars (or on 4s and 6s if the 5s are not well erupted), incisor capping, ball-ended incisor clasps, blocks. The division between upper and lower blocks should be at a steep angle to the occlusal plane and should be mesial to the lower first molars, permitting removal of the lower molar crib (if present) and grinding of the upper block if accelerated eruption of these teeth is required. A double crib on the premolars permits early eruption of the lower molar whilst having good retention. We feel that secure retention of both appliances is likely to secure higher rates of patient compliance and that this outweighs many other considerations - hence secure cribbing. Lower incisor capping is favoured to prevent overeruption

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of these teeth, deepening of the overbite and of the lateral open bite. Lower ball-ended clasps are effective at increasing lower appliance retention and are particularly useful if the premolars are not available for retention.

Taking the bite As a general rule, the bite is taken horizontally either at an edge to edge incisor relationship or at the maximum forward posture minus 2 mm - whichever is the smallest forward posture. This recipe therefore takes into account the variation in a patient’s ability to protrude the mandible. Vertically, the dimension that Figure 17.1: Dynamax with removable lower half. The matters most with twin blocks is the height of the minimal mandibular opening required is evident blocks and we advise a vertical separation of the buccal teeth (and hence height of blocks) of approximately 6 mm. Blocks of smaller height run the risk that the patient may comfortably be able to avoid forward posture when closing the teeth together. Taller blocks intrude unnecessarily on the patient’s freeway space, comfort and ability to seal the lips. The vertical incisor separation will vary with the depth of overbite.

The actual method of taking the bite is a distinct matter of personal preference and experience, but the ‘Projet’ or ‘Exactobite’ plastic jigs are a simple and effective aid if difficulties are being encountered in routinely obtaining the desired position at the first attempt. They do have the disadvantage of reducing the ability to customise the A-P and vertical dimensions of the bite to the needs of a particular patient, but the different vertical and horizontal options provided cater for the large majority of patients.

The Dynamax appliance Neville Bass has developed, described and demonstrated the Dynamax appliance, which has an inbuilt and relatively easy mechanism for incremental advancement. A paper in the Journal of Orthodontics (Bass and Bass 2003) describes this appliance and further illustrations can be seen on the Dynamax website. NH has found this appliance to be as well tolerated and effective as the twin-block appliance when it remains intact, but so prone to breakage that we stopped using it three years ago. A substantial RCT involving this appliance and twin-block appliances was conducted in the UK (Thiruvenkatachari et al 2010) but was discontinued after 18 months by the data monitoring committee on the grounds that the Dynamax was significantly less effective and much more prone to breakages, soft-tissue trauma and unscheduled attendances. This is a pity because the appliance has some definite potential advantages. An increase in the breakage rate for Dynamax in comparison with twin-block was also found in an earlier study (Lee et al 2007).

Suggested Dynamax advantages • one less-mentioned but definite advantage of an appliance with incremental advancement and minimal opening is the lack of requirement for a postured bite. The retruded and completely closed bite registration required (as for study models) is much more rapid and much more reproducible • the vertical opening of the mandible is minimal (Figure 17.1). This produces a less ‘goldfish’ appearance in patients with reduced or open bites and may increase compliance in those patients • the anterior bite plane effect is useful in deep bite cases • conversely, the posterior occlusal stop helps control molar eruption in cases with reduced overbite • with a lower lingual arch, simultaneous full lower arch fixed appliance treatment can take place, easing the transition to the non-functional phase and potentially shortening treatment. This is a potentially powerful source of treatment efficiency, but is probably better harnessed by fixed functional appliances.

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Dynamax disadvantages and problems • the pre-formed wire ‘hangers’ can fatigue and frequently break spontaneously or on adjustment (Figure 17.2). This is a major problem and probably results from metal fatigue caused by repeated flexing of the hangers on closure. It is very hard to adjust the hangers to eliminate this.

• the hangers need care and skill to adjust optimally (Figure 17.3). The size of the lingual ‘steps’ in the lower appliance needs careful control. Too small and the patient can posture past one of them and deflect the hanger lingually on every closure – probably increasing the chance of wire fatigue. Too big and they can be uncomfortable on the tongue.

• breakage of the lower molar bands. This can reportedly be reduced by the use of bands of a thicker gauge. Stocking an additional set of lower molar bands is a nuisance. Using thicker bands for all purposes might require better separation. We use relatively few molar bands, preferring to bond except when lingual or palatal arches etc are required such as in this instance.

Clinical tips with Dynamax appliance Many of these are directed at minimising breakage

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when fitting, and particularly after advancing, the appliance, try to ensure that the width is perfect between the hangers and that a hanger is not being deflected lingually by the lower ‘step’ on closure. This can be hard to see, but is usually possible (Figure 17.3). Hangers that are slightly too lingual may slip past a step and leave an incomplete interdigitation of upper and lower appliances.

This may prevent full forward posture and may predispose to wire fatigue and fracture. use the fixed (lingual arch) lower half of the appliance option where possible. make sure the steps on the lingual arch run in the coronal plane or posteriorly and medially, but definitely not forwards and medially (Figure 17.4). This latter configuration enhances the tendency of the upper appliance to expand the lower lingual arch. A thicker wire for the lingual arch (1.14 mm) also helps in this regard.

Consider an initial advancement of 5-6 mm rather than the recommended 3 mm. This reduces the number of advancements of the hangers and hence the risk of breakage during adjustment. do not expand the upper appliance at the first visit. when expanding the upper appliance take care to keep the two halves of the URA in the same plane and keep the expansion gentle or retention will be jeopardised.. when expanding the upper, remember at the next visit to slightly narrow the transverse width between the hangers to prevent mucosal contact in the lower lingual sulcus. do not extend the upper bite plane below the upper incisor tips – it significantly increases the

Figure 17.2: A hanger broken at a typical site – emergence from the Figure 17.3: The challenge in visualising and adjusting the acrylic. Careful adjustment may lessen the incidence of this problem relationship between the upper hangers and the lower steps as the mouth closes can be seen

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conspicuousness of the appliance.

The Dynamax works very well when it does not break!

It needs more skill and thought when being constructed and adjusted than may be recognised. It is still possible that further refinement will improve the ratio of success to frustration.

Integration with the fixed appliance phase Timing of treatment As discussed above, we feel that the functional phase is usually best timed to produce a reduced overjet at a stage of dental development that permits the full fixed appliance phase to follow immediately. This avoids a long delay during which patient enthusiasm may be needlessly wasted. Since the sagittal correction is rapid, it is sensible to start both upper arch expansion with a twin-block (and headgear if required), at the first appointment. Following overjet correction, a subsequent two-month period of nights-only wear may allow some adaptation to a possibly postured condyle. Nights-only wear cannot be started if upper arch expansion is still required and hence the sense in a prompt start to expansion to avoid prolonging the period of full-time wear for this reason alone. If earlier `interceptive' treatment is performed, the patient and parent must be aware of the lengthy overall treatment time, whilst eruption of further teeth is awaited.

Figure 17.4: A thick (1.14 mm) lingual arch with transverse not oblique steps to minimise lower molar expansion

Clinical tip: Start when the first premolars have erupted It is sensible to reduce the overjet to 2 mm or less with the functional appliance to give an element of over-correction

The anchorage effect of distal tipping All the upper teeth will frequently be distally angulated relative to their starting angulation and the consequent uprighting with fixed appliances is an immediate anchorage demand. This distal tipping is variable. In addition, if the functional appliance has caused a temporary, but undetectable, anterior position of the condyles, the rebound of this effect will put an additional demand on anchorage at this stage. There may be some rebound of overjet in the early stages of fixed appliance treatment, and class 2 traction can be added from an early stage, particularly if self-ligating brackets are guaranteeing good tooth control. Headgear can easily be added if required, or as a precaution, it can be continued through the changeover stage, but we never add headgear these days.

Lower incisor proclination and extraction decisions Lower incisor proclination is a feature of almost all functional appliance treatment. Studies show a wide range of proclination with any given appliance and a wider range between different appliances. Appliances which are tooth-borne, such as the Herbst appliance, seem to produce greater proclination as might be expected (average 2.4 mm) for class 2 division i cases in Obijou and Pancherz (1997), 3.2 mm or 11 degrees in Hansen, Koutsonas and Pancherz(1997). Conversely, there is evidence from several papers (e.g. Cura et al (1996), Cura and Sarac (1997), Illing et al (1998), that the Bass appliance which places no direct pressure behind the lower incisors can produce very little labial incisor movement, albeit with slower overjet reduction. Pancherz and Hansen (1988), demonstrated the effects of various modifications of the Herbst appliance, all of which failed to prevent lower incisor proclination. Lund and Sandler (1998), reported average proclination of 8 degrees with a large standard deviation of 7 degrees. This is a little more than values found by Harradine and Gale (mean 4.6 degrees or 1.7 mm and sd 4.0 degrees) and these differences may be related to slight differences in design – eg: the appliances in the latter study all had lower incisor capping. Mills and McCulloch used a lower labial ‘squasher’ of acrylic on their twin blocks and reported average proclination of 5.2 degrees sd 3.9 degrees. Trenouth (2000) used Southend clasps on the lower incisors and reported almost no lower incisor proclination.

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Clinical conclusion: The important fact is that the proclination is remembered and even more, that the variability is remembered, because it should clearly influence extraction decisions when continuing with fixed appliances

Extraction decisions at the change to fixed appliances The additional and variable potential anchorage demands outlined above should be borne in mind when making extraction decisions, but it is rarely sensible to extract more 'radically' than four second premolars, all the teeth being in a class 1 relationship or better at this stage. If it is thought - very unusually - that additional anchorage will be required, it is possibly better to add headgear at nights rather than extract upper first premolars. This reasoning arises from the fact that the exact anchorage requirement can be hard to predict - as explained above and headgear can be started or stopped, whereas extraction decisions are irreversible. Although this is logical, we have not used headgear for many years. In other respects, the extraction decision protocol is the same as that suggested in the earlier chapter on Treatment Planning. A cephalometric lateral skull radiograph can therefore extremely useful when planning extractions at the end of the functional phase. The lower incisors vary significantly in their labial movement during functional treatment. Only a lateral cephalometric radiograph can reveal this and appropriately inform the extraction decision.

It is of interest that in the UNC study reported by Tulloch (2004), 38% of the functional cases had extractions. This is in a climate of non-extraction fashion and in a treatment regimen where people might be tempted to extract less often.

Headgear decisions Functional appliances do not require headgear to reduce overjets and we do not use it.

However there are papers that support the view that the addition of headgear alters the effects of a functional appliance in ways which may be useful. A very good paper on the effect of additional headgear is that by Ozturk and Tankuter (1994). This showed modest but clinically significant effects. Additional headgear produced more maxillary restraint and less lower incisor proclination. This has again been shown by Weiland in 1997, where the addition of headgear to a Herren activator reduced the mean lower incisor proclination from 2.35 degrees to 0.25 degrees (again with a wide range) and to a lesser extent by Parkin et al (2000). Similar effects are apparent in the paper by Du, Hägg and Rabie (2002). Headgear is easily added to the twin-block type of functional appliance and the preformed headgear tubes are a very useful aid to the technicians. Concurrent use of headgear is, however, entirely optional and the policy can be argued several ways. Headgear could be thought of as potentially useful in all cases or alternatively as superfluous until the fixed appliance stage for some cases.

Possible specific indications for concurrent headgear with functional appliances:-

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non-extraction cases 'high angle' cases maxillary prominence cases

It makes theoretical sense to advocate headgear in cases where it is hoped to avoid extractions since it is in these cases that some overall labial movement of the lower incisors is very probable, so minimising this labial movement is particularly useful. If extractions are definitely planned, lower incisor proclination during the functional phase can be recovered by intratraction during the fixed phase and headgear would be much less useful. Another possible indication for headgear is a long face/'high angle' case where the intrusive headgear forces are of potential benefit. Thirdly, if the cephalometric and clinical analysis suggest that the maxilla is very prominent, the additional potential for horizontal maxillary restraint is appropriate.

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Fixed functional appliances The Herbst appliance In spite of the attractiveness of a functional appliance that is fixed to the teeth, this group of appliances has been slow to gain popularity in Great Britain. This has been partly due to reports of difficulty with robustness and cement retention of the appliance. The recent availability of commercially produced pistons and sleeves, which also permit more lateral mandibular movement, has encouraged wider use.

The version of the Herbst appliance as personally recommended by Hans Pancherz was used in the MRC-funded multicentre study (O’Brien et al 2003a) and the rate of failure to complete overall treatment was very similar in the twin-block and Herbst groups, although the failure rate during the functional phase was surprisingly high in the twin-block group (34%) and much lower in the Herbst group (13%). The PhD thesis by Tse (1994), supervised by Urban Hägg in Hong Kong, reported a very high dislodgement rate with cast Herbst appliances and a very high breakage rate with banded Herbst appliances. However, an increasing number of highly regarded clinicians are sufficiently happy with the incidence of problems to make the Herbst appliance their only functional and to use it extensively. More recent versions have more freedom of movement and seem more user-friendly. The version of this appliance which best meets the requirements of being inexpensive, rapid to fit, robust and almost never coming uncemented, will probably be much clearer in the near future.

A paper by Schaefer et al (2004), compared treatment results with a stainless-steel crown Herbst and twin-blocks.

No differences of significance were found in length of treatment or the nature of the changes. The cases were not randomised to each appliance and were not ideally matched. “Consecutive cases” were used but there are no clear details about failure rates. The functional phase averaged 13 months in both groups which differs from the results of O’Brien 2003a.

Many of the most helpful papers on the effects of functional appliances have been written by Hans Pancherz (see the bibliography for this chapter) and have involved the Herbst appliance, which he has championed. Our personal experience is relatively limited, but thoroughly documented (O’Brien 2003a) and recently growing through the use of Flip-Lock (TP Orthodontics) Herbst attachments on a full fixed appliance. Combining the extensive research literature on the Herbst with this clinical experience produces the following summary of our current views. These views may change with further personal experience.

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the Herbst appliance may reduce overjets slightly more rapidly than the Twin-block on average patients find the appliance comfortable and not excessively intrusive after the first week – similar to a twin block • there is a high rate of decementation with cast Herbst appliances. All potential users should be prepared for a problem in this respect • conversely, etching the enamel and using resin-reinforced glass-ionomer cements can make removal of the cast Herbst extremely difficult. Subsequent cement removal prior to placement of bonds is then rather lengthy • piston assemblies can become detached through mechanical failure or separated into their two halves through wide yawning. This is a moderate rather than major nuisance • some literature supports the view that there is more lower incisor proclination with the Herbst than with most other functional appliances which are less tooth-borne e.g. McNamara 1990 This may lead to more extractions as part of the Figure 17.5: TP Fliplock Herbst. This is fairly easy to add to a treatment. However, it must be remembered that fixed appliance. A thick stainless steel archwire is indicated, so all the alignment must precede the Herbst phase with Herbst appliances, a full lower fixed

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appliance is usually included during the functional phase and this will produce lower incisor proclination that would happen anyway at a later stage with more sequential use of functional and then fixed appliances.

• a functional appliance that can be rapidly and reliably incorporated with a conventional fixed appliance will probably prove very popular. Such a Herbst appliance is aiming at very similar

Figure 17.6: Diagram of MARA appliance viewed from the front from the paper by Ghislanzoni et al. Buccal arms provide the interaction between the arches

needs as the forms of fixed class ii traction discussed in the chapter on Anchorage. We have used a Fliplock Herbst appliance assembly Figure 17.5 with the ‘male’ attachments welded to rectangular tubing, which is slid over a rectangular archwire. This mechanism is simple to install and is encouragingly robust.

Fixed Twin-Blocks The fixed twin-block appliance developed by Mike Read (2001) was a very interesting development. There are two large potential advantages of this type of fixed functional appliance when compared to a Herbst or to a fixed form of class 2 traction.

• •

the appliance is on the occlusal plane and not in the buccal sulcus and therefore not confined by the narrow zone between the teeth and the cheek. This should assist robustness and possibly patient comfort because the two halves of the appliance are not permanently linked together, the problems of leverage on the fixation points does not arise during mandibular excursion

An area of potential weakness in the original design was the need for lower premolar bands to remain securely cemented. It remains to be seen how well this appliance passes the tests of being quick and easy for all clinicians to make, fit and adjust whilst also being robust. To date it has not gained widespread popularity.

The MARA appliance The Mandibular Advancement Repositioning Appliance (MARA), a noncompliance device for Class II treatment, was first proposed by Eckhart and Toll in 1998. This two-part fixed functional appliance has its interaction buccal to the line of the arch via attachments on stainless steel crowns. A recent paper by Ghislanzoni et al (2011) gives a good description of the appliance (Figure 17.6) and investigates its cephalometric effects which are very similar to all other functional appliances. We have never tried this appliance, but it has enthusiastic users and addresses the aim of simultaneous fixed and functional treatment which has obvious potential advantages. A very interesting study by Al-Jewair et al (Angle on-line ahead of print) compares effects and effectiveness in a retrospective study between this appliance and the Advansync. The results were essentially similar for both appliances, although for some reason, treatment in the MARA group (each group was treated by a different single clinician) averaged 3 years which was a year longer than the average in the Advansync group. In the study by Ghislanzoni, treatment with the MARA averaged 2.1 years with a large standard deviation.

The AdvanSync appliance

This molar-to-molar fixed functional assembly (Figure 17.7) has been developed by Terry Dischinger who has been a keen advocate of Herbst appliances and wished to integrate the fixed and functional phases. Unlike the Fliplock Herbst, the AdvanSync can be placed at the start of treatment with fixed appliances. The name of the appliance therefore reflects that the mandible can be postured forward synchronously with the start of all the other fixed appliance tooth movements.

This involves some sound interpretation of process design; there are four ways to improve a process (best remembered by the acronym SECS):

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• • • •

simplify the process (remove steps) eliminate steps combine steps or sequence the steps differently

The AdvanSync appliance seeks to shorten time by combining the anterior-posterior correction and fixed appliance phases – a logical hypothesis that requires more clinical data to prove that it works.

The intention of synchronous functional and fixed treatment using a user-friendly attachment is clearly hugely worthwhile.

Figure 17.7: AdvanSync appliance. The telescopic assembly is attached to the bands with an Allen key screw.

The appliance requires no laboratory work. Molar band separation at one visit permits selection and cementation of the molar attachments at the next visit. These attachments (Figure 17.8 to Figure 17.10) are similar to a hybrid between a molar band and a preformed crown. It is still fairly early in our experience with these appliances. This experience has been very encouraging, although as with all appliances and especially novel appliances, some problems have been experienced.

Good features of the AdvanSync • it is quick and easy to place - essentially the same as choosing and cementing four molar bands.

• the appliance can be placed on its own (as in Figures 17.8 to 17.10) or with a partial or full fixed appliance. This versatility enables placement in the mixed and permanent dentitions and a variety of biomechanical actions such as differential distal movement of upper molars to accommodate crowded teeth or ‘two-by-four’ appliances.

• the telescoping arms have a long range of action, permitting good lateral excursion • the appliance is very easily advanced either by means of the alternative screw position on the lower molars or via C spacers which are crimped over the pistons • they are usually well tolerated by patients • it effectively delivers the intended simultaneous functional and fixed appliance actions Features requiring further development Most of these points are currently being addressed in the design and manufacture.

•

de-cementation of the molar attachments is not uncommon in spite of the use of reinforced glassionomer cements. The loss of adhesion is always at the cement-band interface and would be improved by a roughened, retentive inner band surface as is frequently a feature of conventional bands

Figure 17.8: The AdvanSync Figure 17.9: The right appliance. The appliance and the fixed when mouth is fully opened appliance are frequently placed at the same visit

telescope Figure 17.10: The appliance sits neatly and comfortably at the back of the mouth.

The centreline should have been corrected with a C-spacer on the right telescope.

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only four sizes of band are provided in the kit and the addition of perhaps three more sizes would increase the probability of an optimal fit. Customised fitting is available through AOA laboratory, but we have not used that option and see the lack of need for laboratory work as a major advantage in terms of speed, convenience and cost some bands split the ends of some early piston casings detached. The design has been modified to eliminate this. the archwire tubes and hooks are gingivally placed and can impinge on the gingivae in some cases.

None of these problems is major and all are amenable to modest changes in design.

Placement of AdvanSync The best sequence is to cement the bands, place bonds in the upper and lower arches, place the archwires and then fit the telescopes (dip the Allen screws in CekaBond to prevent them coming loose). There is no need to smear the molar bands in toothpaste nor to secure them closed with an elastic as described in the appliance instructions; it is quite straightforward to fit the telescopes after the bands have been cemented. Attach the telescope to the upper molar first.

Using AdvanSync visit-to-visit • Place premolar bonds gingivally to match the gingival molar tube positioning • Unless relative distal movement of upper molars is desired, the upper molars should be tied forward to the other upper teeth.

• Expect to place one, two or more C spacers to get the overjet fully reduced, even though the molars are automatically postured to a class 1 relationship by the appliance.

• The pistons are attached to the bands with an Allen key. Give patients an Allen key to take home. If a band comes loose, it is then easy for a parent/friend to unscrew the piston. The pressing need for a return to the dental chair to sort this uncomfortable and intrusive loose piston is eliminated.

• It is inconvenient to incorporate the second molars until the class 2 relationship is fully corrected and the pistons are no longer required. The Advansync bands may well need replacing with bonds to refine the posterior occlusion at that stage.

• Although the vertical component of the force from the pistons is on the buccal side, we have not seen any adverse buccal flaring of the molars in either arch.

In summary, these appliances are inherently a good concept and with modest further refinements may be free of any practical drawbacks. Class 2 treatment in class 1 time may well be routinely achievable.

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Baccetti T, Franchi L, Toth LR, McNamara JA (2000) Treatment timing for twin block therapy American Journal of Orthodontics and Dentofacial Orthopaedics 118:159-70 Baltromejus S, Ruf S, and Pancherz H (2002) Effective temporomandibular joint growth and chin position changes: Activator versus Herbst treatment. A cephalometric roentgenographic study European Journal of Orthodontics 24:627-637 Banks P, Wright J, O’Brien K (2004) Incremental versus maximum bite advancement during twin-block therapy: A randomised controlled clinical trial American Journal of Orthodontics and Dentofacial Orthopedics 126:583-8 Bass NM (1982) Dentofacial orthopedics in the correction of skeletal class II malocclusion British Journal of Orthodontics 9: 3-31 Bass NM and Bass A (2003) The Dynamax system: a new orthopaedic appliance Journal of Clinical Orthodontics 37: 268-277 Bass DynamaX system http://www.bassdynamax.com/ Accessed: 12 February 2012 Caldwell S and Cook P (1999) Predicting the outcome of twin-block functional appliance treatment: a prospective study European Journal of Orthodontics 533-539 Carmichael GJ, Banks PA and Chadwick SM (1999) A Modification to Enable Controlled Progressive Advancement of the Twin Block Appliance 26: 9-13 Chintakanon K, Sampson W, Wilkinson T and Townsend G (2000) A prospective study of Twin-block appliance therapy assessed by magnetic resonance imaging American Journal of Orthodontics and Dentofacial Orthopedics 118:494-504 Clark WJ (1982) The twin-block traction technique European Journal of Orthodontics 4:129-38 Clark WJ (1988) The Twin-Block traction technique: a functional orthopaedic appliance system American Journal of Orthodontics and Dentofacial Orthopaedics 93: 1-17 Cohen C (1981) A study of Class 2 division I malocclusion treated with the Andresen appliance British Journal of Orthodontics 8: 159-162 Courtney M, Harkness M, Herbison P (1996) Maxillary and cranial base changes during treatment with functional appliances American Journal of Orthodontics and Dentofacial Orthopaedics 109: 616-24 Cozza P, Baccetti T, Franchi L, De Toffol L and McNamara J (2006) Mandibular changes produced by functional appliances in Class II malocclusion: A systematic review American Journal of Orthodontics and Dentofacial Orthopedics 129: 599.e1-599 Cura N, Saraç M, Öztürk Y and Sürmeli N (1996) Orthodontic and orthopaedic effects of activator, activator-headgear combination appliances and Bass appliances. A comparative study American Journal of Orthodontics and Dentofacial Orthopaedics 110: 36-45 Cura N and Sarac M (1997) The effect of treatment with the Bass appliance on skeletal Class II malocclusions: a cephalometric investigation European Journal of Orthodontics 19: 671-702

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DeVincenzo JP (1991) Changes in mandibular length before during and after successful orthopaedic correction of Class II malocclusions using a functional appliance American Journal of Orthodontics and Dentofacial Orthopaedics 99: 241-57 DeVincenzo JP and Winn MW (1989) Orthopaedic and orthodontic effects resulting from the use of a functional appliance with different amounts of protrusive activation American Journal of Orthodontics and Dentofacial Orthopaedics 97: 181-190 Dolce C, McGorray SP, Brazeau L, King GJ and Wheeler TT (2007) Timing of Class II treatment: Skeletal changes comparing 1-phase and 2-phase treatment American Journal of Orthodontics and Dentofacial Orthopaedics 132:481-9 Du X, Hägg U, Rabie ABM (2002) Effects of advancement Herbst treatment with Headgear Herbst and mandibular step-by-step advancement versus conventional Herbst appliance and maximal jumping of the mandible European Journal of Orthodontics 24:167-174 Ghafari J, Shofer FS, Jacobsson-Hunt U, Markowitz DL, Laster LL (1998) Headgear versus function regulator in the early treatment of class II division I malocclusion: A randomised clinical trial.

American Journal of Orthodontics and Dentofacial Orthopedics 113:51-61 Ghislanzoni, LTH, Toll, DE, Defraia E, Baccetti T, Lorenzo Franchi L (2011) Treatment and posttreatment outcomes induced by the Mandibular Advancement Repositioning Appliance; A controlled clinical study The Angle Orthodontist 81: 684-691 Gianelly AA (1995) One-phase versus two-phase treatment American Journal of Orthodontics and Dentofacial Orthopaedics 108: 556-559 Gill DS, Sharma A and Lee RT (2002) A prospective clinical trial comparing the dentoskeletal effects of two functional appliances Journal of Orthodontics 29:335 Gill DS and Lee RT (2005) Prospective clinical trial comparing the effects of conventional twin-block and mini-block appliances: Part 1. Hard tissue changes American Journal of Orthodontics and Dentofacial Orthopaedics 127:465-72 Hägg U, Rabie A, Bendeus M, Wong RKW, Wey MC, Du X and Pengt J (2008) Condylar growth and mandibular positioning with stepwise vs maximum advancement American Journal of Orthodontics and Dentofacial Orthopaedics 134: 525-536 Hansen K, Koutsonas TG and Pancherz H (1997) Long-term effects of Herbst treatment on the mandibular incisor segment: A cephalometric and biometric investigation American Journal of Orthodontics and Dentofacial Orthopaedics 112:92-103 Hansen K, Pancherz H, and Hägg U (1991) Long-term effects of the Herbst appliance in relation to the treatment growth period: a cephalometric study.

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American Journal of Orthodontics and Dentofacial Orthopaedics 113:40-50 Konik M, Pancherz H and Hansen K (1997) The mechanism of Class II correction in late Herbst treatment American Journal of Orthodontics and Dentofacial Orthopaedics 112:87-91

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American Journal of Orthodontics and Dentofacial Orthopedics 91:143-151 Manfredi C, Cunino R, Trani A, and Pancherz H (2001) Skeletal changes of Herbst appliance therapy investigated with more conventional cephalometrics and European norms.

Angle Orthodontist 71: 170-176 Meikle MC (2005) What do randomised clinical trials tell us about the treatment of class II malocclusions? A personal viewpoint European Journal of Orthodontics 27:105-114 Mills CM and McCulloch K (1998) Treatment effects of the twinblock appliance: a cephalometric study American Journal of Orthodontics and Dentofacial Orthopaedics 114:15-24 Mills CM and McCulloch K (2000) Posttreatment changes after successful correction of class II malocclusions with the twin-block appliance.

American Journal of Orthodontics and Dentofacial Orthopaedics 118:24-33 Mills JRE (1978) The effect of orthodontic treatment on the skeletal pattern British Journal of Orthodontics 5: 133-143 Mills JRE (1983) Clinical control of craniofacial growth - a sceptic's viewpoint In: Clinical Alterations Of The Growing Face, Monograph 14. Centre For Human Growth And Development, University Of Michigan Morris DO, Illing HM, Lee RT.(1998) A prospective evaluation of Bass, Bionator and Twin Block appliances. Part II--The soft tissues.

European Journal of Orthodontics 20:663-84.

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Nelson C, Courtney M, and Herbison P (1993) Mandibular changes during functional appliance treatment American Journal of Orthodontics and Dentofacial Orthopaedics 104: 153-161 Obijou C, Pancherz H. (1997) Herbst appliance treatment of Class II, division 2 malocclusions American Journal of Orthodontics and Dentofacial Orthopedics 112: 287-91 O’Brien K et al (2003a) Effectiveness of treatment for class II malocclusion with the Herbst or twin-block appliances: a randomized, controlled trial American Journal of Orthodontics and Dentofacial Orthopaedics 124: 128-137 O’Brien K et al (2003b) The effectiveness of early treatment for Class II malocclusion with the Twin Block appliances: A multicentre randomized controlled trial. Part 1:dental and skeletal effects American Journal of Orthodontics and Dentofacial Orthopaedics 124: 234-43 O’Brien et al (2003c) Effectiveness of early orthodontic treatment with the twin-block appliance: A multicentre randomized controlled trial.

Part 2:psychsocial effects 124: 488-495 American Journal of Orthodontics and Dentofacial Orthopaedics 124: 488–95 O’Brien et al (2009a) Early treatment for Class II Division 1 malocclusion with the Twin-block appliance: A multi-center, randomized, controlled trial American Journal of Orthodontics and Dentofacial Orthopaedics 135:573-579 O’Brien et al (2009b) Early treatment for Class II malocclusion and perceived improvements in facial profile American Journal of Orthodontics and Dentofacial Orthopaedics 135: 580-585 Omblus J, Malmgren O and Hägg U (1997) Mandibular growth during initial treatment with the Bass orthopaedic appliance in relation to age and growth periods.

European Journal of Orthodontics 19: 47-56 Ozturk Y and Tankuter N (1994) Class II: a comparison of activator and activator headgear combination appliances European Journal of Orthodontics 16: 149-157 Pancherz H (1991) The nature of class II relapse after Herbst appliance treatment. A cephalometric long-term investigation American Journal of Orthodontics and Dentofacial Orthopaedics 100: 220-33 Pancherz H and Anehus-Pancherz M (1993) The headgear effect of the Herbst appliance: A cephalometric long-term study American Journal of Orthodontics and Dentofacial Orthopaedics 103: 510-520 Pancherz H and Fackel U (1990) The skeletofacial growth pattern pre- and post- dentofacial orthopedics. A long term study of Class II malocclusions treated with the Herbst appliance European Journal of Orthodontics 12: 209-218 Pancherz H and Fischer S (2003) amount and direction of temporomandibular joint growth changes in Herbst treatment: A cephalometric long-term investigation Angle Orthodontist 73:493-501 Pancherz H and Hägg U (1985) Dentofacial orthopaedics in relation to somatic maturation American Journal of Orthodontics and Dentofacial Orthopaedics 88: 273-287 Pancherz H, Malmgren O, Hägg U, Omblus J, and Hansen K (1989) Class II correction in Herbst and Bass therapy European Journal of Orthodontics 11:17-30 Pancherz H, Ruf S and Kohlhas P (1998) “Effective condylar growth” and chin position changes in Herbst treatment: A cephalometric roentgenographic longterm study American Journal of Orthodontics and Dentofacial Orthopaedics 114: 437-46 Pancherz H and Hansen K (1986) Occlusal changes during and after Herbst treatment: a cephalometric investigation European Journal of Orthodontics 8: 215-228

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Pancherz H and Hansen K (1988) Mandibular anchorage in Herbst treatment European Journal of Orthodontics 10: 149-164 Parkin NA, McKeown HF, and Sandler PJ (2001) Comparison of 2 modifications of the Twin-block appliance in matched class II samples American Journal of Orthodontics and Dentofacial Orthopedics 119:572-7 Read MJF (2001) The integration of functional and fixed appliances The Journal of Orthodontics 28:13-18 Ruf S and Pancherz H (1997) The mechanism of Class II correction during Herbst therapy in relation to the vertical jaw base relationship: A cephalometric study Angle Orthodontist 67(4): 271-276 Ruf S and Pancherz H ( 1998) Temporomandibular joint adaptation in Herbst treatment: a prospective magnetic resonance imaging and cephalometric roentgenographic study European Journal of Orthodontics 1998;20:375-388 Schaefer AT, Mc Namara JA, Franchi L, Baccetti T (2004) A cephalometric comparison of treatment with the twin-block and stainless steel Herbst appliances followed by fixed appliance therapy.

American Journal of Orthodontics and Dentofacial Orthopedics126:7-15 Serbesis-Tsarudis C and Pancherz H (2008) “Effective” TMJ and chin position changes in class 2 treatment Angle Orthodontist 78:813–818 Sharma A, Gill D, and Lee RT (2002) Soft tissue changes produced by two types of twin-block appliances Journal of Orthodontics 29:338 Sullivan P (1983) Prediction of the pubertal growth spurt by measurement of standing height European Journal of Orthodontics 5: 189-197 Teuscher U (1978) A growth related concept for skeletal class II treatment American Journal of Orthodontics 74: 258-275 Thiruvenkatachari B, Sandler J, Murray A, Walsh T, O’Brien K (2010) Comparison of Twin-block and Dynamax appliances for the treatment of Class II malocclusion in adolescents: A randomized controlled trial American Journal of Orthodontics and Dentofacial Orthopedics 138: 144.e1-144.e9 Trenouth MJ (2000) Cephalometric evaluation of the Twin-block appliance in the treatment of Class II Division 1 malocclusion with matched normative growth data American Journal of Orthodontics and Dentofacial Orthopedics 117: 54-59 Tulloch J, Medland W, and Tuncay OC (1990) Methods used to evaluate growth modification in class II malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 98: 340-347 Tulloch J, Proffit WR, and Phillips C (1997a) Influences on the outcome of early treatment for Class II malocclusion.

American Journal of Orthodontics and Dentofacial Orthopaedics 111: 533-42 Tulloch J, Proffit WR, Phillips C and Koch G (1997b) The effect of early intervention on skeletal pattern in Class II malocclusion: A randomised clinical trial.

American Journal of Orthodontics and Dentofacial Orthopaedics 111: 391-400 Tulloch J, Proffit WR, and Phillips C (1998) Benefit of early Class II treatment: Progress report of a two-phase randomised clinical trial.

American Journal of Orthodontics and Dentofacial Orthopaedics 113: 62-72 Tulloch J, Proffit WR, and Phillips C (2004) Outcome in a 2-phase randomised clinical trial of early class II treatment American Journal of Orthodontics and Dentofacial Orthopaedics 125:657-67

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Tung AW and Kiyak HA (1998) Psychological influences on the timing of orthodontic treatment American Journal of Orthodontics and Dentofacial Orthopaedics 113: 29-39 Turpin D (2007) The long-awaited Cochrane review of 2-phase treatment American Journal of Orthodontics and Dentofacial Orthopaedics 132:423-424 Vardimon AD, Koklu S, Iseri H, Shpack N, Fricke J, and Mete L (2001) An assessment of skeletal and dental responses to the functional magnetic system (FMS) American Journal of Orthodontics and Dentofacial Orthopedics 120:416-26 Von Bremen J and Pancherz H (2002) Efficiency of early and late class II division 1 treatment American Journal of Orthodontics and Dentofacial Orthopaedics 121:31-7 Weiland FJ and Bantleon H (1995) Treatment of class II malocclusions with the Jasper Jumper appliance - a preliminary report American Journal of Orthodontics and Dentofacial Orthopaedics 108: 341-50 Weiland FJ, Ingervall B, Bantleon H-P, and Droschl P (1997) Initial effects of treatment of Class II malocclusion with the Herren activator, activator-headgear combination, and Jasper Jumper American Journal of Orthodontics and Dentofacial Orthopaedics 112:19-27 Wheeler TT, Mc Gorry SP, Dolce C, Taylor MG and King CG (2002) Effectiveness of early treatment of class II malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 121:9-17 Wieslander L (1993) Long-term effect of treatment with the headgear- Herbst appliance in the early mixed dentition. Stability or relapse?

American Journal of Orthodontics and Dentofacial Orthopaedics 104: 319-329 Wigal TG, Dischinger T, Martin C, Razmus T, Gunel E and Ngan P (2011) Stability of Class II treatment with an edgewise crowned Herbst appliance in the early mixed dentition: Skeletal and dental changes American Journal of Orthodontics and Dentofacial Orthopedics 140: 210-223 Yaqoob O, DiBiase AT, Fleming PS and Cobourne MT (on line ahead of print 2011) Use of the Clark Twin Block functional appliance with and without an upper labial bow: a randomized controlled trial Angle Orthodontist

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18 Managing overbites Nigel Harradine

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Introduction This chapter will cover the problem of increased overbites. Anterior open bites will be discussed in the chapter on The Orthodontic Management of Open Bite Cases.

Changes in overbite are influenced by skeletal growth, but within the control of the orthodontist, there are essentially only three tooth movements that can be employed to reduce an overbite:

• • •

molar (and premolar) extrusion incisor (and canine) intrusion incisor proclination

Incisor proclination reduces overbites by directing the long axis of the teeth away from the line of shortest distance between the maxillae in the incisor region. This line is approximately a perpendicular to the functional occlusal plane. This effect has been analysed by Eberhart et al (1990) who, for example, stated that 5 degrees of incisor proclination would reduce the overbite by 1 mm on average. The converse must apply equally. This is therefore a significant factor in alteration of overbite.

Mechanics for overbite reduction The following mechanisms are available for overbite reduction and will be discussed in turn.

• removable acrylic anterior bite planes • fixed anterior bite planes • • • • • • • • •

o composite bite buttons o metal eg: bite turbo Dahl appliances high-pull headgear to incisors archwire curves of Spee archwires with step-down T loops sectional archwires auxiliary archwires class 2 elastics banding second molars segmental surgery

Removable anterior bite planes These are very effective in growing patients. If a removable appliance is indicated before fixed appliances (e.g. an upper space maintainer, a pre-functional appliance or a `nudger') then this effect can be harnessed to great advantage. In some severe class 2 division ii cases, an upper removable appliance can be used to permit placement of a lower fixed appliance at the start of treatment or as part of a preliminary appliance to procline the upper incisors prior to a functional appliance. It must be borne in mind that the levelling of the lower curve of Spee achieved by the removable appliance will rapidly relapse if a good class 1 incisor relationship is not immediately established (unlikely at the start of a fixed appliance treatment in a deep bite case), or if the levelling is not immediately maintained with a lower fixed appliance with suitably stiff wires. Bite planes used before, or at the start of fixed appliance treatment definitely have a useful role, but only in a minority of cases. It is possible but awkward to employ a bite plane simultaneously with a fixed appliance but, because it is awkward, we very rarely resort to this.

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Fixed bite planes

These are increasing a little in popularity. They follow the lead suggested by Dahl (1975) in providing bite planes not made from acrylic and not necessarily removable, but focus more on a non-compliance approach specifically tailored for orthodontics. Composite buttons are easy to place freehand behind the relevant incisors. Bite turbos (Figure 18.1) are similar to lingual brackets, but without an archwire slot.

They can be made of metal, of composite or acrylic (use Orthoarch’s MiniMolds). Generous composite is often required to get a good ‘fit’.

Both of these techniques are only useful where Figure 18.1: Bite turbos the overjet is not increased and the patient cannot bite posterior to the fixed bite plane, which is necessarily limited to approximately 3 mm antero-posterior depth. This is a significant limitation of use but these are a useful adjunct to the overbite weaponry. There are three potential reservations:

• • •

one is the simple chore of removing composite from behind the incisors when the bite is reduced another is the possibility of detachment and inhalation of a fixed component, particularly a metal bite turbo, which is not retained by an archwire or by attachment to other teeth finally, there is a risk of patients choking through not being able to chew food with their buccal segment teeth. A warning to make sure that food is cut up into small pieces that require little chewing is sensible

Norbert Abels, the designer of the OPAL aesthetic self-ligating bracket is also a keen proponent of fixed bite ramps, especially when combined with class 2 elastics in a class 2 division I case. His results seem impressive and it may be that the disclusion produced by this combination is more effective than we previously thought.

Class 2 elastics These are an effective means of extruding lower molars. Additionally, they will extrude upper incisors, but the upper arch wires can be fabricated to oppose this incisor extrusion. Also, a millimetre of molar extrusion will open the bite even if accompanied by a millimetre of incisor extrusion, because the molar is closer to the condylar hinge axis. Lower arch extractions frequently necessitate class 2 elastics if lower incisor retroclination is to be avoided and the accompanying bite opening effect is frequently useful. This theory seems sound, but the author has experienced the opposite effect in practice and Figure 18.3 is an example. This is not easily explained. We should keep a vigilant eye for unexpected vertical effects of unilateral intermaxillary elastics.

Figure 18.2:

The Twin Force bite corrector

Fixed intermaxillary class 2 traction is possible through mechanisms which push rather than pull.

Jasper jumpers, Bite Fixers, Twin Force bite correctors (Figure 18.2) and Eureka springs are examples of such devices whilst the Herbst and MARA appliances are fixed functional devices which harness musculoskeletal forces in a similar direction.

A more comprehensive list of these devices and their relative merits is included in the chapter on Anchorage.

However, these ‘pushing’ devices intrude lower incisors and upper molars and unlike conventional class 2 elastics, are approximately neutral in their bite opening effect. In fact the

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absence of molar extrusive forces is a correctly advocated advantage in cases where opening mandibular rotation is a disadvantage. Intrusive effects are significant and have been quantified for the Eureka spring in a paper by Stromeyer, Caruso and de Vincenzo (2002), which showed an average of 1 mm of maxillary molar intrusion and a possible 2 mm of mandibular incisor intrusion in 4 months.

High-pull headgear to the upper incisors We have not used this form of mechanics for many years. We are wary of adding heavy forces to the teeth which studies show are the most prone to root resorption. Safety devices with J-hook headgear have not been developed. Also, headgear may be simultaneously required at the back of the arch for horizontal anchorage.

Lastly, headgear requires cooperation and at best can only be a part-time appliance. The discussion in the chapter on Anchorage apply here too.

Bonding/banding second molars This is a frequently quoted aid to bite opening. It is worth considering the possible ways in which this aid may occur, since this is less frequently explained.

Possible mechanisms: • additional vertical posterior anchorage leads to less molar extrusion and more incisor intrusion • incorporation of more posterior teeth means that any molar extrusion is more distal and therefore a more effective wedge in the occlusion.

• less distal tipping of the first molars means more effective incisor intrusive forces.

• The contribution of these mechanisms would be hard to measure accurately, both cephalometrically and in terms of controlling all the variables in a study. However, a study by Clifford et al (1999) using a typodont set in photoelastic gelatine shed some light on this issue by indicating that with a reverse curve of Spee in the lower archwire, the second molars in fact intrude rather than extrude and that the maximum extrusion if second molars are incorporated in the arch is in the second premolar and first molar region (Figure 18.4). This may suggest that the second hypothesis in the list above is not likely to be correct. However, it would be interesting to see the results of repeating this experiment without the second molars included. It is possible that the maximum extrusion would move mesially one tooth. This study using modern technology agrees with the study from 1973 (Mitchell and Stewart), which monitored the vertical changes of teeth relative to mandibular implants. They found that the largest movement was premolar extrusion and both molars and incisors were slightly intruded (an average of 1.5 mm).

The contribution of these mechanisms would be hard to measure accurately, both cephalometrically and in terms of controlling all the variables in a study. However, a study by Clifford et al (1999) using a typodont set in photoelastic gelatine shed some light on this issue by indicating that with a reverse curve of Spee in the lower archwire, the second molars in fact intrude rather than extrude and that the maximum extrusion if second molars

Figure 18.3:

The unexpected result of class 2 traction on the patients’ right side. The overbite has reduced on the left.

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Figure 18.4: Data from Clifford et al (1999) showing maximum extrusion with a reverse curve of Spee is at the second premolar and the second molar is intruded

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are incorporated in the arch is in the second premolar and first molar region (Figure 18.4). This may suggest that the second hypothesis in the list above is not likely to be correct. However, it would be interesting to see the results of repeating this experiment without the second molars included. It is possible that the maximum extrusion would move mesially one tooth.

This study using modern technology agrees with the study from 1973 (Mitchell and Stewart), which monitored the vertical changes of teeth relative to mandibular implants. They found that the largest movement was premolar extrusion and both molars and incisors were slightly intruded (an average of 1.5 mm).

Whatever the mechanism by which second molars may contribute to bite opening, we are sometimes unable to utilise the second molars because they have not erupted sufficiently until near the end of treatment or later.

Nevertheless, although bite opening can sometimes be rather slow, we rarely find overbite reduction a significant problem; so second molars may be a help in bite opening but are not a major consideration. On the few occasions when bite opening is a persistent problem, banding/bonding the second molars does not seem to make a significant difference and these cases are perhaps showing adverse vertical growth or excessive masticatory forces. Conversely, the evidence that bonding second molars is a sure way to exacerbate an anterior open bite is also mainly an unsupported opinion. The distal tipping of a first molar is a definite nuisance if curves of Spee are used for a considerable time and the second molars are not bonded.

(NB: second molars may well require banding/bonding for reasons unrelated to reduction of the overbite. We normally do bond second molars. This is covered in other chapters).

Segmental surgery This is included here simply for completeness. We have very rarely needed to employ this in our orthognathic cases. We avoid segmental surgery if at all possible, because of the risk of damage to adjacent teeth and the difficulty of achieving good occlusion and intra-arch alignment. The other means of levelling occlusal planes are almost always successful.

Curves of Spee, sectional archwires and segmental mechanics

Figure 18.5: Segmental bite-opening mechanics. Ricketts utility arch and stabilising buccal sectional wires

These are the principal mechanisms by which overbites are reduced. A recent paper by Bernstein et al (2007) examined the long-term effects of levelling the lower curve of Spee using continuous arches with reverse curves. The authors examined cases treated by â&#x20AC;&#x2DC;Wickâ&#x20AC;&#x2122; Alexander both during treatment. In line with previously mentioned studies they found that the largest contributor to overbite reduction was premolar extrusion with a smaller component from incisor intrusion. The small average relapse of levelling in later years was associated with lower incisor extrusion whilst

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the previous premolar extrusion seemed to be stable.

Segmented archwires are only attached to some of the teeth and more than one archwire is therefore required per arch. The segmentation method of treatment has been advocated by several clinicians over many years, most notably by Charles Burstone (1962), (1982) who makes a distinction between sectional archwires where the teeth in a section are always adjacent and segmental mechanics where the teeth attached to a given archwire are not necessarily adjacent. A well-known example of the latter type of wire would be a Ricketts utility arch Ricketts (1976), Ricketts et al (1976b) which is specifically designed to reduce overbites (see Figure 18.5). For the purposes of this chapter, however, no such distinction will be made between segmental and sectional since the two very frequently coexist in the treatment of a case by segmental mechanics. Bench, Gugino and Hilgers (1977) wrote a series of three articles in the Journal of Clinical Orthodontics which sum up much of the core thinking on segmental mechanics as a generally preferred form of biomechanics. It is fair to say that such ‘bioprogressive’ biomechanics is not widely advocated today. However, as usual, there are advantages in understanding and applying the less frequently-used segmental mechanics in certain circumstances.

Advantages of segmental mechanics Most of these arise from the ability to join teeth which are not adjacent and which exclude the intervening teeth from the sectional wire (Braun and Marcotte 1995). If we consider a Ricketts utility arch, it demonstrates:

• • • •

a long range of action, because of the long inter-bracket span a relatively constant direction of action more easily estimated biomechanical effects the ability to simultaneously use wires of differing load/deflection characteristics (stiffness) in the same arch • the avoidance of some unwanted effects of reciprocal forces • avoidance of frictional forces The long range of action arises from the scope for a longer spring length, which also produces a smaller angular deflection as the spring goes passive and therefore a relatively constant direction of force. A full plain archwire is in effect a succession of short springs, which individually have a short range of action and collectively are biomechanically complex.

Disadvantages of segmental mechanics • complexity of wire fabrication (in spite of some authors’ claims to the contrary) • poorer control of overall arch form • less ‘fail-safe’ effect if the case is unsupervised for a period Physical complexity has a potential price in terms of chairside time, oral hygiene difficulties and patient discomfort if the wires impinge on the mucosa. Almost all cases are easier to finish with full continuous archwires and the more difficult control of archform with segmental mechanics can increase the tooth movements required during this finishing stage. When using segmental mechanics it is necessary to ensure that the biomechanical gain is worth these potential problems.

With specific reference to overbite reduction, these pros and cons compared to full plain arches with curves of Spee are as follows.

Advantages of sectional arches (West and Levin 1989):

• more rapid relative incisor intrusion • longer range of action of the archwire • probably slightly greater incisor intrusion

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The disadvantages of sectional arches are:-

• more likely to be left active until over-correction of the overbite occurs • greater relative extrusion of the canines • a second arch levelling phase may be required to reunite the buccal and labial segments Curves of Spee have the converse strengths and disadvantages. An increased archwire curve in the upper arch and a reverse curve in the lower arch are simple to place and they maintain good control of archform.

Investigations comparing Curves of Spee to sectional arches for overbite reduction The proposed differences in intrusion and extrusion have been investigated in several studies. The paper by Dake and Sinclair (1989) is a useful insight into the relative merits in practice of the two mechanics. They found more similarities than differences between the two methods and the differences they did find do not necessarily reflect solely on the different biomechanics employed. Also, the two operators may well have had different treatment aims. A useful and incidental finding was that overcorrection of the overbite tends to be associated with labial flaring of the lower incisors and subsequent relapse to a normal overbite. This was also a feature in the cases studied by Canut and Arias (1999). Overcorrection of the deep overbite is therefore not sensible.

Interestingly, a study by Parker et al (1995) comparing curves of Spee, utility arches, Tweed anchorage preparation wires and step up/step down wires found no significant differences in the cephalometric changes produced. This is perhaps surprising especially since the changes were measured at the end of treatment and not after a retention period following active treatment, during which convergence of the differences might be expected as in the Dake and Sinclair study.

Clinical tip: We find that plain arches with curves of Spee work well in almost all cases. Although frequently initially slower than sectional arch techniques, the other advantages outlined above usually outweigh this factor.

Auxiliary archwires

Burstone-type piggyback arches (see Figure 18.6) have the potential advantage, especially in the upper arch, of permitting simultaneous overbite reduction and alignment. The potential increase in speed of overbite reduction should be weighed against the extra complexity involved, the increased oral hygiene impediment, the aesthetic detriment of having two archwires and the chance of gingival trauma. However, the lack of engagement of the auxiliary wire in the anterior brackets makes these wires easier to adapt than Ricketts ‘utility arches’ which are engaged in the slot.

In relation to overbite reduction, it is important to note that proponents such as Burstone (1977) and (Schroff 1995) recommend that no more than the four incisors should be incorporated in the intrusive segment, since if the canines were also included, this would shift the anchorage balance unacceptably towards distal tipping of the buccal segment teeth. This restriction of the intrusive forces to the incisors therefore leaves the same potential inconvenience of having to pick up the canines later as applies to a utility arch sectional wire. If the incisors are markedly proclined, then the intrusive force anterior to the centre of resistance will flare the incisors further and Burstone recommends some simultaneous intra-traction to counteract this or alternatively to construct a ridged sectional for the anterior teeth with distal extensions which permit the intrusive sectional to apply its force distal to the centre of resistance of the incisors. Both of these further modifications are biomechanically very sound but begin to make the mechanics unacceptably complex. Happily, proclined incisors are less frequently associated with deep and difficult overbites so this problem does not frequently arise.

Indications for auxiliary archwire mechanics • perhaps the situation in which this approach is most appropriate is when the incisors are upright, the canines distally angulated and an intrusive force anterior to the centre of resistance of the

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incisors in the early stages is quite helpful. This canine angulation would of course tend to place an initial extrusive force on the incisors if a continuous wire was tied in • another instance is the combination of a deep overbite and gingivally placed canines intruding the incisors to the level of the canines seems more sensible than initial extrusion of the canines • a third situation would be a very ‘gummy’ smile when every effort is being made to maximise upper incisor intrusion.

Figure 18.6: Burstone-style bite-opening mechanics with an auxiliary bite-opening wire

Fabrication of auxiliary intrusive archwires These auxiliary archwires can suitably be fabricated from 0.016 x 0.022" stainless steel with a stop bend or circle anterior to the molar tube to maintain A-P stability.

Burstone recommends a force of approximately 50 g/tooth for such intrusive wires, although some authors have used very light forces of 10 to 15 g per tooth. If more than two central incisors are being intruded in this way, then an auxiliary tube on the molars is essential, as it is for utility arch mechanics, to take the stabilising buccal sectional wires which prevent distal tipping of the molar.

Cephalometric effects of auxiliary archwires for overbite reduction The paper by Weiland et al (1996) is of particular interest since it compares Burstone mechanics with continuous arch mechanics for overbite reduction in adults. The absence of growth is an excellent feature of this sample because it enables cephalometric identification of the effects of the differing mechanics. It is not explicit in the paper whether the Burstone mechanics involved auxiliary archwires or segmented and fully engaged archwires, but the cephalometric effects would probably not differ significantly. The authors found small but definite differences. Upper incisor intrusion was 1.36 mm greater and lower incisor intrusion 0.69 mm greater in the group treated with Burstone mechanics. Also, upper molar extrusion was 1.75 mm greater and lower molar extrusion 0.74 mm greater in the continuous wire group, resulting in a greater opening of the mandibular plane angle of 1.42 degrees. These differences are not enormous and there was large variation around the means. Both methods successfully reduced the overbite. The Burstone mechanics took an average of four months longer, perhaps reflecting the greater complexity of the mechanics or perhaps the fact that in this study there was less control of lower incisor inclination in the continuous arch group (a difference which could easily have been prevented).

There is therefore little doubt that intrusive mechanics work, but the question is whether in a particular case, the size of the cephalometric differences is clinically significant in relation to the added mechanical complexity. Cases in which upper incisor intrusion would be particularly appropriate are probably the most sensible to select for Burstone mechanics.

Clinical tip: We have used Burstone–type mechanics in some such cases in a spirit of enquiry, but are yet to be fully convinced of the overall benefits and rarely consider using it now

‘Rocking chair’ Ni-Ti wires Nickel-titanium wires with pronounced curves of Spee and also pronounced horizontal curvature were originally promoted as a means of simultaneously reducing overbites and closing spaces without adverse tipping and “lingual collapse” into extraction sites. Because the wires are flexible, they also offer the prospect of full bracket engagement early in the course of treatment. Table 18.1 summarises the main points in favour and against such wires.

These wires have a definite place in the choice of mechanics for overbite reduction, but we do not use them for space closure, because intra-traction in an arch which still has a curve of Spee, works against forces in the archwire designed to level an occlusal plane. For space closure, we prefer to use stiffer stainless steel wires that need less

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Advantages and indications 1.

non-extraction arches (no need for space closure and also small inter-bracket spans mean elastic limit of stainless steel easily exceeded)

2.

earlier engagement of brackets with a rectangular wire is possible, which may speed overbite reduction.

3.

long range of action

4.

{anterior open bites :- Kim-type mechanics}

Disadvantages 1.

horizontal curvature - can cause molar rotation and premolar expansion

2.

easily left too long - do not go passive. This causes incisor proclination

3.

lingual crown torque cannot be placed in the wire

4.

asymmetric bite opening sometimes occurs

Table 18.1: Advantages, indications and disadvantages of ‘rocking chair’ nickel-titanium wires

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extravagant bends to prevent adverse tipping, since this strategy makes it easier to balance the opposing forces. Also, nickel titanium has a higher surface friction than stainless steel and is less suited to sliding mechanics on thick wires. However, if space-closing forces are not applied to a rocking chair wire, the extravagant horizontal bends in the wire may produce undesirable premolar expansion and distolingual molar rotation if the arches are left in place for long periods.

These archform changes can cause premolar crossbites (if these wires are used only in one arch).

Molar rotation is diminished by banding/bonding the second molars. The vertical curve can also act through too large a range if the wire is left in place for too long (Figure 18.7).

A more recent development is the production of wires of this type made in β-titanium (TMA). These wires have a higher modulus of elasticity and coincidentally have been produced with a smaller horizontal curve. We feel that a rocking chair archwire is of little benefit in the small gauges (eg: 0.016") since such a wire is only in place for one visit. However, in larger sizes (e.g.: 0.019" x 0.025") the very high elastic limit may be a real advantage in preventing archwire distortion and ensuring a continuing bite opening force. It may seem sensible in a difficult deep bite case to place a 0.016" x 0.022" rocker instead of the 0.016" x 0.022" or 0.016” x 0.025” plain nickeltitanium wire that would otherwise have been placed at that visit. We have also used nickel titanium rocker archwires in a number of open bite cases as a simpler means of applying Kim (1987) type mechanics (discussed in the chapter on The Orthodontic Management of Open Bite Cases). Such rocking chair wires are proving to have a useful role in certain situations and their use will probably increase without becoming the routine method of overbite reduction. They are certainly not a panacea and a small minority of cases are slow and obstinate whatever mechanics are used. These are usually the low MMA class 2 division ii cases.

Overbite control and specific features of pre-adjusted appliances Three aspects of the pre-adjusted appliances and the way in which they are placed and used are of specific relevance to the control of overbite:

•

mesial angulation in the canine brackets In a case with more distally angulated canines than the ideal, this angulation exacerbates labial segment extrusion in the early stages until the canine is at its ideal angulation. This is a larger factor in the upper arch where the canine is larger (and thus more anchorage demanding) and the required mesial angulation is greater.

We use upper canine brackets with 6 degrees of tip (angulation) which is less than for most prescriptions and so reduces this potential effect.

• placing the brackets on the FA point Adopting this bracket position frequently means that the archwires will need to diverge in order for the occlusal planes to be parallel. The operator's eye may not appreciate this need, especially in the upper arch where the difference Figure 18.7: Nickel-titanium ‘rocker’ archwires left unsupervised in clinical crown length between premolar and for too long in both arches. The resulting lower incisor proclination has incisor is often greater than in the lower arch. drawn the wire out of the second molars

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• the level-slot line up of a fully programmed appliance This facilitates sliding mechanics and thus inclines the operator more towards full, plain archwires i.e. curves of Spee in relation to bite opening. .

The importance of the upper arch

Figure 18.8: Hypothetical 15 degrees of (unwanted) labial crown torque which would result from leaving a curve of Spee of 5 mm at its' greatest depth in a full-size archwire (0.022 x 0.028") to go completely passive.

The first two features listed above focus attention on the upper arch. To fulfil the six keys, the curve of Spee in the lower arch must be between zero and 2.5 mm at its deepest concavity.

However, Andrews lays very little emphasis on the need to also get the upper curve of Spee correct and the upper arch suffers from relative neglect in discussions on overbite reduction. The following list shows some features that require more attention to be focused on the upper arch.

• •

Figure 18.9: Diagram showing labial crown tipping if a round or smaller rectangular cross-section wire with reverse curve of Spee is used to level with no measures to prevent labial tipping.

the effect of the FA point described above the upper arch is frequently ‘at fault’ with extruded incisors and canines • applying palatal root torque to incisors extrudes them. This torque is almost never applied in the lower arch • retroclining incisors extrudes them. Lower incisors are much less frequently in need of retroclination.

• correcting the angulation of distally angulated canines extrudes incisors. Upper canines are larger and need more mesial angulation.

• gummy smiles can be exacerbated. This only applies to the vertical control of upper incisors

Whatever mechanics are used, these factors must be recognised and steps taken to counteract the upper incisor extrusion. The only factor working against this advocacy of controlling the upper labial segment vertically, is the long-term tendency for less upper incisor show and more lower incisor show with age. This is discussed in the chapter on Facial Appearance, the Smile and Tooth Aesthetics.

Unwanted torque and unwanted labial tipping when levelling curves of Spee In his 1989 book, Andrews illustrates various potential pitfalls when placing curves of Spee into round and rectangular archwires. He differentiates between undesirable tipping from round wires and undesirable torque from rectangular wires.

Unwanted torque Andrews pointed out that when levelling increased curves of Spee it is possible to produce unwanted labial crown torque and unwanted buccal root torque. This possibility is however much more theoretical than real. The potential proclination effect of labial crown torque is illustrated in Figure 18.8. However, unless the rectangular archwire is almost full-size in relation to the slot (e.g. 0.021" x 0.025" in a 0.022" slot) and unless the archwire is permitted to continue acting past a flat occlusal plane, there will in reality be no labial crown torque from a wire with zero degrees of built-in torque when levelling a curve of Spee. (There may well be some labial tipping due to a less than full size archwire being employed - vide infra). In relation to Andrews' comments about buccal root torque, if a curve of Spee is placed in a straight length of wire, no torque will result. The buccal segment portion of an archwire has only slight horizontal curvature, so a little buccal crown torque will result from placing a curve of Spee and this potential problem should therefore be noted but need not be over-emphasised.

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Unwanted tip when levelling curves of Spee This, however, is a real potential problem. As mentioned above, a less than full-size archwire (whether round or rectangular), acting vertically through a bracket on the labial surface, permits labial tipping (proclination or retroclination) of that tooth (Figure 18.8). This effect - unlike the labial crown torque discussed above - starts to act as soon as the bracket is labial to the centre of resistance of the incisor and usually well before the curve of Spee is levelled. This applies to all vertically active wires including segmental archwires such as utility arches. If no concurrent or subsequent intra-traction is carried out (eg: in non-extraction arches), this labial tipping may well persist and be unwanted in the lower arch. Most rectangular archwires are less than full size and therefore carry this potential for undesirable incisor proclination. Lingual crown torque in the wire (if it is rectangular wire) would prevent this but a more convenient and controlled way of achieving this effect is to place brackets with lingual crown torque on the lower incisors. This is discussed below. The effectiveness of rectangular wire in preventing lower incisor tipping during arch levelling was investigated by AlQabandi et al (1999). Using 0.016" x 0.022" rectangular wires in an 0.018" slot they found no less labial tipping than with round wires. They correctly attribute this to the slop or play between archwire and rectangular bracket which should be 6.7 degrees of torque with this combination, although actual wires and brackets of these nominal dimensions have been reported as giving torque slop varying between 10 and 14 degrees. With 0.019" x 0.025" wires in an 0.022" slot the theoretical minimum third order play would be 8 degrees. The chief means of preventing unwanted labial tipping of lower incisors during levelling of the curve if Spee are therefore:

• • • •

a lower incisor prescription with lingual crown torque This is easy and advisable lingual crown torque in the rectangular wire This is relatively easy, but infrequently required if our favoured incisor prescription is used (Figure 18.9) intra-traction This requires space in the lower arch – usually via extractions – and may not be appropriate for that case class 3 traction This requires cooperation and may cause unwanted anchorage loss in the upper arch.

Andrews’ Class 3 (C series) brackets – lingual crown torque

It is an interesting note in orthodontic history (which tends to repeat itself if not remembered) that these lower incisor brackets with inbuilt lingual crown torque were originally intended by Andrews to enable dentoalveolar compensation for a class 3 skeletal pattern - in the lower arch this means incisor retroclination. Slightly ironically however, their most useful role is to limit unwanted lower incisor labial tipping (proclination) in class 2 cases where undersize archwires are being used to level the curve of Spee. (This is very analogous to the original intention the class 3 upper incisor brackets which were intended to permit dentoalveolar compensation in class 3 cases but became part of the Roth prescription to prevent upper incisor retroclination in class 2 cases). Series C lower incisor brackets had 6 degrees of lingual crown torque, they have become the standard Andrews prescription for the lower incisors and have now been widely adopted in many eponymous prescriptions which have for some years featured -or had as an option – lower incisor brackets with lingual crown torque. This is frequently 6 degrees. We have used such a prescription on a majority of our cases. Damon Q brackets now have a prescription with -11 degrees which in view of the 10 degrees of play with an 0.019” x 0.025” wire in an 0.022” slot is an excellent prescription in this respect. This prescription means that with a 0.0192 x 0.025” wire and a lower incisor at an almost average starting inclination, there will be essentially no labial tipping as the arch is levelled with such a wire. If the lower incisors are already Figure 18.10: Diagram showing lingual crown torque being proclined relative to the occlusal plane, then such a placed to counteract unwanted labial tip or torque of the incisors. (N.B. prescription will place active lingual crown torque on if this torque were placed in a full-size archwire, it would cause unwanted lingual crown torque unless the wire was left to go insertion. completely passive)

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Only cases where we are keen to procline the lower incisors (e.g. when decompensating a class 3 case prior to surgery) or to prevent retroclination (eg. closing excess space in a hypodontia case) are less suitable for this prescription.

It should be noted in passing that some clinicians are wary of placing a 0.019” x 0.025” wire in the lower arch of a class 3 case because of the fear of labial crown torque being applied or retroclination being limited by such a wire.

A moments’ thought confirms that with the common lower incisor prescription of -6 degrees, given the 10 degrees of slop, a tooth would need to be retroclined by 16 degrees from an average inclination before any labial crown torque was applied.

Wires with inbuilt torque in the labial segment are available and although and may be a useful addition to inclination control.

Stability of overbite reduction Investigation has shown that this is a multifactorial phenomenon. Houston (1989) has clearly shown that interincisal angulation is only a very partial explanation of the depth of overbite. He recommends paying more attention to the relationship between the upper incisor centroid and the lower incisor tip because this has a stronger correlation with depth of overbite. This is probably because it reflects other factors such as skeletal pattern. It is also a relatively easy relationship to measure when estimating the tooth movements required to achieve a potentially stable relationship.

Proclination of incisors is one of the easier ways of obtaining a good incisor tip-centroid relationship in class 2 cases and such movement is the only way of obtaining a good tip-to-cingulum contact in severe class 2 division ii cases, but the evidence is that the soft tissues will remain keen over many years to cause relapse of the proclination and it is necessary to plan for indefinite retention in such cases.

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References AlQabandi AK, Sadowsky C and BeGole EA (1999) A comparison of the effects of rectangular and round arch wires in levelling the curve of Spee American Journal of Orthodontics and Dentofacial Orthopaedics 116: 522-9 Bench R, Gugino C and Hilgers J (1977) Bioprogressive therapy, part 1 Journal Clinical Orthodontics 11: 616-627 Bernstein RL, Preston CB and Lampasso J (2007) Leveling the curve of Spee with a continuous archwire technique: A long term cephalometric study American Journal of Orthodontics and Dentofacial Orthopaedics131: 363-371 Braun S and Marcotte MR (1995) Rationale of the segmented approach to orthodontic treatment American Journal of Orthodontics and Dentofacial Orthopaedics 108: 1-8 Burstone CJ (1962) The rationale of the segmented arch American Journal of Orthodontics 48: 805-821 Burstone CJ (1982) The segmented arch approach to space closure American Journal of Orthodontics 82(5): 361-78 Burstone CR (1977) Deep overbite correction by intrusion American Journal of Orthodontics 72: 1-22 Canut JA and Arias S (1999) A long-term evaluation of treated Class II division 2 malocclusions: a retrospective study model analysis.

European Journal of Orthodontics 21: 377-386 Clifford PM, Orr JF and Burden DJ (1999) The effects of increasing the reverse curve of Spee in a lower archwire examined using a dynamic photo-elastic gelatine model.

European Journal of Orthodontics 21: 213-222 Dahl BL (1975) Alternative treatment in cases with advanced localised attrition Journal of Oral Rehabilitation 2: 209-214 Dake and Sinclair (1989) A comparison of the Ricketts and Tweed-type arch levelling effects American Journal of Orthodontics and Dentofacial Orthopaedics 95: 72-78 Eberhart BB, Kuftinec MM, Baker IM (1990) The relationship between bite depth and incisor angular change Angle Orthodontist 60: 55-58 Houston WJB (1989) Incisor edge-centroid relationships and overbite depth European Journal of Orthodontics 11: 139-143 Kim YH (1987) Anterior open bite and its treatment with multiloop edgewise archwire Angle Orthodontist 57: 290-321 Mitchell DL and Stewart WL (1973) Documented levelling of the lower arch using metallic implants for reference.

American Journal of Orthodontics 63:526-32 Parker CD, Nanda RS, and Currier GF. (1995) Skeletal and dental changes associated with the treatment of deep overbite malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 107:382-93 Ricketts, RM (1976) Bioprogressive therapy as an answer to orthodontic needs. Part I American Journal of Orthodontics 70: 241-268

3 6 1

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Ricketts RM (1976b) Bioprogressive therapy as an answer to orthodontic needs. Part II. American Journal of Orthodontics 70:359-97 Scroff B, Lindauer SJ, Burstone CJ and Leiss JBl (1995) Segmented approach to simultaneous intrusion and space closure: Biomechanics of the three-piece base arch appliance American Journal of Orthodontics and Dentofacial Orthopaedics 107: 136-43 Stromeyer EL, Caruso JM, and De Vincenzo JP (2002) A cephalometric study of the class II correction effects of the Eureka spring.

Angle Orthodontist 72: 203-210 Weiland FJ, Bantleon H-P and Droschl H (1996) Evaluation of continuous arch and segmented arch levelling techniques in adult patients - a clinical study American Journal of Orthodontics and Dentofacial Orthopaedics 110:647-52 West VC and Levin B (1989) Cephalometric evaluation of Bioprogressive therapy in the treatment of overbite Journal of Clinical Orthodontics 23:740-747

Useful related references not referred to in this chapter Lindskog-Stokland B, Wennstrom JL, Nyman S, and Thilander B (1993) Orthodontic tooth movement into edentulous areas with reduced bone height. An experimental study in the dog.

European Journal of Orthodontics 15:89-96

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19 Managing class 3 malocclusions David Birnie

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Introduction Mild class 3 malocclusions can be treated in the same manner as class 1 malocclusions with the use of some light class 3 traction to produce a class 1 buccal segment and incisor relationship.

The diagnosis and management of more severe class 3 malocclusions is however more challenging. The treatment of class 3 malocclusions has not proved as amenable to orthopaedic management or the use of functional appliances as have class 2 malocclusions.

This chapter explores the background to and current concepts in the management of the class 3 malocclusion.

Characteristics Contributing Factor

Percentage Range

Maxillary retrusion

19.5% to 37.5%

Mandibular protrusion

19.1% to 45.2%

Both the above

1.5% to 30%

Table 19.1: malocclusions

The incidence of class 3 malocclusion is variable ranging from 4% to 14% in Chinese and Japanese studies, 4% in Sweden and 1% in white Americans. The incidence of anterior crossbite in the 1993 Child Dental Health Survey in England and Wales was 10%.

Although class 3 malocclusion has often been ascribed to mandibular prognathism, a number of studies have demonstrated the problem to be more complex as shown in the

The composition of class 3

Table 19.1.

In a paper by Guyer, Ellis, Behrents and McNamara (1986), the components of class 3 malocclusion were explored and is shown in Figure 19.1. In this paper, 56% of class 3 malocclusions had maxillary deficiency as one of the components of the malocclusion.

The same paper showed that 59% of class 3 malocclusions had reduced or neutral lower facial heights and that 41% had increased lower facial heights.

Transverse discrepancy is often a feature of class 3 malocclusions and Chen et al (2008) shed some light on this. In a study that analysed the development of the dental arches and the skeletal mandibular-maxillary bases in untreated subjects with Class III malocclusions compared with a class 1 control group, they measured the maxillary skeletal base width, biantegonial widths, and maxillary and mandibular intermolar widths from cephalometric radiographs at annual intervals between the ages of 10 and 14 years. The maxillary skeletal base widths were (statistically) significantly smaller in the class 3 than in the class 1 group. No statistically significant differences were found for biantegonial widths. However, the maxillary intermolar widths were smaller in the class 3 group than in the class 1 group. This difference was statistically significant at all ages. The mandibular intermolar widths showed no significant differences between the groups. Interestingly, the class 3 group had increasing differences between the upper and lower intermolar widths as age increased from 10 to 14 years. The 30% data for maxillary and mandibular molar n=144 26% widths is shown in Figures 19.2 and 19.3.

25% 25%

22%

The implication of this finding might be to support the concept of early treatment for class 3 cases as by deferring treatment, it would seem that the malocclusion deteriorates.

20% 15%

12%

10%

8% 4%

5%

3% 1%

0% Mn+

Figure 19.1:

Mx-

Mx-/Mn+

Neutral

Mx+/Mn+

Mx-/Mn-

Mx+

Mn-

Components of class 3 malocclusions (from Guyer et al 1986)

Baccetti et al (2007) have carried out a large cross-sectional study of growth trends in class 3 patients. They found that the pubertal peak of mandibular growth occurred between stages CS3 and CS4 in the

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2

61

1.5

60

1

59

0.5

58

0

57

-0.5 mm

56 mm

365

55 54

-2 -2.5 12

13

14

Age in years Mx molar width Class 1 Mn molar width Class 1

12

13

14

-1

52 11

11

-1.5

53 10

10

-3 Age in years

Mx molar width Class3 Mn molar width Class 3

Figure 19.2: The intermolar widths from Chen et al (2008). Note how narrow the class 3 maxillary intermolar width is

Mx-Mn width Class 1

Mx-Mn width Class 3

Figure 19.3: The difference in intermolar widths from Chen et al (2008) showing the progressive narrowing of the maxillary intermolar width

Cervical Vertebral Maturation (CVM) method (see page 371) with average increases in mandibular length of 8 mm and 5.5 mm in boys and girls respectively. The duration of this phase was approximately 18 months in both sexes.

Significant changes in mandibular length continued until approximately 18 years of age with increases in the late maturation stages CS4-CS6 that were twice and three times as big respectively in girls and boys compared with subjects with normal occlusions. Increases in vertical facial dimensions in class 3 subjects occurred at both the pubertal growth spurt (corresponding with the eruption of canines and premolars) and late developmental stages (corresponding with the complete eruption of second and third molars).

Baccetti et al (2005) have previously commented on the gender differences in class 3 malocclusion. This study showed that class 3 malocclusion is associated with a significant degree of sexual dimorphism in craniofacial dimensions particularly after the age of 13 and that female subjects with class 3 malocclusion present with significantly smaller linear dimensions in the maxilla, mandible, and anterior facial heights when compared with male subjects during the circumpubertal and postpubertal periods.

Types of class 3 malocclusion Lin (2007) has written a thought-provoking book entitled Creative Orthodontics: Blending the Damon System and TADS to manage difficult malocclusions which is well worth reading. Class 3 malocclusion is far more common in the East and not surprisingly, countries such as China, Korea and Taiwan are adept at the non surgical treatment of class 3 malocclusion.

Lin divides class 3 malocclusion into three categories according to the following definitions.

•

pseudo class 3 o bilateral class 1 buccal occlusions and majority of teeth in anterior crossbite • true class 3 o anterior crossbite cases with bilateral buccal occlusions in class 3 • class 3 subdivision o anterior crossbite cases with one of the bilateral buccal occlusions in class 1 and the other in class 3 The pseudo class 3 malocclusion is often due to collapse of the arch perimeter – due to caries in some Eastern societies (caries-collapse) – or due to palatal positioning of the upper incisors in others as a result of small, missing or impacted teeth (perimeter-collapse); some cases do not fall easily in to either category and are therefore categorised as ‘regular’.

Pseudo-class 3 cases are not identified by the presence or absence of a mandibular displacement. They are an intermediate stage between class 1 and true class 3 malocclusion. The best cephalometric discriminators between

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a pseudo class 3 and a true class 3 malocclusion are lower incisor to mandibular plane inclination followed by gonial angle and SN to the mandibular plane.

Reasons for early treatment of class 3 malocclusions Hägg et al (2004) and Ngan (2005) cite the reasons for early treatment as:

•

•

• • • • •

to eliminate CR-CO discrepancies which may cause o progressive and irreversible soft tissue periodontal damage (normally labial to lower incisors) o progressive and irreversible hard tissue periodontal damage (normally labial to lower incisors) o occlusal wear as a result of the anterior crossbite temporomandibular joint o the joint may be more susceptible to dysfunction if there is a CR-CO discrepancy o remodelling may occur in the joint making correction of the crossbite more difficult at a later date to provide a more favourable environment for growth and development of the maxilla and mandible with a reduction in dental compensation to simplify later treatment and reduce the requirement for orthognathic surgery to correct the anterior displacement of the mandible before the eruption of the canines and premolars so that they can be guided into a class 1 relationship to provide space for the eruption of the buccal segments as a result of proclination of the upper incisor psychological benefits resulting from improved dental and facial appearance

Development of treatment Pseudo class 3 malocclusions Pseudo class 3 malocclusions are characterised by retroclination of the upper incisors and a forward mandibular displacement on closure. A high proportion of class 3 cases are pseudo class 3 malocclusions.

Correction of anterior crossbite (Reynolds method) Ian Reynolds (1978) described a simple way of correcting anterior cross bites which were amenable to treatment by dental compensation. This involves the use of vertical cross elastics from the palatal of the upper incisors to the labial of the lower incisors; TP Red elastics work well. Correction is normally accomplished within 14 days.

4 x 2 appliance Hägg et al (2004) have described the use of a 4 x 2 (four incisor bonds and two molar bonds/bands) appliance with advancing loops to correct pseudo class 3 malocclusions. 75% of the cases were treated with the 4 x 2 appliance only while 25% required a further phase of full fixed appliances. In no patients did the negative overjet return.

Disclusion The use of molar build-ups with glass-ionomer or composite is a method of correcting pseudo-class 3 malocclusions that we have known about and used successfully for some years. We have not seen it written up before but Tzatzakis and Gidarakou (2008) have now done so.

Orthopaedic change in class 3 malocclusions Dermaut and Aelbers (1996) have reviewed the possible effects of orthopaedic treatment in class 3 malocclusions.

50% of the studies looked at showed stimulation of maxillary growth and surprisingly, 90% showed an inhibition of mandibular projection as measured by SNB. The annual change expected was calculated as 1.8° in ANB. The changes detected are small and there is continued doubt about their clinical relevance.

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Fixed appliances The use of fixed appliances is largely confined to pseudo class 3 malocclusions. However, China shows particular expertise in the non-surgical management of challenging class 3 Lin and Gu (2004) have reported on 18 patients with severe class 3 malocclusion who had previously been diagnosed as requiring orthognathic surgery. The average age of the patients was 14.6 years and patients were treated with either Begg or Tip-Edge appliances. The selection criteria were:

• • • • • •

mesial or superior class 3 molar relationship no mandiblar displacement ANB <= -1.5º high angle cases with average value of SN-MP 34.9º ± 5.9º (four cases had an open bite) concave facial profile originally classified as surgical cases

Normal overjet and overbite were established with proclination of the upper incisors (+ 5.9º) and retroclination of the lower incisors (-6.6º). The position of the upper lip and lower lip to Sn-Pog’ at the beginning of treatment changed to positive values at the end of the treatment.

Mandibular skeletal appliances The use of chincups was a popular treatment modality based on the belief that the mandible was the major contributor to the class 3 malocclusion; they remain a method of treatment in Far Eastern populations. Chincups are of two types:

•

occipital pull o used for patients with mandibular prognathism • vertical pull o used for patients with increased anterior face height Normal wear is 14 hours a day and the recommended force levels are 300-500 g.

Most studies have found little difference in mandibular dimensions in patients treated with chincup therapy compared with a control group. Chincups cause lingual tipping of the lower incisors (Thilander 1963) and clockwise rotation of the mandible. Forces of 250g to 900g were used.

In a long-term study of chincup therapy on skeletal profile by Sugawara et al (1990), chincup therapy was effective in reducing mandibular prognathism before puberty but this advantage was then lost. The final skeletal profile with respect to the anteroposterior position of the mandible was no different between the experimental and control groups. The average duration of chincup therapy in this study was 4.5 years.

Time does not seem to result in any improvement in techniques and the disappointing results of chincup therapy are again reported in 1995 by Üner et al.

Sugawara and Mitani (1997) comment that:

• • •

the skeletal framework of class 3 malocclusion is established before puberty chincup appliances greatly improve the skeletal profile in the short term such changes are however rarely maintained during the pubertal growth spurt

However, Deguchi and McNamara (1999) have reported that chincup therapy in class 3 malocclusions results in the following changes:

• •

an increase in SNA (0.8° per year) a decrease in SNB (0.7° per year)

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•

a smaller increase in Co-Gn

This hints that chincup therapy may result in a reduction in mandibular growth. Many Asian patients have excessive mandibular growth as part of their class 3 syndrome. Retardation and redirection of mandibular growth and posterior repositioning of the mandible is therefore a desirable treatment strategy for class 3 malocclusions.

The effects of chincup therapy have been reported as:

• backward rotation or distal displacement of the mandible • retardation of mandibular growth redirection of mandibular growth vertically • remodeling of the mandible with closure of the gonial angle retardation of downward growth and reinforcement of forward growth in the maxilla

Few, if any, UK orthodontists use chincups. Ko et al (2004) investigated cephalometric determinants of successful chincup therapy – treatment in which a good facial profile, positive overbite and overjet, and Class I canine and molar occlusal relationship without severe facial and dental asymmetry (less than 2 mm) where achieved at age of 17 years or later. The authors found that patients with significant anteroposterior discrepancy, lower incisor compensation and open bite tendency had results with chincup therapy that were not subsequently maintained.

Patients were asked to wear the chincup for 12 to 14 hours per day with a force of 300 to 500 g per side during the early treatment period. The chincup force was directed toward the mandibular condylar head from the chin.

Once the anterior crossbite was corrected, the patient was instructed to wear the chincup at least 10 hours per day until slight Class II canine and molar relationships were established.

Yoshida et al (2006) studied the successful outcomes of treatment with maxillary protraction and chincaps.

Discriminant analysis showed that lower anterior facial height (ANS-Me) and gonial angle provided a two-variable model as follows: z = –0.197 x1 – 0.125 x2 + 28.5 The predictive accuracy of the equation was 84.4%.

There is as yet no method of orthodontic treatment that has been shown to reduce effectively the size of the mandible. If suitable camouflage of the malocclusion cannot be achieved then orthognathic surgery should be considered.

Intermaxillary skeletal appliances The use of intermaxillary appliances such as functional appliances (e.g.: the FR 3) has had some popularity. For most operators the results have been disappointing. The FR 3 has no effect on maxillary retrusion and the lip pads would seem to be of limited effectiveness. These appliances again rotate the mandible down and back allowing the mesial and vertical eruption of the upper first molars to contribute to the class 3 correction. They are however used by many orthodontists as a retaining appliance once successful correction of a class 3 malocclusion has taken place with maxillary protraction.

Levin et al (2008) compared 32 patients treated with an FR3 (Function Regulator 3) with an untreated control group. Patients wore the FR3 for 2.5 years followed by a retention period of at least three years. All patients were prepubertal at the start of treatment. The authors concluded that the FR3 appliance induced significant improvements in both maxillary size and position; there was an increase in effective midfacial length of 3.5 mm compared with the control group and this continued into the post treatment phase. There was no long-term inhibition of mandibular growth but there was closure of both the gonial angle and the mandibular plane angle and all skeletal and dental changes were sustained during the pubertal growth spurt.

Maxillary skeletal appliances The technique of maxillary protraction is based on work by Nanda (1978), with young and adult rhesus monkeys in which he showed that a force of approximately 500g could produce anterior displacement of the maxilla. The use

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of maxillary protraction headgear has been popularised by Delaire and Cozzani (1981) and is discussed later. It is worth remembering that rapid maxillary expansion also frequently causes forward movement of the maxillary complex.

Diagnosis Differential diagnosis of class 3 malocclusion should include the following aspects:

• • • • • •

social and medical history extraoral assessment cephalometric assessment function dental assessment growth status

Social and medical history

Many class 3 malocclusions a have a genetic basis and a familial history of significant class 3 malocclusion is a contraindication to early orthodontic treatment. Patients with cleft lip and palate may present with class 3 malocclusions. Acromegaly is a rare but a frequently quoted medical condition resulting in class 3 malocclusion.

Extraoral assessment

A full face and profile extraoral assessment is essential. Much of this is covered in the chapter on Facial Appearance, the Smile and Tooth Aesthetics. The zero meridian of Gonzalez-Ulloa, originally developed to assess the likely success of genioplasty, is a good method of assessing chin position. Soft tissue pogonion normally lies, ± 5 mm, on a vertical line through soft tissue nasion.

Lin (2007) has described his Three Rings diagnosis which attempts to classify and assess the prognosis for class 3 malocclusion without recourse to cephalometrics.

Profile in centric relation The facial profile is assessed in centric relation and classified as orthognathic or prognathic. Most studies however do not differentiate clearly between CR and CO profiles. Most pseudo class 3 cases and some true class 3 cases are orthognathic and these cases have a good prognosis for non-surgical class 3 treatment. For true class 3 cases where centric relation and centric occlusion are not coincident, the facial profile in centric relation may give a more accurate indication of prognosis thane cephalometry.

One consequence of this is that we should take facial photographs (full, three quarter and profile) of class 3 patients in both centric relation and centric occlusion when the teeth are in contact using natural head position.

Class in centric occlusion Occlusion is classified in centric occlusion according to the three categories previously described. The canine and molar relationship should be evaluated in centric occlusion. Use the mesial step to classify second deciduous molars noting that early loss of deciduous teeth may complicate classification. Where one side is class 1 and the other class 3, the diagnosis is class 3 subdivision Treatment is much easier when molar relationship is class 1. The prognosis for anterior deep bite is favourable; for anterior open bite unfavourable Figure 19.4:

Lin’s Three Rings diagnosis

Functional shift

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The presence or absence of a displacement is noted. Pseudo class 3 cases are defined by class 1 molar relationship in CO rather than presence or absence of functional shift; wear facets on labial side of upper incisors may help in diagnosing functional shift. Mild to moderate true class 3 cases may have a functional shift but severe true class 3 cases do not. Patients with a functional shift can usually be treated by compensation Lin argues that usually, orthognathic profiles remain orthognathic and prognathic profiles continue to be prognathic; exceptionally, orthognathic profiles become prognathic or orthognathic profiles develop anterior open bites.

Cephalometric assessment Individual cephalometric measurements often give different interpretations of diagnostic features and treatment changes (Kelson et al 2003).

Useful cephalometric measurements:

• • • •

ANB Maxillary-mandibular length o (Co-prognathion) – (Co – lower ANS) • normally 23 mm at age 12 Wits appraisal SN:mandibular border length o normally 1:1 in pseudo-class 3 cases

Stellzig-Eisenhauer et al (2002) have looked at distinguishing between those patients with class 3 malocclusions who can be treated orthodontically and those patients who require orthognathic surgery in an attempt to further refine the work of Proffit and Ackerman and that of Kerr et al. They used discriminant analysis to determine which cephalometric measurements would best aid the decision to treat a patient surgically or non-surgically according to the following treatment objectives:

• • • • •

stable occlusion in sagittal, transverse, and vertical dimensions correct overjet and overbite proper incisal inclination good facial esthetics and long-term stability

The authors found that the Wits analysis was the most important factor in discriminating between the surgical and non-surgical group with the surgical group having a Wits analysis value of –12.2 ± 4.3 mm and the non-surgical group -4.6 ± 1.7 mm. Thus the Wits analysis is another useful discriminator between patients requiring surgical or non-surgical treatment.

Rabie et al (2008) have suggested that a 12° Holdaway angle (soft tissue nasion-soft tissue pogonion-labrale superius) is a discriminatory for borderline class 3 cases. Thus cases with a Holdaway angle of greater than 12° were likely to be successfully treated by orthodontics; it is worth noting that the population in this paper was Southern Chinese. This is much higher than the 3.5° suggested by Kerr et al in 1992. Interestingly in this study, although class 3 correction by camouflage is often thought to be helped by upper incisor proclination, most of the cases in the study showed mild upper incisor retroclination. This means that there also has to be lower incisor retroclination and rotation of the mandible were essential to achieve crossbite correction. To prevent overretroclination of the lower incisors, lingual root torque is required.

Function The type of class 3 case that it is becoming possible to treat orthodontically is that with a moderate amount of maxillary retrusion and a decreased lower facial height. However, moderate class 3 malocclusions are often

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complicated by a mandibular displacement caused by the incisor relationship. This makes it difficult to assess the true occlusal relationships. The suggestion that the ability to achieve an edge to edge incisor relationship is a favourable prognostic indicator for treatment with simple appliances cannot be sustained. This is not an accurate indicator of skeletal base discrepancy as it is significantly affected by the amount of incisor compensation.

Dental assessment A rather more simple technique is to estimate the molar relationship (in the retruded axis position if necessary).

This should be corrected for mesial drift due to early tooth loss anterior to the first molar. Malocclusions with molar relationships greater than ¼ of a unit class 3 should be viewed with caution. Molar relationships less than this combined with maxillary retrusion and mild mandibular protrusion orthodontic management of the malocclusion may be possible.

Kerr et al (1992) set out to refine Proffit’s envelopes of discrepancy that set boundaries for the limits of orthodontic treatment in class 3 malocclusions. It was concluded that the critical factors in differentiating patients who required surgery from those who did not were anteroposterior discrepancy (ANB = -4°; maxillary mandibular ratio = 0.84), lower incisor inclination (LI/MP = 83°) and soft tissue profile (Holdaway angle = 3.5°). Interestingly, vertical dimension had little influence on treatment decision.

Growth status Much debate has been expended on the use of growth markers such as height charts, weight charts, hand wrist radiographs, the development of secondary sexual characteristics and cervical vertebra maturation data to identify the optimum time to start early treatment. These measures tend to have poor predictive value but are perhaps better at showing what has already happened.

Height charts are simple to do and non-invasive. And they are routinely recommended for class 3 cases who may possibly require orthognathic surgery.

Cervical vertebral maturation (CVM) method An alternative method of measuring skeletal maturity is to examine the morphology of the cervical vertebra.

Cervical vertebra maturation data is available from a cephalometric radiograph without further radiation.

Originally described by Lamparski (1972), this method was modified by Hassel and Farman (1995) (CVMI) and latterly by Baccetti et al in 2002 (CVMS). It is worth becoming familiar with the CVMI and slightly simpler CVMS methods as this maturational information is available from the lateral skull radiograph.

The CVMS method (which uses only C2, C3 and C4) published by Baccetti et al (2002) in 2002.

Now known as the Cervical Vertebra Maturation (CVM) method undergoes continual refinement and the latest version is published by Baccetti et al (2005). It is shown in Figure 19.5 and described in Table 19.2.

Baccetti et al (2005) suggest that class 3 patients treated with protraction headgear and a facemask well before the pubertal growth spurt (CS 1 or CS 2) have a different outcome to those treated at the peak of the pubertal growth spurt (CS 3).

Furthermore, prepubertal treatment is effective in both the maxilla and the mandible whereas treatment at puberty is only effective at the mandibular level.

Figure 19.5: The Cervical Vertebra Maturation (CVM) method (after Baccetti et al 2005)

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CVM stage

Cervical vertebral development

Peak mandibular growth

1

The lower borders of the cervical vertebrae are flat The bodies of C3 and C4 are trapezoid with the upper surface sloping downwards and anteriorly

Not earlier than 1 year after this stage; on average two years after this stage

2

The lower borders of C2 are concave. The bodies of C3 and C4 still trapezoid

Within 1 year after this stage

3

The lower borders of C2 and C3 are concave The bodies of C3 and C4 are either trapezoid horizontally rectangular

Will occur during the year after this stage

4

The lower borders of C2, C3 and C4 are still concave The bodies of C3 or C4 are horizontally rectangular

Has occurred within 1 or 2 years before this stage

5

The lower borders of C2, C3 and C4 are still concave At least one of the bodies of C3 or C4 has now become square; if not square, the body of the other vertebra is horizontally rectangular

Ended at least 1 year before this stage

6

The lower borders of C2, C3 and C4 are still concave. At least one of the bodies of C3 or C4 are vertically rectangular in shape; if not if not vertically rectangular, the body of the other vertebra is square

Ended at least 2 years before this stage

Table 19.2:

The Cervical Vertebral Maturation method (CVM) (from Bacetti et al 2005)

Chen et al (2008) have described a quantitative method of assessing cervical vertebral maturation (QCVM) which seems to correlate closely with Fishman’s Skeletal Maturity Indicators (SMI). QCVM has four stages:

• • • •

I II III IV

period of accelerating velocity period of high velocity period of decelerating velocity period of completing velocity

Three decisive variables were identified:

• • •

H4/W4 the height/width ratio of C4 AH3/PH3 the anterior height/posterior height ratio of C3 @2 the anterosuperior angle of the lower border of C2

The equation used to estimate accurately CVM was: CVMS = -4.13 + 3.57 x H4/W4 + 4.07 x AH3/PH3 + 0.03 x @2 The definition of each stage was derived from this as follows:

• • • •

QCVM I CVMS < 1.7404 QCVM II 1.7404 < CVMS < 2.623 QCVM III 2.623 < CVMS < 3.5199 QCVM IV CVMS > 3.5199

While this paper at first sight seems complex, it provides a useful refinement of the CVM system and repays a careful read.

Growth Treatment Response Vector (GTRV) analysis Ngan (2005) has described this as a method of determining whether a class 3 malocclusion can be treated by camouflage or if surgical treatment will be required at a later date. It is calculated from two serial cephalometric

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radiographs at least one year apart. The lines AO and BO are constructed in the same way as for the Wits analysis on the first radiograph; the first radiograph is then superimposed on the second using the stable structures of the cranial base. New lines AO and BO are then constructed using the occlusal plane of the first radiograph. The GTRV is then given by the following formula:

The normal GTRV of patients from the Bolton Growth Study is 0.77 – ie: mandibular growth usually exceeds maxillary growth by 23% between the ages of 8 and 16 years. In a study on 20 patients carried out by Ngan, the GTRV for a group successfully treated with facemask therapy was 0.49 ± 0.14 with a range of 0.33 to 0.88. A second, unsuccessfully treated group, had a GTRV of 0.22 ± 0.10 with a range of 0.06 to 0.38. The GTRVs for the two groups were significantly different at the 0.05 level.

The graph in Figure 19.6 shows how much change there has to be in B point for every 1 mm change in A point.

For a GTVR of 0.49 therefore, B point moves forward 2 mm for every 1 mm change in A point. However, for a GTVR of 0.2, B point moves forward 4 mm for every 1 mm change in A point. It would almost certainly be possible to detect this without recourse to serial cephalometric films!

Monitoring of class 3 malocclusions is extremely important as it is only in this way that a worsening skeletal pattern can be detected. The most effective way of doing this is probably careful observation of the molar and incisor relationship; digital photographs and careful notes in the health record are probably the most efficient way of doing this!

Principles of treatment If, as has been shown, that it is not possible to alter the dimensions of the mandible then the only possibilities for the correction of class 3 malocclusions are as follows:

• • •

dental compensation skeletal maxillary protrusion clockwise mandibular rotation to reduce the prominence of B point (by posterior vertical extrusion) caused by downward movement of the maxilla during protraction a combination of the above (orthognathic surgery)

• •

Turley (2002) has published an excellent review article on the management of early class 3 malocclusions with palatal expansion and facemask therapy.

1.2 We are very excited about Hugo de Clerck’s use of Bollard miniplates in class 3 malocclusion and have now started to use these as shown in Figures 19.7 and 19.8. The results of one year’s treatment are shown in Figures 19.9 and 19.10.

1

GTRV ratio

0.8 0.6 0.4 0.2 0 1

1.4

1.8

2.2

2.6

3

3.4

3

4.2

4.6

5

Change in B point per 1 mm change in A point

Figure 19.6: A graph showing the change in B point for each 1 mm change in A point. It can bee seen that for a GTVR of 0.2, The change in B point is approximately 4 mm for every 1 mm change in A point!

Nguyen et al (2011) have published a paper describing the three dimensional changes that take place in the maxilla with bone anchored protraction. In 25 consecutive cases, the maxilla came forward on average 3.7 mm, the zygomas 3.7 mm and the maxillary incisors 4.3 mm.

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Figures 19.7 and 19.8:

De Clerck Bollards being used to correct a class 3 malocclusion; start of treatment.

Figure 19.9: The result of one year’s treatment with class 3 elastics to the de Clerck Bollards

Figure 19.10: Superimposition of changes achieved in one year.

ANB increased by 4º; Wits increased by 7 mm, the maxillary mandibular unit length decreased by 2.3 mm and the upper incisors retroclined slightly.

Treatment of maxillary retrusion Intra-oral intermaxillary appliances and skeletal change There are few, if any, intra-oral appliances which can effectively influence a class 3 malocclusion through skeletal change. Possible candidates are the Frankel III, the bionator, the mandibular retractor and the two piece corrector.Originally described by Eganhouse in 1997, the two piece corrector works like a Clark Twin Block in reverse (but with rather gentler ramps) and is augmented with class 3 elastics. Üçem et al (2004) compared the effects of the two piece corrector and facemask therapy and not surprisingly found that the two piece corrector produced more dental change and less skeletal change than the facemask therapy. There was less increase in lower facial height with the two piece corrector than with face mask therapy, perhaps due to some bite block effect from the wholly intraoral appliance.

Protraction headgears The preferred treatment for skeletal maxillary retrusion is anterior movement of the maxilla using a protraction headgear. This technique is described by McNamara (1993). Although it is suggested that this is best done before the age of 8 years for maximum skeletal effect, there are few studies that positively support early treatment.

Sakamoto (1981) showed that better results in the treatment of class 3 malocclusions were achieved in younger age groups although the treatment methodology involved chincups and URAs rather than maxillary protraction.

In addition more favourable change was obtained where the ANB difference was less class 3. In older children the

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changes are more likely to be due to dental rather than skeletal change. Overambitious attempts to use this in patients with large ANB differences are unlikely to be successful.

The use of maxillary protraction seeks to obtain the following treatment effects:

• • • • •

elimination of a CR-CO discrepancy maxillary protraction forward movement of the maxillary dentition lingual tipping of the lower incisors vertical mandibular development

It can be seen that the movements are not limited just to maxillary protraction and it is perhaps more appropriate to refer to this type of treatment as facemask therapy.

In order to maximise the amount of skeletal change in young children, a removable full coverage acrylic splint is used with a protraction headgear. We have not found the need for custom chincups and forehead pads and have routinely used a Great Lakes type headgear in a single (medium) size; the Petit style with a single central vertical bar is also well tolerated and recent price changes have made it economically much more attractive. Perspiration within the chin cup may be a problem and some patients have lined the chin cup to make it more comfortable.

The direction of pull should be slightly below the occlusal plane. The force used is approximately 750g per side and the headgear is worn for at least 12 hours in every 24 hours. It may be helpful to use light elastics while the patient becomes accustomed to the appliance. The acrylic splint should have clasps on the first molars and auxiliary clasps on the primary molars together with a Southend clasp anteriorly. There is full acrylic coverage of the occlusal and incisal surfaces of the teeth (Proffit 1986).

McNamara (1987) has described the use of a Biocryl and wire splint that is bonded in the mouth. The splint material should be at least 3 mm thick with a 0.045" stainless steel wire framework. The two halves of the splint are joined by an expansion screw. Traction hooks to receive the elastics from the headgear are placed in the first premolar region. Sarver and Johnston (1989) have described the addition of a buccal loop which extends over the occlusal surface and which is used to make removal of the splint easier. The bonded expander is however difficult to keep clean and most patients develop significant reversible gingival disease at the time of removal.

An alternative design is to use upper first molar bands and bonded rests on the first deciduous molars with a wire skeleton (similar to a Pendex appliance) and a Superscrew. This is easy to fit and robust; the rests should approach from the distal of the deciduous first molars thus allowing hooks for the protraction head gear to run mesially.

Ishii et al (1987) describe the effects of providing the protraction force from the first molars or the premolar region.

Protraction from the first molars results in more anterior movement and a forward and upward rotation of the maxilla; protraction from the premolars results in less forward movement but less tendency to upward and forward rotation.

A meta-analysis of the effectiveness of protraction facemask therapy has been published by Kim et al (1999).

Many of the articles are discussed in this chapter. They concluded that protraction headgear was less effective in patients older than 10 years of age. Patients who did not have palatal expansion had longer treatment times and ended up with more upper incisor proclination - i.e.: more dental change and less skeletal change. The technique however still needs considerable evaluation in order to optimise its application.

Franchi et al (2004) concluded that it was possible to achieve a 2 mm advancement of the maxilla that would withstand the active growth period if RME and protraction head gear was undertaken in the deciduous dentition or early mixed dentition. It is suggested that later treatment results only in a restriction of mandibular growth and that at whatever age treatment takes place, correction is due to adaptations in the skeletal bases rather than dentoalveolar movement.

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Clinical Summary • maxillary protraction is best carried out before the age of 8 years • it is facilitated by rapid maxillary expansion • a significant amount of maxillary protraction may be lost during subsequent growth • overall gains may be modest but nevertheless worthwhile Yoshida et al (2007) compared the effects of a maxillary protraction device (without rapid maxillary expansion) and a chin cap appliance on different craniofacial morphologies (low and high maxillary-mandibular planes angle groups). Comparison of high angle and low angle groups at the start of treatment showed that upper and lower face heights and gonial angle were significantly greater in the long-face type. Both groups demonstrated significant increases in SNA, maxillary length and ANB were observed during treatment. They found that the low angle group however demonstrated more forward displacement and size increment of the maxillary body. Thus the prognosis for the successful treatment of class 3 malocclusions is probably greater in low angle cases.

Palatal expansion associated with maxillary protraction

Mode of action The associated use of palatal expansion in conjunction with protraction headgear has been advocated. The type of expansion used is rapid maxillary expansion seeks to exploit two effects:

• •

the forward movement of the maxillary complex which often accompanies maxillary expansion the sutural loosening which occurs during maxillary expansion which may extend upward the age range in which a significant skeletal effect may be observed

Baik (1995) carried out an interesting study which sought to answer the following questions:

• •

does age influence the success of maxillary protraction? does rapid maxillary expansion, either prior to or concurrent with, maxillary protraction influence the amount of protraction obtained?

The appliances used were a labiolingual appliance and a banded RME device with a Delaire type protraction headgear used with 300g to 500g of force. The RME regime is not described.

The results were as follows:

• •

the sample ranged in age between 8 and 13 years. Age had no significant effect on the amount of maxillary protraction although older children obtained less protraction rapid maxillary expansion increased the amount of protraction significantly (measured at A point) by about 1 mm. Concurrent RME resulted in a non significant increase in protraction and a significant decrease in the angle between the X-axis (taken as 6° below the SN line) and the palatal plane. This therefore means that PNS dropped down more in the group that had RME during protraction.

Sung and Baik (1998) confirmed the independence of age on treatment effect. This study achieved a change in ANB of 2.5° during treatment which relapsed by 0.5° post treatment.

The rapid maxillary expansion screw may be turned a quarter of a turn either once or twice a day.

Types of screw Hyrax Perhaps the most popular type of screw, this reliable and easy to incorporate into an appliance. The more recent longer plastic handled keys eliminate any danger of the patient swallowing the key.

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Superscrew The ORTHOdesign Superscrew is an updated version of the Hyrax screw with added refinements including a nylon friction washer, the use of a spanner rather than a conventional “key”, a scale which indicates the amount of expansion already completed and an “end of screw threads” warning. It is capable of expanding by at least 18 mm of expansion and produces 2 mm of expansion for every 1 mm of screw length. Be careful to instruct the laboratory to insert the screw in accordance with the patient instructions for operating it - there is no arrow on the screw to indicate which way it opens! Otherwise, this screw is a potentially worthwhile advance and is now our preferred type of expansion screw. It is described by Klapper (1995) in the Journal of Clinical Orthodontics.

Case selection This technique is best suited to patients with:

• • •

deep overbites anteroom-posterior and vertical maxillary deficiency normal to mildly prognathism mandibular dimensions

Franchi et al (1997) studied class 3 patients treated with functional appliances to try and determine predictive variables for the of class 3 treatment. They found that patients having wider mandibular arches (measured from study models), a more upward and forward inclination of the mandibular condyle in relation to the cranial base, and an increased maxillary planes angle had unsatisfactory long-term treatment outcomes.

Tahmina et al (2000) concluded that for chincup treatment, patients with large gonial angles, large nasion-A pointpogonion and a large ramus plane to sella-nasion plane had less stable results than those with smaller values. In addition, the degree of inclination of the ramus to the corpus of the mandible, and the degree of mandibular protrusion, were key factors in determining the long-term outcome of chincup therapy in growing class 3 patients.

Zentner et al (2001) suggested the sizes of the apical bases for the maxilla and the mandible, along with the gonial angle and mandibular ramus and body dimensions, were the discriminating factors between good and poor responders to early class 3 treatment an investigation using conventional appliances.

Baccetti et al (2004) attempted to develop a predictive model that could identify good or bad responders to early orthopedic treatment of class 3 malocclusion with maxillary expansion and protraction. Good responders were predicted by the equation:

where:

• • • • • •

Co is condylion Goi is the gonial intersection of the ramal plane and the mandibular plane Ba is basion T is the superior point of the anterior wall of the sella turcica and the tuberculum sella the SBL (stable basicranial line) runs through T and tangent to the lamina cribrosa of the ethmoid ML is the mandibular plane

Baccetti et al (2004) therefore found that the three most useful predictive cephalometric values were:

• • •

the length of the mandibular ramus Co-Goi the angulation of the cranial base Ba-T-SBL the angulation of the mandibular plane to the cranial base

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This study used the same sample material as Franchi et al (2004) which included the following key inclusion criteria:

• • •

white European-American ancestry class 3 malocclusion at the time of the first observation characterized by an anterior crossbite or edge-to-edge incisal relationship and a Wits appraisal of -1.5 mm or less no permanent teeth congenitally missing or extracted before or during treatment

The outcome of class 3 cases is therefore dependent on the relative anteroposterior position of the maxilla and mandible and their relative size and morphology as determined anteroposteriorly, transversely and vertically.

Ghiz et al (2005) several cephalometric measurements to try and find a predictive model for class 3 malocclusion in a similar manner to Baccetti et al (2004). Ghiz used the following formula:

where

• •

P is the probability that early treatment will be successful L = 30.557+0.196(Co-GD)-0.129(Co-Pog)+0.162(Co-Goi)-0.206(Ar-Goi-Me)

• •

Co is condylion GD is the Great Divide o a line drawn through sella at right angles to sella horizontal Pog is pogonion Goi is the gonial intersection Ar is articulare Me is menton

and

• • • •

Ghiz et al (2005) claim that this model successfully predicts successful cases 95% of the time and unsuccessful cases 70% of the time.

These types of prediction model tend to be better at predicting successful cases rather than unsuccessful cases – which is the opposite way round to what orthodontists would prefer! Both the predictive equations discussed here place a negative (prognostically unfavourable) weighting on:

• • •

an acute cranial base angle o the glenoid fossa is situated further forward in the face an increased mandibular plane angle increased mandibular length

Baccetti et al (2004) considered that long mandibular ramal length (increased posterior face height) was an adverse factor while Ghiz et al (2005) believed small ramal length an adverse factor.

What age?

In determining what age is best to start treatment, it is helpful to consider:

•

chronologic age

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• •

379

stage of dental development skeletal age Chronologic age

Merwin et al (1997) compared the effectiveness of protraction headgear and maxillary expansion in class 3 patients before and after the age of 8 years. One group had an average age of 6.8 years and the other 10.2 years.

The appliances consisted of a Hyrax screw to stainless steel bands and a Tubinger style protraction headgear. A similar skeletal response was seen in both groups of patients suggesting that the need to start treatment before the age of 8 years is not necessarily correct (compare with Baik 1995 in paragraph above). Note that no patients were older than 12 years and orthopaedic results should not be expected in post-pubertal children.

Kapust et al (1998) compared the effects of facemask expansion therapy in three age groups (4-7 years, 7-10 years and 10-14 years). Generally, more treatment change occurred in the younger groups than in the older groups.

This represented an approximately 4 degree change in ANB for the combined groups compared with the control; this change was contributed to by a slightly greater increase in SNA than a decrease in SNB. Baccetti et al (1998) compared early treatment (6 years 9 months at T1) and a later treatment group (10 years 3 months at T1). Patients were treated with a bonded maxillary expander and a Petit type protraction headgear. The early treatment group showed effective forward displacement of the maxillary structures whereas the late treatment group showed no change compared with controls. Although both early and late facemask treatment reduced mandibular protrusion, significantly smaller increments in total mandibular length associated with more upward and forward direction of condylar growth were recorded only in the early treatment group.

Saadia et al (2000) found similar results in a study of 112 patients divided into 3 age groups. Younger patients achieved greater treatment change with less appliance wear.

Yüksel et al (2001) carried out a small study which compared early (mean age 9 years 8 months) and late treatment (mean age 12 years 6 months) groups with a control (mean age 9 years 5 months). Treatment took, on average, 7 months and patients were treated with a Delaire type facemask and an upper removable appliance. Both treatment groups demonstrated significant forward movement of the maxilla, the upper incisors and the upper molars. There was a downward and backward movement of the mandible and the mandibular dentition.

Although no differences were found between the two treatment groups, the authors concluded that the improvement in facial aesthetics produced psychosocial advantages that favoured early treatment.

There is a consensus that the best results with protraction headgear are obtained if treatment is completed by the age of eight years.

Stage of dental development Baccetti and Tollaro (1998) retrospectively compared the effect of a functional appliance (removable mandibular retractor) on class 3 malocclusions in the deciduous and mixed dentitions. The group treated in the deciduous dentition showed more significant skeletal change than the group treated in the mixed dentition; these changes resulted in a more upward and forward direction of condylar growth and hence reduced mandibular protrusion and total mandibular length. The mixed dentition group showed greater dentoalveolar rather than skeletal change.

Baccetti, Franchi and McNamara (2000) compared the skeletal response to a bonded acrylic-splint expander and protraction headgear in a retrospective study. There was an early mixed dentition group (incisors and first molars erupting, mean age 7 years at the start of treatment) and a late mixed dentition group (canines and premolars erupting, mean age 8 years 8 months at the start of treatment). Records were available at the end of active treatment (7 years 9 months, 9 years 7 months) and post treatment (8 years 10 months, 10 years 9 months). A significant increase in sagittal growth of the maxilla (A-vertT) occurred only in the early mixed dentition group.

The late mixed dentition group encountered a backward rotation of the mandible with corresponding increase in lower facial height. The class 3 growth pattern was re-established in the post-treatment year although no

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skeletally based retention appliance (e.g.: FR 3, chincup etc.) was used. A significant relapse tendency affected the maxillary change in the early mixed dentition group and the sagittal position of the mandible in the late mixed dentition group.

Skeletal age Suda et al (2000) suggested that evaluating bone age would assist in determining the optimum age for protraction treatment. These workers compared two groups of 30 patients (palatal arch, chincup, protraction headgear and palatal arch and/or chincup) which were subdivided into younger and older groups. The younger boys showed greater maxillary advancement than older boys and there was a greater increase in SNA in boys who were less skeletally mature.

In 2003, Cha investigated the effects of rapid maxillary expansion and protraction headgear in three different maturational groups as defined by Fishman’s skeletal maturity indicators (SMI) and based on hand wrist radiographs. He divided his study into three groups, increasing growth velocity (SMI 1-3, mean age 9.8 years), peak growth velocity (SMI 4-7, mean age 11.3 years) and decreasing growth velocity (SMI 9-11, mean age 13.1 years). There was no difference in maxillary skeletal advancement in the first two groups but less skeletal advancement and more dentoalveolar compensation in the decreasing growth velocity group.

How much?

Realistically, one can probably expect a 1° positive change in SNA, a corresponding negative change in SNB and therefore a positive change of approximately 2° in ANB. The change in SNB obviously represents a change in position rather than a change in dimension. Nartallo-Turley and Turley (1998) have demonstrated changes of + 2.35° in SNA and 3.66° in ANB as well as linear changes of approximately 3 mm in A point and ANS. The mean age at the start of treatment was 7.26 years and treatment lasted 11.05 months. The maxillary molar and incisor moved forward 1.7 mm and 1.75 mm respectively which is similar to that found by Ngan et al (1996).

There is usually a statistically significant increase in vertical face height due to downward and backward rotation of the mandible (Silva et al 1998).

Franchi et al (2004) carried out a postpubertal assessment of treatment timing for maxillary expansion and protraction headgear. In their criteria for admission to the study, the patients had to have a Wits appraisal of – 1.5 mm or less.

Compare this with the results obtained by Stellzig-Eisenhauer et al (2002) which suggested that patients with Wits values of -4.6 ± 1.7 mm were probably manageable with orthodontic treatment and the paper by Burns et al (2010).

Stability of facemask treatment The stability of facemask therapy is open to question. At the moment, it would seem that following the cessation of active treatment, class 3 patients revert to a class 3 pattern of growth with deficient maxillary growth. The growth pattern does not become normalised. This supports the need for overcorrection during active treatment and the need for additional facemask therapy during the phase 2 stage of treatment.

Shanker et al (1996) carried out a similar study on Chinese children but who all had maxillary expansion with a Hyrax screw. In this study there was a statistically significant forward movement of “A” point of 2.4 mm compared with 0.2 mm in the control group. In the year after treatment, the change in “A” point between the two groups was similar and no relapse occurred in the treatment group.

Chong et al (1996) compared the post treatment growth of 16 patients treated with facemasks and labiolingual appliances or bonded palatal expanders with 13 untreated matched class 3 controls over a period of 3.6 years. No difference was found between the treated patients and the class 3 controls during the post-treatment observation period, although reduction in overjet occurred in the treated group.

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Gallagher et al (1998) have shown that in late treatment group, there is considerable relapse post-treatment (ANB pre-treatment = -0.3°, ANB post-treatment = 1.1°, ANB at follow-up = 0.3°).

Ngan et al (1998) looked at maxillary expansion and protraction in a Chinese population treated at 8.4 years of age. In this study, RME was only carried out for 7 days before protraction compared with the more usual 10-14 days. Changes of 1.6° were found in SNA and 3.0° in ANB during treatment although some relapse occurred in the two-year period after treatment (-0.3° and -2.0° respectively). Substantial amounts of relapse were found in the upper arch expansion but not in the mandibular arch; RME did not result in a net increase in arch perimeter. The study did not continue into puberty when it might be expected that further relapse might occur.

MacDonald et al (1999) compared the post treatment growth of a treated class 3 sample with a class 3 and a class 1 sample over 2.3 years. When the untreated class 1 and class 3 samples were compared, the class 3 group had less maxillary growth and greater forward mandibular growth. After treatment, the treated class 3 group reverted to a class 3 type of growth.

Finally, Hägg et al (2003) carried out a long term follow up of patients who had been treated with rapid maxillary expansion and reverse pull headgear. The average age of the patients at the start of treatment was 8.7 years and the average treatment time 0.8 years; all patients had a positive overjet at the end of treatment. After a follow-up period of 8.2 years, only two thirds of the patients had positive overjet. In the patients that relapsed, mandibular growth was four times that in the maxilla. So potentially, this type of treatment has a 33% failure rate and probability of orthognathic surgery as a final treatment solution.

Wells et al (2006) reported on a study carried out in North Carolina in which 41 patients who had had reverse pull headgear treatment were examined at five year follow-up and a further 18 were examined at 10 year follow-up.

The percentage of failures rose from 20% at 5 years to 25% at 10 years due to late mandibular growth. Before treatment, reverse overjet, maxillary length, and maxillary position were similar for the two groups, but the failure group tended to have a larger and more anteriorly positioned mandible. The authors found four variables that might be useful in deciding whether a case might be a success or a failure. These were:

• • • •

the y-coordinate of posterior nasal spine the y-coordinate of gonion overbite mandibular unit length

The equation used to predict success or failure was: D = 1.29 - (0.61)PNSy - (.029)Goy - (0.30)OB - (0.43)MdUL D(success) was 0.025 and D(failure) was 2.84 This equation incorrectly identified 9 of the 31 successes as potential failures and 2 of the 10 failures as potential successes. During treatment, the maxilla in both groups moved forward a similar amount but the successful group had greater overjet correction and more upper incisor proclination. The failure group had a greater increase in maxillary-mandibular planes angle during treatment, a lower anterior facial height and a more acute facial axis which indicates a downward and backward rotating mandible during treatment. The authors found no difference in N-S-Ar between the success and failure groups. There was no difference in the success of treatment where it was started before 10 years of age but after the age of 10 years, the percentage of successful outcomes declined.

Fitting The splint is fitted by etching the buccal and palatal surfaces of the upper posterior segment teeth only (to ease removal). The appliance is then bonded in place using a slow setting acrylic adhesive such as Excel (Reliance). The patient is asked to bite on cotton wool rolls to fully seat the splint. Excess adhesive can be removed with a scaler

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or bur (when fully set). It is easier to sit the patient upright to fit the appliance as this prevents slow setting acrylic from running out of the back of the splint.

The screw can be turned 0.25-0.5 mm per day (rapid expansion) or 1 mm per week (slow expansion) as suggested

by Proffit (1986).

The headgear or facemask is given to the patient two weeks after the start of maxillary expansion to allow some sutural loosening to take place. McNamara suggests full-time wear of the facemask but this is impractical for most patients. The direction of pull should be slightly below the occlusal plane. The wear of the mask is continued until a positive overjet of 2-5 mm is obtained. The result is then stabilised for 3-6 months with occasional night time wear of the facemask. A removable retainer is worn after the splint and facemask are removed.

Sarver (1989) investigated the difference in effect between banded RME appliances and bonded appliances with bite blocks. This study did not involve the use of protraction headgear but simply the correction of posterior crossbites. The bite blocks were 2-3 mm in height. Sarver found that the use of bite blocks was associated with:

• • •

a slight superior movement of PNS inferior and posterior movement of ANS inferior and posterior movement of the upper incisors

and therefore less likely to lead to a decrease in overbite than the use of a banded appliance. However, Reed et al (1999) concluded that there were no clinical differences in the amount of inferior movement of the palatal plane between patients treated with bonded and banded appliances and that patients with high mandibular plane inclinations did not exhibit greater vertical change than those with lower inclinations. Overall, there is perhaps little to choose between the two methods.

Ngan et al (1996) showed that significant dentoskeletal changes and improvements in dentofacial profile could be obtained from 6 months treatment with maxillary expansion and protraction.

Velázquez et al (1996) hypothesised that the adverse effects of RME were dissipated by normal growth in the years post treatment.

This is supported by Chang et al (1997) who investigated the hypotheses that RME opens the bite and also moves the maxilla downward and forward. The study defined bite opening as an increase in anterior facial height or opening of the maxillary mandibular planes angle or both. It compared an RME group (Haas type appliance), being treated for transverse maxillary deficiency, a standard edgewise group and a control group. The study found no evidence to support the suggestion that RME caused bite opening or that it caused forward and downward movement of the maxilla. However, the study only included class 1 and class 2 cases and may not be applicable to class 3 cases.

Patrick Turley (1996) offers the following advice:

• • •

• • •

use a rigid expansion appliance to expand the maxilla 24 hour wear of the protraction headgear using a custom appliance avoid camouflaging movements such as: o proclination of the maxillary incisors to correct crowding or an anterior crossbite o avoid lower incisor retroclination o and hence avoid class 3 elastics for as long as possible overcorrect to an end on canine relationship retain with night time only protraction headgear for a further three to six months until there is good posterior interdigitation and a positive overbite monitor

MANAGING CLASS 3 MALOCCLUSIONS EXCELLENCE IN ORTHODONTICS 2012

•

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reinstate protraction headgear during phase 2 treatment

An interesting paper from Seattle has been published by Chong et al (1996). This compared the treatment effects and post treatment changes following maxillary protraction in 16 patients compared with 13 matched and untreated control subjects. The age at the start of treatment ranged from 4.58 to 8.25 years. Palatal expansion was only carried out in three patients who had pre-existing crossbites. Protraction treatment was discontinued when a positive overjet or flush postlactal plane was achieved. Treatment resulted in significant changes in ANB and the overjet; although the treated subjects showed an increase in SNA, this was not statistically significant. The major reason for the improvement in the overjet was downward and backward rotation of the mandible. There may be some temporary growth retardation at the condyles as the mandibular length increased less in the treated patients than in the controls. Improvement in the overjet was less marked at the time of follow-up; despite this a positive overjet was maintained at the end of follow-up in the patients. The treatment was considered unsuccessful however if the overjet was less than 2 mm; 5 out of the 16 cases fell into this category.

Ngan et al (1997) suggested that:

• • • •

correction of class 3 malocclusion was achievable in 6-9 months and was stable 2 years after appliance removal maxillary expansion in conjunction with protraction produced greater forward movement of the maxilla significant and beneficial soft tissue profile change can be expected during treatment treatment works best in patients with retrusive maxillas and hypodivergent growth patterns

The treatment effects of maxillary protraction with or without rapid expansion therefore require further study before we have a clear idea of the treatment effects. Vaughn et al (2001) carried out a prospective randomised control trial to determine whether rapid maxillary expansion enhanced the amount of maxillary protraction. Two groups were used: one treated with facemasks and active palatal expansion, the other with facemasks and passive expansion appliances. The results of this study showed no differences between the expansion and the nonexpansion groups in any cephalometric variable, in overall treatment time, or in the time for initial crossbite correction. The authors argue that, without other reasons for expansion, such as maxillary width or space deficiency, expansion does not significantly aid in Class 3 correction.

This study was further reported by Vaughn et al (2005). The authors concluded that significant and similar changes in ANB (up to almost 4 degrees) and the Wits appraisal (up to almost 4 mm) could be obtained from the use of protraction facemasks with or without RME. The study was only continued up to the end of treatment and no report of what happened during and post-retention is included.

Williams et al (1997) have quantified the amount of change that takes place with protraction and RME and compared it with figure for normal growth (Riolo). Protraction and RME have a small skeletal effect and a moderate dentoalveolar effect.

Labial root torque Most class 3 patients demonstrate considerable proclination of the upper labial segment at the end of treatment.

Although we have not tried it much, the use of labial root torque (achievable by inverting the upper incisor brackets) with advancement of the upper labial segment is food for thought. The case published by Catania et al (1990) demonstrates significant maxillary development with only mild to moderate proclination of the incisors using this technique.

The problems of anterior open bites In patients with a class 3 malocclusion and an increased lower facial height, problems may arise using this approach because as the maxilla is protracted it also moves downward decreasing the overbite. Every attempt must be made to prevent downward growth of the maxilla and posterior tooth eruption.

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In many cases, successful management of this type of case will require orthognathic surgery.

Phase 2 treatment It is sensible to wait for the second molars to erupt before starting phase 2 treatment to allow evaluation of post phase 1 growth and to minimise the length of fixed appliance treatment. Males seem to show greater adverse growth in class 3 cases in the teenage years than females. This is probably because males show more latent mandibular growth than females. Björk and Helm (1967) showed that condylar growth may continue for up to two years after cessation of growth in physical height. Males show greater condylar growth than females and this growth occurs in a more forward direction which may contribute to the tendency for adverse growth during the second decade.

References Baccetti T and Tollaro I (1998) A retrospective comparison of functional appliance treatment of class III malocclusions in the deciduous dentition European Journal of Orthodontics 20: 309-317 Baccetti T, Franchi L and McNamara JA (2000) Treatment and post treatment craniofacial changes after rapid maxillary expansion and facemask therapy American Journal of Orthodontics and Dentofacial Orthopaedics 118: 404-413 Baccetti T, Franchi L and McNamara JA Jr (2002) An improved version of the cervical vertebral maturation (CVM) method for the assessment of mandibular growth Angle Orthodontist 72: 316-323 Baccetti T, McGill JS, Franchi L, McNamara JA and Tollaro I (1998) Skeletal effects of early treatment of class III malocclusion with maxillary expansion and face-mask therapy American Journal of Orthodontics and Dentofacial Orthopaedics 113: 333-343 Baccetti T, Franchi L and McNamara JA (2004) Cephalometric variables predicting the long-term success or failure of combined rapid maxillary expansion and facial mask therapy American Journal of Orthodontics and Dentofacial Orthopaedics 126: 16-22 Baccetti T, Franchi L and McNamara JA (2005) The Cervical Vertebral Maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopaedics Seminars in Orthodontics 11: 119-129 Baccetti T, Reyes BC and McNamara JA (2005) Gender differences in class III malocclusion Angle Orthodontist 75: 510–520 Baccetti T, Reyes BC, McNamara JA (2007) Craniofacial changes in Class III malocclusion as related to skeletal and dental maturation American Journal of Orthodontics & Dentofacial Orthopaedics 132: 2, 171.e1-171.e12 Baik HS (1995) Clinical results of the maxillary protraction in Korean children American Journal of Orthodontics and Dentofacial Orthopaedics 108: 583-592 Björk A and Helm S (1967) Prediction of the age of maximum pubertal growth in body height Angle Orthodontist 37: 134-143 Burns NR, Musich DR, Martin C, Razmus T, Gunel E and Ngan P (2010) Class III camouflage treatment: What are the limits?

American Journal of Orthodontics and Dentofacial Orthopaedics 137: 9.e1-9.e13 Catania JA, Cohen BD and Deeney MR (1990) The use of labial root torque and the tie-forward technique in the treatment of maxillary skeletal retrusion and severe arch length discrepancy American Journal of Orthodontics and Dentofacial Orthopaedics 98: 12-18 Cha KS (2003) Skeletal changes of maxillary protraction in patients exhibiting skeletal class 3 malocclusion: a comparison of three skeletal maturation groups.

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Chang JY, McNamara JA and Herberger TA (1997) A longitudinal study of skeletal side effects induced by rapid maxillary expansion American Journal of Orthodontics and Dentofacial Orthopaedics 112: 330-337 Chen F, Terada K, Yang L, Saito I (2008) Dental arch widths and mandibular-maxillary base widths in Class III malocclusions from ages 10 to 14 American Journal of Orthodontics & Dentofacial Orthopaedics 133: 65-69 Chen L-L, Xu T-M, Jiang J-H, Zhang X-Z, Lin J-X (2008) Quantitative cervical vertebral maturation assessment in adolescents with normal occlusion: A mixed longitudinal study American Journal of Orthodontics and Dentofacial Orthopaedics 134: 720.e1-720.e7 Chong Y-H, Ive JC and Årtun J (1996) Changes following the use of protraction headgear for early correction of class III malocclusion Angle Orthodontist 66: 351-362 Cozzani G (1981) Extra-oral traction and class III treatment American Journal of Orthodontics and Dentofacial Orthopaedics 80: 638-650 Deguchi T and McNamara JA (1999) Craniofacial adaptations induced by chincup therapy in class III patients American Journal of Orthodontics and Dentofacial Orthopaedics 115: 175-182 Dermaut LR and Aelbers CMF (1996) Orthopaedics in orthodontics: Fiction or reality. A review of the literature—Part II American Journal of Orthodontics and Dentofacial Orthopaedics 110: 667-671 Eganhouse GR (1997) Two piece corrector for class 3 skeletal and dental malocclusions Journal of Clinical Orthodontics 31: 246-251 Fishman LS (1982) Radiographic evaluation of skeletal; maturation: a clinically oriented method based on hand –wrist films Angle Orthodontist 52: 88-112 Franchi L, Baccetti T and Tollaro I (1997) Predictive variables for the outcome of early functional treatment of Class III malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 112: 80-86 Franchi L, Baccetti T and McNamara JA (2004) Postpubertal assessment of treatment timing for maxillary expansion and protraction therapy followed by fixed appliances American Journal of Orthodontics and Dentofacial Orthopaedics 126: 555-568 Gallagher RW, Miranda F and Buschang PH (1998) Maxillary protraction: treatment and post treatment effects American Journal of Orthodontics and Dentofacial Orthopaedics 113: 612-619 Ghiz MA, Ngan P and Gunel E (2005) Cephalometric variables to predict future success of early orthopedic Class III treatment American Journal of Orthodontics and Dentofacial Orthopaedics 127: 301-306 Guyer EC, Ellis EE, McNamara JA and Behrents R (1986) Components of class III malocclusion in juveniles and adolescents Angle Orthodontist 56: 7-30 Hägg U, Tse A, Bendeus M and Rabie ABM (2003) Long-term follow-up of early treatment with reverse headgear European Journal of Orthodontics 25: 95-102 Hägg U, Tse A, Bendeus M and Rabie ABM (2004) A follow-up study of early treatment of pseudo class III malocclusion Angle Orthodontist 74: 465-472 Hassell B and Farman AG (1995) Skeletal maturation evaluation using cervical vertebra American Journal of Orthodontics and Dentofacial Orthopaedics 107: 58-66 Ishii H, Morita S, Takeuchi Y, Nakamura S (1987) Treatment effect of combined maxillary protraction and chincap appliance in severe skeletal class III cases American Journal of Orthodontics and Dentofacial Orthopaedics 92: 304-312

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Kapust AJ, Sinclair PM and Turley PK (1998) Cephalometric effects of face mask/expansion therapy in class III children: a comparison of three age groups American Journal of Orthodontics and Dentofacial Orthopaedics 113: 204-212 Kelson A, Fields H, Beck M et al (2003) Concordance of multiple A-P cephalometric measurements in long- normal- and short-faced individuals at varied treatment stages Journal of Dental Research 82: (Special Issue A) 1490 (abs 1490) Kerr WJS, Miller S and Dawber JE (1992) Class III malocclusion: surgery or orthodontics?

British Journal of Orthodontics: 19: 21-24 Kim J-H, Viana MAG, Graber TM, Omerza FF and BeGole EA (1999) The effectiveness of face mask therapy: a meta-analysis American Journal of Orthodontics and Dentofacial Orthopaedics 115: 675-685 Klapper L and George R (1995) A new telescopic maxillary expander Journal of Clinical Orthodontics 29: 114-116 Ko Y-I, Baek S-H, Mah J, and Yang W-S (2004) Determinants of successful chincup therapy in skeletal Class III malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 126: 33-41 Lamparski D (1972) Skeletal age assessment using cervical vertebra Pittsburgh, University of Pittsburgh (Thesis) Levin AS, McNamara JA, Franchi L, Baccetti T and Fr채nkel C (2008) Short-term and long-term treatment outcomes with the FR-3 appliance of Fr채nkel American Journal of Orthodontics and Dentofacial Orthopaedics 134: 513-524 Lin JX and Gu Y (2004) Preliminary study of non-surgical treatment of severe Class III malocclusion in 18 patients of 12-20 years old Zhonghua Kou Qiang Yi Xue Za Zhi 39: 91-96 Lin J J-L (2007) Creative orthodontics: Blending the Damon System and TADS to manage difficult malocclusions Taiwan, Yong Chieh Co ISBN: 978-986-83331-1-6 MacDonald KE, Kapust AJ and Turley PK. (1999) Cephalometric changes after the correction of Class III malocclusion with maxillary expansion/facemask therapy American Journal of Orthodontics and Dentofacial Orthopaedics 116: 13-24 McNamara JA (1987) An orthopaedic approach to the treatment of class III malocclusion in young patients Journal of Clinical Orthodontics 11: 598-608 McNamara JA (1993) Orthodontic and orthopaedic treatment in the mixed dentition Ann Arbor, Needham Press Merwin D, Ngan P, Hagg U, Yiu C and Wei SHY (1997) Timing for effective application of anteriorly directed orthopaedic force to the maxilla American Journal of Orthodontics and Dentofacial Orthopaedics 112: 292-299 Nanda R (1978) Protraction of maxilla in rhesus monkeys by controlled extraoral forces American Journal of Orthodontics and Dentofacial Orthopaedics 74: 121-141 Nartallo-Turley PE and Turley PK (1998) Cephalometric effects of combined palatal expansion and facemask therapy on class III malocclusion Angle Orthodontist 68: 217-224 Ngan P, H채gg U, Yiu C, Merwin D and Wei S (1996) Soft tissue and dentoskeletal profile changes associated with maxillary expansion and protraction headgear treatment American Journal of Orthodontics and Dentofacial Orthopaedics 109: 38-49 Ngan P, H채gg U, Yiu C and Wei S (1997) Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction Seminars in Orthodontics 3: 255-263

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Ngan P, Yiu C, Hu A, Hägg U, Wei SHY and Gunel E (1998) Cephalometric and occlusal changes following maxillary expansion and protraction European Journal of Orthodontics 20: 237-254 Ngan P (2005) Early timely treatment of class 3 malocclusion Seminars in Orthodontics 11: 140-145 Nguyen T, Cevidanes L, Cornelis MA, Heymann G, de Paula LK, De Clerck H (2011) Three-dimensional assessment of maxillary changes associated with bone anchored maxillary protraction American Journal of Orthodontics and Dentofacial Orthopaedics 140: 790-798 Proffit WR (1986) Contemporary Orthodontics St Louis, The CV Mosby Company Rabie AB, Wong RW and Min GU (2008) Treatment in borderline class III malocclusion: orthodontic camouflage (extraction) versus orthognathic surgery Open Dental Journal 2: 38-48 Reed N, Ghosh J and Nanda RS (1999) Comparison of outcomes with banded and bonded RPE appliances American Journal of Orthodontics and Dentofacial Orthopaedics 116: 31-40 Reynolds IR (1978) The anterior crossbite: a simple method of treatment British Dental Journal 144: 143-146 Saadia M and Torres E (2000) Sagittal changes after maxillary protraction with expansion in Class III patients in the primary, mixed, and late mixed dentitions: a longitudinal retrospective study American Journal of Orthodontics and Dentofacial Orthopaedics 117: 669-680 Sakamoto T (1981) Effective timing for the application of orthopaedic force in the skeletal class III malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 80: 411-416 Sarver D and Johnston MW (1989) Skeletal changes in vertical and anterior displacement of the maxilla with bonded rapid palatal expansion appliances American Journal of Orthodontics and Dentofacial Orthopaedics 95: 462-466 Shanker S, Ngan P, Wade D, Beck M, Yiu C, Hägg U and Wei SHY (1996) Cephalometric A point changes during and after maxillary protraction and expansion American Journal of Orthodontics and Dentofacial Orthopaedics 110: 423-430 Silva Filho OG, Magro AC and Filho LC (1998) Early treatment of the class III malocclusion with rapid maxillary expansion and maxillary protraction American Journal of Orthodontics and Dentofacial Orthopaedics 113: 196-203 Stellzig-Eisenhauer A, Lux CJ and Schuster G (2002) Treatment decision in adult patients with Class III malocclusion: Orthodontic therapy or orthognathic surgery?

American Journal of Orthodontics and Dentofacial Orthopaedics 122: 27-38 Suda N, Suzuki MI, Hirose K, Hiyama S, Suzuki S, and Kuroda T (2000) Effective treatment plan for maxillary protraction: is the bone age useful to determine the treatment plan?

American Journal of Orthodontics and Dentofacial Orthopaedics 118: 56-62 Sugawara J and Mitani H (1997) Facial growth of skeletal class III malocclusion and the effects limitations, and long term adaptations to chincap therapy Seminars in Orthodontics 3: 244-254 Sugawara J, Asano T, Endo N and Mitani H (1990) Long-term effects of chincap therapy on skeletal profile in mandibular prognathism American Journal of Orthodontics and Dentofacial Orthopaedics 98: 127-133 Sung SJ and Baik HS (1998) Assessment of skeletal and dental changes by maxillary protraction American Journal of Orthodontics and Dentofacial Orthopaedics 114: 492-502 Tahmina K, Tanaka E and Tanne K (2000) Craniofacial morphology in orthodontically treated patients of Class III malocclusion with stable and unstable treatment outcomes American Journal of Orthodontics and Dentofacial Orthopaedics 117: 681-690

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Thilander B (1963) Treatment of Angle class III malocclusion with chin-cap Transactions of the European Orthodontic Society 39: 384-398 Turley PK (1996) Orthodontic correction of class III malocclusion; retention and phase II therapy Journal of Clinical Orthodontics 30: 313-324 Turley PK (2002) Managing the developing Class III malocclusion with palatal expansion and facemask therapy American Journal of Orthodontics and Dentofacial Orthopaedics 122: 349-352 Tzatzakis V and Gidarakou IK (2008) A new clinical approach for the correction of anterior crossbites World Journal of Orthodontics 9: 355-365 Üçem TT, Üçüncü N and Yüksel S (2004) Comparison of double plate appliance and facemask therapy in treating class 3 malocclusions American Journal of Orthodontics and Dentofacial Orthopaedics Üner O, Yüksel S and Üçüncü N (1995) Long term evaluation of chincap therapy European Journal of Orthodontics 17: 135-141 Vaughn G, Mason B, Moon H-B and Turley PK. (2001) The effects of maxillary protraction therapy with or without rapid palatal expansion: a prospective, randomized clinical trial [abstract] Journal of Dental Research 80: SI: 541(0117) Vaughn G, Mason B, Moon H-B and Turley PK (2005) The effects of maxillary protraction therapy with or without rapid palatal expansion: A prospective, randomized clinical trial American Journal of Orthodontics and Dentofacial Orthopaedics 128: 299-309 Velázquez P, Benito E and Bravo LA (1997) Rapid maxillary expansion. A study of the long-term effects American Journal of Orthodontics and Dentofacial Orthopaedics 109: 361-367 Wells AP Sarver DM and Proffit WR (2006) Long-term efficacy of reverse pull headgear therapy Angle Orthodontist 76: 915–922 Williams MD, Sarver DM, Sadowsky PL and Bradley E (1997) Combined rapid maxillary expansion and protraction facemask in the treatment of class III malocclusions in growing children: a prospective long-term study Seminars in Orthodontics 3: 265-274 Yoshida I, Yamaguchi N and Mizoguchi I (2006) Prediction of post-treatment outcome after combined treatment with maxillary protraction and chincap appliances European Journal of Orthodontics 28: 89-96 Yüksel S, Ücem TT and Keykubat A (2001) Early and late facemask therapy European Journal of Orthodontics 23: 559-568 Yoshida I, Shoji T and Mizoguchi I (2007) Effects of treatment with a combined maxillary protraction and chincap appliance in skeletal Class III patients with different vertical skeletal morphologies European Journal Orthodontics 29: 126-133 Zentner A, Doll GM and Peylo SM (2001) Morphological parameters as predictors of successful correction of Class III malocclusion European Journal of Orthodontics 23: 383-392

THE ORTHODONTIC MANAGEMENT OF OPEN BITE CASES EXCELLENCE IN ORTHODONTICS 2012

Chapter

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20 The orthodontic management of open bite cases David Birnie

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Introduction Many orthodontists are concerned about the difficulties of management of high angle and open bite cases. It is usually neither clear which angle is increased nor what the relationship between facial morphology and open bite is. The underlying implication is that the establishment of a normal overbite may be difficult in such cases. Some of the angles implicated in the term high angle are the SN/MnP angle, the FH/MnP angle, the SN/MxP angle and the MxP/MnP angle. In reality, the term high angle covers a number of conditions that include the long face syndrome, posterior growth rotation, anterior open bite and open bite tendency.

Betzenberger et al (1999) have shown that considerable dentoalveolar compensation may occur in individuals with high angle malocclusions which they defined as those having a SN/MP angle ≥ 40°. Of the 191 subjects, 50% had a normal overbite (0-4 mm), 30% had a deep overbite (>4 mm) and only 20% had an open bite (<0 mm).

Skeletally, the open bite group had SN/MnP and an MxP/MnP angles which were 3.2° higher than those in the deep bite group. Oral habits (mouth breathing, digit sucking and tongue thrusts) were more common in the open bite group.

The difficulty of establishing a positive overbite or the development of an unexpected open bite tendency during orthodontic treatment is however of concern to all orthodontists.

Facial morphology Long faces Proffit, with characteristic clarity, sums up the problem in the first paragraph of his paper with Fields et al (1984) on Facial pattern differences in long face children and adults: “Children and adults who have excessive vertical facial growth demonstrate a characteristic facial appearance and have been described as having ‘long-face syndrome’. Because the disproportionately long lower face is often accompanied by an open bite, this condition has also been labelled ‘skeletal open bite’. This terminology has led to confusion in the literature since samples of persons suspected of having vertical problems have been chosen on the basis of overbite or open bite or mandibular plane angle. Not all long-faced patients have open bite and not all open bite patients are long faced. Not surprisingly, these studies have yielded different conclusions as to exactly where the morphologic problems associated with vertical dysplasia are located.”

This study looked at 42 children and 42 adults and classified them as long, normal or short faced based on their clinical appearance. There were differences between all groups for SN/MnP and MxP/MnP. Although all groups had differences in anterior total face height there were no differences in posterior face height. If total face height was split into upper and lower, both anterior and posterior face heights were similar thus leaving lower anterior face height as the principal difference between the groups.

Further evaluation showed that the ramus and body sizes were similar but that the gonial angle was increased in long face children and decreased in short face children.

Long face children had greater posterior upper and lower dental height than normal children although upper anterior dental height was not larger.

Adults showed similar findings but with a tendency to short rami and excessive tooth eruption Proffit and Fields (1983) have reported that occlusal forces in long faced children are no different from those in normal children but that long faced adults have less occlusal force. It would seem unlikely therefore that long faces are due to weak muscular patterns.

Open bite

Cangialosi (1984) suggested that patients with anterior open bite had increased PFH/AFH and UFH/LFH ratios. In addition, the SN/MnP, the gonial and the MxP/MnP angles were all increased in the open bite group. The study emphasised the great variability which can occur in dental and skeletal morphology in patients with open bite.

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Jones (1989) has looked at the cephalometric differences between black and white patients. Jones found that:

â&#x20AC;˘ â&#x20AC;˘ â&#x20AC;˘

black anterior open bite patients had normal SNAs but that SNB was less than normal. Interincisal angles were more acute than normal and both upper and lower incisors were more procumbent than normal. dental anterior open bite cases had maxillary protrusion and a greater upper incisal proclination.

However, skeletal open bite patients showed backward and downward rotation of the mandible, greater lower incisal proclination, and SN/MnP values above the norm. a comparison of anterior open bite data for black and white subjects showed that black subjects had longer lower facial heights and white subjects had numerically larger SN/MnP values.

Katsaros and Berg (1993) have suggested that orthodontic treatment can be successful in producing incisor contact post-retention in about 75% of cases and that cases with an increased facial convexity in which the incisors can be retroclined have a favourable prognosis. Root resorption of greater than 10% of the upper incisor root length occurred in 20% of this sample.

The validity of diagnostic tests Condition present

Condition absent

Positive test

True positive (TP)

False positive (FP)

Negative test

False negative (FN)

True negative (TN)

Table 20.1:

A 2 x 2 decision matrix for a diagnostic test

patient has a specific condition as shown in Table 20.1.

An interesting paper was published Wardlaw et al in 1992. This attempts to assess the reliability and validity of cephalometric tests for the presence of anterior open bite. The paper gives a good summary of the effectiveness of diagnostic tests. Diagnostic tests have cut-off point to determine whether or not a

From this decision matrix, a number of characteristics of a diagnostic test can be calculated.

The sensitivity of a test is its ability to correctly identify a patient with a specific condition and is given by the following formula. Similarly, specificity is the ability of a test to correctly identify a patient without a specific condition and is given by the adjacent formula.

Predictive values of a test indicate the probability of a condition being present or absent when the test is positive or negative respectively. Hence:

The likelihood ratio for a positive result indicates the odds that a patient with that cut-off value has the condition, as opposed to not having it. A likelihood ratio of 1.0 implies that a test is of no value in changing the initial diagnostic certainty. The likelihood ratio is given by the following formula:

Aetiology An important message in this chapter is that the aetiology of open bite is not that one of the vertical angular measurements relating the maxilla and mandible is increased.

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The principal aetiological factors in open bite are:

• • • •

increased facial proportions digit sucking soft tissue habits and posture the influence of lymphoid tissue on o tongue posture o mandibular posture o airway

Tongue movement during swallowing Stage

Description

1

Loss of contact of the dorsal tongue with the soft palate

2

Passage of the bolus head across the posterior/inferior margin of the ramus of the mandible

3

Bolus head enters the oesophagus

Table 20.2: et al (2004)

• • •

The three stages of swallowing described by Fujiki

The role of soft tissues in orthodontics has been difficult to determine largely due to the difficulty in quantifying and describing soft tissue behaviour. Fujiki et al (2004) have investigated the behaviour of the tongue during swallowing in patients with and without anterior open bites using cineradiography and related these findings to the maxillomandibular morphology of the patients. During swallowing and compared to patients with normal occlusions, patients with anterior open bite have:

tongue tip protrusion slower movement of the dorsal part of the tongue earlier closure of the nasopharynx

Fujiki et al (2004) divided swallowing into three phases as shown in Table 20.2. The patients with anterior open bites had different maxillomandibular morphology compared to the patients with normal occlusion and these differences were similar to those described by Cangialosi in 1984. The key question is whether the morphological differences were caused by the different swallowing patterns or were an adaptation to existing structural differences.

There is evidence that the tongue movement during swallowing adapts to or is affected by the presence of intraoral appliances or maxillary expansion and Proffit has shown that the intermittent nature of the forces produced during swallowing are too small to affect the morphology of open bite. Fujiki et al (2004) concluded that:

• • • • •

tongue behaviour during swallowing was adaptive to the skeletal open bite skeletal open bite leads the front part of the dorsum of the tongue to assume a lower position after stage 2 of swallowing, the front part of the dorsum of the tongue became more elevated and the degree of elevation was positively correlated with the severity of the anterior open bite the degree of tongue tip protrusion was unrelated to the degree of anterior open bite tongue movement during swallowing was related to the maxillomandibular morphology but that this represented adaptation or compensation.

The authors are carrying out a further study on tongue behaviour in patients with corrected anterior open bites but preliminary data suggests that this results in a normalisation of tongue movement during swallowing.

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Measurement

Diagnosis

Criteria

SN/MP angle or greater

393

40°

OP/MP angle

22° or greater

MxP/MnP angle

32° or greater

Increased facial proportions

Patients with an anterior open bite due to increased facial proportions can normally be diagnosed clinically; if you have 58% or less PFH/AFH to resort to cephalometrics then perhaps the facial proportions are not increased that much. In the absence of 0.700 or less UFH/LFH other factors the open bite is assumed to be due to the Table 20.3: Cephalometric measurements and criteria incisors reaching the limit of their eruptive potential before used in Dung and Smith's sample (1988) incisor contact is made. These patients will require surgery to correct their facial disproportion – a task to which orthodontics has found itself unequal.

AOB

negative overbite

Digit sucking Anterior open bites due to digit sucking are characterised by an anterior open bite frequently limited to the incisor region. Asymmetry of the open bite which corresponds with the digit being sucked is common as is damage to the sucked digit. Patients usually freely admit to a digit sucking habit even as adults.

Soft tissue habits and posture The presence of an anterior open bite in the absence of increased facial proportions or a digit sucking habit leaves us in a diagnostic void. Soft tissue habits and posture are a vague and imprecise concept whose proof of existence depends largely on treatment success following an attempt to modify the soft tissue problem.

Nevertheless this an area which merits further thought rather than the dismissal it has been given over the past decade and a half.

The influence of lymphoid tissue

Once thought to be important, the role of lymphoid tissue in the development and maintenance of anterior open bite is now thought to be minor due to the natural changes occur in the size of lymphoid tissue occur with maturity and the wish to minimise unnecessary surgery.

The role of cephalometric analysis

Dung and Smith published an interesting paper on Cephalometric and clinical diagnoses of open bite tendency in 1988. In this paper, the authors obtained pretreatment lateral cephalometric radiographs between 10 and 16 years of age selected on the basis of six cephalometric measurements. For each measurement, a value was selected which defined open bite tendency and patients in a practice were selected on the basis of meeting this criterion. Fifty patients were chosen for each value. The measurements and criteria used are shown in Table 20.3.

A seventh measurement, the overbite indicator (ODI) was measured for all groups. The ODI has been described by Kim (1974) and is defined as the angle the A-B plane makes with the mandibular plane combined with the 1.2 angle of the palatal plane to the Frankfort horizontal. If Increasing diagnostic value the latter angle is positive it is added and if negative 1 subtracted. A value of less than 68 degrees is said to indicate an open bite tendency.

0.8 0.6 0.4 0.2

No diagnostic value

0 0

Figure 20.1:

0.1

0.2

0.3

0.4

A ROC curve

0.5

0.6

0.7

0.8

0.9

1

The paper shows that conventional cephalometric measurements do not always work as well as assumed in indicating the presence of an anterior open bite. For the values considered, which are typical of values generally quoted in the literature, the success rate ranged from 12% for the Jarabak ratio to 62% for the overbite depth indicator.

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The paper went on to look at the cephalometric values in each group defined by whether or not the individual case showed an open bite tendency during treatment on a scale of 1 to 5 with the first point on the scale representing no open bite tendency and the last point severe open bite tendency.

This again showed that most measurements seemed little help in predicting clinical open bite tendency. The occlusal plane to mandibular plane angle did show a significant association but for a decreasing rather than an increasing angle. The only measurements that were statistically significant were the over depth indicator (ODI) and the presence of an open bite at the start of treatment.

The ROC (receiver operating characteristic) curve The ROC curve plots the true positive rate (sensitivity) against the false positive rate (1-specificity). An example is given in Figure 20.1. Curves that are closer to the upper left hand corner of the graph have higher sensitivities and lower false positive rates at all cut-off points and are therefore better tests.

Wardlaw et al (1992) looked at a number of cephalometric values using ROC curves to determine their validity for indicating the presence of open bite. The results are given in Figure 20.2.

In this analysis, the ODI, the anterior facial height ratio and the interincisal angle were the best diagnostic tests for anterior open bite whereas the PFH/AFH ratio, the gonial angle, the LFH ratio and the symphysis angle were the least good. Although the mandibular plane is considered a useful component of measurement for anterior open bite tendency by many clinicians, the angular measurements incorporating the mandibular plane were no better than average in this study.

It should be clear that high angle cases and open bite tendency should be treated separately. High angle cases will tend to include more frequently long face syndromes but given a satisfactory overbite at the start of treatment should not cause undue concern about overbite control. Cases with anterior open bites at the start of treatment require careful management to obtain a satisfactory overbite at the end of treatment.

Predicting mandibular rotation Bjork (1969) has published a seemingly helpful paper on the prediction of mandibular growth rotation and this led Skieller, Björk and Linde-Hansen (1984) to propose a method for predicting future mandibular growth rotation from an initial prepubertal lateral cephalogram. The authors reported that a combination of four variables accounted for 86% of the variability observed. These included: mandibular inclination, intermolar angle, shape of the lower border of the mandible, and inclination of the symphysis. Regression equations were given based on these variables that could be applied to an initial prepubertal lateral cephalogram and were believed to predict future mandibular growth rotation.

These papers are probably well known to all orthodontists and represent ‘classical’ orthodontic theory.

90 80 70 60 50 40 30 20 10

Figure 20.2: Areas under the ROC curves for various cephalometric measurements

Symp ang

LFH

Go ang

PFH/AFH

Y-axis

OP-MP

SN-MP

PP-MP

II Ang

AFH

ODI

0

Leslie et al (1998) have however published an interesting paper that casts considerable doubt on Skieller, Björk and Linde-Hansen’s method. The Skieller study was repeated on 40 patients and it was that individually, the four variables only predicted 5.6% of mandibular rotation, and in combination, 9%. Furthermore, running a Monte Carlo simulation with random data showed that 84% of variability could be accounted for using completely meaningless data. In conclusion, information derived from pre-treatment lateral cephalometric radiographs using the Skieller, Björk, and Linde-Hansen method does not permit clinically useful predictions to be made in a general population relative to the direction of future mandibular growth rotation.

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A simple diagnostic classification

A simple clinical diagnostic classification might be as follows:

• • •

anterior open bite with increased facial proportions anterior open bite with history of digit sucking and normal facial proportions anterior open bite with no history of digit sucking and normal facial proportions

Patients with a history of digit sucking and normal facial proportions have a favourable prognosis for treatment by orthodontic means alone provided the digit sucking habit is stopped. Patients with increased facial proportions frequently require orthognathic surgery to close the open bite.

The middle category is an enigma. What causes the anterior open bite? Our belief in soft tissue habits has been reduced by the difficulty in deriving objective diagnostic indicators. It is worth reading the paper by John Parker (1971) in which spurs soldered to upper central incisor bands produce dramatic changes in anterior open bite and posterior crossbite by altering tongue posture. The suggestion is that anterior tongue posture is responsible for anterior open bites in cases of normal skeletal proportions with no history of a digit sucking habit.

The use of tongue spurs is currently proposed by Roberto Justus. The tongue spurs should be placed approximately 3-4 mm behind the upper incisors and should be angled backwards and downwards so that they establish a positive overlap with the lower incisors.

Parker and Justus’ concern that sharpened tongue spurs might cause psychological problems was allayed by Haryett et al (1967, 1970). The suggestion is that provided a good relationship exists between patient and orthodontist, no treatment will cause psychological damage. Careful explanation of the purpose of tongue spurs is therefore essential before embarking on treatment; Roberto Justus claims to have given patients John Parker’s 1971 paper to read before starting treatment.

We have little experience of tongue spurs but these are perhaps worth consideration in selected cases; the experience we do have is encouraging.

Management of open bite tendency The key to the management of open bite tendency is:

• •

elimination of the aetiology the avoidance of the extrusion of posterior teeth and if possible to produce relative or real intrusion of these teeth.

There is a lack of evidence about the best way to treat early anterior open bites as shown by Cozza et al 2004.

The elimination of the aetiology

Digit sucking habits Patients should be encouraged to give up their digit sucking habit as soon as it appears to be having an adverse effect on the dentition. Patients frequently respond to verbal advice from their orthodontist rather than their parents. We rarely use appliances to discourage the habit but taping a rolled up tea towel to the inside of the elbow as a reminder often works well (it is difficult to suck your thumb if you cannot bend your elbow) as does the wearing of a boxing glove on the hand with the offending digit.

Anterior tongue posture Roberto Justus’ work is undergoing a resurgence of interest. It is suggested that the relapse of anterior open bites may be due to adverse tongue posture or function. Modification of tongue behaviour might therefore improve stability. In a paper by Huang et al (1990), the stability of anterior open bite treated with a crib or spur appliance was investigated. A growing and a non-growing group was used. Both groups had pre-treatment anterior open

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bites of -2.88 mm and -2.71 mm respectively. During treatment, 23 out of 26 patients had a positive overbite at the end of treatment; one year after appliance removal, all 23 patients still had a positive overbite. Four patients showed relapse of more than 0.5 mm of overbite and loss of incisor contact. In the non-growing group, six patients had a positive overbite at the end of treatment and all seven patients had a positive overbite one year after appliance removal. During the one-year follow-up period, all seven patients had an increase in overbite.

Giuntini et al (2007) studied the effects of fixed and removable crib appliances in patients with open bite in the mixed dentition. Both appliances produced favourable dental effects but the fixed quad-helix with cribs produced more favourable skeletal effects which was attributed to the lesser compliance required to wear it.

Taslan et al (2010) studied tongue pressures in open bite patients with and without crib appliances which were worn for at least 10 months. They found a decrease in tongue pressure in the group wearing the crib appliance which was maintained two months after crib removal. The overbite decreased from -2.12 mm to + 0.62 mm in the group that wore the crib appliance and from -2.83 mm to -2.33 mm in the group that did not. The authors concluded that:

• • •

the crib appliance wear resulted in a disturbance in intraoral pressure equilibrium resting and swallowing tongue pressures remained essentially the same in the control group while resting tongue pressures at the twelfth month remained lower than initial values in the experimental group swallowing tongue pressures returned to baseline values in the experimental group at the twelfth month

Significant decreases in resting and swallowing pressures on the crib appliance in the experimental group suggested tongue adaptation to the new position created by the appliance.

Further interesting reading is Muscle Wins: Treatment in Clinical Orthodontics by Etsuko Kondo.

Preventing the extrusion of posterior teeth This can be done using transpalatal bars, high pull headgear in conjunction with transpalatal bars, attempting to prevent the downward growth of the maxilla using a maxillary intrusion splint, the extraction of terminal molars and by the intrusion of terminal molars. The intrusion of terminal molars can be achieved by fixed appliances (Kim 1987), bite blocks or magnets. Defraia et al (2007) have reported on the use of open-bite bionators in patients with high-angle open bites (MMP ≥ 25°). Open-bite bionators have posterior bite blocks to prevent extrusion of the posterior teeth. The bite is taken with just sufficient opening to allow the placement of the posterior bite blocks. The lower lingual acrylic extends into the maxillary incisor region as a lingual shield, without touching the upper incisors to inhibit tongue movements. The study demonstrated modest effectiveness of early treatment of skeletal open bite with the open-bite bionator. Intermaxillary divergence improved in the treatment group compared with the control group but no favourable effects on the extrusion of posterior teeth were found.

Which patients require surgery?

Orthognathic surgery should be considered in patients with severe facial disproportion in whom correction of the disproportion is a treatment goal. Not all patients will however perceive the correction of mild to moderate facial disproportion as a treatment goal. The orthodontic techniques described in this lecture will not significantly influence facial proportions.

Treatment techniques

Occlusal adjustment Janson et al (2008) have described the use of occlusal adjustment under very specific circumstances in order to close anterior open bites. This study looked at 20 patients who had had previous orthodontic treatment for anterior open bite which had relapsed. A overbite increase of 2.83 mm was achieved using the method of occlusal adjustment described by Jeffrey Okeson. There was a significant increase in dentine sensitivity following treatment which subsided 4.6 months after the occlusal adjustment.

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Tongue cribs The use of tongue cribs and spurs described by Parker (1971), Haryett (1967 and 1970) and Huang et al (1990) merits consideration. The rationale behind such treatment is that the use of spurs or cribs permanently alters tongue posture or behaviour. It is worth listening to Roberto Justusâ&#x20AC;&#x2122; guest lecture on the April 1999 Educational Reviews tape. Tongue cribs or spurs should be worn for six months after a positive over bite is achieved; careful patient motivation is required and sharpened spurs are preferred to smooth ones. The spurs may be carried over to the retainer if desired. Ortho Technology produces bondable tongue spurs called Tongue Tamers. MeyerMarcotty et al (2007) showed that the use of tongue spurs the height of the alveolar process in the maxilla by a mean of 1.61 mm and of the alveolar process in the mandible by a mean of 1.36 mm; overbite increased by an average of 1.95 mm. The lower incisors uprighted causing an increase in overjet. The duration of spur therapy was 9 months.

Hi-pull headgear and transpalatal bars For minimal overbites and small anterior open bites, successful results can be achieved by careful control of the buccal segments in the vertical dimension. The use of a transpalatal bar on the first molars can prevent dropping of the palatal cusps of the first molars but the use of transpalatal bars on the first and second molars is cumbersome and seems to offer little advantage.

High pull headgear is claimed to intrude the first molars or at least reduce their vertical development. The point of application of the force however tends to result in more intrusion of the buccal cusps than the palatal cusps. A transpalatal bar is mandatory under these circumstances.

In a study by Wise et al (1994) which compared 20 nonextraction patients in which a transpalatal bar was used for at least 5 months with similar patients in whom it was not used, no significant differences were found between the two groups. The transpalatal bar design used was fitted 1-2 mm off the palate.

Adjunctive masticatory muscle exercises English and Olfert (2005) have reported three cases where adjunctive masticatory muscle exercises have helped in closing anterior open bites. Patients received rapid maxillary expanders followed by a transpalatal arch with an acrylic button 2â&#x20AC;&#x201C;3 mm off the palatal tissue with high pull headgear and a fixed lingual arch. After the expansion was complete, patients were allocated to an exercise or non-exercise group. The exercise group was asked to clench on a soft bite wafer five times a day for one minute. During the one minute period, the patient was asked to clench isometrically (80% bite force) for five seconds and rest for five seconds. One patient had an increased exercise regime with isometric clenching for a minimum of five minutes very hour for at least six hours a day and achieved a reduction of 4.2 degrees in her SN-MP angle from 37.7 to 33.5 degrees.

Smithpeter and Covell (2010) reported that oral myofunctional therapy with orthodontic treatment was efficacious in closing and maintaining closure of dental open bites in class I and class II malocclusions, and it reduced the relapse of open bites in patients who had forward tongue posture and tongue thrust by reducing these behaviours. Overbite relapse was 0.5 mm (range, 0.0-4.0 mm) in the experimental group and 3.4 mm (range, 1.0-7.0 mm) in the control group, a difference that was both clinically and statistically significant. Speech errors and oral habits were associated with relapse but were often correctable with oral myofunctional therapy. In addition to dental anterior open bites, common denominators in both cohorts at the initial oral myofunctional therapy examination were forward tongue rest posture and tongue thrust swallows, and the only common denominators in the stable experimental subjects were palatal tongue rest posture and swallow. The oral myofunctional therapy was based on the work of Weiss and van Houten (1972).

Kim mechanics The use of a multiloop archwire to intrude buccal segments as described by Kim (1987) is an interesting approach.

Kim bases his technique on the fact that the characteristic features of anterior open bite are an obtuse mandibular plane and gonial angle, a palatal plane that is tipped upward and forward and mesial tipping of the dentition.

Treatment should therefore be based on the extraction of terminal molars and distal tipping of the dentition. This is achieved using multiloop edgewise archwires made from 0.016" x 0.022" stainless steel archwires. Kim recommends an 0.018" slot and standard edgewise brackets for reasons that are obscure. Use of the technique

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with an 0.022" Straight-Wire Appliance system has produced no problems. The archwires are ideal in shape with five L-loops on each side starting from between the lateral incisor and canine and working distally. The vertical dimensions of the loops should be 2-3 mm and the horizontal dimensions 5 mm except in the molar region where this is increased to 8 mm. Tipbacks of 3-5 degrees are placed on each loop. This effectively produces a curve of Spee in the upper arch and a reverse curve of Spee in the lower arch. These are counteracted by placing 3/16" heavy elastics vertically between the most anterior loops in the maxilla and mandible. This transfers all the active force in the archwire to the posterior segments thus intruding the posterior buccal segments.

Aras (2002) has confirmed that extracting further back in the arch, i.e.: first molars or second premolars compared with first premolars, results in a reduction in the maxillary mandibular plane during treatment.

For some years we have used reverse curve nickel-titanium archwires instead of multiloop wires and these seem to work just as well. Hooks are provided by using crimpable hooks such as those made by TP. The use of nickeltitanium wires has been written up by Enacar et al (1996) and Küçükkeles et al (1999). These studies indicated that open bite closure was achieved mainly by extrusion of the lower incisors and uprighting of the upper incisors; the functional occlusal plane was levelled by extrusion of lower premolars and uprighting of lower molars.

The pattern of elastic wear has been modified to that suggested by Schudy. During treatment a stage is reached when the terminal molars are out of contact and no further reduction of the anterior open bite occurs; at this stage, flat 0.016" x 0.022" archwires are placed to upright the molars while continuing the anterior elastics. This normally closes down any residual anterior open bite.

Chang and Moon (1999) studied the treatment changes in anterior open bite cases treated with the MEAW technique and found that most changes occurred in the dentoalveolar regions of the upper and lower occlusal planes. After treatment, the structural features of the open bite group were similar to those of the control group.

This study suggested that multiloop edgewise archwire technique could not really intrude the molars although it did upright the molars which could improve the inclination of the maxillary or mandibular occlusal plane thus assisting the correction of an anterior open bite.

Functional appliances The use of functional appliances in the management of open bite has been described by Frankel and Frankel (1983) and Weinbach and Smith (1992). These appliances combine a bite block effect with freedom to allow the incisors to erupt. They are probably used to treat class 2 cases where eruption of the posterior buccal segments is felt to be undesirable rather than to manage skeletal open bites. Interestingly, Weinbach and Smith’s study suggested that the use of headgear to the functional appliance was of no additional benefit in closing down the anterior open bite.

Magnets The use of magnets was in orthodontics was originally described by Blechman and Smiley (1978). The types of magnet originally used were aluminium-nickel-cobalt (AlNiCo5) but the development of rare earth magnets such as samarium-cobalt (SmCo17) and neodymium-iron-boron (Nd2Fe14B) have reduced the volume of a magnetic unit per unit of force by sixteen times. Magnets are coated with a thin vaporised coating (250 µm) of parylene (polypara-xylene) to protect the magnets against corrosion (Vardimon et al 1991).

The use of magnets for vertical dysplasias was pioneered by Dellinger in 1986 but no scientific study of his treatment results has been published. Kalra, Burstone and Nanda (1989) have suggested that magnets may be beneficial in treating anterior open bites by:

• •

intruding upper and lower posterior teeth so as to allow mandibular autorotation and distracting the condyle downwards and forwards to allow compensatory condylar growth which would again favour mandibular autorotation

The results of the study showed that:

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• • • •

399

some class 2 correction was achieved the upper and lower dental arches were intruded there was autorotation of the mandible (the MxP/MnP angle decreased by 1.3° in the experimental group) temporary buccal crossbites were created to the shearing forces produced by the magnets

Looking at the vertical dimension, the changes produced in this study were disappointingly small.

The use of magnets is also not without its difficulties as described by Kiliardis et al (1990) and at this time must be considered both experimental and ineffective.

Temporary anchorage devices The last five years have seen a rapid growth in the use of miniplates or miniscrews used as temporary anchorage devices to intrude molar teeth and thus reduce anterior open bites.

Umemori et al (1999) used titanium miniplates to intrude mandibular molars by 3 to 5 mm in conjunction with multi-loop edgewise archwires. In 2002, Sherwood et al tested the feasibility of using miniplates in the maxilla and demonstrated mean reduction in anterior open bite of 3.6 mm with a range of 3.0 to 4.5 mm.

Erverdi et al (2006) have described the use of zygomatic anchorage combined with an intraoral appliance to allow en masse intrusion of the posterior buccal segments without buccal flaring of the teeth due to the direction of pull of the zygomatic anchorage. A cephalometric analysis of 10 patients done by Everdi et al (2004) showed a reduction of approximately 2 degrees in the maxillary-mandibular planes angle during treatment.

Miniscrew implants can be used buccally and palatally in the maxilla to facilitate molar intrusion and this has been described by Park et al (2004) and Park et al (2006). This latter paper also combines the use of mini-screws in the lower arch combined with a lower lingual arch to simultaneously intrude lower molars.

Both techniques can deliver impressive results (see Kuroda et al 2004). Whether miniplates or miniscrews are the optimum method of treatment remains a matter of debate as does whether to intrude in the posterior maxillary segments only or in both maxillary and mandibular posterior buccal segments. These techniques are very operator sensitive and should only be attempted after appropriate training. Park et al (2006) have discussed the factors affecting the success of implants for orthodontic anchorage but as pointed out by Graham (2006), omitted screw design or handedness of the operator.

A further interesting case involving an anterior open bite and temporomandibular joint disorder is shown by Kuroda (2007).

Xun et al (2007) described a study of 12 non-growing patients with anterior open bites. The cases were selected as:

• • • •

the patient's growth was completed or primarily completed long-face pattern with anterior open bite and mild Class II skeletal relation non-acceptance of orthognathic surgery patient had previously received premolar or molar extraction

In 11 patients, microscrews were inserted after the teeth had been aligned and the extraction space closed, while the overbite remained negative. In only one case, with extraction of first molars, microscrews were inserted before the space was closed. A self-drilling titanium alloy microscrew (1.6 mm in diameter and 7 mm in length) was inserted into the buccal alveolar bone between the first and second molars on each side and a 9 mm long microscrew (1.6 mm in diameter) was inserted in the posterior midpalatal area opposite the upper first molars.

0.022” preadjusted appliances and sliding mechanics were used with 0.019” × 0.025” stainless steel working archwires. Transpalatal and lingual arches were attached to the upper and lower first molars and located 5 mm

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from the palatal or lingual tissues; traction hooks were soldered onto the transpalatal arch close to the first molars.

Nickel titanium coil springs were placed bilaterally in the maxillary arch between the microscrew and traction hooks on the transpalatal arch and power chain was connected bilaterally between the miniscrew and main arch in the mandible; the force level was approximately 150 g each side.

The upper and lower molars achieved intrusion of 1.8 mm and 1.2 mm respectively in a mean of 6.8 months of treatment. The anterior teeth extruded without anterior elastics, helped closure of the open-bite. The mandibular plane angle also had a significant decrease (mean 2.3°) caused by molar intrusion and these effects results contributed to the 4.2-mm increase in anterior overbite.

Park et al (2008) has described the closure of an anterior open bite using three 2 mm diameter and 8 mm long miniscrews placed buccally in the interdental spaces between first premolar and second molar and using an RME splint to ensure intrusion took [place without buccal tipping. The anterior open bite closed down in 5 months.

Elastomeric chain was used to apply the force of 150g to 200g per side. The FMPA decreased from 41° to 36° during treatment and the class 2 malocclusion corrected. The authors make the following points:

•

consider the skeletal relationship including the vertical, transverse, and anterior-posterior relations.

For example, a skeletal class 2 open bite with a long anterior facial height can be treated successfully by the intrusion of the posterior teeth as this would produce a closing counterclockwise rotation of the mandible with a shortening of the anterior facial height and a correction of the open bite. Sugawara et al (2002) reported that during intrusion of the molars with a skeletal anchorage system, the anterior lower facial height, mandibular plane angle, and ANB difference reduced significantly, whereas the overbite and Wits appraisal increased significantly.

Hence, the intrusion of the molars is best suited to skeletal open bite patients who show long face types with class 1 or mild class 2 skeletal patterns whereas in class 3 open bites, the class 3 malocclusion would get worse as the anterior open bite closed • incisor exposure at rest and smile are important objectives to consider before treatment. Patients who do not show sufficient incisor exposure should not be treated by molar intrusion, making the more conventional method of incisor extrusion a more suitable option for open bite correction • for patients with a dual occlusal plane, segmental intrusion of the posterior buccal segments is indicated. However, during the active intrusion phase, careful monitoring of the first, second, and third order relationship of the intruded molars should be monitored. In segmental force application, the in and out position of molars and the archform integrity are difficult to maintain.

In terms of the angulation, control of the intruded molars is important because anterior bite closure is more effective the closer the teeth are intruded to the hinge axis. Posterior torque control is the most important factor for molar intrusion; for a pure intrusion of molars, the force should be applied from both the buccal and palatal direction. This can be achieved by placing miniscrews on both the buccal and palatal, by using a transpalatal bar or a splint (such as in this case). An alternative design of splint is shown in Figure 20.3.

• periodontal condition should be carefully considered. When intruding molars with periodontal disease, Melsen et al (1988) suggested that that the periodontal tissue recovers by new attachment through intrusion, whereas Vanarsdall (1995) suggested that for the health of the periodontal tissue, the tooth should be extruded rather than intruded, because bone deposition occur with tensions rather than with pressure. In patients with periodontal disease therefore, adequate Figure 20.3: Acrylic splint suitable for use in fully bonded cases: the two segments of the splints are joined together by palatal arches periodontal treatment is essential before approximately 5mm off the palate undergoing any orthodontic treatment and

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surgical intervention is the treatment of choice for open bite correction if the periodontal condition is unsuitable for molar intrusion.

Stability The stability of long term anterior open bite correction in orthodontically treated patients has been looked at by Lopez-Gavito et al (1985). This study looked at 41 patients all of whom had had an anterior open bite of at least 3 mm. Ten years after treatment, 35% of patients had an anterior open bite of at least 3 mm. No reliable predictor of post-treatment relapse could be found.

Very few studies have been carried out which objectively analyse Young Kim’s approach. Nalchajian (1990) looked at 24 patients treated with multiloop edgewise archwires (MEAW) cephalometrically and found that:

• • • • •

few skeletal changes took place several significant dental changes occurred all patients ended up with a positive overbite most changes tend to relapse somewhat but remained significantly changed 2 years after treatment

Goto et al (1994) made similar observations.

millimetres

Kim et al (2000) have reported (in a retrospective study) on the stability of anterior open bite correction following MEAW therapy during a two-year follow-up period. 55 patients were looked at; 29 growing patients and 26 nongrowing patients. The average duration of treatment 5 was 27 months for the growing group and 17 months 3 for the non-growing group. On average, overbite increased by 4 mm during treatment in both the 1 growing and non-growing groups; this correction was -1 very stable and relapse over a 2-year follow-up period was less than 0.5 mm for both the growing (0.23 mm) -3 and non-growing (0.35 mm) group. The open bite was -5 corrected by retraction and extrusion of the anterior teeth, uprighting of the posterior teeth and -7 convergence of the upper and lower occlusal planes.

-9 Pretreatment

Posttreatment

Postretention

Figure 20.4: Maximum, minimum and mean ± 1 sd of overbite for Janson's study (2003) 3 1

millimetres

-1 -3 -5 -7 -9 Pretreatment

Posttreatment

T3

Figure 20.5: Maximum, minimum and mean ± 1 sd of overbite for de Freitas‘ study (2004)

Studies are beginning to appear with longer postretention times and one of these has been produced by Janson et al (2003). This looked at patients with an anterior open bite of at least 1mm who were treated with nonextraction edgewise mechanics; the anterior open bite was closed with intermaxillary elastics. Myofunctional therapy was used to 'control tongue function and posture' but no details of this are given. The retention method was an upper Hawley retainer and a lower canine to canine retainer. Overbite was measured parallel to the occlusal plane. The mean follow-up period was 5 years post-retention (range 3.1 to 9.3 years). The values for overbite before and after treatment and after retention are shown in Figure 20.4.

62% of patients in the experimental group had a positive overbite at the end of retention; the reason for the decrease in overbite during the retention period was vertical development of the posterior mandibular

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teeth. These results are helpful but demonstrate the tenuous nature of closure of anterior open bites and the relapse tendency postretention despite clinician's best efforts.

De Freitas et al (2004), who shared a number of co-authors with Janson’s study, looked at the stability of anterior open bite correction treated with extraction at an average of 8.4 years post treatment (T3). Anterior open bite (or overbite) was measured using the same method as Janson et al (2003). A variety of treatment methods was used including rapid maxillary expansion, high pull headgear, cervical pull headgear and anterior elastics. They found that 74.2% of cases had a positive overbite at the end of the observation period. Not surprisingly, patients who had a smaller anterior open bite at the start of treatment obtained better results and those patients who had most change in overbite did least well in the post-treatment period.

It should be remembered that even surgery has a 42.9% relapse rate (Denison et al 1989); in this sample, six out of twenty-eight patients relapsed to a negative overbite post-treatment.

References Aras A (2002) Vertical changes following orthodontic extractions in skeletal open bite subjects European Journal of Orthodontics 24: 407-416 Betzenberger D, Ruf S and Pancherz H (1999) The compensatory mechanism in high-angle malocclusions: a comparison of subjects in the mixed and permanent dentition Angle Orthodontist 69: 27-32 Bjork A (1969) Prediction of mandibular growth rotation American Journal of Orthodontics 55: 585-599 Blechman AM and Smiley H (1978) Magnetic force in orthodontics American Journal of Orthodontics and Dentofacial Orthopaedics: 435-443 Cangialosi TJ (1984) Skeletal morphologic features of anterior open bite American Journal of Orthodontics and Dentofacial Orthopaedics 85: 28-36 Chang Y and Moon SC (1999) Cephalometric evaluation of the anterior open bite treatment American Journal of Orthodontics and Dentofacial Orthopaedics 115: 29-38 Cozza P, Mucedero M, Baccetti T and Franchi L (2004) Early orthodontic treatment of skeletal open-bite malocclusion: a systematic review Angle Orthodontist 75: 707-713 Defraia E, Marinelli A, Baroni G, Franchi L, Baccetti T (2007) Early orthodontic treatment of skeletal open-bite malocclusion with the open-bite bionator: A cephalometric study American Journal of Orthodontics & Dentofacial Orthopaedics 132: 595-598 De Freitas MP, Baltrão RTS, Janson G, Henriques JFC and Cançado RH (2004) Long term stability of anterior open bite extraction treatment in the permanent dentition American Journal of Orthodontics and Dentofacial Orthopaedics 125: 78-87 Dellinger EL (1986) A clinical assessment of the Active Vertical Corrector - A nonsurgical alternative for skeletal open bite treatment American Journal of Orthodontics and Dentofacial Orthopaedics 89: 428-436 Denison TF, Kokich VG, and Shapiro PA (1989) Stability of maxillary surgery in openbite versus non openbite malocclusions Angle Orthodontist 59: 5-10 Dung DJ and Smith RJ (1988) Cephalometric and clinical diagnoses of open bite tendency American Journal of Orthodontics and Dentofacial Orthopaedics 94: 484-490 Enacar A, Ugur T and Toroglu S (1996) A method of correction of open bite Journal of Clinical Orthodontics 30: 43-48

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English JD and Olfert KDG (2005) Masticatory muscle exercise as an adjunctive treatment for open bite malocclusions Seminars in Orthodontics 11: 164-169 Everdi N, Keles A and Nanda R (2004) The use of skeletal anchorage in open bite treatment: a cephalometric evaluation Angle Orthodontist 74: 380-391 Everdi N, Usumez S and Solak A (2006) New generation open-bite treatment with zygomatic anchorage Angle Orthodontist 76: 519-526 Fields HW, Proffit WR, Nixon WL, Phillips C and Stanek E (1984) Facial pattern differences in long-faced children and adults American Journal of Orthodontics and Dentofacial Orthopaedics 85: 217-223 Fränkel R and Fränkel C (1983) A functional approach to treatment of skeletal open bite American Journal of Orthodontics and Dentofacial Orthopaedics 84: 54-68 Fujiki T, Inoue M, Miyawaki S, Nagasaki T, Tanimoto K and Takano-Yamamoto T (2004) Relationship between maxillofacial morphology and deglutitive tongue movement in patients with anterior open bite American Journal of Orthodontics and Dentofacial Orthopaedics 125: 160-167 Giuntini V, Franchi L, Baccetti T, Mucedero M, Cozza P (2008) Dentoskeletal changes associated with fixed and removable appliances with a crib in open-bite patients in the mixed dentition American Journal of Orthodontics & Dentofacial Orthopaedics 133, 77-80 Goto S, Boyd RL, Nielson IL and Iizuka T (1994) Case report: nonsurgical treatment of an adult with skeletal open bite Angle Orthodontist 64: 311-318 Graham JG (2006) Screw implant anchorage (letter) American Journal of Orthodontics and Dentofacial Orthopaedics 130: 431 Haryett RD, Hansen FC, Davidson PO and Sandilands ML (1967) Chronic thumbsucking: the psychologic effects and the relative effectiveness of various methods of treatment American Journal of Orthodontics 53: 569-585 Haryett RD, Hansen FC and Davidson PO (1970) Chronic thumb sucking: a second report on treatment and its psychological effects American Journal of Orthodontics 57: 164-178 Huang GJ, Justus R, Kennedy DB and Kokich VG (1990) Stability of anterior open bite treated with crib therapy Angle Orthodontist 60; 17-24 Janson G, Valarelli FP, Henriques JFC, de Freitas MR and Cançado RH (2003) Stability of anterior open bite nonextraction treatment in the permanent dentition American Journal of Orthodontics and Dentofacial Orthopaedics 124: 265-276 Janson G, Crepaldi MV, de Freitas KMS, de Freitas MR and Janson W (2008) Evaluation of anterior open-bite treatment with occlusal adjustment American Journal of Orthodontics and Dentofacial Orthopaedics

134:10.e1 -10.e9

Jones OG (1989) A cephalometric study of 32 North American black patients with anterior open bite American Journal of Orthodontics and Dentofacial Orthopaedics 95: 289-296 Katsaros C and Berg R (1993) Anterior open bite: a follow-up study of orthodontic treatment effects European Journal of Orthodontics 15: 273-280 Kalra V, Burstone, CJ and Nanda R (1989) Effects of a fixed magnetic appliance on the dentofacial complex American Journal of Orthodontics and Dentofacial Orthopaedics 95: 467-478 Kiliardis S, Egermark I and Thilander B (1990) Anterior open bite treatment with magnets European Journal of Orthodontics 447-457

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Kim YH (1974) Overbite depth indicator with particular reference to anterior open bite American Journal of Orthodontics and Dentofacial Orthopaedics 65: 586-611 Kim YH (1987) Anterior open bite and its treatment with multiloop edgewise archwire Angle Orthodontist 57: 290-321 Kim YH, Han UK, Lim DD and Serraon MLP (2000) Stability of anterior open bite correction with multiloop edgewise archwire therapy; a cephalometric follow-up study American Journal of Orthodontics and Dentofacial Orthopaedics 118: 43-54 Kondo E (2008) Muscle wins! Treatment in clinical orthodontics Seoul, Daehan/Narae Publishing ISBN: 978-89-5741-112-4 Küçükkeles N, Acar A, Demirkaya AA, Evrenol B and Enacar A (1999) Cephalometric evaluation of open bite treatment with NiTi arch wires and anterior elastics American Journal of Orthodontics and Dentofacial Orthopaedics 116: 555-562 Kuroda S, Katayama A and Takano-Yamamoto T (2004) Severe anterior open-bite case treated using titanium screw anchorage Angle Orthodontist 74: 558-567 Kuroda S, Sugawara Y, Tamamura N, Takano-Yamamoto T (2007) Anterior open bite with temporomandibular disorder treated with titanium screw anchorage: Evaluation of morphological and functional improvement American Journal of Orthodontics & Dentofacial Orthopaedics 131: 550-560 Leslie LR, Southard TE, Southard KA, Casko JS, Jacobsen JR, Tolley EA, Hillis SL, Carolan C and Logue M (1998) Prediction of mandibular growth rotation: assessment of the Skieller, Björk and Linde-Hansen method American Journal of Orthodontics and Dentofacial Orthopaedics 114: 659-667 Lopez-Gavito G, Wallen TR, Little RM and Joondeph JR (1985) Anterior open bite malocclusion: a longitudinal 10 year post retention evaluation of orthodontically treated patients American Journal of Orthodontics and Dentofacial Orthopaedics 87: 175-186 Melsen B, Agerbaek N, Eriksen J and Terp S (1988) New attachment through periodontal treatment and orthodontic intrusion American Journal of Orthodontics and Dentofacial Orthopaedics 94: 104–116 Meyer-Marcotty P, Hartmann J, Stellzig-Eisenhauer A (2007) Dentoalveolar open bite treatment with spur appliances Journal of Orofacial Orthopaedics 68: 510-521 Nalchajian GA (1990) Correction of open bite malocclusion using multiloop edgewise archwires: a cephalometric evaluation Thesis: Eastman Dental Centre, Rochester, New York In: American Journal of Orthodontics and Dentofacial Orthopaedics (1992) (Abstract) 101: 291 Park HS, Kwon TG and Kwon OW (2004) Treatment of open bite with microscrew implant anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 126: 627-136 Park HS, Jeong SH and Kwon OW (2006) Factors affecting the clinical success of screw implants used as orthodontic anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 130: 18-25 Park HS, Kwon OW and Sung JH (2006) Nonextraction treatment of an open bite with microscrew implant anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 130: 390-402 Park Y-C, Lee H-A, Choi N-C, and Kim D-Y (2008) Open bite correction by intrusion of posterior teeth with miniscrews Angle Orthodontist 78: 699–710 Parker J (1971) The interception of the open bite in the early growth period Angle Orthodontist 41: 24-44 Proffit WR and Fields HW (1983) Occlusal forces in normal and long face children Journal of Dental Research 62: 571-574

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Sherwood KH, Burch JG and Thompson WJ (2002) Closing anterior open bites by intruding molars with titanium miniplate anchorage American Journal of Orthodontics and Dentofacial Orthopaedics 122: 593-600 Skieller V, Björk A and Linde-Hansen T (1984) Prediction of mandibular growth rotation evaluated from a longitudinal implant sample American Journal of Orthodontics 86: 359-70 Smithpeter J and Covell D (2010) Relapse of anterior open bites treated with orthodontic appliances with and without orofacial myofunctional therapy American Journal of Orthodontics and Dentofacial Orthopaedics 137: 605-614 Sugawara J, Baik UB, Umemori M, Takahashi I, Nagasaka H, Kawamura H and Mitani H (2002) Treatment and posttreatment dentoalveolar changes following intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction International Journal of Adult Orthodontics and Orthognathic Surgery 17: 243–253 Taslan S, Biren S and Ceylanoglu C (2010) Tongue pressure changes before, during and after crib appliance therapy Angle Orthodontist 80: 533-539 Umemori M, Sugawara J, Mitani H, Nagasaka H and Kawamura H (1999) Skeletal anchorage system for open-bite correction American Journal of Orthodontics and Dentofacial Orthopaedics 115: 166-174 Vanarsdall RL (1995) Orthodontics and periodontal therapy Periodontology 2000 9: 132–149 Vardimon AD, Graber TM, Drescher D, and Bourauel C (1991) Rare earth magnets and impaction American Journal of Orthodontics and Dentofacial Orthopaedics 100: 494-512 Wardlaw DW, Smith RJ, Hertweek DJ and Hildebolt FC (1992) Cephalometrics of anterior open bite: a receiver operating characteristic (ROC) analysis American Journal of Orthodontics and Dentofacial Orthopaedics 101: 234-243 Weinbach JR and Smith RJ (1992) Cephalometric changes during treatment with the open bite bionator American Journal of Orthodontics and Dentofacial Orthopaedics 101: 367-374 Weiss CE and van Houten JT (1972) A remedial program for tongue-thrust American Journal of Orthodontics.62: 499–506 Wise JB, Magness WB and Powers JM (1994) Maxillary molar vertical control with the use of transpalatal arches American Journal of Orthodontics and Dentofacial Orthopaedics 106: 403-408 Xun C, Zeng X and Wang X (2007) Microscrew anchorage in skeletal anterior open-bite treatment Angle Orthodontist 77: 47-56

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21 Unerupted and ectopic teeth David Birnie and Nigel Harradine

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Introduction Despite its title, this chapter is principally about the management of ectopic maxillary canines! However the principles involved are applicable to many unerupted, impacted and ectopic teeth. Other teeth that are commonly impacted are maxillary central incisors, maxillary first molars, mandibular second premolars, mandibular second molars and mandibular third molars. There is little doubt that our knowledge of the surgical and orthodontic management of these teeth has increased dramatically over the past two decades and for the majority of cases, bringing an ectopic tooth into the line of the arch is a routine procedure with a high chance of success. Good reviews on ectopic maxillary canines are given by MacSherry (1998) and Bishara (1998).

Dental age and treatment of delayed eruption Delayed shedding of deciduous teeth can be a 6.00 9.00 First molars contributing cause of 6.25 9.25 Mandibular central incisors delayed eruption of the successor teeth. In order to 7.25 10.25 Mandibular lateral incisors decide probable cause and 7.00 10.00 Maxillary central incisors effect it is helpful to assess 8.00 11.00 Maxillary lateral incisors dental age. This is best done 10.25 13.25 First premolars and mandibular canines by looking at root 11.25 14.25 Maxillary canines and second premolars development because 11.75 14.75 Second molars eruption time may be Table 21.1: Eruption times and approximate dates of completion of root development (derived affected by local factors from Van der Linden 1983) such as the early loss of, or prolonged retention of deciduous teeth. The stage of root development that is easiest to assess is closure of the root apex which is characterised by the disappearance of the dental papilla and the development of a continuous lamina dura which closely follows the outline of the root and apex. Root development of the permanent teeth is completed approximately two and a half to three years after eruption. Thus dental age can be determined from Table 21.1, as suggested by Becker (1998). The eruption times are taken from Van der Linden (1983).

Tooth

Eruption Time (years)

Root development complete (years)

This gives rise to six possible scenarios when considering extraction of deciduous teeth to assist delayed eruption of permanent successors:

• • • •

•

•

the development of the dentition is consistent with chronological age – no action required the development of the dentition is occurring earlier than the chronological age – no action the development of the dentition is occurring later than the chronological age and root development is consistent with this finding. In this case, the extraction of deciduous teeth to assist delayed eruption is again not indicated. the development of the dentition is occurring later than the chronological age but root development of the unerupted teeth is greater than three-quarters formed. Here the deciduous teeth are ‘over-retained’ and should be extracted; the problem is usually localised to one or two teeth. the development of the dentition is normal but there are one or two late developing teeth; commonly mandibular second premolars. In these cases the deciduous predecessor should be allowed to exfoliate naturally or not extracted until three-quarters root development of the permanent tooth is completed. combinations of the above

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Multiple failure of eruption Multiple failure of eruption is rare but nevertheless perplexing when it occurs. There are many possible causes and a guide, developed from Sivakumar et al (2007), is reproduced here in Figure 21.1. This paper also gives a good clinical assessment triage diagram.

Multiple failure of eruption

Local

Systemic

Mucosal barrier Genetic disorders Supernumerary teeth Trauma to primary teeth Regional odontoplasia Arch length deficiency and skeletal pattern Radiation damage Oral clefts

Figure 21.1:

Idiopathic

Endocrine/metabolic disorders

Lack of eruptive force?

Others

Cleidocranial dysplasia

Hypothyroidism

Phenytoin

Osteopetrosis

Hypopituitarism

Coeliac disease

GAPO syndrome

Traumatic displacement of secondary tooth germs Defect of eruption (primary failure of eruption)

Hypoparathyroidism

Osteoglophonic dysplasia

Nutrition

Gardiner syndrome

Vitamin D resitant rickets

Mucopolysaccharidosis

Hyperimmunoglobulinaemia E syndrome

Causes of multiple failure of eruption (from Sivakumar 2007)

Primary failure of eruption Primary failure of eruption is a frustrating condition because of its lack of response to orthodontic forces. Frazier– Bowers et al (2007) shed some light on this condition.

Distinction is made between primary failure of Primary failure of eruption (PFE) eruption (PFE) and mechanical failure of eruption - eruption path cleared, no eruptive movement along path (MFE) – frequently ankylosis. The diagnostic criteria for - teeth distal to most mesial affected tooth also involved these conditions is given in Table 21.2. PFE affects only - any or all posterior quadrants involved posterior teeth and all teeth distal to the affected tooth Mechanical failure of eruption (MFE) are involved. It is frequently unilateral. A non- radiographic appearance of submergence due to ankylosis ankylosed tooth with PFE is likely to become ankylosed - no clearance of eruption path when orthodontic force is applied. The cause of PFE is - teeth distal to most mesial affected tooth apparently normal though to be genetic. Three subtypes of PFE are recognised: Indeterminate failure of eruption (IFE) - distinction between PFE and MFE not clear - too young to determine whether teeth distal to most mesial affected tooth are affected or normal Other affected teeth not in occlusion but not submerged as in PFE or MFE Table 21.2: The diagnostic differences between primary failure of eruption and mechanical failure of eruption (from Frazier-Bowers et al 2007)

• Type 1 all affected teeth have a similar lack of eruption potential and there is a progressive posterior open bite towards the distal • Type 2 the tooth (or teeth) distal to the affected tooth show more but still inadequate eruption

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•

Type 3 Both Type 1 and Type 2 are present in the same patient

Correct diagnosis is important as it can prevent years of frustration and time inadvisably spent for both orthodontist and family. It is suggested that PFE is heritable but further research is required to determine the genetic aetiology. If a first permanent molar is affected by MFE, extraction is usually the only practicable course of action.

Intervention or sequelae Space loss Second surgical procedure Third surgical procedure Orthodontic treatment

Percentage 77.6% 53.8% 9.4% 85.0%

Table 21.3: Percentages of sequelae or interventions in Askenazi’s study (2007) Supernumerary type

Supernumerary teeth Ashkenazi et al (2007) looked at the fate of unerupted teeth after the removal of supernumeraries. The interventions or sequelae following supernumerary removal are summarised in Table 21.3 and the percentages of unerupted teeth that erupted spontaneously following removal of the supernumerary are given in Table 21.4. In this study, the authors found that:

Per cent erupting

• surgery after the estimated time of eruption decreased the probability for spontaneous eruption • tuberculate supernumeraries and odontomes were significantly more often associated with eruption failure than the other types Table 21.4: Percentage of unerupted teeth • the lower the stage of root development of the that erupted spontaneously by type of supernumerary in Askenazi’s study supernumerary tooth, lessened the likelihood of spontaneous eruption of the unerupted tooth • there was no correlation between stage of root development of impacted teeth and the probability of spontaneous eruption • the greater the angle of the long axis of the impacted tooth to the mid-palatal suture, lessened the likelihood of spontaneous eruption of the unerupted tooth • the presence of three or more supernumeraries lessened the likelihood of spontaneous eruption of the unerupted tooth • the greater the distance of the apex of the impacted tooth from its correct position, the less likely spontaneous eruption of the impacted tooth was to occur • the deeper the impaction compared to the antimere, the less likely spontaneous eruption of the impacted tooth was to occur Supplemental (normal) Supplemental (small) Conical Tuberculate Odontome

83.0% 75.0% 46.0% 19.0% 32.0%

The authors concluded that because a very high proportion of patients would need orthodontic treatment and that long follow-up times were required, it was sensible to start orthodontic traction to the unerupted tooth at the time of the first surgery.

Clinical tip: When removing the supernumerary tooth, always place a bond and chain to the unerupted tooth at the same time

Ectopic maxillary canines Incidence and epidemiology

The incidence of impacted maxillary canines is around 2-3% (Thilander and Myrberg 1973, Ericson and Kurol 1986, Zahrani 1993). They occur more commonly in females than males in the ratio of 2:1 (Dachi and Howell 1961); the impacted canine crown is palatal in 61% of cases, in the line of the arch in 34% of cases and buccal or labial in 4.5% of cases (Stivaros and Mandall 2000). In this chapter, the term “ectopic canine” used without qualification can be taken to mean palatally ectopic canine.

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Palatal canine displacement: guidance theory or an anomaly of genetic origin?

It is not the purpose of this chapter to discuss the theories relating to the aetiology of palatally displaced canines; it would make the chapter unacceptably long and is not really relevant to their management. If you really need to know, then the debate between Peck et al (1994, 1995) and Becker (1995) is essential reading. There is certainly a strong genetic component (Peck et al 2002, Sacerdoti and Baccetti 2004) Dental anomalies – small upper lateral incisors A number of authors have reported on the association between lateral incisor size, and root length and the presence of palatal canine displacement – for example Becker et al (1981, 1984), Brin et al (1986, 1993), Oliver et al (1989), Zilberman et al (1990). Largely as a result of Brins’ paper in 1986 which reported small upper laterals in 40% of cases of ectopic canine, it is widely thought that small upper laterals are a common indicator of impacted canines, but in fact the findings from studies have varied markedly. Mossey et al (1994) and Brenchley and Oliver (1997) found no association between small upper laterals and ectopic canines and whilst Brin (1986), Oliver et al (1989), Becker (2002), Langberg and Peck (2000) and Al-Nimri and Gharaibeh (2005) did find an association, it was not as strong or as clear cut as we might think. Becker (2002) found that the small dimension was only true in the bucco-lingual dimension and not in the mesio-distal which we usually look at.

Al-Nimri and Gharaibeh (2005) found only 6% of cases had small upper laterals. Langberg and Peck found generally small incisors, not differentially small upper laterals whereas Al-Nimri et al (2008) found that the upper incisors overall were not small in relation to the lowers in the same patient i.e the Bolton ratio was normal in patients with impacted canines. Oliver et al (1989) found that upper laterals were indeed smaller in Caucasian males on the side of the ectopic canine, but in Oriental males the lateral was actually wider on the side of the ectopic canine.

For buccally displaced canines, sexual dimorphism seems to exist (Chaushu et al 2003). Females with buccally displaced canines had larger incisors than a control sample. Male subjects however had similar mesio-distal tooth widths with buccally displaced canines and in controls. Buccally placed canines are found in a different genetic pool.

Dental anomalies – absent upper lateral incisors The same authors and others have investigated the association with absent upper laterals, but again the association is not as strong as we might feel. Whilst Pirinen (1996) found a definite association, Peck et al (1996, 2002) in two studies found no such relationship. Becker (1995) reported that a random population has a 1.3% incidence of absent upper lateral and in people with a palatally ectopic canine the incidence is only slightly raised at 6%. Al-Nimri and Gharaibeh (2005) found a higher incidence but still only 12% and Sacerdoti and Baccetti (2004) found a positive association for unilateral ectopic canines but not for bilateral. In contrast to this uncertain strength of association with absent upper laterals, absent second premolars and third molars are much more strongly associated with ectopic canines (Peck et al 1996), but this is of course of almost no help in the early detection of ectopic canines.

Key point: Absent or small lateral incisors should make us more suspicious that there may be a palatally ectopic canine, but these features are only present in approximately 18% of cases.

Dental age in patients with ectopic maxillary canines It has been suggested that ectopic canines are associated with delayed dental development. Becker and Chaushu (2000) compared the dental ages of a group of ectopic palatal canines, a group of ectopic buccal canines with a control group. Half the patients with ectopic palatal canines had a delayed dental development whereas patients with buccally displaced canines did not. The authors conclude that the results support the hypothesis that there are different aetiologies for buccal and palatally displaced canines. In addition it is suggestive that on the basis of dental development, palatally displaced canines may be of two distinct aetiologies.

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General causes of failure of eruption and impaction Abnormalities of eruption • an abnormal eruptive path • disturbance in the eruption mechanism of the tooth Obstruction to eruption Intra-alveolar

• • •

failure to resorb the roots of the deciduous teeth the presence of a supernumerary tooth or odontome pathology, such as a dentigerous cyst Mucosal

•

thickened mucosa following early extraction of deciduous teeth (particularly in the lower premolar region) Extra-alveolar

•

dental crowding

Localising unerupted teeth There are three methods of localising unerupted teeth; inspection, palpation and radiology. The location of the majority of canines can be determined without radiographs; but that is not to say that radiographs are unnecessary. The use of radiographs confirms the morphology, position, height, angulation and the presence or absence of associated pathology.

Inspection The position of many canines can be identified by looking for the bulge of the canine either buccally or palatally.

The lateral incisor may also give a clue to the canine’s position – a proclined lateral incisor is frequently caused by the crown of a labial canine pressing on the root of the lateral incisor. The lateral incisor is more commonly affected than the first premolar as most canine impactions are mesio-angular. Ectopic palatal upper second premolars are also usually quite easy to see.

Palpation Palpation of the upper canines is a vital step in assessing the developing dentition. It is possible to confuse the canine eminence with a developing canine. Where an ectopic canine is suspected, careful palpation often reveals its whereabouts; make sure that the contralateral side is palpated for comparison. Deciduous canines should be checked for mobility although this does not always mean that the permanent canine is developing normally.

Diagnostic imaging and unerupted teeth Two radiographs at right angles to one another The use of two radiographs taken at right angles to one another allows three-dimensional localisation of the canine; e.g.: lateral and posteroanterior cephalometric films. This does however significantly increase exposure and an intra-oral film is often also required to check for pathology around the crown of the canine and the apex of the lateral incisor.

Parallax technique Originally described by Clark, in 1910, using two periapical radiographs and a horizontal tube shift, this was substantially modified by Keur (1986).

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Keur suggested using two occlusal radiographs for a horizontal tube shift rather than periapical films. He also suggested using a panoramic radiograph with an occlusal radiograph thus giving a vertical tube shift from which to determine the position of the unerupted tooth by parallax. The technique was also described independently by Southall and Gravely (1987).

If you have difficulty remembering how parallax works, then close one eye, extend your right arm straight in front of you with your index finger up in the air and place your left hand, index finger extended half way between your eye and your right index finger. Moving your head from side to side will clearly demonstrate that the object (finger) further away moves in the same direction as your eye. Or if you prefer, the SLOB rule (Same Lingual Opposite Buccal).

Parallax depends on there being adequate vertical (or horizontal) movement of the tube and the distance between the impacted tooth and the reference tooth. The former is easily controlled and the later given. Hence when an impacted tooth is very close to the line of the arch, parallax may not clearly indicate whether it is buccal or lingual.

Jacobs (1999a, 1999b) has written two excellent articles on vertical tube shift identification of unerupted maxillary canines.

Jacobs recommended increasing the vertical angulation of the xray tube from 60-65 degrees to 70-75 degrees to increase the effect of parallax. See Figure 21.2.

Figure 21.2: Vertical tube shift. The DPT ray is at +7 degrees and the anterior occlusal is taken at 70-75 degrees as recommended by Jacobs (1999)

Armstrong et al (2003) compared the use of horizontal and vertical parallax for localising ectopic maxillary canines. They found that operators were unsure of the position of ectopic canines in 12% of cases using vertical parallax and 5% of cases with horizontal parallax. With horizontal parallax, 83% of canines were correctly located with horizontal parallax while only 68% were correctly located with vertical parallax. The diagnostic sensitivity of the horizontal parallax was 88% and 69% for vertical parallax for palatally displaced canines; for buccally displaced canines, both methods performed poorly with a diagnostic sensitivity of only 63%. The reason for horizontal parallax being a better method is that the reference tooth roots are essentially a narrow vertical structure which makes horizontal shift easier to assess.

In reality, radiography is the third stage of localisation and most canines will be localised by visualisation or palpation. In a sense parallax works worst when it is needed most which is when the crown of the canine and the root of the lateral incisor are closely related.

The single panoramic radiograph Chaushu, Chaushu and Becker (1999) have described a method of localising maxillary canines using only a panoramic radiograph. This depends on the fact that objects nearer the x-ray source (and further from the film) project a larger image than objects closer to the film and further from the x-ray source. Thus palatal canines will appear larger than buccal canines (remember that the x-ray source from a panoramic radiograph comes from behind the head). In the coronal and middle thirds of the homolateral incisor, the ectopic canines that were positioned buccally had a canine-incisor width ratio of 0.78-0.1.11 and the palatal canines a canine-incisor width ratio of 1.5-1.7. In the apical area there was an overlap of ratios (0.94-1.45 for buccal canines and 1.15-1.29 for palatal canines) probably because of the backward slope of the alveolar bone just below the anterior nasal spine.

While not an infallible method of localising canines, this can be a useful adjunct to other methods and may help to provide a positive diagnostic localisation.

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Recommended radiographs: We often need a DPT anyway. A periapical intraoral is usually the best non-tomographic radiograph for checking root pathology. A combination of these two (treating the DPT as an anterior radiograph in the incisor region) usually gives a sufficient horizontal parallax effect from two radiographs which also have other diagnostic merits CT scanning It used to be argued that while CT scanning allowed excellent visualisation of tooth position, its large radiation dose made it unsuitable for routine use. Its principal use at that present time is in the presence of multiple impacted and unerupted teeth such as in cleidocranial dysostosis.

The introduction of spiral CT reduced examination time (thus reducing movement artefacts) and the increasing sophistication of CT scanners means that slices can be taken at varying angulations and reformatted into multiplanar reformations. Preda et al (1997) highlighted the use of spiral CT for the localisation of impacted maxillary canines and particularly possible contact and incisor root resorption. They confirmed that the degree of overlap on a panoramic film and the probability of root contact or resorption were not correlated. The study did not support the hypothesis that cystic degeneration of the follicle (> 3 mm) was a cause of root resorption.

The characteristics of the dental follicle in normal and ectopic maxillary canines have been investigated by Ericson and Bjerklin (2001) using CT scans. Follicular size did not vary with eruptive status (canines embedded in bone and just about to penetrate alveolar crest). Ectopic canines tended to have larger follicles than normally developing canines but the difference was small and not clinically useful (2.5 mm versus 2.9 mm). The size of the follicle varied according to the position of the ectopic canine but again this was not clinically very useful (apically 3.5 mm, palatally 2.8 mm and buccally 3.2 mm). It was not possible to distinguish between follicles undergoing cystic change and normal follicles radiologically. Clinically, this diagnostic difficulty is of minor importance as the follicle will be destroyed when the canine erupts.

It was not possible to conclude that widened follicles had an increased risk of displacing lateral incisor roots or causing root resorption could not be determined.

Radiation dose and risk assessment Frederiksen et al (1994) calculated the effective dose and estimated the risk from the use of a Scanora imaging system. Using a tissue equivalent human phantom and thermoluminescent dosimeters (TLDs), they found that panoramic radiography resulted in an effective dose of 26 microSv (1 sievert is equivalent to 1 joule per kilogram) and a probability for stochastic effects of 1.9 x 10-6, while the Scanora imaging system resulted in an effective dose for <1 microSv to 30 microSv with a probability of stochastic effects from < 1 x 10-6 to 2.2 x 10-6.

In 1995, Frederiksen et al carried out a similar study on CT scans of the maxillofacial complex. Equivalent doses were between 0.11 mSv (bone marrow, maxilla) to 0.20 mSv (salivary glands, mandible). It was calculated that two contiguous axial slices in the maxilla result in an effective dose of 0.1 mSv and four contiguous axial slices in the mandible result in an effective dose of 0.76 mSv; these represent a probability of stochastic effects of between 8 x 10-6 and 56 x 10-6.

Dula et al (1996), using 40 axial slices and 120 kV/165 mAs as exposure parameters, calculated the effective dose in the maxilla and mandible as 0.58 mSv and 0.48 mSv respectively. Dose reduction methodology produced a significant decrease in radiation dose of between 40% and 65%. This reduced the mortality risk from 46.2 x 10-6 to 19.2 x 10-6 for 20-year-old men and from 11.2 x 10-6 to 5.5 x 10-6 for 65-year-old women.

Computed tomography increases radiation dose. The probability of stochastic effects, expressed as an equivalent whole body radiation dose is increased about 2 to 8 times compared with panoramic, conventional full mouth, and film tomography examinations. It can be argued that this is still acceptable because of the low total risk for stochastic effects. The question that really needs answering is whether the benefits of more accurate diagnosis of the ectopic maxillary canines balance the drawbacks of using CT scans. For a very limited number of cases, this is probably true and conventional CT scanning came to be recommended as an investigation for cases of ectopic

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Examination

Radiation dose μSv

Cone beam volumetric tomography (NewTom QR DVT 9000)

Reference

10.2

Mah et al (2003)

CT mandible

124.9 – 528.4

Mah et al (2003)

CT maxilla

17.6 – 656.9

Mah et al (2003)

Dental panoramic x-ray

2.9 – 9.6

Danforth and Clark (2000)

Full mouth x-rays

33 - 84

Danforth and Clark (2000)

Full mouth x-rays

14 - 100

Gibbs (2000)

Table 21.5:

Comparison of radiation doses for various dental x-ray examinations

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maxillary canines where the position of the canine in relation to other teeth was significantly uncertain or where the treatment plan depends on whether or not resorption of an adjacent tooth is taking place and this cannot be determined by simpler means.

Cone beam volumetric tomography

Cone beam volumetric tomography (CBVT) has recently become much more widely available and has a dramatically lower dose than previous CT methods. It is therefore much more frequently indicated in cases where the question of possible significant resorption of adjacent teeth by an ectopic canine cannot be resolved by conventional radiography. We have already found this technology to be of substantial therapeutic value in treatment planning. Typical radiation doses for various types of examination are shown in Table 21.5. CBVT can replace multiple x-ray examinations, such as dental panoramic examinations and lateral skull films but its routine use to replace these radiographs still cannot be justified because of the higher dose and the greater time and complexity involved in scrutinising the larger amount of data on a CBVT. If a radiograph it taken, all the data on it should be examined. CBVT gives a lot of data per exposure and orthodontists may not feel qualified to report on all the anatomical structures and potential associated pathology.

The role of CBVT in imaging unerupted maxillary canines was discussed by Walker et al (2005). In this study, 92.6% of the canines were palatal and 7.4% buccal. They found that 66.7% of the lateral incisors and 11.1% of the central incisors showed resorption. One premolar tooth also showed resorption. A key factor is the ability to better assess the amount of any resorption.

The authors concluded that CBVT was useful for identifying the following features of ectopic maxillary canines:

• • • • • • • • •

presence or absence of the canine size of the follicle inclination of the long axis of the tooth relative buccal and palatal positions amount of the bone covering the tooth 3D proximity and resorption of roots of adjacent teeth condition of adjacent teeth local anatomic considerations overall stage of dental development

Whilst CBVT can certainly give good information on all of these, from this long list we would feel that the condition of the adjacent tooth roots is the only powerful additional diagnostic ability for CBVT and ectopic canines with a lesser benefit in occasionally giving more accurate localisation of the tooth to a clinically useful extent.

Root resorption from ectopic canines Ericson and Kurol (1987) used conventional radiographs to assess canine position and then conventional CT to examine possible resorption of adjacent roots. They felt that CT was additionally required in 27% of cases and that CT doubled the incidence of detected root resorption to 12% of cases. Later, (Ericson and Kurol 2000) in a further CT study reported a sample with resorption in 48% of cases. The degree of root resorption in lateral and central incisors is shown in Table 21.6. It can be seen that 38% of lateral incisors showed some degree of root resorption and this was severe (involving the pulp) in 23%. Resorption occurred as early as 9 years of age and reached a peak

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None

Mild (up to half dentine thickness)

Lateral incisors

62.0%

Central incisors

91.0%

Table 21.6:

Moderate (resorption midway to pulp or more)

Severe (pulpal involvement)

12.0%

3.0%

23.0%

3.0%

2.0%

4.0%

The extent and prevalence of incisor resorption in cases of ectopic maxillary canines. (from Ericson and Kurol 2000)

frequency around 10-11 years. Resorption was again seen 50% more frequently with CT than with plain radiography indicating the relatively poor sensitivity of intra-oral x-rays in diagnosing root resorption.

In a later paper (Ericson et al 2002) they again reported that 38% of laterals had some resorption and as we have seen, Walker in 2005 found resorption of some degree in 67% of cases. This sequence of papers perhaps suggests that there has been a trend to finding a higher percentage of resorption as the usage and quality of CT has increased. What matters more than the presence of resorption is the amount of resorption, small areas of root damage being self-limiting once the canine is moved away from the root. It is probable that CT disproportionately increases the detection of minor degrees of root resorption, but the percentage of serious resorption also seems much higher than is our clinical experience. An interesting study by Algerban (2009) compared CBCT with DPT radiographs using a skull and simulated resorption cavities of precisely known size. The CBCT was much more sensitive, detecting extremely small cavities and only giving 5% false negative results compared to 22% with a DPT. Although CBCT also gave 25% false positive diagnosis of resorption this was still much better than the 63% with a DPT. There is no doubt that CBCT is substantially superior in this area of diagnosis. The question is how often the extra diagnostic information would change the treatment plan e.g. very small resorption cavities are probably of little significance and the addition of a periapical radiograph to a DPT might narrow the gap in performance.

The percentage of cases in which CBVT is appropriate as an investigation which changes the treatment plan is therefore still not a well established number. Perhaps at present we should follow the diagnostic pattern of Ericson and Kurol (1987) and employ CBVT in the approximately 30% of cases where we are not sure about the presence of significant root resorption. This view may change as we use CBVT more.

Clinical tip: At present, the evidence perhaps suggests that we should employ CBVT in approximately 30% of cases of palatally ectopic canine

Interceptive treatment of palatal ectopic canines

The most commonly impacted, ectopic and unerupted teeth that orthodontists have to treat are maxillary canines and so most of this chapter relates to these teeth. Comments on other ectopic teeth are made later in the chapter.

The principles of interceptive treatment for palatal canines are:

• •

remove any obstruction – this usually means removal of the deciduous canine ensure adequate space for eruption

Extraction of the deciduous canine had been advocated for decades in case reports but it was the prospective study reported in Ericson and Kurol’s classical paper (1988) on the removal of deciduous canines to change the path of eruption of palatal maxillary canines that made this procedure the linchpin of interceptive treatment for palatal maxillary canines in the 10-13 year old age group. The overall success rate was 72%. Any change in the eruption path of the permanent canine was not likely to occur later than 12 months after the extraction of the deciduous canine.

The effect of canine position on the success of interception Ericson and Kurol (1988) estimated the position of the ectopic canine according to its most medial position in the sectors defined in Table 21.7. Canines distal to the midline of the lateral incisors had a 91% chance of erupting

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normally, whereas only 64% of those mesial to the midline of the lateral incisor did so. Power and Short (1993) also The normal position of the maxillary canine I The distal half of the lateral incisor found that the prognosis was “poor” if there is greater II The mesial half of the lateral incisor III overlap of the adjacent teeth and in fact reported that if the The distal half of the central incisor IV overlap was more than 50% of the adjacent tooth ( still a The mesial half of the central incisor or greater V relatively mildly ectopic canine), success was very unlikely. If Table 21.7: The sector definitions from Ericson and the canine tip was medial to the lateral incisor, the success Kurol’s paper (1988). rate was only 12%. Their success rates were therefore lower than Ericson and Kurol – an overall success rate of 63%.

However, 28% of their cases started with no overlap of the upper lateral incisor by the ‘ectopic’ canine. These canines would be classified as being in sector 1 and one wonders exactly how such teeth were defined as ectopic.

The inclusion of such cases leads to a view that the actual success rate for significant ectopia in this study was much less than 63%.

Sector

Definition

Does interception actually work at all?

A more recent RCT reported by Leonardi et al (2004) contained the eyebrow – raising finding that a control group who had no extraction of the deciduous canine and were followed for the 18 month period of the prospective study had a success rate which at 50% was no different from the group in which deciduous canines were removed! i.e. interception conferred no benefit. This conclusion was a bit hard to verify in the tables in that paper because for example the authors stated that one experimental group (see below) had a success rate of 80% which was “three times the rate for the control group” which would make the success rate in the control group only 26% and not the 50% which was implied in the conclusions. Confusing! Nevertheless, this was a highly important conclusion from this RCT which was the first to include the highly important element of a control group. This previous omission of a control group was in spite of reports (Thilander and Jacobsson 1968) that some ectopic canines spontaneously improved and erupted well. However, just when the literature was casting significant doubt on the efficacy of deciduous canine extraction, the same group (Baccetti et al 2008) reported that when the Leonardi sample was increased from 46 to 75 subjects to satisfy power calculation requirements, this apparent lack of effectiveness of interception was refuted. In that latter paper, the success rate was 65% compared with 36% in the control group. It is not easy to know whether the problem in the first report Leonardi et al (2004) was entirely an insufficient sample or also a misreading by the authors of their own results. Either way, this latest paper (Baccetti et al 2008) seems a very significant piece of work in rectifying the previous conclusion and providing robust evidence that interception works.

Literature tip: Ignore Leonardi conclusions and note those of Baccetti What constitutes successful interception?

It is important to note that the definition of success can vary. For Baccetti et al success meant sufficient eruption that a bracket could be bonded to the canine. The definition did not include a decrease in overlap of the lateral incisor. In their group with extracted deciduous canines, the median improvement in overlap (measured by Ericson and Kurols sectors) was in fact zero.

The effect of crowding on the success of interception Power and Short (1993) also importantly identified that there was poor success in cases with crowding of the canine. In crowded cases (17 out of the 42 total) the success rate was 14% as opposed to 86% in uncrowded cases.

This is a powerful indicator that crowding matters. Importantly, Ericson and Kurol (1988), Leonardi et al (2004) and (Baccetti et al 2008) all specifically excluded crowded cases from their samples. It is not clear why they did that, but it is important for us to remember that these figures for success rates are in the absence of crowding.

Age and success with interception Since the original prospective study by Ericson and Kurol in 1988, the generally accepted view has been that interception works best in younger patients. In fact, there is little evidence on this matter. Ericson and Kurol

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reported on cases ranging from 10 to 13 years and stated that they had “little experience with older cases”. Short and Power had a sample with average age 11.4 yrs. Older patients in that sample tended to have slightly more ectopic canines. The sample chosen by Leonardi had an average age of 11.8 yrs. Of course there is a good case for starting treatment as soon as an ectopic canine is detected. Aside from the risks of root resorption, the findings of (Thilander and Jacobsson 1968) suggest that those ectopic canines which do not spontaneously improve, tend to worsen with time.

The effectiveness of interception with creation of additional space The study reported by Leonardi et al (2004) and (Baccetti et al 2008) investigated the effectiveness of adding space creation to the extraction of deciduous canines. In addition to their control group, they had two experimental groups – one with extraction of the deciduous canine only and a second in which the deciduous canine was extracted and headgear was provided to increase arch length. In the group in which only the deciduous canine was extracted, 65% of the palatally displaced canines erupted satisfactorily. In the group that had extraction of the deciduous canine and headgear, 88% of the canines erupted satisfactorily. This creation of space was in a sample of uncrowded cases, so an ‘over-provision’ of space is clearly an effective measure. A more recent RCT study by Baccetti et al (2009) found a similar effect with the use of rapid maxillary expansion (RME). When started at an average age of 9.6 years, RME increased the percentage of erupted ectopic canines to 66% compared to 14% in a control group. Interestingly, this group had an average pre-treatment basal maxillary width, but a smaller intermolar width, suggesting that dent-alveolar narrowing may be an aetiological factor.

The treatment strategy of providing excess space for the canine has been significantly extended by Richard Olive in Australia. Olive (2002) reported the treatment of impacted maxillary canines by the extraction of the deciduous canine and creation of excess space for the impacted tooth. The space created was 1 cm more than the space required for the canine with the incisors being proclined and displaced up to 3 mm across the midline. This is assertive space creation! The results were impressive. In 94% of cases, the severity of the underlying impaction improved and in the sample of 28 patients who had impactions between sectors II and IV (Ericsson and Kurol 1988), 75% of the impacted teeth erupted without surgical exposure. Younger patients tended to have less severe impactions (sector II) than older patients (sector IV), once more suggesting that over the age range 11 to 16 years, the position of many ectopic canines will worsen. Older patients were more likely to eventually have surgical exposure (which was on offer to all patients at any stage) and Olive reports that in his opinion most of these patients would have avoided exposure if more time had been allowed for spontaneous eruption. For example in 6 out of the 8 patients who had surgical exposure, the canine could be felt labially as a bulge for some months and patients took this as a sign of delay and wished to speed the process by surgical exposure. This study firmly suggests that opening generous excess space may be a powerful tool in the treatment of impacted maxillary canines.

Clinical conclusion: Space creation is very important in the interception of palatal canine impaction.

This question of duration of treatment if surgical exposure is not performed lead to a further paper (Olive 2005) in which he explored the factors which contributed to length of treatment. There were more severe (sector IV) impactions in the longer group. Canines impacted in sector IV (the tip is medial to the lateral incisor) took an average of 21 months to erupt in a mid-alveolar position whereas canines in sectors II and III (the tip is behind the lateral incisor) took eight months. More cases of incisor-premolar hypodontia were found in the shorter treatment group. Olive concluded that the sector displacement and hypodontia are the best guides to the length of treatment prior to eruption of the ectopic tooth.

Literature point: How is success defined? Olive defines success as eruption of the canine in a mid-alveolar position. This is a more testing criterion than Baccetti whose successes included many canines which erupted in the palate This work extends the concept of space creation as a part of interception to an older age group. It should lead to less surgical exposure. Although the studies by Olive did not really investigate the success of this strategy in

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patients over 14 years of age, he is probably right in suggesting that in these older patients, surgical exposure is probably required either to achieve success or to speed success.

In addition to distance from the appropriate eruption site and the mesial movement vector of the displaced permanent canine, it is not clear whether the regional acceleratory phenomenon (an aspect of bone healing resulting in localized osteoporosis) plays a role in the correction of eruption of the displaced permanent canine following extraction of an ipsilateral primary canine. Perhaps in addition to the movement vector, the correction is less likely because the further away the displaced canine is from the location of the extracted ipsilateral primary canine, the less affect the regional acceleratory phenomenon has on bone density (Rutledge and Hartsfield 2010).

Two conclusions follow from this:

• •

the space needs to be made at the root apices so that the canine has room to move – and increase the effect of the regional acceleratory phenomenon orthodontically extruding/extracting the canine might increase the regional acceleratory phenomenon and increase the success of canine eruption (Dave Paquette, personal communication)

Extraction of the ectopic canine It is rarely sensible to attempt movement of a very ectopic canine into an arch where almost all the space for the canine has been lost. Premolars can make acceptable canine substitutes with some mesial rotation and some judicious reshaping. Grossly displaced and crowded canines should be considered for extraction. An exception might be cases where arch expansion and incisor proclination are a treatment aim.

Similarly, the extraction of premolars (or deciduous canines) should not normally be undertaken until the clinician is sure that the ectopic canine will move.

Surgical exposure of the canine – open or closed?

Open exposure refers to simple exposure whilst closed exposure refers to exposure, bonding of an attachment with a chain or ligature and then closing the wound so that the unerupted tooth can be actively erupted using traction from the attachment to an appliance.

Closed exposure is the treatment of choice for buccally placed ectopic canines because there are advantages in terms of aesthetics and perhaps periodontal health in having attached mucosa at the gingival margin. Very occasionally, palatally ectopic canines are so high that there is a risk of an open exposure closing again prior to eruption. Most palatal ectopic canines however are in a favourable position for open exposure. Is open or closed exposure the most appropriate technique under these circumstances?

Periodontal health with the two methods of exposure This has been quite extensively investigated. Becker (1996) was firmly of the view that the closed technique was of periodontal benefit. However, almost all other investigators have found no difference in this respect (Wisth and Boe 1976), and a review of this topic by Burden et al (1999). In fact no clinically significant periodontal damage has been found in several investigations of either method - Woloshyn 1994 with simple exposure, Crescini et al (2007) and Zasciurinskiene et al (2008) with the closed method.

Olive has continued to publish work on ectopic maxillary canines and in 2007, co-authoring with Ling et al (2007a), he compared the periodontal and pulpal outcomes of ectopic canines which had been exposed surgically and those which had been allowed to erupt naturally following the creation of excess space. There were no significant differences in the plaque index scores, the gingival index scores or the periodontal outcomes between the impacted canines in the two groups.

The two techniques were compared by Pearson et al (1997). Open exposure was found to require less surgical resource than closed exposure and was just as an effective procedure 30.7% of the closed exposures required a second surgical procedure while only 15.3% of the open exposures required a further surgical procedure. In

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addition, the average operating time for the open exposure was one third of that for a closed exposure for a single tooth and 56% for two teeth.

Where open exposure has been carried out, the canine is allowed to erupt until an attachment can be placed on the buccal surface of the tooth or at least on the distal corner, but never on the palatal surface. A disadvantage of bonding an attachment on a palatal canine at the time of surgery is that the palatal surface is frequently the only surface available.

Speed of treatment with the two methods of exposure This was investigated by Iramaneerat et al (1998). They found no difference in the average time from exposure to the canine being in the line of the arch (17.7 months with simple exposure and 19.3 months in the expose and bond and close group).The average time from exposure to debond was also the same but lengthy in both groups (29 months). Pearson et al (1997) found that simple exposure lead to longer treatment because the cases were left for an average of 6 months between exposure and appliance placement.

Surgical resource with the two methods of exposure Pearson et al (1997) fond that open exposure required less surgical resource than closed exposure and was equally effective. Importantly, 31% of the closed exposures required a second surgical procedure while only 15% of the open exposures required this. In addition, the average operating time for the open exposure was one third of that for a closed exposure for a single tooth and was halved for two teeth.

Patient comfort with the two methods of exposure An open wound is potentially more uncomfortable for the patient in the early post-operative period. We would recommend provision of a simple removable appliance to cover the palate – a bandage plate – with open exposure. This also retains the periodontal pack which therefore does not need suturing and is much more comfortable for the patient at removal.

Clinical tip: We strongly recommend open exposure for almost all palatal canines

Transplantation Autotransplantation has been reported as a useful technique where it is important to bring a very awkwardly placed ectopic canine into the line of the arch. An excellent review paper on the autotransplantation of teeth has been published by Thomas et al (1998).

The following circumstances will usually exist:

• •

the arch would be unacceptably spaced if the canine is not brought into place the canine will not be amenable to open or closed exposure because of its height or angulation, transposition or (apparent) ankylosis

Teeth for transplantation should have root development that is half to three-quarters complete.

Surgical technique for transplantation The most important aspect of the surgery of transplantation is the application of a careful and atraumatic surgical technique designed to preserve an intact periodontal ligament. Transplantation may not be possible as a onestage procedure particularly where transposition is involved. In these cases, ‘parking’ of the ectopic tooth (usually on the contralateral side) may be required.

It is important that the tooth should be reimplanted at the same level as in the donor site.

UNERUPTED TEETH EXCELLENCE IN ORTHODONTICS 2012

Figure 21.3:

421

Sectional 0.017” x 0.025” TMA with palatal arch. Minimal appliance required until late alignment stage

Once the tooth has been transplanted, it should be held in place with a flexible ligature (e.g.: 4-0 Vicryl sutures for 7-10 days).

Orthodontics – applying the aligning forces

Canine attachments The use of an eyelet allows the engagement of a tooth well out of the line of the arch, initially by using either elastomeric thread, such as PowerTube or with a wire ligature to an active archwire. As the canine nears the line of the arch, a flexible archwire can be placed through the eyelet. The eyelet should be positioned as close to the FA point as possible and with the plane of the loop parallel to the FACC to permit an archwire to be threaded through.

Caplin hooks (GAC International) are recommended for closed exposures. These are extremely low profile and have an attached gold chain; they are available with contoured or flat bonding pads. If possible, they should be placed on the long axis of the clinical crown of the unerupted tooth.

Biomechanical requirements Unerupted or very ectopic erupted teeth are an excellent example of a situation where one tooth has very different biomechanical requirements to all the others. The biomechanics should ideally provide:

• a long range of action (the tooth has a long way to go) • good control over force direction - both horizontally and vertically • no forces on the adjacent teeth (lateral incisor and first premolar) tending to move these teeth together and palatally

• no need for an archwire with a large deflection to slide through the adjacent brackets in order to go passive • an immediate start to canine movement since this tooth has the farthest to travel • no need for patient co-operation in placing the force on the tooth

The remaining teeth in the arch are usually modestly irregular and are extremely suited to alignment and space redistribution by means of a full continuous archwire.

Sectional arches with a palatal arch In practice a 0.017" x 0.025" TMA sectional archwire from first molar to canine meets all these requirements (Roberts Harry and Harradine 1995). It provides a low (60 gm approx.) force over a very long range and is controllable vertically and horizontally, remaining sufficiently stable in an 0.022" slot. The vertical activation and hence control enables the canine to clear the bite by a direction of pull which is above the plane of a full archwire.

Once the canine is buccal to the lower arch, an extrusive or additional buccal activation is easily possible permitting good access to the correct site for a bond on the labial surface, with no need for gingivectomy or loops

422

Figure 21.4:

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The catapult method

in a base archwire. An additional benefit is that treatment can frequently be confined to the palatal arch and the sectional for a substantial part of the treatment (Figure 21.3). This has an aesthetic benefit which is particularly appreciated by patients who have a late diagnosis of ectopic canine. A palatal arch prevents any adverse rotational or buccolingual effects from the reciprocal forces. A palatal arch is also very helpful at preserving arch width whilst the palatal canines are moved buccally. If required, an anterior sectional wire stopping at the second premolars enables simultaneous alignment and space creation amongst the other teeth. The only disadvantage of this biomechanics is the fabrication of a palatal arch and the corresponding need for an extra visit.

Absolute anchorage using miniscrews Chaushu et al (2008) have described using a miniscrew with a Ballista spring to move palatal canines into the line of the arch. Like sectionals, miniscrews are an unobtrusive way of providing anchorage and are likely to become a more common method of moving ectopic palatal canines in the future.

Elastomeric chain or string Many patients require a full upper fixed appliance to either open space or correct tooth alignment. In these cases, the space can be opened with a coil spring and the canine tied to the archwire using PowerTube. Elastic chain can be used as a direct force from the eyelet to the archwire, but it is more convenient to run the chain in a slingshot or catapult arrangement from the premolar bracket, through the eyelet and to the lateral incisor bracket (Figure 21.4). The space-closing element of this catapult force requires a coil spring over the archwire to keep the space for the canine.

A thin continuous archwire This can be attached to the eyelet by a wire ligature and at a later stage is passed through the eyelet. It has the

Figure 21.5:

A thin continuous archwire with compressed coil to make space

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great merit of simplicity. It requires the wire to slide through adjacent brackets as it goes passive and self-ligating brackets are therefore a substantial advantage. Even so, if the tooth is very ectopic, the binding may prevent such a wire from easily going passive. If a coil spring is need over the archwire to keep sufficient space at the stage when the archwire passes through the eyelet, then it will need to be in two parts, mesial and distal to the eyelet (Figure 21.5).

Piggy-back archwires The differing force requirements of the canine and the other teeth can be met by using two archwires – a very flexible one to apply a light force over a long range to the canine and a more rigid wire to meet the requirements of alignment, space and archform for the other teeth. With conventionally ligated brackets, this has the substantial disadvantage of the friction arising from two archwires competing for space in the same slot under the same elastomeric ligature. Some self-ligating brackets such as In-Ovation, SPEED and Damon Q have a horizontal auxiliary slot and this substantially enhances the attractions of a piggy- back technique.

Archwires with loops Loops can add the needed local flexibility, but are time-consuming to bend and can traumatise the mucosa.

However, they can become a viable approach for a visit or two as the canine gets to the line of the arch if a conventional bracket cannot be placed on the FA point without a gingivectomy (either scalpel or laser). A looped archwire can move the canine buccal to the line of the rest of the archwire and can extrude it – both of which can bring the FA point into view.

Clinical tip: Simple flexible archwires with self-ligating brackets are often very effective. If the canine is substantially ectopic a palatal arch and TMA sectionals can be a better method Problems Hard tissue impaction Ectopic buccal canines can impact on buccal cortical bone and it is easy to think that the tooth has become ankylosed. It is worth surgical intervention to remove some of the cortical bone and allow the tooth to start moving again. This is not always successful but is always worth a try. Teeth are probably not ankylosed if they have moved a noticeable distance and have then stopped moving; they are probably ankylosed if they simply resist all attempts at movement.

Root resorption of adjacent teeth Becker and Chaushu (2005) have published a paper on the long term follow-up of patients with severely resorbed incisors associated with impacted maxillary canines. The authors conclude that:

Table 21.8: Distribution of resorption in buccally placed, palatally placed and canines in the line of the arch in the study by D'Amico et al (2003)

• early radiographic monitoring of patients with ectopic canine eruption is needed to detect resorption as early as possible • when resorption of an incisor root occurs as the result of an impacted canine, the process is rapid, and the patient should be treated with urgency • treatment should be designed to move the canine away from the resorbing tooth as quickly as possible • once the impacted canine has been distanced from the root area, resorption almost always ceases, although in this study 17.2% increase in the crown/root ratio occurred as the canine was being moved away

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• • • • •

the resorbed incisor can be subsequently moved orthodontically, with a minimal risk of further resorption, although radiographic monitoring is advised as a precautionary measure. the radiographic reappearance of an intact lamina dura, periodontal ligament and bony trabeculation in the periapical area are signs of cessation of the resorption process at the 1-year (and longer) post-treatment follow-up even markedly resorbed teeth are not unduly mobile root canal treatment, as a means of reducing further resorption, is inappropriate the teeth were not discolored and appeared to have a fairly good long-term prognosis

Outcome D'Amico et al (2003) have investigated the medium term results of the treatment of impacted maxillary canines. In a study of 83 canines with a mean follow-up time of 3.5 years, they found 11 lateral incisors had been extracted because of severe root resorption. Of the 83 canines, 45 canines were associated with the resorption of nine central incisors and 40 lateral incisors. Table 21.8 shows the distribution of resorption found (by CT scanning) between the different locations of the ectopic canines. Orthodontists could identify whether the canine was buccal or palatal approximately 50% of the time; palatal canines seemed easier to identify the original position of.

Periodontal condition was similar between normally erupting and ectopic canines (but read the paper!). The one area that was different was canine rise which was less good on the side with the ectopic canine.

Ling et al (2007a) also studied pulpal health in cases where palatal canines had been corrected either with surgical exposure or by space creation alone. Although more lateral incisors, canines and premolars on the impacted side had partially obliterated pulps than the corresponding teeth on the control side, the teeth in both groups had similar pulpal responses and the authors concluded that canines exposed surgically had a higher incidence of pulpal changes. Ling et al (2007b) also looked at the aesthetic outcomes of two similar groups but this time assessed the colour and position of the canine. In the surgical exposure group, 64% of the canines were significantly more intruded than in the natural eruption group. The American Board of Orthodontics Objective Grading System scores of the canines in the two groups were similar although a lack of labial root torque, and gingival margin changes, were detected in the canines in the surgical exposure group.

Missing lower second premolars Just to draw attention to the paper by Bjerklin and Bennett (2000) who investigated patients with agenesis of lower second premolars and retained second deciduous molars. Mean infra-occlusion was 0.5 mm at 11-12 years increasing to 1.4 mm at 17-18 years. Forty five per cent of patients showed no infra-occlusion. The authors concluded that if the second deciduous molars were still present at 20 years of age then they had a good prognosis for the longer term.

Where space closure is required in cases with missing lower second premolars, serial reduction of the crown width of the retained lower second deciduous molar or even hemisection of the lower second deciduous molar can produce good results.

• • • •

Valencia et al (2004) compared the effects of controlled slicing and extraction on space closure in patients with retained second deciduous molars and missing second premolars. Then sample was divided into three: groups: controlled slicing of mandibular second deciduous molars extraction of mandibular second deciduous molars extraction of maxillary second deciduous molars

Each group was divided into two age groups:

• •

eight to nine years older than 10 years

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The results of the maxillary extractions were all good. The quality of space closure was good (80% space closure, no or slight mesial rotation or inclination of first molar, no midline shift) when serial slicing was carried out in 90% of the younger group but only 25% of the older group. The response in the mandibular extraction group was similar in both age groups: 29% has good space closure, 43% were average (60% to 80% space closure, slight mesial rotation or inclination of first molar, slight midline shift) and 29% were poor (<60% space closure, significant rotation or inclination of first molar or midline shift). One caveat is that although the best results were obtained with controlled slicing at the age of eight to nine years, it is not always possible to be sure that the second premolar is indeed congenitally absent at this age. Reduction of the crown width in order to leave a tooth of premolar width can be inconveniently limited by the width of the roots.

Northway (2004) has described the technique of hemisection and shows impressive results. This involves hemisecting the retained second deciduous molar so that the mesial portion is removed and the pulp capped with calcium hydroxide paste. The first molar moves rapidly forward perhaps as a result of osteopenia or regional accelerated phenomenon (Frost 1983).

Uprighting impacted terminal molars This is another example of a situation where one tooth may have very different biomechanical requirements to all the others. A continuous full archwire would need to be very flexible between the first and second molars and therefore unsuitable for other purposes e.g. overbite reduction, space closure, intermaxillary elastics. Use of a separate sectional wire can permit the localised use of much lower stiffness. Even in these days of nickel-titanium wires with constant radius but moduli of elasticity which vary along their length – such as GAC Sentalloy Bioforce the advantages of varying the stiffness by means of segmental mechanics are still very strong in certain circumstances.

References Algerban A, Jacobs R, Souza PC, Willems G (2009) In-vitro comparison of 2 cone-beam computed tomography systems and panoramic imaging for detecting simulated canine impaction-induced external root resorption in maxillary lateral incisors American Journal of Orthodontics and Dentofacial Orthopaedics 136: 764.e1-764.e11 Al-Nimri K and Gharaibeh T (2005) Space conditions and dental and occlusal features in patients with palatally impacted maxillary canines: an aetiological study.

European Journal of Orthodontics 27:461-5 Al-Nimri K, Adwan I, Gharaibeh T, Hazza’a AM (2008) Tooth size discrepancies in female patients with palatally impacted canines Australian Journal of Orthodontics 24:129-33 Armstrong C, Johnston C, Burden D and Stevenson M (2003) Localising ectopic maxillary canines – horizontal or vertical parallax European Journal of Orthodontics 25: 585-589 Ashkenazi M, Greenberg BP, Chodik G, Rakocz M (2007) Postoperative prognosis of unerupted teeth after removal of supernumerary teeth or odontomas American Journal of Orthodontics and Dentofacial Orthopaedics 131: 614-619 Baccetti T, Leonardi M and Armi P (2008) A randomized clinical study of two interceptive approaches to palatally displaced canines European Journal of Orthodontics Baccetti T, Mucedero M, Leonardi M, Cozza P (2009) Interceptive treatment of palatal impaction of maxillary canines with rapid maxillary expansion: A randomized clinical trial American Journal of Orthodontics and Dentofacial Orthopaedics 136:657-661 Becker A (1995) Palatal canine displacement: Guidance theory or an anomaly of genetic origin?

Angle Orthodontist 65: 95-98

=

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Becker A (1998) The orthodontic treatment of unerupted teeth London, Martin Dunitz Ltd Becker A and Chaushu S (2000) Dental age in maxillary canine ectopia American Journal of Orthodontics and Dentofacial Orthopaedics 117: 657-662 Becker A, Smith P and Behar R (1981) The incidence of anomalous maxillary lateral incisors in relation to palatally-displaced cuspids Angle Orthodontist 51: 24–9 Becker A, Zilberman Y and Tsur B (1984) Root length of lateral incisors adjacent to palatally-displaced maxillary cuspids Angle Orthodontist 54: 218–25 Becker A, Sharabi S and Chausu S (2002) Tooth size variation in dentitions affected by palate canine displacement European Journal of Orthodontics 24: 313-318 Becker A and Chausu S (2005) Long-term follow-up of severely resorbed maxillary incisors after resolution of an etiologically associated impacted canine American Journal of Orthodontics and Dentofacial Orthopaedics 127: 650-654 Bishara SE (1998) Clinical management of impacted maxillary canines Seminars in Orthodontics 4: 87-98 Bjerklin K and Bennett J (2000) The long term survival of lower second primary molars in subjects with agenesis of then premolars European Journal of Orthodontics 22: 245-255 Brenchley Z and Oliver RG (1997) Morphology of anterior teeth associated with displaced canines British Journal of Orthodontics 24:41-45 Brin I, Becker A and Shalhav M. (1986) Position of the maxillary permanent canine in relation to anomalous or missing lateral incisors: a population study European Journal of Orthodontics 8: 12–16 Brin I, Becker A and Zilberman Y (1993) Resorbed lateral incisors adjacent to impacted canines have normal crown size American Journal of Orthodontics and Dentofacial Orthopaedics 104: 60–66 Burden DJ, Kullay BH and Robinson SN (1999) Palatally ectopic canines: closed eruption versus open eruption.

American Journal of Orthodontics and Dentofacial Orthopaedics 115: 640-644 Chaushu S, Chaushu G and Becker A (1999) The use of panoramic radiographs to localise maxillary canines Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics 88: 511-516 Chaushu S, Sharabi S and Becker A (2003) Tooth size in dentitions with buccal canine ectopia European Journal of Orthodontics 25: 485-491 Chaushu S, Becker A and Chaushu G (2008) Lingual orthodontic treatment and absolute anchorage to correct an impacted maxillary canine in an adult American Journal of Orthodontics and Dentofacial Orthopaedics 134: 811-819 Clark CF (1910) A method of ascertaining the relative position of unerupted teeth by means of film radiographs Proceedings of the Royal Society of Medicine Odontological Section 3: 87-90 Crescini A, Nieri M, Buti J, Baccetti T and Prato GPP (2007) Orthodontic and periodontal outcomes of treated impacted maxillary canines Angle Orthodontist 77: 571-577 Dachi SF and Howell FV (1961) A survey of 3,874 routine full mouth radiographs Oral Surgery, Oral Medicine and Oral Pathology 14: 1165-1169

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D'Amico RM, Bjerklin K, Kurol J and Falahat B (2003) Long-term results of orthodontic treatment of impacted maxillary canines Angle Orthodontist 73: 231-238 Danforth RA and Clark DE (2000) Effective dose from radiation absorbed during a panoramic examination with a new generation machine Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology 89: 236-243 Dula K, Mini R, van der Stelt PF, Lambrecht JT, Schneeburger P and Buser D (1996) Hypothetical mortality risk associated with spiral computed tomography of the maxilla and mandible European Journal of Oral Science 104: 503-510 Ericson S and Bjerklin K (2001) The dental follicle in normally and ectopically erupting maxillary canines: a computed tomography study Angle Orthodontist 71: 333-342 Ericson S and Kurol J (1986) Radiographic assessment of maxillary canine eruption in children with clinical signs of eruption disturbances European Journal of Orthodontics 8: 133-140 Ericson S and Kurol J (1987) Radiographic examination of ectopically erupting maxillary canines American Journal of Orthodontics and Dentofacial Orthopaedics 91:483-492 Ericson S and Kurol J (1988) Early treatment of palatally erupting maxillary canines by extraction of the primary canines European Journal of Orthodontics 10: 283-295 Ericson S and Kurol J (2000) Resorption of incisors after ectopic eruption of maxillary canines: a CT study Angle Orthodontist 70: 415-423 Ericson S, Bjerklin K, and Falahat B (2002) Does the canine dental follicle cause resorption of permanent incisor roots? A computed tomographic study of erupting maxillary canines Angle Orthodontist 72: 95-104 Frazier-Bowers SA, Koehler KE, Ackerman JL and Proffit WR (2007) Primary failure of eruption: Further characterization of a rare eruption disorder American Journal of Orthodontics and Dentofacial Orthopaedics 131: 578.e1-578.e11 Frederiksen NL, Benson BW and Sokolowski TW (1994) Effective dose and risk assessment from film tomography used for dental implant diagnostics Dentomaxillofacial Radiology 23: 123-127 Frederiksen NL, Benson BW and Sokolowski TW (1995) Effective dose and risk assessment from computed tomography of the maxillofacial complex Dentomaxillofacial Radiology 24: 55-58 Frost HA (1983) The regional acceleratory phenomena, a review Henry Ford Hospital Medical Journal 31: 3-9 Gibbs SJ (2000) Effective dose equivalent and effective dose: comparison for common projections in oral and maxillofacial radiology Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology 90: 538-45 Iramaneerat S, Cunningham SJ and Horrocks EN (1998) The effect of two alternative methods of canine exposure upon subsequent duration of orthodontic treatment International Journal of Paediatric Dentistry 8: 123-129 Jacobs SG (1999a) Localisation of the unerupted maxillary canine: how to and when to American Journal of Orthodontics and Dentofacial Orthopaedics 115: 314-322 Jacobs SG (1999b) Radiographic localisation of unerupted maxillary anterior teeth using the vertical tube shift technique: the history and application of the method with some case reports American Journal of Orthodontics and Dentofacial Orthopaedics 116: 415-423 Keur JJ (1986) Radiographic localisation techniques Australian Dental Journal 31: 86-90

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Langberg BJ and Peck S (2000) Tooth-size reduction associated with occurrence of palatally displaced canines Angle Orthodontist 70: 126-128 Leonardi M, Armi P, Franchi L and Baccetti T (2004) Two interceptive approaches to palatally displaced canines: a prospective longitudinal study Angle Orthodontist 74: 581-586 Ling KK, Ho CT, Kravchuk O, Olive RJ (2007a) Comparison of surgical and non-surgical methods of treating palatally impacted canines. I. Periodontal and pulpal outcomes Australian Orthodontic Journal 23: 1-7 Ling KK, Ho CT, Kravchuk O, Olive RJ Comparison of surgical and non-surgical methods of treating palatally impacted canines. II. Aesthetic outcomes Australian Orthodontic Journal 23: 8-15 MacSherry PF (1998) The ectopic maxillary canine: a review British Journal of Orthodontics 25: 209-216 Mah J, Danforth RA, Bumann A and Hatcher D (2003) Radiation absorbed in maxillofacial imaging with a new dental CT Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology 96: 508-513 Mossey PA, Campbell HM, Luffingham JK (1994) The palatal canine and the adjacent lateral incisor: a study of a west of Scotland population British Journal of Orthodontics 21:169-174 Northway W (2004) Hemisection: one large step toward management of congenitally missing lower second premolars Angle Orthodontist 74: 792-799 Olive RG (2002) Orthodontic treatment of palatally impacted canines Australian Orthodontic Journal 18: 64-70 Olive RJ (2005) Factors influencing the non-surgical eruption of palatally impacted canines Australian Orthodontic Journal 21: 95-101 Oliver RG, Mannion JE and Robinson JM (1989) Morphology of the lateral incisor in cases of unilateral impaction of maxillary canine British Journal of Orthodontics 16: 9â&#x20AC;&#x201C;16 Pearson MH, Robinson SN, Reed R, Birnie DJ and Zaki GA (1997) Management of palatally impacted canines; the findings of a collaborative study European Journal of Orthodontics 19: 511-515 Peck S, Peck L and Kataja M (1994) The palatally displaced canine as a dental anomaly of genetic origin Angle Orthodontist 64: 249â&#x20AC;&#x201C;56 Peck S, Peck L and Kataja M (1995) Palatal canine displacement: Guidance theory or an anomaly of genetic origin?

Angle Orthodontist 65: 99-102 Peck S, Peck L and Kataja M (1996) Site-specificity of tooth agenesis in subjects with maxillary canine malpositions Angle Orthodontist 66: 473-476 Peck S, Peck L and Kataja M (2002) Concomitant occurrence of canine malposition and tooth agenesis: Evidence of orofacial genetic fields American Journal of Orthodontics and Dentofacial Orthopaedics 122: 657-660 Pirinen S, Arte S and Apajalahti S (1996) Palatal displacement of canine is genetic and related to congenital absence of teeth Journal of Dental Research 75: 1742-1746 Power SM, Short MB (1993) An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption British Journal of Orthodontics 20:215-223

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Preda L, La Fainza A, Di Maggio EM, Dore R, Schifino MR, Campani R, Segu C and Sfondrini MF (1997) The use of spiral computed tomography in the localisation of impacted maxillary canines Dentomaxillofacial Radiology 26: 236-241 Roberts-Harry DP and Harradine NWT (1995) A sectional approach to the alignment of ectopic maxillary canines British Journal of Orthodontics 22: 67-71 Rutledge MS and Hartsfield JK (2010) Genetic factors in the etiology of palatally displaced canines Seminars in Orthodontics 16: 165-171 Sacerdoti R and Baccetti T (2004) Dentoskeletal features associated with unilateral or bilateral palatal displacement of maxillary canines Angle Orthodontist 74: 725-732 Southall PJ and Gravely JF (1987) Radiographic localisation of unerupted teeth in the anterior part of the maxilla; a survey of methods employed British Journal of Orthodontics 14: 235-242 Sivakumar A, Valiathan A, Gandhi S, Mohandas AA (2007) Idiopathic failure of eruption of multiple permanent teeth: Report of 2 adults with a highlight on molecular biology American Journal of Orthodontics and Dentofacial Orthopaedics 132: 687-692 Stivaros N and Mandall N (2000) Radiographic factors affecting the management of impacted upper permanent canines Journal of Orthodontics 27: 169-173 Thilander B and Jacobsson SO (1968) Local factors in impaction of maxillary canines Acta Odontologica Scandinavica 26:145-68 Thilander B and Myrberg N (1973) The prevalence of malocclusion in Swedish school children Scandinavian Journal of Dental Research 81: 12-20 Thomas S, Turner SR and Sandy JR (1998) Autotransplantation of teeth: is there a role?

British Journal of Orthodontics 25: 275-282 Valencia R, Saadia M and Grinberg G (2004) Controlled slicing in the management of congenitally missing second premolars American Journal of Orthodontics and Dentofacial Orthopaedics 125: 537-543 Van der Linden FPGM (1983) Development of the dentition Chicago, Quintessence Publishing Company Inc. Walker L, Enciso R and Mah J (2005) Three-dimensional localization of maxillary canines with cone-beam computed tomography American Journal of Orthodontics and Dentofacial Orthopaedics 128: 418-423 Wisth PJ, Norderval K and Boe OE (1976) Periodontal status of orthodontically treated impacted maxillary canines Angle Orthodontist 46: 69-76 Woloshyn H, Artun J, Kennedy DB and Joondeph DR (1994) Pulpal and periodontal reactions to orthodontic alignment of palatally impacted canines Angle Orthodontist 64:257-264 Zaciurinskiene E, Bjerklin K, Smailiene D, Sidlauskas A and Piusys A (2008) Initial vertical and horizontal position of palatally impacted maxillary canine and effect on periodontal status following surgical-orthodontic treatment Angle Orthodontist 78:275-280 Zahrani AA (1993) Impacted cuspids in a Saudi population Egyptian Dental Journal 39: 367-374 Zilberman Y, Cohen B and Becker A (1990) Familial trends in palatal canines, anomalous lateral incisors, and related phenomena European Journal of Orthodontics 12: 135â&#x20AC;&#x201C;139

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Useful references not referred to in this chapter Elefteriadis JN and Athanasiou AE (1996) Evaluation of impacted canines by means of computerized tomography.

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Chapter

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22 Root resorption David Birnie

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Introduction Root resorption in the permanent dentition is an increasingly rare complication of orthodontic treatment. Its occurrence may be of little significance when mild but may be devastating to both patient and operator when severe. This chapter summarises current thinking on its aetiology and management.

Root resorption in the deciduous dentition Root resorption of the deciduous dentition is, of course, a normal physiological process which permits the eruption of the permanent teeth. Even deciduous teeth without a permanent successor undergo root resorption to a variable extent.

Why does this occur? One suggestion is that the adhesion and activation of odontoclasts is mediated through the temporospatial expression and maturation of extracellular matrix proteins (ECM). Lee et al (2004) compared the pattern of expression of bone sialoprotein (BSP) and osteopontin (OPN) on deciduous and permanent roots of extracted human teeth. The study examined non-resorbed areas of deciduous tooth roots, resorbed areas of deciduous tooth roots and non-resorbed areas of permanent teeth. BSP and OPN were found on deciduous roots to be localised to the cell layer of the periodontal ligament closest to the tooth root and in particular were highly concentrated around odontoclasts and resorptive lacunae. In permanent teeth however, BSP and OPN were evenly distributed through the periodontal ligament. The authors suggest that the differential expression of ECMs might be a molecular signal for the odontoclasts to preferentially adhere to deciduous tooth surface and hence start resorption.

It is also interesting to note that orthodontic treatment does not stop root development – teeth with developing roots continue to develop these roots as orthodontic treatment progresses – although these teeth will end up with shorter roots than had they developed without the insult of orthodontic treatment (Harris and Baker 1990).

Physical properties of cementum Mineral content Rex et al (2005) studied the mineral content of human root cementum. They found that although there was considerable individual variation, the following general observations could be identified:

• • • •

there was no difference in calcium (Ca), phosphorus (P) and fluoride (F) concentrations between the buccal and lingual surfaces of the root except that the F concentration was higher in the cervical region of the buccal surface there was a decreasing concentration gradient for Ca, P and F from cervical to apical third there is an increasing concentration gradient for Ca and P from the outer to the inner third of the root at the cervical and middle thirds of the root there is a decreasing concentration gradient from the outer to the inner third of the root along the entire length of the root

Elastic modulus Cementum has a lower elastic modulus than dentine to cope with movement of the root during function. The hardness and elastic modulus of cementum decreases steadily from cervical to apical third. The average hardness of cementum in the middle third of the root is 0.24 GPa (gigapascals) and the average modulus of elasticity is 3.3 GPa (Srivicharnkul et al 2005)

Definitions Tronstad (1988) has produced an excellent summary on the aetiology, terminology and clinical signs and symptoms of root resorption.

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It is helpful to consider root resorption as either inflammatory or replacement. Both categories may be transient or progressive. Transient root resorption occurs in traumatised teeth, teeth subject to orthodontic forces and due to normal wear and tear. The root resorption by phagocytic cells is not sustained simply by a denuded dentine or cementum surface but requires continuous stimulation. Transient root resorption therefore normally ceases after 2-3 weeks unless there is continued stimulation or insult – in which case the resorptive process is continued and the condition becomes progressive. Cessation of the stimulation is accompanied by cessation of resorption.

Transient root resorption is normally clinically or radiographically undetectable.

Inflammatory root resorption Inflammatory root resorption occurs when the precementum or predentine, which protects the dentine of the inside of the root canal and the external surface of the root from root resorption, becomes mineralised or in the case of precementum, damaged. This results in the colonisation of the surfaces of the mineralised or damaged tissues by multinucleated cells and resorption occurs. Internal root resorption involves mineralised predentine and therefore involves the internal surface of the root canal while external root resorption involves precementum and occurs on the external surface of the root.

Prolonged stimulation of the resorptive process can be produced by:

• •

•

•

mechanical irritation As in teeth with root fractures. Progressive inflammatory root resorption causes rounding of the surfaces of the fracture pressure resorption This occurs physiologically in the transition of the deciduous to the permanent dentition and sometimes pathologically in the permanent dentition, such as where an erupting maxillary canine resorbs a lateral incisor. It also occurs during orthodontic treatment. Slow growing cysts and tumours are also capable of producing root resorption. infection Normally as a result of endodontic or periodontal disease and it may occur internally or externally depending on whether the bacterial stimulus comes from the root canal or from the gingival sulcus. systemic disease Root resorption may occur in certain systemic diseases which involve the dentoalveolar process e.g.: Paget's disease.

External root resorption This occurs on the external surface of the root and is commonly divided into apical and cervical resorption External apical root resorption (EARR) This will be the primary topic of discussion in this chapter. EARR is of particular interest to orthodontists and when stimulated by orthodontic forces is referred to as orthodontically induced inflammatory root resorption (OIIRR).

Once orthodontic forces cease, so does the root resorption and reparative processes take over.

Cervical root resorption This is a variant of progressive external root resorption and follows damage, such as dentoalveolar surgery, to the cervical root surface below the epithelial attachment. The resorption may penetrate through to the pulp although may initially be prevented from reaching the pulp by predentine resulting in irregular resorption patterns on the outer surface of the root canal. This is sometimes also called external-internal resorption.

Internal root resorption A rather interesting process! In progressive internal root resorption, the resorption is sustained by necrotic and infected pulp tissue coronal to the resorption lacunae in the pulp. However, the resorptive process requires the

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presence of living cells; the bacteria reach the area of resorption from the necrotic area via the dentinal tubules.

This requires a rather tortuous formation of the dentinal tubules and may go some way to explain why progressive internal root resorption is relatively rare (Tronstad 1988).

Replacement resorption

This is ankylosis between tooth and alveolar bone and in which bone forms on the root surface following necrosis of the periodontal membrane. It is common in teeth that have been subjected to dental trauma but may also be idiopathic. If only small areas of the root surface are involved this may be reversible but otherwise the tooth is resorbed and eventually replaced with bone over a long period of time. In cases of ankylosis, a periodontal ligament space is absent. There is no effective treatment to reverse the ankylosis. Teeth that have undergone EARR do not also undergo replacement resorption.

Measuring root resorption It may be helpful to know how long, on average, the roots of various teeth are and this information, together with crown heights, is given in Figure 22.1. Several Degree or type of Description classifications of root resorption have been resorption proposed. Massler and Perreault (1954) used the No resorption 0 scheme shown in Table 22.1 originally described Questionable resorption ?

by Malone (1951).

1 mm to 2 mm of resorption 1+ 2+

2 mm to 4 mm of resorption

3+

Resorption > 4mm and less than half length of root

4+

Resorption > half length of root

*5

Resorption due to endodontics or cyst

periapical

infection,

Table 22.1: Degree of root resorption according to Malone (1951) and quoted in Massler and Perreault (1954)

• •

A commonly used contemporary classification is that of Levander and Malmgren (1988) which divides apical root resorption into four categories.

In this classification,

•

grade 1 indicates an irregular root

•

grade 2, < 2 mm root resorption

outline

(minor) grade 3, > 2 mm to one third of root length (severe) grade 4, resorption > one third of root length (extreme)

This classification is shown graphically in Figure 22.2. A grade of 0 (zero) is sometimes added to indicate no root

Figure 22.1: in the permanent dentition

Average root lengths and crown heights

Figure 22.2: Malmgren (1988)

Root resorption index of Levander and

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resorption but this was not in Levander and Malmgren's original classification.

In order to measure root length accurately, a standardised radiographic technique is required. The use of Rinn film holders and a long cone paralleling technique improves repeatability. Panoramic radiography is not sufficiently accurate but developments in existing, and the introduction of new imaging modalities, such as cone beam volumetric tomography, mean that this will be a changing scenario. In a very few cases, the use of CT may be helpful in determining the amount of root resorption in cases with ectopic teeth.

In 2006, Bjerklin and Ericson analysed the treatment outcome and treatment planning before and after a computerized tomography investigation of children with retained and ectopically positioned maxillary canines.

Intraoral and panoramic radiographs, computerized tomographs, and, in some cases, lateral head films were taken of 80 children with 113 retained maxillary canines. The incisor roots of approximately half of the sample had some measure of resorption. Forty-two children with retained maxillary canines also had a space deficiency. The diagnosis and a treatment plan were originally based on extraoral and intraoral photographs, study models, the patientâ&#x20AC;&#x2122;s history, conventional radiography, and, if available, lateral head films. Approximately one year later, the same examiner drew up a new treatment plan based on the same records but with a supplemental CT examination. The treatment plans of 35 (43.7%) of the 80 children were modified to reflect this new information.

Of those patients with root resorption on the incisors adjacent to retained canines, more than half of the treatment plans were altered. Without the CT investigation, 11 children would not have been treated for resorption that had exposed the pulp of an incisor root and 13 who had no root resorption on their incisors would have had one or both lateral incisors extracted. The treatment plans of the latter were changed to nonextraction or extraction of premolars. A CT investigation can therefore be an important source of information for treatment planning for children with retained or ectopically erupting maxillary canines.

Alqerban et al (2009) have demonstrated that in vitro, simulated external root resorption of lateral incisors from a palatally impacted canine was better detected with cone beam CT rather than panoramic imaging. In an in vivo study, Dudic et al (2009) concluded that root resorption after orthodontic treatment was underestimated when suing an OPT compared with cone beam CT.

Heritability of EARR The magnitude in force levels during orthodontic treatment does not account for the variation in extent of root resorption seen among orthodontic patients. The same force may generate different effects in different people suggesting that EARR may have a genetic component. Harris et al (1997) carried out a study on full sibling pairs who received orthodontic treatment by the same technique from the same orthodontist. The root length of the maxillary central incisors, the mandibular incisors and the left and right lower first molars were measured from pretreatment and posttreatment lateral skull radiographs. The authors found that all teeth underwent significant resorption and there was a significant genetic factor in susceptibility to EARR as demonstrated by heritability estimates which averaged 70% on three of the four roots examined (but not for the lower central incisor). There was therefore more variation in the amount of root resorption between families than between siblings in the same family. This shows that most of the variation in outcome in relation to root resorption is outside the orthodontists control although he is still capable of influencing root resorption through the transmission of excessive force to the apical areas of the teeth by careless mechanics. Interestingly, this study tested whether EARR was controlled by the type of malocclusion which it was not although EARR was affected by the extent of the treatment of the malocclusion. It might be argued that siblings had similar amounts of root resorption because they had similar malocclusions. However, since malocclusion is accepted to be principally an acquired rather than inherited characteristic, any familial association between external root resorption and type of malocclusion should be weak.

One clinical application from this study is that a patient's likely experience of EARR may be predicted from that of a sibling who has previously undergone orthodontic treatment.

A paper by Al-Qawasmi et al (2003) support the suggestion that EARR is influenced by factors other than the force levels during orthodontic treatment. They found that the IL-1B gene contributed a significant predisposition to this problem and 15% of the total variation of maxillary incisor EARR. Continued evidence of the heritability of susceptibility to root resorption associated with orthodontic force continues to appear (Abass et al 2008).

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In summary, it is becoming clear that EARR, while a common sequelae of orthodontic treatment, is principally moderated by genetic influences rather than its extent being under the control of the orthodontist.

External apical root resorption in non-orthodontically treated patients Several naturally occurring and non-orthodontic situations can put a patient at risk of developing root resorption.

Any excessive force on the periodontium, particularly intrusive forces, may do this. Heavy mastication may be one cause of root resorption. Hylander (1977), in an extensive treatise on the adaptive changes in craniofacial morphology in Eskimos, comments on the extensive root resorption amongst the East Greenland and Canadian Thule Eskimo populations. He cites this as evidence of excessive occlusal forces in addition to the fractures and chipping of the crowns of the teeth and the high occurrence of bony exostoses in the maxilla and mandible.

Harvey and Zander (1959) suggest that excessive masticatory forces, and hence root resorption, may result from reduced bony support as a result of periodontal disease; they found that 80% of healthy teeth, 91% of periodontally diseased teeth and 97.5% of teeth from India exhibited some root resorption when sections stained with haematoxylin and eosin were examined under a microscope.

Other causes of excessive masticatory loading are bruxism (Ramfjord and Ash 1971) and occlusal interferences.

The periapical tissues are insensitive to the source of the force – simply to its magnitude.

Massler and Perreault (1954) studied 'idiopathic' root resorption in young adults; they concluded that 100% of those they examined (radiographically) showed some root resorption in four or more permanent teeth. In only 0.9% of the teeth in females and 2.7% of the teeth in males was there any evidence of a cause of root resorption such as periapical infection or endodontic treatment. In the paper, there is no suggestion of increased occlusal stress being a considered cause of root resorption and perhaps simply indicates that periapical infection is not a common cause of root resorption.

An excellent paper which seeks to throw some light on the subject of idiopathic root resorption was published by Harris, Robinson and Woods (1993). This investigated the relationship between:

• • •

missing teeth periodontal probing depths crestal bone loss

and EARR in a population of 306 non-orthodontically treated patients at the University of Tennessee. The authors used a slightly modified version of Levander and Malmgren's classification. 10% of the sample had detectable resorption (Grade 2 or above) and severe root resorption occurred in 1% to 2% of the sample. This was more common in single rooted teeth (the study only looked at upper central incisors, mandibular canines and mandibular second molars). The study found that:

• • •

tooth loss increased the risk if EARR in the remaining teeth patients with EARR tended to have greater probing depths crestal bone height is lower around teeth with EARR than those without resorption

All these results suggest that lack of tooth stability and increased occlusal forces are important causes of EARR.

Orthodontically induced inflammatory root resorption (OIIRR) Basic science Excellent reviews of the basic science aspects of OIIRR is given by Brezniak and Wasserstein (1993a), Brezniak and Wasserstein (2002a) and Killiany DM (1999). This highlights the fact that orthodontic forces initiate a process

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characteristic of inflammation and which is essential to tooth movement; unfortunately, this same process is capable of producing root resorption. This paper highlights three degrees of severity of OIIRR:

• • •

cemental remodelling. In this process, only the outer layers of the cementum are resorbed and then completely remodelled. The process is similar to trabecular remodelling and therefore may be undetectable dentinal resorption. The resorption extends in dentine and is repaired with cementum. The final shape of the root may or may not be identical to its original form circumferential apical root resorption. Full resorption of all components of the root occurs and root shortening is evident

OIIRR is part of a hyaline zone elimination process; this process can damage the outer surface of the root covered with cementoid which then exposes the cementum rendering it susceptible to attack from macrophages; orthodontic forces may themselves directly damage the cementoid layer thus exposing the cementum.

Resorption lacunae are a mechanism for decompressing the forces on the root surface.

It also now seems clear that the outer layers of the root, comprising cementoblasts and cementoid, have a protective function.

Repair starts about two weeks after cessation of the force with the formation of acellular cementum which is then replaced with cellular cementum.

Clinical aspects Useful review papers are Brezniak and Wasserstein (1993b), Brezniak and Wasserstein (2002b) and Harris (2000).

The clinical study by Sameshima and Sinclair (2001a, 2001b) Informed consent All patients should be warned of the possibility of microscopic root resorption and severe root resorption as part of the informed consent process. Any particular risk factors should be identified. There is a strong familial relationship and sibling records, if available, should be consulted to help quantify risk. This may influence the decision as to whether end of treatment radiographs are necessary in that they may play a role in prevention of untoward sequelae for siblings or other family members.

Patient factors Race In a study by Sameshima and Sinclair (2001a) shown in Figure 22.3, Asian patients had significantly less posttreatment OIIRR than either white or Hispanic patients. Although not statistically significant, Hispanic patients tended to have more OIIRR than white patients. Årtun et al (2005) showed that 20.2%, 7.7%, and 5.3% of the patients had more than 1 tooth with greater than 2.0, 3.0, and 4.0 mm resorption 12 months after the fitting of fixed appliances respectively.

Age In the mixed dentition, patients treated before root formation is completed experience less root resorption; however, after treatment, the roots are shorter.

In general, most studies have found little relationship between root resorption and age. It would seem, therefore, that the wear and tear on the dentition throughout life has little effect on root length. Bishara et al (1999) in a longitudinal radiographic survey of root length from early to mid-adulthood found no evidence of systematic root shortening as a result of age. A similar result was found by Woods et al (1990) in a cross-sectional study which would clearly be less sensitive and more likely to obscure individual variation. Harris (2000) helpfully points out that this may be as a result of modern western diets which place little axial stress on the periapical tissues and in which most of the food processing is done by machine before ingestion!

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Sex Studies have been equivocal and it is generally accepted that the effect of sex on root resorption is trivial and that neither sex is more prone to EARR or OIIRR. systemic factors As previously mentioned some systemic diseases may affect EARR. Endocrine disorders, such as hypothyroidism, hyperparathyroidism and hypopituitarism have all been implicated in root resorption. High doses of corticosteroids may increase root resorption while low doses may decrease it.

Alcohol consumption in adults during orthodontic treatment increase root resorption due to vitamin D hydroxylation in the liver.

Clinically, however, systemic factors will rarely be significant mediators of root resorption.

Tooth factors tooth series and tooth type OIIRR is principally a problem affecting anterior or single rooted teeth. Sameshima and Sinclair (2001a) confirm this finding in their study of 868 orthodontically treated patients and this data is shown in Figure 22.4. It is thought that if neither the maxillary nor the mandibular incisors show signs of resorption, then it is extremely unlikely that resorption will be found in any other teeth. Brezniak and Wasserstein (1993b) suggest that the most vulnerable teeth to OIIRR are:

• • • • • •

maxillary lateral incisors maxillary central incisors mandibular incisors distal root of mandibular first molars mandibular second premolars maxillary second premolars

This is a slightly different order to that given by Sameshima and Sinclair but the emphasis on anterior teeth remains.

1.8

1.6

1.6

1.4

1.4

1.2

1.2

1

0.8 0.6 0.4

mm

mm

1 0.8 0.6 0.4

0.2

0.2

0

0 U2

Figure 22.3: Amount (mean ± 1 sd) of OIIRR by racial type (Sameshima and Sinclair 2001a)

U1

U3

L3

L2

L1

L5

L6

L4

U5

U6

U4

Figure 22.4: Vulnerability of specific teeth to OIIRR (Sameshima and Sinclair 2001a). Note that single rooted teeth are more susceptible to root resorption than multi-rooted teeth.

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Endodontically treated teeth In general, it is felt that endodontically treated teeth are less susceptible to root resorption than normal teeth and this is substantiated by Remington et al (1989), Owman-Moll et al (1995) and Costopoulos and Nanda (1996). traumatised teeth Traumatised teeth may undergo EARR as a consequence of their trauma even if they do not undergo orthodontic treatment; if this is the case, then these teeth behave in the same way as teeth with pre-existing root resorption.

Traumatised teeth that do not exhibit root resorption prior to orthodontic treatment behave normally. teeth with pre-existing root resorption These teeth are very much more susceptible to root resorption as indicated by Massler and Malone (1952), Goldson and Henrikson (1975) and Linge and Linge (1983). As a rough guide, the rate of root resorption seems to double on teeth with pre-existing root resorption; this however is very variable and will be affected by the type of mechanics used and the distance teeth are moved among other factors.

Transplanted teeth Transplanted teeth are no more susceptible to OIIRR than normal teeth provided the transplant is without complication and the orthodontist waits three months before attempting tooth movement (Paulsen et al 1995).

Tooth shape Levander and Malmgren (1988) have shown that roots with abnormal shape or size such as , short, blunted, bent (dilacerated) or pipette shaped roots have a higher susceptibility to OIIRR. These root morphologies are shown in Figure 22.5. It is arguable that teeth with defects or abnormalities of crown formation may also have defects of root formation that renders them more likely to resorption. Mirabella and Ă&#x2026;rtun 1995a showed that diminutive and peg-shaped lateral incisors are not more susceptible to OIIRR. Kook et al (2003) also confirmed that pegshaped and small lateral incisors (those with a smaller mesiodistal width than the mandibular lateral incisor (Becker et al 1981)) are not at more risk of OIRR than normally shaped lateral incisors. Ă&#x2026;rtun et al 2005 found no indications that teeth with short blunted roots were an indication for root resorption and although atypical root shape was a risk for increased resorption at 6 months, the association did not exist at twelve months.

Specific malocclusions and OIIRR Any malocclusion which increases the load on the teeth above a physiological threshold may initiate root resorption. Thus patients with hypodontia (Levander et al 1998) and mutilated occlusions where the occlusal load is not distributed evenly across a sufficient number of teeth may exhibit root resorption.

Malocclusions may be more at risk of root resorption because of the orthodontic mechanics used to treat them and that discussion properly belongs in another section of this chapter. However, patients with anterior open bites have more EARR before treatment and in addition less facial bone height (the distance from the amelocemental junction to the alveolar crest) than patients with a deep bite before treatment. The additional loss in patients with anterior open bite was estimated as 15% by Harris and Butler (1992). Once again, this can be attributed to non-physiological forces acting on the teeth as a result of soft tissue activity from the tongue and musculature.

Conjecturally, a similar pattern should be seen in patients with digit-sucking habits.

Figure 22.5: Abnormal root shapes are more susceptible to OIIRR (after Levander and Malmgren 1988)

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Odenrick and Brattström (1985) studied the effect of nail biting on root resorption during orthodontic treatment using a similar scale to that of Levander and Malmgren (1988). They defined severe nail biting as:

• • • •

patient being aware of nail biting habit no free nail margin present flesh of finger risen above the end of the nail all fingers involved

Of the sample of 1025 13-15 year old patients, 151 or 14.3% were classified as severe nail biters. Nail biters had more root resorption both before and after orthodontic treatment. Once again, this can be attributed to overloading of the periodontal structures.

Treatment factors Tooth movements It is appropriate to remind the reader that OIIRR is a pressure related phenomenon and that those tooth movements most likely to place non-physiological forces on the periapical tissues are those most likely to produce OIIRR. Thus treatment time itself may not be directly associated with increased incidence of OIIRR but is indirectly as presumably longer treatment times may be an indicator of more extensive tooth movement. Thus bodily movement, intrusion (particularly), palatal expansion and torque have all been implicated as aggravators of OIIRR. EARR and OIIRR enter a repair phase once the external force drops to physiologic levels; therefore intermittent forces may be kinder to the periapical tissues than continuous forces. This however very much depends on there being sufficient time within the intermittent force cycle for significant healing to take place. Jiggling, although an intermittent force, is harmful because of its short cycle.

Tooth rotation is not usually considered a significant cause of root resorption but Jiminez-Pellegrin and AranaChavez (2004) have shown that resorption occurs particularly on the prominent part of the root in the medial third and that this resorption increases the longer the tooth is subject to rotation. Although after two weeks, the resorption was confined to cementum, by six weeks it had reached root dentine.

Han et al (2005) have demonstrated that intrusion of teeth causes approximately four times as much root resorption as no vertical movement or extrusion. The teeth tested were premolars scheduled for extraction as part of the extraction plan. The amount of root resorption due to intrusion or extrusion was correlated and so care should be taken in susceptible patients as they may be at risk from root resorption even when the tooth is extruded.

Chiqueto et al (2008) have demonstrated that the use of accentuated or reverse curves of Spee that the treatment of malocclusions with increased overbites with accentuated curves of Spee results in more root resorption (1.87 mm) compared with the treatment of patients with normal overbites (1.54 mm). Changes in overbite and vertical displacements of the maxillary central incisor apices had significant correlations to root resorption.

extraction patterns Although some studies have not found extraction pattern to affect root resorption, Sameshima and Sinclair (2001b) determined otherwise. They found that patients who had four first premolar extraction treatment had more root resorption than patients who were treated non-extraction. Other extraction patterns such as four second premolars, and asymmetric extractions also showed greater root resorption. Surprisingly, patients with upper first premolar only extraction patterns did not have levels of root resorption which were significantly different to the non-extraction group.

ROOT RESORPTION EXCELLENCE IN ORTHODONTICS 2012

Level of force

441

250

200 Volume (106 Îźm3)

Chan and Darendeliler (2005) studied the effect of light (25g) and heavy forces (225g) on cementum on human premolar teeth that were subsequently extracted. The cervical buccal region and the lingual apical region had most resorption craters; the mean volume of the resorption craters in the light force group was 3.49 times that of the control group and in the heavy force group 11.59 times that of the control group. Although more resorption was recorded in the light force group than the control group, this was not statistically significant. The mean resorption volume per tooth for the control, light and heavy force groups is shown in Figure 22.6.

150

100

50

0

Figure 22.6: The volume of resorption craters per tooth for light and heavy forces (from Chan and Darendeliler 2005)

Root resorption in the initial stages of treatment

Smale et al (2005) studied root resorption in the first six months of orthodontic treatment. The mean root resorption was 0.53 mm and the mean of the most resorbed tooth in patients in the sample was 1.18 mm. 4.1% of patients had at an average of at least 1.5 mm of resorption and 15.5% had a tooth with at least 2 mm of resorption.

The greatest amount of resorption seen was 4.4 mm. Increased observation period and deviated or long root form were risk factors for resorption whereas normal or wide root form seemed to be protective factors. The use of rectangular archwires, incisor irregularity and a history of trauma were not identified as risk factors. The explained variance of risk due to narrow or deviated roots was less than 25%. Ă&#x2026;rtun et al (2006) have shown that patients with detectable root resorption in the first six months are more likely to have root resorption in the following six months than those without. Patients with more than 1 mm of root resorption in the first six months were 3.8 times more likely to have more than 1 mm or more of root resorption in the second six months.

Appliance systems The evidence that some appliance systems are associated with less root resorption than others is equivocal. This even extends to comparisons between fixed and removable appliance systems. Once again, the important factor is the force applied to the periapical tissues. Appliance systems (and operators!) which apply forces within the physiological range are less likely to produce root resorption than those that do not. Thus one might expect removable appliances to produce less root resorption than fixed appliances and pre-adjusted edgewise appliances to produce less root resorption than standard edgewise appliances.

16 14 12 10

%

8 6 4 2 0 UR2

UR1 Edgewise

UL1

UL2

SWA

Figure 22.7: Comparison of root resorption in patients treated with standard edgewise and pre-adjusted edgewise (straight-wire) appliances

Mavragani et al (2000), from the University of Bergen, compared premolar extraction class 2 division i cases treated with conventional 0.018" edgewise technique and 0.018" straight-wire technique (3M/Unitek New Bergen Technique). All cases had standardised intra-oral x-rays taken with the long cone paralleling technique. For the conventional edgewise technique, the mean root resorption for upper central incisors was 13.75% and for lateral incisors 11.9%; for the straight-wire technique, it was 7% for upper central incisors and 9% for lateral incisors. This data is shown in Figure 22.7. Only the difference in root resorption on the central incisors was significant (at the 5% level). The study concludes that the straight-wire appliance may offer more gentle and constant forces thus

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reducing the likelihood of root resorption. However, the mean overjet for the edgewise group was 8.06 mm and for the straight-wire group 6.11 mm.

In a retrospective study of one and two phase treatment, Brin et al (2003) showed that in class 2 division I malocclusions with overjets greater than 7 mm, 66.4% of patients had mild root resorption and 12.4% had severe resorption (>2 mm). Maxillary lateral incisors had slightly more resorption than central incisors. Two-phase treatment seemed to be associated with slightly less root resorption than one phase treatment but significant associations were found between EARR and the amount of overjet reduction and the duration of fixed appliance treatment. Makedonas et al (2009) reviewed root resorption in patients who had terminated active fixed or removable orthodontic treatment during 2004 at the University of Gothenburg. The prevalence of light root resorption was 1.9%, 3.2%, 4.9% and 8.6% at the beginning, after 6 and 12 months and at the end of treatment, respectively. Severe root resorption was found in 1.9% at the end of treatment. The most common strategies when moderate root resorption was diagnosed during treatment were the use of lower forces, resting periods and decrease of the treatment duration.

Weilland (2003) has shown that while superelastic archwires move teeth more rapidly than stainless steel archwires, they do so with significantly more root resorption (140%) probably due to the continuous forces exerted by the superelastic wires which do not allow time for the root surface to recover from damage; the intermittent forces delivered by a stainless steel wire do.

Pandis et al (2008) studied root resorption between conventional and self-ligating appliance systems. There was no difference in the amount of root resorption between the two appliance systems which averaged 1.3 mm.

Treatment duration resulted in increased root resorption at a rate of 0.035 mm per month.

Barbagallo et al (2008) studied the effect of clear thermoplastic aligners (TPAs) on root resorption compared with a control group, a light force (25 g) group and a heavy force (225 g) group. They found that all treatments produced more root resorption than the control group. The light force and the TPA group produced about 6 times, and the heavy force 9 times more root resorption than the control group.

Miniscrews Hembree et al (2009) studied the effects of intentional damage to the roots and surrounding structures caused by self-tapping mini-screw implants placed with a stent into the teeth of beagle dogs. The effects were studied over the short term (six weeks) and long term (12 weeks). Histology showed damage to 73.8% of the teeth, ranging from displacement of bone into the periodontal ligament to invasion of the pulp chamber. Displacement of bone into the periodontal ligament and direct damage to the periodontal ligament occurred in 7.2% of cases. Damage was isolated to the cementum of 19.0% of teeth, whereas damage occurred in the dentin of 26.2% of teeth. Loss of bone in the furcation was evident in 7.2% teeth, and severe damage into the pulp occurred in 14.2% teeth. No differences in the amounts of damage were evident between the immediate, short and long term groups. Healing often occurred with cementum around the unloaded mini-screw implants. Resistance might be a better indication of root contact than radiographs taken after placement. Normally, resistance increases as the miniscrew implant is placed, but the increases are small. The resistance that was noted during placement of the miniscrew implant approximately doubled when the roots were contacted or penetrated. Importantly, the operator felt no obvious change in resistance when fracturing the root or contacting the cementum. In contrast to resistance, the periapical radiographs included several instances when damage was thought to have occurred, but it actually had not. The histology showed that damage did not occur 26.2% of the time, despite radiographs indicating damage or contact.

Brisceno et al (2009) studied healing of roots after intentional damage to the roots. A randomized split-mouth design was used to evaluate healing six and 12 weeks after intentional root damage. Seven beagle dogs had miniscrew implants placed into the roots of eight mandibular teeth. After root contact had been verified by using insertion torques and radiographs, the mini-screw implants were immediately removed, and the sites were allowed to heal for 6 or 12 weeks. The authors found that under favourable conditions (no infection or pulpal invasion), root healing occurred in 64.3% of the teeth after damage with mini-screw implants. In the teeth with normal healing, the percentage of cementum in the defect significantly increased between 6 and 12 weeks.

Partial or no healing was evident for teeth with pulpal invasion and inflammatory infiltrate.

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A further study on beagle dogs using sixty self-drilling and self-tapping miniscrews was carried out by Renjen et al (2009). The films taken after miniscrew placement identified sites with evidence of root approximation and 20 sites were selected for further study and 16 of these had root injury. In four sites, the injury was limited to abrasion of the cementum up to but not including the dentine; seven sites showed dentin penetration up to 50% of the miniscrew diameter and five sites had miniscrew penetration into the pulp space with root fragmentation and ankylosis (defined as replacement resorption of root cementum with the adjacent alveolar bone). In each site with root injury, evidence of continuous cementum repair was seen along the injured root surface. Only in cases of severe injury with displacement of root fragments was ankylosis with the lamina dura noted. There was no evidence of external root resorption in response to root injury, inflammatory infiltrate or necrosis in the pulp tissue or on the injured root surfaces. At each site, woven bone was present along the miniscrew threads.

Retention OIIRR ceases once forces drop to physiological levels and healing of the cementum commences. Thus almost all root resorption should cease at the end of active orthodontic treatment although some minor alteration of root shape may be seen posttreatment as a result of smoothing of the root contour. It is clearly possible to have retention devices that place teeth in traumatic occlusion and thus institute jiggling forces. In these cases, root resorption may continue or be initiated during the retention phase. If root resorption does continue into retention, then careful examination of the occlusion should be carried out and any interferences causing jiggling or excessive axial forces removed. Where root resorption continues, then serial endodontic treatment with calcium hydroxide is advised; obtunding the canal with gutta percha is only carried out once the root resorption has ceased. This may be detected when an intact and continuous periodontal ligament space is seen around the root; this may take from six to 12 months to appear (Tronstad 1988).

Treatment There is no effective treatment for root resorption although it fortunately ceases once the insult is removed. ElBialy et al (2004) had reported on the use of low intensity pulsed ultrasound (LIPUS) that can reduce the number of areas of root resorption in experimentally tipped teeth; this was achieved by healing of the root surface by hypercementosis. While by no means a clinically feasible technique, it does suggest that in the future, orthodontists may have much greater control over the degree of root resorption occurring in patients.

The effect of EARR and OIIRR On periodontal support

Attachment remaining (%)

In general, a small amount of apical root resorption is unlikely to prejudice the long term survival of individual teeth. Kwalkorf et al (1986) studied the amount of periodontal attachment remaining per millimetre of root resorption. This is shown in Figure 22.8 where it can be seen that the slope of the columns from 0 to 2 mm of root resorption is less steep than for the subsequent columns. This relates to the very conical shape of the apex of single rooted teeth. The authors estimate that for 100 between 0 and 3 mm of apical loss, 3 mm of apical 90 root resorption is equivalent to 1 mm of crestal bone 80 loss; after 2 mm of apical root loss, the ratio is closer 70 to 2 mm of root resorption being equivalent to 1 mm of crestal bone loss.

60 50

Loss of crestal (marginal) attachment is also more detrimental because of the presence of large amounts of periodontal fibres in the crestal area compared with the apical area (Goldin 1989).

40 30 20 10 0 0

1

2

3

4

5

6

7

8

9

10

11

12

13

Root resorption (mm)

Figure 22.8: Relationship between root resorption and amount of periodontal attachment remaining (from Kwalkorf, Krejci and Pao 1986)

On healing Falahat et al (2008) looked at what happened to maxillary lateral incisors with root resorption due to ectopic canines several years after the correction of the canine position. The severity of resorption was

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graded as:

• • •

slight o up to half the thickness of the dentine moderate o midway to the pulp or more but with the pulp lining being unbroken severe o the pulp was exposed

Root resorption was assessed at the start of treatment using CT scans and the follow-up was done using intra-oral films (with a few requiring CT scans for additional information). The authors concluded that:

•

• • •

the long-term prognosis for maxillary incisors with root resorption associated with ectopically positioned canines was good and that in most cases the resorption heals after repositioning or surgical removal. Even in cases with severe resorption, the incisor roots still showed good longterm healing resorption sites, which are recorded at initial registration and subsequently undergo repair, might be difficult to identify at follow-up if evidence is limited to intraoral radiographs Incisors with root resorption can be used in an orthodontic appliance system no indications were present for endodontic treatment to arrest further root resorption

On tooth longevity Tooth loss due to apical root shortening is rarely reported in the literature. Remington et al (1989) examined 100 patients 14 years after treatment and found no tooth loss with hypermobility present in only two patients. Many teeth with severe root resorption can be retained in the mouth for significant lengths of time providing a functional occlusion with excellent aesthetics (Savage and Kokich 2002).

On the use of teeth as abutments The use of teeth with extreme root resorption (>

1 3

of the root length) as abutment teeth for restorations is

contra-indicated.

Clinical considerations: • patients should be informed of the risk of root resorption through the informed consent process.

Particular risk factors such as pre-existing root resorption or abnormally shaped roots should be highlighted • a history from other family members who have had orthodontic treatment may be helpful in determining any genetic component • take pre-treatment radiographs and when receiving a transfer case • encourage patients to stop habits such as nail biting or digit sucking • forces should be light and intermittent to allow healing. Longer appointment intervals may aid this • keep treatment times a short as reasonably possible • carefully consider the necessity for biomechanics that unduly stress the periapical tissues • consider taking a dentopantomograph six months into treatment to check both bracket position and incipient root resorption • if root resorption is detected, revise the treatment plan. This may include using lower forces, ceasing treatment for between four to six months to allow healing take place or reducing the scope of the treatment objectives

ROOT RESORPTION EXCELLENCE IN ORTHODONTICS 2012

References Abass SK, Hartsfield JK, Al-Qawasmi RA, Everett ET, Foroud TM and Roberts WE (2008) Inheritance of susceptibility to root resorption associated with orthodontic force in mice American Journal of Orthodontics and Dentofacial Orthopaedics 134: 742-750 Al-Qawasmi RA, Hartsfield JK, Everett ET, Flury L, Liu L, Foroud TM, Macri JV and Roberts WE (2003) Genetic predisposition to external root resorption American Journal of Orthodontics and Dentofacial Orthopaedics 123: 242-252 Alqerban A, Jacobs R, Souza PC and Willems G (2009) In-vitro comparison of 2 cone-beam computed tomography systems and panoramic imaging for detecting simulated canine impaction-induced external root resorption in maxillary lateral incisors American Journal of Orthodontics and Dentofacial Orthopaedics 136: 764.e1-764.e11 Ash MM (1993) Wheeler's Dental Anatomy, Physiology and Occlusion Philadelphia, W B Saunders Company Årtun J, Smale I, Behbehanic F, Doppeld D, Van’t Hofe M and Kuijpers-Jagtman AM (2006) Apical root resorption six and 12 months after initiation of fixed orthodontic appliance therapy Angle Orthodontist 75: 919–926 Barbagallo LJ, Jones AS, Petocz P, Darendeliler MA (2008) Physical properties of root cementum: Part 10. Comparison of the effects of invisible removable thermoplastic appliances with light and heavy orthodontic forces on premolar cementum. A microcomputed-tomography study American Journal of Orthodontics and Dentofacial Orthopaedics 133: 218-227 Becker A, Smith P and Behar R (1981) The incidence of anomalous maxillary lateral incisors in relation to palatally displaced cuspids Angle Orthodontist 51: 24-29 Bishara SE, Vonwald L and Jakobsen JR (1999) Changes in root length from early to mid-adulthood: resorption or apposition American Journal of Orthodontics and Dental Orthopaedics 115: 563-568 Bjerklin K and Ericson S (2006) How a computerized tomography examination changed the treatment plans of 80 children with retained and ectopically positioned maxillary canines Angle Orthodontist 76: 43–51 Brezniak N and Wasserstein A (1993a) Root resorption after orthodontic treatment: Part 1. Literature review American Journal of Orthodontics and Dentofacial Orthopaedics 103: 62-66 Brezniak N and Wasserstein A (1993b) Root resorption after orthodontic treatment: Part 2. Literature review American Journal of Orthodontics and Dentofacial Orthopaedics 103: 138-146 Brezniak N and Wasserstein A (2002a) Orthodontically induced inflammatory root resorption. Part 1: The basic science aspects Angle Orthodontist 72: 175-179 Brezniak N and Wasserstein A (2002b) Orthodontically induced inflammatory root resorption. Part 2: The clinical aspects Angle Orthodontist 72: 180-184 Brin I, Tulloch JFC, Koroluk L and Philips C (2003) External apical root resorption in class II malocclusion: a retrospective review of 1- and 2- phase treatment American Journal of Orthodontics and Dentofacial Orthopaedics 124: 151-156 Brisceno CE, Rossouw PE, Carrillo R, Spears R and Buschang PH (2009) Healing of the roots and surrounding structures after intentional damage with miniscrew implants American Journal of Orthodontics and Dentofacial Orthopaedics 135:292 -301 Chan E and Darendeliler MA (2005) Physical properties of root cementum: Part 5. Volumetric analysis of root resorption craters after application of light and heavy orthodontic forces American Journal of Orthodontics and Dentofacial Orthopaedics 127: 186-195 Chiqueto K, Martins DR and Janson G (2008) Effects of accentuated and reversed curve of Spee on apical root resorption American Journal of Orthodontics and Dentofacial Orthopaedics 133: 261-268

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Costopoulos G and Nanda R (1996) An evaluation of root resorption incident to orthodontic intrusion American Journal of Orthodontics and Dentofacial Orthopaedics 109: 543-548 Dudic A, Giannopoulou C, Leuzinger M and Kiliaridis S (2009) Detection of apical root resorption after orthodontic treatment by using panoramic radiography and cone-beam computed tomography of super-high resolution American Journal of Orthodontics and Dentofacial Orthopaedics 135: 434-437 El-Bialy T, El-Shamy I and Graber TM (2004) Repair of orthodontically induced root resorption by ultrasound in humans American Journal of Orthodontics and Dentofacial Orthopaedics 126: 186-193 Falahat B, Ericson S, D'Amico RM and Bjerklin K (2008) Incisor root resorption due to ectopic maxillary canines Angle Orthodontist 78: 778-785 Goldin B (1989) Labial root torque: effect on the maxilla and incisor root apex American Journal of Orthodontics and Dentofacial Orthopaedics 95: 209-219 Goldson L and Henrikson CO (1975) Root resorption during Begg treatment. A longitudinal roentgenologic study American Journal of Orthodontics and Dentofacial Orthopaedics 68: 55-66 Han G, Huang S Von den Hoff JW, Zeng X and Kuijpers-Jagtman AM (2005) Root resorption after orthodontic intrusion and extrusion: an intraindividual study Angle Orthodontist 75: 912-918 Harris EF (2000) Root resorption during orthodontic therapy Seminars in Orthodontics (Biology of tooth movement: clinical implications) 6: 183-194 Harris EF and Baker WC (1990) Loss of root length and crestal bone height before and during treatment in adolescent and adult orthodontic patients American Journal of Orthodontics and Dentofacial Orthopaedics 98: 463-469 Harris EF and Butler ML (1992) Patterns of incisor root resorption before and after orthodontic correction in cases with anterior open bites American Journal of Orthodontics and Dentofacial Orthopaedics 101: 112-119 Harris EF, Kineret SE and Tolley EA (1997) A heritable component for external apical root resorption in patients treated orthodontically American Journal of Orthodontics and Dentofacial Orthopaedics 111: 301-309 Harris EF, Robinson QC and Woods MA (1993) An analysis of the causes of apical root resorption in patients not treated orthodontically Quintessence International 24: 417-428 Harvey BLC and Zander HA (1959) Root surface resorption of periodontally diseased teeth Oral Surgery, Oral Medicine and Oral Pathology 12: 1439-1443 Hembree M, Buschang PH, Carrillo R, Spears R and Rossouw PE (2009) Effects of intentional damage of the roots and surrounding structures with miniscrew implants American Journal of Orthodontics and Dentofacial Orthopaedics 135: 280.e1-280.e9 Hylander WL (1977) The adaptive significance of Eskimo craniofacial morphology In Dahlberg AA and Graber TM (eds.); Orofacial growth and development pp 129-169 The Hague, Mouton Jiminez-Pellegrin C and Arana-Chavez VE (2004) Root resorption in human mandibular first premolars after rotation as detected by scanning electron microscopy American Journal of Orthodontics and Dentofacial Orthopaedics 126: 178-185 Killiany DM (1999) Root resorption caused by orthodontic treatment: an evidence-based review of literature Seminars in Orthodontics (Evidence-based Orthodontic Practice) 5: 128-133 Kook Y-A, Park S and Sameshima GT (2003) Peg-shaped and small lateral incisors not at higher risk for root resorption American Journal of Orthodontics and Dental Orthopaedics 123: 253-258

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Kwalkorf KL, Krejci RF and Pao YC (1986) Effect of apical root resorption on periodontal support Journal of Prosthetic Dentistry 56: 317-319 Lee A, Schneider G, Finkelstein M and Southard T (2004) Root resorption: the possible role of extracellular matrix proteins American Journal of Orthodontics and Dentofacial Orthopaedics 126: 173-177 Levander E and Malmgren O (1988) Evaluation of the risk of root resorption during orthodontic treatment: A study of upper incisors European Journal of Orthodontics 10: 30-38 Levander E, Malmgren O and Steinback K (1998) Apical root resorption during orthodontic treatment of patients with multiple aplasia: a study of maxillary incisors European Journal of Orthodontics 20: 427-434 Linge BO and Linge L (1983) Apical root resorption in upper anterior teeth European Journal of Orthodontics 5: 173-183 Makedonas D, Odman A and Hansen K (2009) Management of root resorption in a large orthodontic clinic Swedish Dental Journal 33: 173-178 Malone AJ (1951) Radiographic study of periapical resorption in human permanent teeth Master's Thesis, University of Illinois College of Dentistry Massler M and Malone AJ (1952) Resorption potential of human permanent teeth Journal of Dental Research 31: 412 (abstract) Massler M and Perreault JG (1954) Root resorption in the permanent teeth of young adults journal of Dentistry for Children : 158-164 Mavragani M, Vergari A, Selliseth NJ, Bøe OE and Wisth PJ (2000) A radiographic comparison of apical root resorption after orthodontic treatment with a standard edgewise and a straight-wire edgewise technique European Journal of Orthodontics 22: 665-674 Mirabella AD and Årtun J (1995a) Prevalence and severity of apical root resorption of maxillary anterior teeth in adult orthodontic patients European Journal of Orthodontics 17: 93-99 Odenrick L and Brattström V (1985) Nailbiting: frequency and association with root resorption during orthodontic treatment British Journal of Orthodontics 12: 78-81 Owman-Moll P, Kurol J and Lundgren D (1995) Repair of orthodontically induced root resorption in adolescents Angle Orthodontist 65: 403-408 Pandis N, Nasika M, Polychronopoulou A and Eliades T (2008) External apical root resorption in patients treated with conventional and self-ligating brackets American Journal of Orthodontics and Dentofacial Orthopaedics 134:646 -651 Paulsen HU, Andreasen JO and Schwartz O (1995) Pulp and periodontal healing, root development and root resorption subsequent to transplantation and orthodontic rotation: a long term study of auto-transplanted premolars American Journal of Orthodontics and Dentofacial Orthopaedics 108: 630-640 Ramfjord SP and Ash MM (1971) Occlusion 2nd edition Philadelphia, Saunders Remington DN, Joondeph DR, Årtun J, Riedel RA and Chapko MK (1989) Long-term evaluation of root resorption occurring during orthodontic treatment American Journal of Orthodontic and Dentofacial Orthopaedics 96: 43-46 Renjen R, Maganzini AL, Rohrer MD, Prasad HS and Kraut RA (2009) Root and pulp response after intentional injury from miniscrew placement American Journal of Orthodontics and Dentofacial Orthopaedics 136:708 -714

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Rex T, Kharbanda OM, Petocz P and Darendeliler MA (2005) Physical properties of root cementum: Part 4. Quantitative analysis of the mineral composition of human premolar cementum American Journal of Orthodontics and Dentofacial Orthopaedics 127:177-185 Sameshima GT and Sinclair PM (2001a) Predicting and preventing root resorption: Part 1. Diagnostic factors American Journal of Orthodontics and Dentofacial Orthopaedics 119: 505-510 Sameshima GT and Sinclair PM (2001b) Predicting and preventing root resorption: Part 2. Treatment factors American Journal of Orthodontics and Dentofacial Orthopaedics 119: 511-515 Savage RR and Kokich VG (2002) Restoration and retention of maxillary anteriors with severe root resorption Journal of the American Dental Association 133: 67-71 Smale I, Årtun J, Behbehani F, Doppel D, van’t Hof M and Kuijpers-Jagtman AM (2005) Apical root resorption 6 months after initiation of fixed orthodontic appliance therapy American Journal of Orthodontics and Dentofacial Orthopaedics 128: 57-67 Srivicharnkul P, Kharbanda OP, Swain MV, Petocz P and Darendeliler MA (2005) Physical properties of root cementum: Part 3. Hardness and elastic modulus after application of light and heavy forces American Journal of Orthodontics and Dentofacial Orthopaedics 127: 168-176 Tronstad L (1988) Root resorption – etiology, terminology and clinical manifestations Endodontics and Dental Traumatology 4: 241-252 Weilland F (2003) Constant versus dissipating forces in orthodontics: the effect on initial tooth movement and root resorption European Journal of Orthodontics 25: 335-342

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23 Finishing David Birnie

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Introduction Finishing procedures may:

• •

enhance aesthetics enhance stability

Finishing starts at the moment of fitting the appliance and is part of a planned treatment strategy - leaving it to the last few months of treatment is far too late!

What to aim for!

It is helpful to have a clear idea of one's treatment goals (see chapter on Occlusal Treatment Goals) and objective measures of these might include:

Arch widths and archform

The intermolar, interpremolar and intercanine widths at the start of treatment are useful reference points as treatment progresses and may be recorded as part of the model analysis.

The Six Keys to normal occlusion A reasonable goal for most orthodontic treatment outcomes is compliance with Andrews' Six Keys to normal occlusion. In addition, well finished cases have no interocclusal ‘black space’.

Peer Assessment Rating (PAR) score

The PAR score is a good measure of outcome but is not so useful for measuring progress towards treatment goals.

The American Board of Orthodontics

The American Board of Orthodontics (ABO) was formed in 1929 by the American Society of Orthodontia in Estes Park, Colorado and has as it aims:

• • • •

evaluation of the knowledge and clinical competency of graduates of accredited orthodontic programs re-evaluation of clinical competency throughout career through recertification contribution to the development of quality graduate, postgraduate, and continuing education programs in orthodontics contribution to certification expertise throughout the world.

There is little doubt that the ABO was both farsighted and has achieved all of these objectives and its activities had been a model for orthodontic boards all over the world.

The American Board of Orthodontics has an excellent website at http://www.americanboardortho.com/about/ which is worth looking through.

The most interesting parts are found under the > Professionals > Road to Certification section. Look up:

• •

the Discrepancy Index at http://www.americanboardortho.com/professionals/road_to_cert/phase_iii/discrepancies.aspx and the Objective Grading System for Dental Casts and Panoramic Radiographs at http://www.americanboardortho.com/professionals/road_to_cert/phase_iii/GradingSystem/

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Feature

Criteria

Tolerance

Anterior alignment

Co-ordination of incisal edges and labial incisal edges of mandibular incisors and canines: co-ordination of incisal edges and lingual incisal edges of maxillary incisors and canines

0.5 mm

0.5 to 1.0 mm

Mandible: mesiobuccal and distobuccal cusps should be in the same mesiodistal alignment Maxilla: mesiodistal central grooves should be in alignment

0.5 to 1.0 mm

Marginal ridges

Marginal ridges of adjacent teeth shall be at the same level

0.5 mm

Buccolingual inclination

Mandible: a flat surface across contralateral molars should contact the buccal cusps Maxilla: a flat surface across the contralateral molars and premolars should contact the lingual cusps

Posterior alignment

> 1.0 mm 0.5 mm > 1.0 mm

0.5 to 1.0 mm > 1.0 mm for lingual cusps: 0.5 mm

0.5 to 1.0 mm > 1.0 mm for buccal cusps: 0.5 mm

Penalty

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Comments and Exceptions

0 -1 -2

Scored out of 64 for anterior and posterior alignment together No more than 2 points are subtracted for any one tooth

0 -1 -2

Scored out of 64 for anterior and posterior alignment together No more than 2 points are subtracted for any one tooth

0 -1 -2

Scored out of 32 No more than 2 points are subtracted for any one tooth

0 -1 -2

Scored out of 40 No more than 2 points are subtracted for any one tooth

> 1.0 mm

0 -1 -2

Occlusal contacts

The buccal cusps of the mandibular premolars and molars and the lingual cusps of the maxillary should contact the occlusal surfaces of the opposing teeth

0.0 mm 0.1 mm to 1.0 mm > 1.0 mm

0 -1 -2

Scored out of 64 No more than 2 points are subtracted for any one tooth Non-functional or diminutive cusps are not counted

Occlusal relationship

The maxillary canine cusp tip should align within 1 mm of the interproximal contacts between the mandibular canine and the adjacent premolar.

The buccal cusps of the maxillary premolars should align with should be within 1 mm of the interproximal contacts between the mandibular premolars The mesiobuccal cusps of the maxillary molars should align within 1 mm of the buccal grooves of the mandibular molars

0 mm to 1 mm 1 mm to 2 mm > 2 mm

0 -1 -2

Scored out of 24 In class 2 molar relationships, the mesiobuccal cusp of the maxillary molar should align with the interproximal contact between the mandibular second premolar and first molar In class 3 molar relationships, the buccal cusp of the maxillary second premolar should align with the buccal groove of the mandibular first molar

Overjet

The buccal cusps of the mandibular molars and premolars will contact the in the buccolingual centre of the maxillary molars and premolars Anteriorly, the mandibular canines and incisors will contact the lingual surfaces of the maxillary canines and incisors

0 mm 0 mm to 1 mm > 1 mm

0 -1 -2

Scored out of 32 No more than 2 points are subtracted for any one tooth

0 mm 0 mm to 1 mm > 1 mm

0 -1 -2

Interproximal contacts

Viewed from the occlusal, the mesial and distal surfaces of the teeth should be in contact

0 mm 0 mm to 1 mm > 1 mm

0 -1 -2

Root angulation (from OPT)

The roots of the maxillary and mandibular teeth should be parallel to one another and perpendicular to the occlusal plane

Deviation of apex: 0 mm to 1 mm 1 mm to 2 mm > 2 mm

0 -1 -2

0.5 to 1.0 mm

Table 23.1:

Scored out of 60 No more than 2 points are subtracted for any one tooth Scored out of 64

The American Board of Orthodontics Objective Grading system for dental casts and panoramic radiographs

The American Board of Orthodontics' Objective Grading System for Dental Casts and Panoramic Radiographs The American Board of Orthodontics has introduced a grading system for models and panoramic radiographs (Casko et al 1998). This is oriented very much towards occlusal detail and has some surprising omissions (such as measurement of intercanine and intermolar widths). The system is also very intolerant of interarch tooth size discrepancies and cases which require unusual solutions. In general, a case which loses more than 30 points will fail and a case that loses less than 20 points will probably pass. A measurement instrument has been devised to ensure reliability in measurement. One of the claimed advantages of this system is that it allows candidates to grade their own results prior to examination.

The system is based on studies of the 1995 and 1996 ABO examinations in which 15 criteria were examined. It was determined that 85% of errors occurred in just seven of the 15 criteria. In 1997, a further study was carried out using a measuring instrument to improve inter-examiner reliability. A further study was carried out in 1998 to

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refine the process. The principal features of the system are given in the following table although reading of the original text and scrutiny of the website is recommended.

Diagnostics and solutions It is important to know what to look for – spotting problems early gives more time for their correction. As a rough guide, it is worth taking time at least every six months during treatment to systematically evaluate progress towards the end of treatment goals. In reality, this is equivalent to repeatedly re-diagnosing the case so that by an iterative process one moves steadily towards the treatment goals.

All problems can be divided into one of three categories:

• • •

aesthetics occlusal oral health

Several authors have written good articles on finishing and these include:

• • •

McLaughlin and Bennett (1991) McLaughlin and Bennett (2003) Kokich (2003)

Poling (1999) has published an interesting article on finishing which is well worth reading; the method is probably over-elaborate but the principles are sound. This involves the use of detail finishing check sheet to record exactly what work needs to be done to finish the case. The bracket positioning sheet shown in the Bracket Placement, Bonding and Debonding Techniques chapter can be used for a similar purpose Aesthetics Extraoral Ask the patient to smile and check for any horizontal occlusal cant, evaluate the amount of incisor displayed at rest and when smiling. Check the consonance of the smile. intraoral

Cycle of refining bracket position

ed ss pre ex ition ate os alu h p Ev toot

ed t ss n re me p e ex c n pla itio ket s po ac h br ot gh o T ou r th

Check to see if any adjustment is required to crown length, width or the shape of the incisor edge; in general it is better to reshape teeth at the start of treatment but be careful to make a careful decision as to whether crown reshaping or restoration is the best option. Often this will be decided by the gingival emergence profile.

Gingival surgery may be required to improve emergence profiles and remove hyperplastic gingivae.

Rarely fraenectomies may be required.

Reposition brackets as necessary

Figure 23.1: Cycle of refining bracket position. At least one iteration is normally required

Occlusal Many occlusal problems relate to bracket positioning.

Carlsson and Johnson (2001) suggest that the key to accurate bracket position is careful attention to the following four elements: base adaptation, vertical

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position, rotation and slot angulation.

Tooth position Vertical For the incisors, vertical tooth position is governed by the relationship of the incisal edges in intact and unworn teeth. Lateral incisors should be positioned with their incisal edges slightly above those of the central incisors to give an attractive smile.

In the posterior segments, the teeth should be positioned so that the marginal ridges are level. During the bonding procedure, the operator should look both for the FA point and also at the existing difference in heights of the marginal ridges in order to position brackets in optimum positions. This is often quite difficult but with care, the need to frequently rebond can be minimised.

Adjusting the position of a bracket vertically on the flat surface of an incisor tooth will have little effect on the torque transmitted to the teeth. However, changes in vertical position on teeth with curved buccal surfaces will result in significant alterations in the torque delivered by the appliance (Sondhi 2003).

Prominence Prominence includes both in-out and rotation (which may be thought of as an asymmetrical in-out?). Errors in prominence arise either from unusual tooth anatomy or poor base adaptation of the bracket to the tooth surface; the former requires some wire bending to correct the discrepancy while the latter may be corrected either by wire bending or rebonding.

Base adaptation Good adaptation of the bracket base is usually required. There are occasions however where it is better to have a variable layer of composite between the bracket and the enamel surface. These include teeth with misshapen crowns and diminutive teeth. In these circumstances, the shape of the composite interlayer can be more accurately controlled with an indirect bonding technique.

Rotations are often due to an uneven layer of composite under the bracket base but sometimes it is just difficult to get a tooth as well derotated as one would wish. Rotation ties can be helpful as can forms of rotation wedge including that described by Abrahmian (1993). This involves placing a figure of eight elastomeric ligature over the tie wing which it is desired to move away from the archwire and tying in the other tiewing with a steel ligature.

Where teeth have been very rotated, accurate positioning of the bracket may be very difficult or impossible initially. For these teeth, it is important to check that the bracket position is correct once they have been derogated. The use of a traction hook and elastic chain to derotate teeth in the early stages is recommended.

Angulation Angulation is usually well managed by preadjusted edgewise appliances. However, sometimes some extra work is required particularly when the gingival papillae does not extend down (or up!) to the contact point leaving a black triangle between the contact point and the gingival margin. Careful interproximal reduction and adjustment of the angulation of the adjacent teeth can often remedy the situation.

Careful study of a recent orthopantomogram during bonding is helpful in identifying problems in angulation which require correction. However, the aim is to get the crowns correctly positioned and normally that will also mean correct root position; the roots can be a more subtle indicator of abnormalities of crown position because of their length. Root angulation should be checked using an orthopantomogram once rectangular wires are placed; these want to be at least 0.018" x 0.025" although there is no need to wait until working stainless steel archwires are in place.

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This check normally comes about six months into treatment and can combined with an evaluation of any signs of early root resorption.

Inclination Inclination is usually more of a problem than angulation and individual teeth frequently need minor torque adjustments. These are best done with Rose torquing plier set (ETM 800-805W) and the 0.018"/0/022" torquing bar is the most useful.

Segments of teeth can be adjusted by applying continuous or progressive torque by one of the established methods. The effect of bracket position and the initial inclination of the teeth on the torque delivered by the appliance are discussed later in this chapter.

Zachrisson (1986) suggests using 0° torque in lower second molars so as to prevent the palatal cusps of the upper second molars erupting and causing balancing interferences.

Interdigitation Good interdigitation can be difficult to achieve with continuous archwires and so it is usually best to go to very light archwires in one arch and to segment the other arch in order to get good interdigitation. In order to get good interdigitation, place a 0.014" archwire in the lower arch and segment the upper rectangular archwire to give a sectional which is then placed from upper canine to upper canine. Make sure that the upper labial segment is ligated together to prevent any unwanted space opening up. Leave the upper posterior segments without any archwire. Give the patient triangular or box elastics to wear in the areas where settling is required; in many bracket systems, these elastics will sit over the tie wings which means that archwire or bracket hooks are not required as shown in Figure 23.2.

This phase of treatment takes from two to six weeks and needs careful monitoring.

Generally, good interdigitation requires a flat occlusal plane; the exception to this is in anterior open bite cases where extrusion of the terminal molars may either make the anterior open bite worse or make its closure difficult.

Figure 23.2: The lower arch is 0.014" nickel titanium.

The upper labial segment is controlled by a 0.019 x 0.025" stainless steel sectional. Note the two crimps either side of the upper central incisors to stop swivelling.

TP Red elastics are worn in triangular and box configuration to maximise the interdigitation in the buccal segments.

Interocclusal Anteroposterior correction It is helpful to err on the side of overcorrection when

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correcting a class 2 or class 3 malocclusion. It is important to get the buccal segments fully class1 which in class 2 cases may mean overcorrecting the incisor relationship.

Vertical correction Correction of deep overbites may be assisted by:

• • •

bonding second molars placing anterior brackets more towards the incisal edge using reverse curves of Spee either in stainless steel or nickel titanium archwires.

Anterior open bites are often difficult to close and even more difficult to keep closed. Ensure that any habits have ceased, pay careful attention to the position of the second molars (see above) and consider positioning anterior brackets slightly to the gingival of the FA point to assist in bite closure.

Transverse correction Make sure that the lower intercanine width is not expanded; some expansion posteriorly is permissible but make sure that the buccolingual inclinations of the teeth are within normal limits. Recording measurements of the intercanine, interpremolar and intermolar widths is a useful discipline during treatment.

Arch coordination can be achieved by using a single archform customised to the patient; there is no need to use upper and lower arch blanks – the forward positioning of the maxillary arch ensures that the upper and lower archforms are coordinated. The advent of fully bonded appliances and perhaps the freedom of tooth movement afforded by self-ligating brackets have greatly reduced the need for intraoral expansion devices such as quadhelices and expansion screws.

Centreline correction Major centreline corrections often require the sequential movement of individual teeth round the arch until centreline correction is achieved. It is worth asking the patient how long it takes for each tooth to move; this is often surprisingly rapid and appointment times can be adjusted accordingly.

Minor centreline correction can be achieved by judicious use of asymmetric class 2 or class 3 traction (two elastics on one side; one elastic on the other), class 2 elastics on one side and class 3 on the other and anterior cross elastics. Anterior cross elastics can be made more tolerable by placing a Kobayashi ligature on the mesial side of the lower central incisor tooth on the side that the cross elastic is attached to the lower arch; the elastic can then be run horizontally along the lower arch before sloping diagonally upwards to the upper arch from the midline.

CR-CO coincidence For patients with class 2 malocclusions, it is important to repeatedly check to ensure that there is no postured bite or that there is no significant CR-CO discrepancy. If so, then the mechanics used for class 2 correction need to be continued for longer.

For all malocclusions it is worth regularly checking for CR-CO slides and then carefully evaluating what is causing them. Incorporating second molars into the appliance seems to have made this problem less than it was in the past.

Anterior interferences Anterior interferences are discussed by Sondhi (2003b). The article is controversial, especially in its assertion that anterior interferences can cause posterior and superior displacement of the condyle on closure. Sondhi asserts that anterior interferences can cause:

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• • • • •

anterior spacing and diastemas fremitus excessive incisal wear periodontal damage (gingival recession) intracapsular derangement of the temporomandibular joints

Despite its controversial nature, this article provides interesting reading and stimulates thought about finishing procedures.

Space closure Complete space closure is normally a treatment goal (although not in hypodontia cases or in cases with diminutive teeth). Check that space is fully closed in the extraction space – and also in the midlines and between first and second molars in extraction cases where intramaxillary traction has been used to the first molars.

During the finishing stages, it is sensible to lace together the anterior segments to stop space opening up and also across extraction spaces if space is likely to reopen.

Oral health Teeth Constantly monitor the crowns of the teeth for signs of decalcification or caries. Encourage the patient when their oral hygiene is excellent. Have some disposable pre-pasted toothbrushes for the patients to brush their teeth with both before they see you and once their archwires have been removed.

Root resorption can be checked for on the same OPT film taken to check root angulation approximately six months into treatment.

Periodontium Again, constant checking for bleeding, redness, recession and pocketing is required.

Temporomandibular joint Check that mouth opening remains at the same level or greater than at the start of treatment. Approximately every six months check mandibular excursions. Be aware of any change in joint noises or behaviour.

The extent to which a gnathologic approach to finishing is elaborated in a paper by Chiappone (1975). The relationship of preference of occlusal scheme to geographical area is another twist on evidence based orthodontics.

Finishing check lists At appliance placement check:

• •

bracket positions in all planes of space for excess adhesive and remove

Continuously during treatment

•

plaque levels

Oral hygiene

FINISHING EXCELLENCE IN ORTHODONTICS 2012

• •

watch for non carious tooth surface loss reinforce oral hygiene message Gingival condition

• •

colour bleeding TMJ

• • • •

clicks mouth opening excursions pain

Six months into treatment • alignment o first order o rotations • incisal edge alignment • angulations • marginal ridges • carry out 1st phase reproximation if desired Twelve months into treatment • space closure • torque o anterior o posterior • overbite • overjet • buccal segment relationship • Cr-Co discrepancy • occlusal guidance scheme • root paralleling Fifteen months into treatment • fully correct/overcorrect all rotations • fully torque/overtorque roots of teeth originally displaced from alveolar housing • develop interdigitation • adjust crown shape o crown length o crown width o reproximation 2nd phase o crown form • gingival surgery o gingival form o pericision

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At end of treatment • all goals achieved • bone levels • root resorption • third molars During retention • check retainer wear • check tightness of contacts with dental floss • reproximation 3rd phase • monitor eruption of third molars El-Beialy et al (2005) have described a finishing checklist to be started three to six months before case completion which maybe helpful and which is shown in Table 23.2.

Facial

Smiling dentogingival display gingival margin level smile arc buccal corridors occlusal plane/interpupillary line

Profile balanced soft-tissue profile facial convexity nasolabial angle chin

Maxillary arch archform symmetry alignment levelled marginal ridges level of anterior teeth rotations angulation inclination buccolingual inclination intercanine width curve of Spee

Mandibular arch archform symmetry alignment levelled marginal ridges level of anterior teeth rotations angulation inclination buccolingual inclination intercanine width curve of Spee

Interarch – static occlusion coincident midlines overjet overbite canine relationship molar relationship intercuspation

TMJ TMJ palpation muscle palpation Joint sounds opening movement restricted right excursion restricted left excursion deviation /deflection

Panoramic and intraoral radiographs root parallelism third molars root resorption

Frontal symmetry lip competency tooth display

Dental

Table 23.2:

Interarch – functional occlusion CR-CO coincidence protrusive interferences interferences on right excursion Interferences on left excursion Lateral cephalometric radiograph canting of occlusal plane interincisal angle upper anterior tooth torque lower anterior teeth torque

Abnormal habits

Finishing checklist (after El-Beialy et al 2005)

Interincisal stripping or reproximation The best times for doing this are:

• • •

once incisor alignment is achieved at debonding during retention as necessary

It is best done using a very, very fine diamond bur in a high speed handpiece. The bur should be ‘stroked’ gently up and down along the contact point until ‘breaks through’.

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Incisal edge recontouring

A comprehensive and practical article on incisal edge recontouring was written by Zachrisson (2005). Increasingly minor adjustment of tooth shape is performed in order to improve the final result. Very minor adjustments can have a significant effect on the final aesthetic result; a high speed finishing bur is capable of removing enamel with little risk of excessive enamel loss.

Root paralleling

This can be achieved by:

• • • •

bracket positioning - err on the side of encouraging root paralleling using gable bends sectionals edgewise uprighting springs

Overcorrecting rotations and overtorquing individual teeth A simple way of overcorrecting rotations has been described by Abrahmian (1993). This involves placing a figure of eight elastomeric ligature over the tie wing which it is desired to move away from the archwire and tying in the other tiewing with a steel ligature. With the introduction of self-ligating brackets, this is less useful.

Overtorquing individual teeth can be very easily achieved using Rose pliers and torquing key. TMA archwires are particularly helpful for this.

Pericision Pericision is:

• • •

indicated where supragingival fibres have been significantly displaced by derotation contraindicated where oral hygiene is poor is not carried out in the mid-labial portion of the lower incisors to prevent recession

Bleaching

The use of bleaching trays at the end of treatment can enhance the appearance of the final result. Preloaded trays with 9% hydrogen peroxide for home use on the prescription of a dentist are available from Optident under the name of 9% H2O2. Examples are shown in Figures 23.3 and 23.4.

The trays are based on an Ultradent product called trèswhite. The suggested time of application is 30-60 minutes

Figure 23.3: 9% H2O2 bleaching trays are packaged as upper and lower trays and come in melon or mint flavour

Figure 23.4: The 9% H2O2 bleaching trays consist of a coloured outer liner and a clear inner liner containing the bleaching gel. The bleaching gel is contained within the trough of the tray by a barrier gel.

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FINISHING EXCELLENCE IN ORTHODONTICS 2012

(which can be done at home). The trays are not suitable for overnight use and it is recommended that no more than ten trays are used.

9% H2O2 trays produce subtle but significant changes and patients are impressed with the results.

References Abrahamian A (1993) Correction of individual tooth rotations with elastomeric ligatures Journal of Clinical Orthodontics 27: 163 Carlson SK and Johnson E (2001) Bracket positioning and resets; five keys to align crowns and roots satisfactorily American Journal of Orthodontics and Dentofacial Orthopaedics 119: 76-80 Casko JS, Vaden JL, Kokich VG, Damone J, James RD, Cangialosi TJ, Riolo ML, Owens SE and Bills ED (1998) Objective grading system for dental casts and panoramic radiographs American Journal of Orthodontics and Dentofacial Orthopaedics 114: 589-599 Chiappone RC (1975) A gnathologic approach to orthodontic finishing Journal of Clinical Orthodontics 9: 405-417 El-Beialy AR, Kortam SI and Mostafa YA (2005) Case finishing checklist Journal of Clinical Orthodontics 39: 322-323 Kokich VG (2003) Excellence in finishing: modifications for the perio-restorative patient Seminars in Orthodontics 9: 184-203 McLaughlin RP and Bennett JC (1991) Finishing and detailing with a preadjusted appliance system Journal of Clinical Orthodontics 25: 251-264 McLaughlin RP and Bennett JC (2003) Finishing with the preadjusted orthodontic appliance Seminars in Orthodontics 9: 165-183 Poling R (1999) A method of finishing the occlusion American Journal of Orthodontics and Dentofacial Orthopaedics 115: 476-487 Sondhi A (2003a) The implications of bracket selection and bracket placement on finishing details Seminars in Orthodontics 9: 155-164 Sondhi A (2003b) Anterior interferences: their impact on anterior inclination and orthodontic finishing procedures Seminars in Orthodontics 9: 204-215 Zachrisson BU (1986) JCO/Interviews Dr Bjorn U Zachrisson on Excellence in Finishing Part 1 Journal of Clinical Orthodontics 19: 460-482 Zachrisson B (2005) Incisal edge recontouring in orthodontic finishing World Journal of Orthodontics 6: 398-405

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

Chapter

461

24 Stability and retention David Birnie

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Introduction This chapter looks at criteria affecting stability, finishing and retention.

Retention has been advocated on the basis of

• •

reorganisation of the periodontal tissues late growth changes

and that after a specified period of time, stability of tooth position would be achieved. This idea is now being challenged and some writers, such as Little, believe that the only way to ensure long-term alignment of the teeth is by the use of fixed or removable retention.

Good reviews of retention philosophy are given by Melrose and Millett (1998), Blake and Bibby (1998) and Shah (2003).

Maturation of untreated malocclusions Sinclair and Little (1983) have identified several characteristics that occur as a result of ageing or maturation of the dentition. These are:

• • • • • •

a decrease in arch length form the mixed dentition into early adulthood decreases in intercanine width stability of intermolar width small increases in overjet and overbite increase in incisor irregularity from 13 to 20 years, with females exhibiting more irregularity than males no predictors of change can be identified

Bishara et al (1998) studied changes in arch length from six weeks to 45 years using a 6 week to two year sample and a three to 45 year sample based on the Iowa Facial Growth Study started by Meredith and Higley in 1946. This study showed that:

• • • • • • •

males had significantly greater arch lengths than females arch length increases from six weeks to two years maxillary arch length increases from three to 13 years (4.0 mm in males, 2.4 mm in females the increase in mandibular arch length was complete by eight years (1.9 mm in males, 2.0 mm in females from eight to 13 years, mandibular arch length started to decrease (2.4 mm in males, 3.2 mm in females) between 13 and 45 years maxillary arch length decreased significantly (5.7 mm in males, 4.6 mm in females between 13 and 45 years, mandibular arch length decreased by 7.4 mm in males and 8.3 mm in females

The same authors (Bishara et al 1997) also looked at intercanine and intermolar width over the same time period.

They found that:

• •

between six weeks and two years of age, significant increases in anterior and posterior arch widths occurred in both male and female children maxillary intercanine width increased from three to 13 years and then started to decrease

80

80

75

75 millimetres

millmetres

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

70 65

463

70 65 60

60

55

55 3

5

8

13

26

3

45

years Males

• • •

8 years Males

Females

Figure 24.1: Changes in mandibular arch length from 3 to 45 years (from Bishara et al 1998)

5

13

26

45

Females

Figure 24.2: Changes in maxillary arch length from 3 to 45 years (from Bishara et al 1998)

mandibular intercanine width increased until the age of eight years and then started to decrease gradually. The important point here is that no increase in mandibular intercanine width occurs after the eruption of the lower incisors maxillary intermolar width increases steeply until 13 years and then stays relatively static in males but decreases a little in females mandibular intermolar width follows a similar pattern to maxillary intermolar width peaking at around 13 years

Agkul and Toygar (2002) studied craniofacial changes in untreated malocclusion during the third decade and confirmed that all dental arch measurements decrease with age and in particular, a significant decrease in arch length in males takes place during the third decade. Total face height increased and there was a significant increase in lower face height and overbite in females.

Dental changes following treatment Principal investigators in this area have been Robert Little at the University of Washington, Seattle, Cyril Sadowsky at the University of Illinois, Chicago and Lee Boese in California.

Generally, Sadowsky has found slightly better results and used different methods of measurement to those of Little. Crowding, for instance, was measured by Sadowsky as the difference between the space available to accommodate a crowded tooth and its mesiodistal size.

Sadowsky and Sakols (1982) found that, on average 20 years after treatment, 72% of patients had dental relationships outside the normal range mainly because of increases in overjet and overbite (5% and 16% respectively). 9% of patients had increased mandibular crowding compared to their start condition.

Arch development

Little et al (1990) have looked at the stability of cases which used space gaining or “arch development” techniques to gain at least 1 mm of arch length using the following methods:

• • • • • •

actively moving the anterior teeth labially with fixed or removable appliances passively moving the anterior teeth labially by removal of lip forces actively pushing the molars distally by extraoral or intraoral means widening the arch with fixed or removable devices widening the lower arch by reciprocal response to upper arch enlargement enlarging the dental arch with a combination of devices and means

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STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

and found that:

• • • •

the Irregularity Index scores at the end of treatment were satisfactory postretention, 89% of cases were clinically unsatisfactory the arch length decreased in all patients during the postretention phase.

20 out of 26 patients showed a decrease in arch length of > 1 mm

Arch development would seem therefore one of the least stable orthodontic techniques according to this study.

However, this paper had a small and a heterogeneous mix of arch development techniques.

Premolar extractions Two classical papers describe the changes occurring in first premolar cases treated by traditional edgewise mechanics were published by Little et al (1981, 1988). Little’s Irregularity Index and Arch Length were used as measures. The Irregularity Index is defined as the summed displacement of adjacent anatomic contact points of the mandibular anterior teeth and arch length as the summed inside measurement from first permanent molars to the central incisor contact point.

The cases selected were well treated and directed towards upright incisor position as a treatment goal. It was found that:

• •

long term alignment was variable and unpredictable there were no predictors of the long-term result

36

40

34 32

35

28

millimetres

millimetres

30

26 24

30

25

22 20

20 3

5

8

years

Males

13

26

3

45

5

8

years

13

Males

Females

Figure 24.3: Changes in maxillary intercanine width from 3 to 45 years (from Bishara et al 1997)

26

45

Females

Figure 24.4: Changes in mandibular intercanine width from 3 to 45 years (from Bishara et al 1997) 50

55

50

45

40 millimetres

millimetres

45

40

35

30

35

30 3

5

8

13

26

45

years Males

3

5

8

13

26

45

years Females

Figure 24.5: Changes in maxillary intermolar width from 3 to 45 years (from Bishara et al 1997)

Males

Females

Figure 24.6: Changes in mandibular intermolar width from 3 to 45 years (from Bishara et al 1997)

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

• • • • •

465

arch dimensions decrease after retention despite expansion, maintenance or constriction of the intercanine width satisfactory alignment of lower incisors occurs in less than 30% of cases changes continue to occur well after cessation of growth from 20-30 years considerable change was seen routinely from 30-40 years, the process continued at a lesser rate

These general findings have been reconfirmed in a systematic review by Bondemark et al (2007).

Boese (1980) favours pericision and reproximation without lower retention. This study focussed attention strongly on the lower labial segment; and neither the study, nor its results, have ever been repeated. The amount of lower incisor stripping was determined using the Peck and Peck (1972) ratio which should not exceed 93% for lower central incisors and 95% for lower lateral incisors. Gilmore and Little (1984) however found only weak associations between incisor widths or MD/FL ratios and lower incisor alignment. We do not use the Peck and Peck ratio and only occasionally carry out lower incisor reproximation.

However, an interesting study not dissimilar to Boese’s was published by Aasen and Espeland (2005). The 56 cases in this study were treated by Aasen whose treatment philosophy and methodology was as follows:

• • • • • • • • • •

proclination of lower incisors was avoided intercanine width was maintained or reduced archform was maintained no class 2 elastics were used in non-extraction cases interproximal stripping was carried out at the start of treatment for cases with anterior crowding and at the end of treatment for other cases. Light interproximal stripping was carried out during the post treatment period if relapse appeared to be occurring rotated incisors were over-corrected during treatment an 0.025” x 0.022” archwire was used for 2 to 3 months to ensure alignment of the lower labial segment prominent marginal crests on the upper incisors were reduced by grinding at the end of the finishing stage, the lower archwire was removed to detect any incipient relapse; if it occurred, the incisors were realigned and additional stripping carried out no retainers were used in the mandibular arch

The results were remarkable and are summarised in Figure 24.1.

Vaden et al (1997) also looked at premolar extraction cases (the four first premolars, the four second premolars or the upper first and lower second premolars). All patients were treated with fixed appliances which lasted on average 2.1 years. Retainers were either upper and lower Hawley's or upper Hawley and lower banded canine-tocanine retainer. Patients were recalled six years and fifteen years after treatment. Little’s Irregularity Index increased after treatment to 1.6 mm at six years and 2.6 mm at fifteen years. More than 90% of the patients in this study were better off 15 years after treatment than they were before it. This study clearly presents a more optimistic view of the success of orthodontic treatment than Little’s work. It is suggested that relapse may be less in cases treated by a single experienced specialist than university-based samples treated by multiple orthodontic residents.

Mean

Sd

Minimum

Pretreatment

5.6

3.7

0.0

15.3

Post treatment

0.4

0.5

0.0

2.1

3 years post treatment

1.1

0.9

0.0

3.3

Table 24.1: Change in Irregularity Index pre and post treatment (from Aasen and Espeland 2005)

Maximum

Boley et al (2003) showed similar results in that cases treated carefully by a single practitioner using a non-expansion approach had much lower levels of incisor irregularity a long time (average 11.7

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STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

years) post retention than were found in Little’s studies.

Erdinc et al (2006) compared relapse in extraction and non-extraction cases at least two years post retention and concluded there was no difference in the incisor irregularity index (IRI) postretention. The pretreatment IRI decreased by 5.51 mm in the extraction group and 2.38 mm in the nonextraction group.

Timing of extractions Haruki and Little (1998) investigated the differences in the long-term stability of orthodontic cases treated in the mixed dentition and in the permanent dentition. Mixed dentition cases had at least one deciduous tooth or did not have successional teeth fully erupted. Active treatment was started after premolar extractions. The mean irregularity index of the early cases was better than that of the later group (3.09 mm compared with 4.15 mm); in addition there was less midline discrepancy in the early group (0.34 mm compared 0.58 mm).

Arches with generalised spacing This was investigated by Little and Riedel (1989). Most of these cases showed minimal crowding after treatment but a few, severe crowding.

Intercanine width A good review of mandibular intercanine width is given by Burke et al (1998). This was a meta-analysis - a statistical analysis of a large collection of results from individual studies for the purpose of integrating their findings. Burke et al found that:

• • • •

mandibular intercanine width increased by up to 2 mm during treatment (T1-T2) mandibular intercanine width decreased post retention by 1.2 mm to 1.9 mm regardless of pretreatment classification or whether the treatment was extraction or nonextraction (T2-T3) mandibular intercanine width showed a net change of +0.5 mm to -0.6 mm regardless of pretreatment classification or whether the treatment was extraction or nonextraction (T1-T3) the net change in mandibular intercanine width between T1 and T3 in 1,233 subjects was zero

There may sometimes however be good reasons for expanding intercanine width and Walkow and Peck (2002) have shown that in severe (100% overbite) class 2 division ii malocclusions, the intermolar and upper intercanine widths are similar to those of a control group where as the lower intercanine width was constricted due to the increased overbite. In these malocclusions, it is suggested that anterior expansion is a reasonable treatment plan but that this has implications for retention.

Interpremolar width

The orthodontic literature is not full of studies on the stability of changes in premolar width, but work by Gonzales and Nielson (1992) suggested that there was greater stability of premolar expansion during treatment than of canine expansion.

This is also supported by Begole et al (1998) who found that significant expansion could be obtained in the premolar region in non-extraction cases. This could be expected to remain stable approximately 10 years after treatment and six to eight years after the end of retention. The cases had been treated on a non-extraction basis with the deliberate intention of expanding the dental arch but maintaining the original archform. This was not the case with extraction cases and the summary data makes interesting reading as shown in Table 24.2.

This is not necessarily a surprising finding and correlates with the work of Gardner and Chaconas (1976), who studied 103 cases on the average of 5.2 years after retention. Although their study evaluated mandibular arches, their results were very similar to the current study. In both studies, significant net expansion of similar magnitude was seen at the premolars and molars, whereas the net canine expansion in the current study was significant for nonextraction cases. Similar findings were reported by Sadowsky et al (1994). The order of greatest arch width gain for each of the sites measured was for the nonextraction cases in the maxilla, the second premolars, followed

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

Arch Maxilla

Tooth Canine

Extraction 0.0

First premolar

Mandible

Nonextraction 2.1

-1.7

5.0

First molar

-0.9

3.5

0.2

0.4

First premolar

1.5

Second premolar

-4.0

1.5

First molar

-2.2

1.7

Table 24.2: Net change in arch width (mm) in extraction and nonextraction cases six to eight years after retention (from Begole et al 1998)

orthodontic treatment. They found that:

• • • • • •

by the first premolars, the molars, and finally the canines, whereas for the mandible, the order was molars, second premolars, and first premolars.

4.3

Second premolar Canine

467

Changes in archform

Information on the stability of archform is scanty.

Changes in archform without tooth irregularity probably pass largely unnoticed and are not regarded as “relapse”. However, a paper by De La Cruz et al (1995) from the Seattle group begins to shed some light on this subject. The study looked at class 1 and class 2 division i patients who had had four premolars extracted as part of their

arch form became more rounded during treatment the arch form tended to revert to its more tapered pretreatment form after retention greater change during treatment was associated with greater postretention change individual variation was considerable (some tapered arches became more rounded postretention) the patient’s pretreatment archform appeared to be the best guide to future stability long term stability is not necessarily obtained by minimising treatment change in archform

Guidelines for stability Zachrisson (1997) has published a paper detailing his personal views on key treatment objectives to ensure longterm stability of treated cases. Not all of these have a significant base although they are worthy of consideration and reflection and the paper is worth reading carefully.

Rotational relapse

Full correction of all rotations Under correction of rotations is common and can be difficult to spot. Careful examination of the pre-treatment records against treatment progress early on in treatment is required. Zachrisson hypothesises that broken contact points are a starting point for later crowding in untreated malocclusions. It may be that small contact points are unstable and that reshaping the contact point may aid stability as described by Tuverson (1980).

Placing the lower lateral incisors outside the lower canines It is suggested that post-treatment relapse can be masked by doing this and that in addition it is particularly important where the distal contact points have been lingual to the lower canine contacts points before treatment.

Early correction of rotations The rationale for this is that the transeptal fibres do not develop until the amelocemental junctions of the developing teeth pass the level of the alveolar process (Kusters et al 1991). Thus early correction of rotations allow the transeptal fibres to develop in a normal anatomic relationship. This however is likely to be only part of the story.

Transverse relapse The importance of maintaining mandibular intercanine width, mandibular archform are discussed elsewhere in this chapter. Some alteration of maxillary archform may be required to coordinate the upper arch with the lower arch. It is emphasised that there is no evidence to suggest that stable enlargement of the basal bone of the maxilla beyond normal growth can be achieved.

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Vertical relapse

Deep overbite Zachrisson emphasises the importance of accurately identifying which teeth are over-erupted, examining the lipmaxillary incisor relationship and establishing an optimal inter-incisal angle.

Vertical relapse and mandibular incisor crowding Establishing an optimal interincisal angle is said to be essential for stability of overbite reduction. Relapsing overbite causes a decrease in the available space for the lower incisors and hence a potential increase in lower incisor crowding. A similar situation can also occur when lower first premolars are extracted and the lower canines are over retracted. This makes it difficult to obtain a satisfactory interincisal angle with accompanying vertical relapse and a consequent increase in lower incisor crowding. However, Fudalej and Årtun (2007) conclude that neither forward rotating nor backward rotating facial patterns at time of appliance removal are associated with increased risk of postretention relapse of mandibular incisor malalignment, and in adolescent orthodontic patients are poor predictors of type of posttreatment growth.

Predictors of post treatment change We have become accustomed to the idea that there are no pre-treatment predictors of crowding or irregularity that would give us an idea as to how a dentition might behave post-treatment. Intuitively, we might think that more crowded and irregular dentitions before treatment might perhaps be at greater risk after treatment but to date have had no evidence to support this hunch. An interesting paper has been published by Surbeck et al (1998) which begins to address this issue.

Three groups of patients were established based on their tooth alignment at a long time out of retention date T3.

The groups consisted of patients with significant spacing, significant irregularity and perfect alignment of the maxillary anterior teeth at T3. The study found that:

• • • • • •

severe irregularity of the maxillary anterior teeth is rare long term out of retention (49 out of 745 cases or less than 7%) pretreatment irregularity or rotation of maxillary anterior teeth is a significant risk factor for postretention relapse incomplete alignment during treatment is a significant risk factor for relapse expansion of the maxillary anterior arch segment during active treatment is a significant risk factor for anatomic contact point displacement and tooth rotation long term out of retention rotational displacement has a high tendency to repeat itself post treatment whereas anatomic contact point discrepancy post retention is random relative to original tooth positions interdental spacing pretreatment is a significant risk factor for interdental spacing post retention

Al Yami et al (1999) found that 67% of the achieved orthodontic result was maintained 10 years post-retention and that approximately half the relapse occurred in the first two years after retention. The presence of a fixed retainer resulted in the PAR score being 3.6 points less five years post-retention and 4.6 points less at 10 years postretention.

Jon Årtun (2001) in re-evaluating their class 2 division i sample (Fidler et al 1995) for incisor irregularity found that the severity of incisor irregularity and the narrowness of the intercanine width prior to treatment as well as treatment increase in intercanine width were risk factors for relapse. No skeletal factors were identified as risk factors for relapse.

Ormiston et al (2005) have re-examined 86 sets of records from the University of Washington post-retention archives which were not restricted to specific malocclusions or methods of treatment but which excluded class 3 cases. Records were divided into two groups – stable and unstable occlusions. Stable occlusions were those which did not change by more than 5 PAR points in either direction in the post treatment and post retention period (a minimum of 7.4 years). Unstable occlusions had an increase of more than 5 PAR points in the post

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

60 50

ABO score

40 30 20 10 0 10-20

20-30

30-40

> 40

ABO score banding at T2

469

retention period; occlusions which decreased their PAR score by more than 5 points were not recorded as stable.

They found that males, and patients who had sustained period of growth (usually males), had PAR scores that tended to deteriorate. Patients with greater irregularity at the start of treatment tended to have less stable results as did class 2 cases. Patients with low ABO scores at the end of treatment deteriorated during the post retention period whereas those with high ABO scores at the end of treatment tended to improve; this is shown in Figure 24.7.

T2 mean

Figure 24.7: Change in ABO scores during post treatment period banded by ABO score at post treatment (T2) (from Ormiston et al 2005)

Increasingly, factors which might predict relapse are becoming evident.

Rationale for retention It is helpful to try and think what treatment changes require retention. Dividing these problems up into the following categories is useful:

• • • •

arch perimeter alignment anteroposterior vertical transverse

It may not be possible to provide an adequate method of retention for certain problems eg: anterior open bite.

A good literature review and the rationale for retention is given by Kaplan (1988) and more recently by Littlewood et al (2006).

Valiathan and Hughes (2010) have conducted a study to identify common retention practices in the United States of America. The most common type of retainer used was a Hawley retainer in the maxillary arch and a fixed retainer in the lower arch. Most orthodontists prescribed a period of full-time wear for removable retainers and more often prescribed full-time wear period for Hawley retainers compared with clear thermoplastic retainers, and a longer full-time wear period for Hawley retainers compared with clear thermoplastic retainers. For patients with removable retainers, most orthodontists instructed the patient to wear their retainers forever. Most orthodontists also did not instruct patients to have the fixed lingual retainers removed at a specific time, thus suggesting lifetime retention.

70

Retaining class 2 sagittal correction obtained with functional appliances

60 50

per cent

40 30 20 10 0 Maxilla Hawley

Clear thermoplastic

Mandible Spring aligner

Fixed

Other

Figure 24.8: The use of various types of retainer in the USA (Valiathan and Highes 2010)

After the use of a functional appliance, the patient is put on night time only retention for three months before moving into fixed appliances if these are necessary. If no fixed appliance was required then retention would be continued at nights only for up to nine months. The treatment objective for the correction of class 2 malocclusions is to overcorrect the most class 2 teeth in the buccal segments by about a quarter of a unit.

Retaining a class 2 buccal segment

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STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

relationship corrected with fixed appliances The final and desired for molar relationship is obtained as early in treatment as possible. Once this has been achieved it is then maintained throughout treatment. This can then be maintained using retainers such as a Damon splint as shown in Figure 24.9. For many young patients however, the change in soft tissue posture brought about by correction of the class 2 division I malocclusion provides sufficient retention.

Figure 24.9: embrasure

Damon splint – note airway extending to canine

Retaining alignment within the dental arches

The papers published by Little over the past decade have provided little clue as to how to prevent the development of late incisor crowding on the basis of diagnostic criteria or treatment methodology. It remains fact that:

• long term alignment is variable and unpredictable • there are no helpful predictors of late crowding • arch dimensions decrease with age Boese advocates a five-step approach to debonding:

• • • • •

overcorrect rotations overcorrect torque for individually displaced teeth pericision reproximation no lower retention

and obtains excellent results using this technique.

A more conventional approach to maintaining alignment is long term retention - until recently a technique that itself had no long-term studies. However, Sadowsky et al (1994) have demonstrated the effectiveness of longterm retention in maintaining lower incisor alignment. This effect does not show up in the Seattle studies largely because the retention time rarely exceeded two years. The benefits of longer retention are also investigated by Destang and Kerr (2003) who compared maxillary incisor alignment in two groups with different retention regimes:

• •

Hawley retainer with three months full time wear and three months night-time only wear Hawley retainer with six months full time wear and six months night-time only wear

The authors found that the group with the shorter retention period relapsed by an average of 50% 1.56 mm to 2.33 mm) three months after the end of retention compared with 23% (1.00 mm to 1.23 mm) for the group that had the longer retention period. Retention for one year would therefore seem to be more effective than retention for six months. Several questions however remain to be answered:

• • •

what does full time retention contribute to the retention process? what are the quantitative benefits of longer retention periods (i.e.: if retention had been continued for 18 months, would the relapse have been in the order of 12.5%) is there a time point at which no benefit is derived from additional retention

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

471

As a general policy and on a pragmatic basis, based on late facial growth activity and the corresponding maxillarymandibular adjustments, retention should be continued in males until the mid-20s and in females until the early 20s (Behrents 1989).

Retention strategy The retention strategy we use is as follows:

• upper and lower clear overlay vacuum formed retainers • optionally an upper • • • •

Bond-A-Braid or Ortho FlexTech retainer and a 0.025” solid

retainer is used in addition to the clear overlay vacuum retainers worn evenings and at nights only from start of retention review after three months and 12 months thereafter, patient advised of risks of post treatment tooth movement resulting from relapse and natural aging changes and it is suggested that retainers are worn alternate nights only but patient should try to titrate wear against tendency for tooth movement. patient is neither discharged nor given a further appointment but advised to contact department if teeth are moving, retainers require maintenance or replacement or they have any other concerns.

It seems certain that post treatment tooth movement is universal (Linklater and Fox 2002) and can occur a long time after the completion of active treatment (Yavari et al 2000).

Removable retainers

Conventional removable appliances These used to be our favoured form of retainer but the time taken for their fabrication and their appearance has discouraged us. Debonding now takes no longer than a routine adjustment visit and booking one-day retainers can be difficult within a busy schedule. Patients are simply debonded on the day they are ready and the laboratory undertakes to deliver the retainers on the next working day.

The design of the retainers is such that there is minimal wirework crossing the occlusion.

In the upper arch, Begg style retainers have been tried but lack retention particularly in cases with erupting second molars or upright incisors. A Hawley style retainer with a labial bow that is soldered to the bridges of the upper first molar clasps works well. Baseplate design and its effect on speech has been studied by Stratton and Burkland (1993) and a horseshoe shaped baseplate considerably improves speech, particularly in adult patients.

Haydar et al (1996) have looked at the effect of retainers on speech and concluded that after seven days speech distortions have either disappeared or become minimal.

In the lower arch, a modified Barrer retainer or spring positioner is used. This is extended lingually and has occlusal rests on the lower first molars. A wire stress breaker separates the lingual extensions from the acrylic bar to the lingual of the lower incisors. This allows retention of the appliance by engagement of the undercuts in the molar region. Retention can be increased by simply flexing the appliance to flare the lingual extensions.

Alternatively, Adam's clasps can be used for retention in which case the lingual stress breaking wire can be omitted.

Vacuum formed retainers Full arch vacuum formed retainers are sometimes said to be difficult to work with for the following reasons:

• the bulk of the appliance is distal to the canines and these areas are prone to fracture • patients find the thickness of the material may create an uncomfortable bite • the thickness of the material posterior to the canines may predispose to an open bite

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STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

In practice, we have not found these objections to be significant and prefer full arch retainers to the classical Essix design. The retainers should cover the mesial half of the second molars to prevent over-eruption of these teeth with the consequent development of an anterior one bite.

Our retention regime is evening and night-time wear (10 to 12 hours out of 24) for a year. After that time retainer wear is at the discretion of the patient but wear an alternate nights is recommended. Patients are not routinely seen after one year but are given instructions on how to identify problems with their retainer wear and asked to contact the department should they feel that their teeth are moving or the retainers require maintenance.

Sheridan et al (1993) have reported a variation on vacuum formed retainers called the Essix retainer. The retainers are fitted only from canine to canine and worn at nights only. They are not recommended for patients who have an anterior open bite.

Essix retainers are made from copolyester resin manufactured by Raintree Products (a company who incidentally donates its profits to the Louisiana State University Department of Orthodontics Alumni Association to fund an endowed research chair). The claimed advantages of Essix retainers are:

• • • • •

the ability to supervise retention without visiting the orthodontist absolute stability of the anterior teeth durability and ease of cleaning low cost and ease of fabrication minimal bulk and thickness

Essix retainer material of thickness 0.75 mm (0.030") is used which during thermoforming thins to 0.015" thickness.

Duplicate retainers are normally provided.

The following construction points should be noted:

• the labial margin should be trimmed so that it extends over the gingiva by 2-3 mm • the palatal portion of the upper flange should be trimmed straight across the palate from canine to

canine • the posterior distogingival part of the canine crowns should be left uncovered by the retainer in order to allow removal with a fingernail • a coloured strip should be placed labially and palatally in order to make the retainer visible when out of the mouth Essix retainers are worn as follows:

• upper and lower retainers: both night times only • single arch retainer:

upper retainer at night, lower during the day for four weeks, then two weeks full-time, then night times only

Additional papers by Sheridan (1994a and 1994b) describe the use of Essix retainers for temporary anterior bridges and for correction of minor tooth irregularities.

Lindauer and Schoff (1988) carried out a prospective nonrandomized clinical trial to compare Essix retainers with Hawley retainers during the first six months of active retention. The sample size (19 Essix and 21 Hawley retainers) was small. No significant differences were found between the two retainer groups when overjet, overbite, and incisor irregularity were examined over the 6-month retention period and the amount of contact point displacement between debond and 6 months into retention was small at 0.3 mm. Sauget et al (1997) compared the changes in the number of occlusal contacts between Hawley and vacuum formed retainers on 30 patients

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

473

between debond and after three months retention. There was a significant increase in the number of contacts on the posterior teeth while there were no significant changes in occlusal contact with the vacuum-formed retainer.

Rowland et al (2007) compared the effectiveness of vacuum formed and Hawley retainers over a six month period of observation and with a large sample in each group. They found that vacuum formed retainers were more affective than Hawley retainers at maintaining correction of the maxillary and mandibular labial segments.

Hichens et al (2007) looked at the same sample and found that vacuum formed retainers were more cost-effective than Hawley retainers from all perspectives. The majority of subjects showed a preference for vacuum formed retainers compared with Hawley retainers and there were also fewer breakages than in the vacuum formed compared with the Hawley group.

Thickett and Power (2010) carried out a randomised controlled trial to determine whether thermoplastic retainers needed to be worn fulltime for a limited period or whether part-time wear would be sufficient. The retention protocols were as follows: Group

0-3 months post debond

3-6 months post debond

6-9 months post debond

9-12 months post debond

1

Full time wear

Part-time wear (10h/day)

Alternate nights

1-2 times per week

2

Part-time wear (10h/day)

Part-time wear (10h/day)

Alternate nights

1-2 times per week

Figure 24.10:

Retention protocols in Thickett and Power’s study

There was no statistical difference between the two groups for overjet, arch length, intermolar width, intercanine width and irregularity index for each time period. At T3 and T4, there was a small but statistically significant increase in overjet in both groups. The authors concluded that part-time retainer wear could be advised for patients who had undergone fixed appliance treatment with extractions.

A similar conclusion was drawn by Gill et al (2007). Over a six month period following debonding, these authors found that patients who wore Essix retainers part-time experienced similar levels to those patients who wore them full-time.

Fixed retainers We have preferred to avoid the use of fixed retainers because they:

• • • •

hinder interdental cleaning require considerable maintenance do not necessarily prevent the development of late crowding or irregularity carry the risk of caries development under partially failed bonding material

However, the increased sophistication and design of fixed retainers has seen us move to the increasing use of fixed retainers. Not all of our concerns are justified, Booth et al (2008) carried out a 20-year follow-up of lower canine to canine retainers, mainly of the 0.025” diameter single strand type although some were 0.036” diameter.

The purpose of the study was to determine the effectiveness and health effects of lower fixed retainers over such a long time frame. Sixty patients were recalled and 45 patients still had their retainers in place; 15 had been removed in orthodontic practices between five and 25 years previously. Of the 45 retainers still in place, 25 had never come detached, eight patients had had a single repair and nine patients had had more than one repair. Of the patients who still had their retainers in place, only one had more than 2 mm of irregularity score. In the patients who had had their retainers removed, 13 had a irregularity score > 3 mm and 5 had > 4 mm. The gingival index data indicate no negative effect on periodontal health from long-term application of a bonded mandibular canine-to-canine retainer. Patients with a lower canine to canine retainer had a better gingival index score in the maxillary anterior segment than those who did not indicating better personal oral hygiene. There were no enamel lesions on the lingual aspect of the mandibular incisors and canines (white spots, decalcification, caries), even in those with poor oral hygiene. Overall, an impressive performance!

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Katsaros et al (2007) have highlighted concern about the use of flexible spiral wire or twistflex retainers bonded to all mandibular anterior teeth which may result in unwanted labiolingual movement or torque of lower anterior teeth. A further study by Sifakakis et al (2011) on the in-vitro assessment of the forces generated by lingual canine to canine fixed retainers using three different multistrand wires showed that the forces recorded from the lingual retainer wires during 0.2 mm simulated intrusion-extrusion and buccal-lingual movements might generate high forces exceeding 1 N and be large enough to produce unwanted tooth movement during retention. The only significant determinant of the generated forces was the amount of wire displacement and not the type of wire used.

Bonded retainers are strongly indicated for maintaining the closure of a median diastema or for the prolonged retention of corrected rotations. Fixed retainers should be regarded as a medium term (2-3 years) method of retention. Reliance (Hilgers) Bond-a-Braid is useful for bonding behind upper incisors; it should be laid flat on the cingulae where its flat profile ensures minimal interference with the occlusion as is Reliance Ortho FlexTech, a flattened white gold wire which can be fitted at the chairside without laboratory support. Årtun et al (1997) carried out a three-year follow-up study of canine-to-canine retainers. The study looked at the tendency for plaque and calculus to build up around fixed retainers. It found that the plaque and calculus scores were lower three years after appliance removal than at the time of appliance removal. The retainer types used were:

• • • •

thick plain wire bonded to canines only thick spiral wire bonded to canines only thin spiral wire bonded to incisors and canines removable retainers

The failure rate amongst bonded retainers was 22.9% and the majority of failures occurred during the third year of observation. The different retainer designs were equally efficient in maintaining alignment but only the retainer bonded to the canines and incisors showed no change in the Irregularity Index three years after appliance removal. Årtun favours the use of a thick 0.036" spiral wire bonded to the canines only. For lower retainers bonded to the mandibular canines only, flossing can be achieved by looping the floss round the mesial and distal surfaces of an incisor so that it slips down below the retainer. Al-Nimri et al (2009) compared the gingival health, plaque accumulation, tooth stability and integrity of multistrand wire and round wire bonded lingual retainers.

Sixty-two patients, who had completed treatment and who required fixed retention for the lower anterior segment, were assigned to one of two groups (single strand wire or multistrand retainer). A 0.036” round stainless steel wire was bonded to the lingual surfaces of both lower canines was used in the single strand group while the multistrand retainer group had a 0.015” multistrand wire bonded to the lingual surfaces of all lower anterior teeth.

At least 12 months after debonding, the subjects were recalled and the following variables were recorded: oral hygiene index, plaque index of the lower anterior teeth, gingival index of the lower anterior teeth, irregularity index of the lower anterior teeth, and the number of broken retainers. The authors found no significant differences between the plaque index and the gingival index between the two groups. More plaque was found on the distal surfaces of the lower anterior teeth in the group with multistrand wire retainers. The lower anterior teeth were significantly more irregular in the group with round wire retainers compared to the group with multistrand wire retainers (p = 0.002). Although the multistrand wire retainers fractured more frequently than the round wire retainers the difference was not statistically significant.

The conclus plaque accumulated on the distal surfaces of the lower anterior teeth in subjects with multistrand wire retainers, multistrand wire retainers were better at maintaining incisor alignment than single strand wire retainers.

Zachrisson also favours bonding to mandibular canines only but uses a 0.032" stainless steel or 0.030 gold-plated wire which is microetched at each end and claims a failure rate of only 8.4% or 4.2% of bonded sites.

Oesterle et al (2001) have shown that optimum bond strength for fixed retainers is achieved with the use of a straight 0.030" stainless steel wire with no terminal bend but a microetched end (Figure 24.11).

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

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300

250

200

MPa

150

100

50

0 Control

Figure 24.11:

Coaxial

Bend

Etch

Bend, etch

Silane

Bend, silane

Etch, silane Bend, etch, silane

Metal primer

Bend, metal Etch, metal Bend, etch primer primer metal primer

Bond strengths of different designs of lower fixed retainers (from Oesterle et al 2001)

Renkema et al (2008) found that a lower 3-3 retainer bonded to the canines only was effective at maintaining alignment of the lower labial segment. From an Irregularity Index of 7.7 mm pre treatment to 0.3 mm post treatment, the irregularity index increased from 0.7 mm to 0.9 mm five years post treatment. 20.4% of patients had retainer failures and these patients had higher levels of incisor irregularity.

The use of a putty jig to place lower fixed plain retainers is preferred by some operators; it makes placing and holding the retainer in place easy during the bonding process and also allows precision placement if you want to use a clear overlay retainer as well. Check the cost before you order! Shah et al (2005) have described a method of securing the retainer using small elastic bands prior to bonding; this is easier and less expensive than a putty jig and works well.

Karaman et al (2003) have described a clever indirect method of placing a lower fixed retainer.

Rogers and Andrews (2004) have claimed a failure rate of 0.009% for lower 3-3 retainers. They suggest using:

• • • • • • • •

maintaining a dry field polishing the lingual surfaces of the lower canines with a finishing bur (other authors have suggested sandblasting) using loops rather than pads for retention (we prefer no loops and microetching) covering the loops with at least 0.25 mm of composite using a posterior composite filling material as a bonding adhesive using 0.025” diameter wire for the retainer so that the increased flexibility makes it less likely that masticatory forces will dislodge the wire contouring the composite carefully only bonding to the canines

An acrylic jig can be used for multistrand wire and the technique is described and well illustrated by Becker and Chausu (2004). The technique is as follows: Laboratory technique • adapt a multistrand wire to the palatal or lingual surfaces of the teeth on a plaster model taken either immediately before or at debond. The model should be painted with cold mould seal.

• the ends of the multistrand wire are taken horizontally off the last tooth one each side and then carried over to the labial side of the teeth

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STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

• the wire is secured to the model with wax • a band of acrylic is adapted to the labial surface of the teeth, joining together the ends of the •

multistrand wires the acrylic is finished but not highly polished prior to placement in the mouth

Clinical technique • prepare the enamel • place acrylic jig with multistrand retainer • bond each tooth with composite adhesive avoiding the interproximal areas • cut the multistrand wire on each side distal to its planned termination and the cut area finished and polished The use of ribbon-reinforced resin fixed retainers has been suggested and we have no experience of these; anecdotally we are probably a little discouraged. Rose et al (2002) compared the longevity of multistrand wire fixed retainers and polyethylene ribbon-reinforced resin composite; it was found that the ribbon reinforced retainers remained in place for an average of 11.5 months while the multistrand retainers remained in place for 23.6 months. Brauchli et al (2009) investigated the shear modulus of five flowable composites to EverStick Ortho fibre-reinforced composite retainer. All flowable composites had similar and adequate bonding characteristics but fractures were consistently found in the FRC retainer. The results of this study also showed that neither the composite nor the glass fiber but, rather, the silanization of the glass fibers is the critical component for failure in the FRC structure as all fracture sites showed exposed glass fibers, free from their surrounding composite/polymethylmethacrylate matrix.

It should be remembered that fixed retainers only retain anterior segments. Transverse changes in the buccal segments require the use of removable retainers; for optimum retention, clear overlay retainers and fixed retainers can be combined (Lang et al 2002).

Clinical tip: We use fixed retainers: • as an adjunct to vacuum formed retainers • to insure againstthe consequences of failure to wear the vacuum formed retainers • where there has been significant tooth irregularity, crowding or spacing • where we have produced tooth movements that we know are prone to relapse

Pericision (circumferential supracrestal fiberotomy - CSF) Pericision, as originally described by Edwards (1970) is a simple procedure that is recommended where teeth have been rotated during treatment by more than 30°. This should be carried out at least four weeks before the fixed appliances are removed so that the teeth are maintained in good alignment during the healing phase. We now almost never do this.

Edwards (1988) reported on a prospective study of CSF where he looked at gingival health and incisor irregularity in the upper and lower arches at the start of treatment, the end of treatment, 4 to 6 years after treatment and 12 to 14 years post treatment. Compared with a control group, the CSF group had less incisor irregularity in both arches. CSF appeared to reduce relapse more in the first 4-6 years after treatment than in the subsequent period.

There was no change in the height of the epithelial attachment or the width of the attached gingivae in the CSF group compared with the control group.

In cases where there is little attached gingivae, the papillae dividing procedure described by Ahrens et al (1981) may be preferred.

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

Taner et al (2000) did a small study to determine if circumferential fiberotomy affected relapse in crowding.

Their study suggests CSF has a role in reducing relapse from crowding but a study with a larger sample and a longer experimental time period is required to investigate this further.

140 120 100 80 grams

477

60

Third molars

40 20 0 1

2

3

4 Initial

Figure 24.12:

5

6

7

8

9

10

After chewing

Interproximal forces before and after chewing

The prophylactic removal of third molars has come under increasing scrutiny and it is no longer acceptable to recommend the routine removal of pathology free third molars.

The NHS Centre for Reviews and Dissemination at the University of York has published an Effectiveness Matters bulletin on third molars (1998).

The role of the third molars in inducing or contributing to late lower incisor crowding has been exaggerated (Ades et al 1990). Harradine et al (1998) investigated the effect of the extraction of third molars on lower incisor crowding. This was a randomised controlled trial on patients who had previously had orthodontic treatment and who had third molars whose presumed path of eruption was through the adjacent second molar. Incisor alignment was measured using Little’s Index of Irregularity. Where third molars were extracted, the mean increase in irregularity was 0.80 mm compared with 1.1 mm for the group whose third molars were retained. It is therefore very unlikely that the removal of third molars has a clinically significant effect on later incisor irregularity.

Indications for the removal of third molars are given by Pratt et al (1998):

• • • • • • • • • • • • • •

caries leading to pulpal exposure periodontal disease periapical pathology fractured tooth orthodontic abnormalities pain single episode of pericoronitis multiple episodes of pericoronitis medical 'prophylaxis' e.g. for cardiac surgery or endocarditis restorative considerations resorption or caries of adjacent teeth in the line of a fracture associated cyst or tumour prior to orthognathic surgery

Causes of post treatment change in alignment Three papers add to our knowledge about post treatment occlusal change. In 1989, Southard, Behrents and Tolley published a paper which quantified the magnitude and distribution of the anterior component of force. This force arises because of the mesial axial inclination of the posterior teeth. Mean forces of 5 lb. on premolars and 1 lb. on canines were found for a conservative chewing load of 20 lb. This force sometimes crossed the midline.

In 1990, the same authors published a second paper which investigated the relationship between dental malalignment and the anterior component of force. A correlation between occlusal forces and dental malalignment was demonstrated in addition to a correlation between contact tightness and dental malalignment.

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STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

In 1992, Southard et al published a further paper on the quantification of periodontal force. This paper hypothesises that the transeptal fibres maintain a continuous compressive force between contact points. Initial interproximal forces ranged from 6.0 to 86.9g (mean 36.7g) and generally increased after chewing to a mean of 57.2g. The results for the individual subjects are shown in Figure 24.12.

References Aasen TO and Espeland L (2005) An approach to maintain orthodontic alignment of lower incisors without the use of retainers European Journal of Orthodontics 27: 209-214 Ades AG, Joondeph DR, Little RM and Chapko MK (1990) A long-term study of the relationship of third molars to changes in the mandibular dental arch American Journal of Orthodontics and Dentofacial Orthopaedics 97: 323-325 Agkul AA and Toygar TU (2002) Natural craniofacial changes in the third decade of life: a longitudinal study American Journal of Orthodontics and Dentofacial Orthopaedics 122: 512-522 Ahrens DG, Shapira Y and Kuftinek MM (1981) An approach to rotational relapse American Journal of Orthodontics and Dentofacial Orthopaedics 80: 83-91 Al-Nimri K, Al Habashneh R and Obeidat M (2009) Gingival health and relapse tendency: a prospective study of two types of lower fixed retainers Australian Orthodontic Journal 25: 142–146 Al Yami EA, Kuijpers-Jagtman AM and van’t Hof MA (1999) Stability of orthodontic treatment outcome: follow-up until 10 years postretention American Journal of Orthodontics and Dentofacial Orthopaedics 115: 300-304 Årtun J (2001) Postretention changes in mandibular tooth alignment Oakstone Medical Reviews Volume 13 No. 6 October 2001 Accessed: 20 February 2010 (NB: subscription required) Årtun J, Spadafora A and Shapiro P (1997) A 3-year follow-up of various types of orthodontic canine-to-canine retainers European Journal of Orthodontics 19: 501-509 Becker A and Chausu S (2004) Non-invasive periodontal splinting with multistrand wire following the realignment of periodontally migrated teeth Orthodontics 1: 159-167 Begole EA, Fox DL and Sadowsky C (1998) Analysis of change in archform with premolar expansion American Journal of Orthodontics and Dentofacial Orthopaedics 113: 307-315 Behrents RG (1989) The consequences of adult craniofacial growth In Orthodontics in an Aging Society Ed. Carlson DS, Monograph 22, Craniofacial Growth Series, Centre for Human Growth and Development, University of Michigan, Ann Arbor pp 53-100 Bishara SE, Jakobsen JR, Treder J and Nowak AN (1997) Arch width changes from 6 weeks to 45 years American Journal of Orthodontics and Dentofacial Orthopaedics 111: 401-409 Bishara SE, Jakobsen JR, Treder J and Nowak AN (1998) Arch length changes from 6 weeks to 45 years Angle Orthodontist 68: 69-74 Blake M and Bibby K (1998) Retention and stability: a review of the literature American Journal of Orthodontics and Dentofacial Orthopaedics 114: 299-306 Boese LR (1980) Fiberotomy and reproximation without lower retention, nine years in retrospect: Parts 1 and 2 Angle Orthodontist 50: 88-97 Angle Orthodontist 50: 169-178

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Boley JC, Mark JA, Sachdeva RCL and Buschang P (2003) Long-term stability of class 1 premolar extraction treatment American Journal of Orthodontics and Dentofacial Orthopaedics 124: 277-287 Bondemark L, Holm AK, Hansen K; Axelsson S, Mohlin B, Brattstrom V, Paulin G and Pietila T (2007) Long-term stability of orthodontic treatment and patient satisfaction: a systematic review Angle Orthodontist 77: 181-191 Booth FA, Edelman JM, Proffit WR (2008) Twenty-year follow-up of patients with permanently bonded mandibular canine-to-canine retainers American Journal of Orthodontics and Dentofacial Orthopaedics 133: 70-76 Brauchli L, Pintus S, Steineck M, Lüthy H, Wichelhaus A (2009) Shear modulus of 5 flowable composites to the EverStick Ortho fiber-reinforced composite retainer: An in-vitro study American Journal of Orthodontics and Dentofacial Orthopaedics 135:54 -58 Burke SP, Silveira AM, Goldsmith LJ, Vancey JM, Stewart AV and Scarfe WC (1998) A meta-analysis of mandibular intercanine width in treatment and postretention Angle Orthodontist 68: 53-60 De La Cruz RA, Sampson P, Little RM, Årtun J and Shapiro PA (1995) Long term changes in arch form after orthodontic treatment and retention American Journal of Orthodontics and Dentofacial Orthopaedics 107: 518-530 Destang DL and Kerr WJS (2003) Maxillary retention: is longer better?

European Journal of Orthodontics 25: 65-69 Edwards JG (1970) A surgical procedure to eliminate rotational relapse American Journal of Orthodontics and Dentofacial Orthopaedics 57: 35-46 Edwards JG (1988) A long-term prospective evaluation of the circumferential supracrestal fiberotomy in alleviating orthodontic relapse American Journal of Orthodontics and Dentofacial Orthopaedics 93: 380-387 Erdinc AE, Nanda RS and Işıksal E (2006) Relapse of anterior crowding in patients treated with extraction and nonextraction of premolars American Journal of Orthodontics and Dentofacial Orthopaedics 129: 775-784 Fidler BC, Årtun J, Joondeph DR and Little RM (1995) Long-term stability of Angle Class II, Division 1 malocclusions with successful occlusal results at end of active treatment American Journal of Orthodontics and Dentofacial Orthopaedics 107: 276-285 Fudalej P and Årtun J (2007) Mandibular growth rotation effects on postretention stability of mandibular incisor alignment Angle Orthodontist 77: 199-205 Gardner S and Chaconas S (1976) Post-treatment and post-retention changes following orthodontic treatment Angle Orthodontist 46: 151-61 Gill DS, Naini FB, Jones A and Tredwin CJ (2007) Part-time versus full-time retainer wear following fixed appliance therapy: a randomized prospective controlled trial World Journal of Orthodontics 8: 300-306 Gilmore CA and Little RM (1984) Mandibular incisor dimensions and crowding American Journal of Orthodontics and Dentofacial Orthopaedics 86: 493-502 Gonzales M and Neilsen I (1992) Stability of dental arch form changes in patients treated with the Straight-Wire archform and preadjusted fixed appliances American Journal of Orthodontics and Dentofacial Orthopaedics 102: 573 (Abstract) Harradine NWT, Pearson MH and Toth B (1998) The effect of extraction of third molars on late lower incisor crowding: a randomised controlled trial British Journal of Orthodontics 25: 117-122 Haruki T and Little RM (1998) Early versus late treatment of crowded first premolar cases: postretention evaluation of stability and relapse Angle Orthodontist 68: 61-68

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Haydar B, Karabalut G, Özkan S, Aksoy A and Ciğer S (1996) Effects of retainers on the articulation of speech American Journal of Orthodontics and Dentofacial Orthopaedics 110: 535-540 Hichens L, Rowland H, Williams A, Hollinghurst S, Ewings P, Clark S, Ireland A and Sandy J (2007) Cost-effectiveness and patient satisfaction: Hawley and vacuum-formed retainers European Journal of Orthodontics 29: 372-378 Kaplan H (1988) The logic of modern retention procedures American Journal of Orthodontics and Dentofacial Orthopaedics 93: 325-340 Karaman AI, Polat O and Büyükyilmaz T (2003) A practical method of fabricating a lingual retainer American Journal of Orthodontics and Dentofacial Orthopaedics 124: 327-330 Katsaros C, Livas C, Renkema A-M (2007) Unexpected complications of bonded mandibular lingual retainers American Journal of Orthodontics and Dentofacial Orthopaedics 132: 838-841 Kusters ST, Kuijpers-Jagtman AM and Maltha JC (1991) An experimental study in dogs of transeptal fibre arrangement between teeth which have emerged in rotated an nonrotated positions Journal of Dental Research 70: 192-197 Lang G, Alfter G, Goz G and Lang GH (2002) Retention and stability--taking various treatment parameters into account Journal of Orofacial Orthopaedics 63: 26-41 Lindauer SJ and Shoff RC (1988) Comparison of Essix and Hawley retainers Journal of Clinical Orthodontics 32: 95-97 Linklater RA and Fox NA (2002) The long term benefits of orthodontic treatment British Dental Journal 192: 583-587 Little RM and Riedel RA (1989) Postretention study of stability and relapse - mandibular arches with generalised spacing American Journal of Orthodontics and Dentofacial Orthopaedics 95: 37-41 Little RM, Riedel RA and Årtun J (1988) An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention American Journal of Orthodontics and Dentofacial Orthopaedics 93: 423-428 Little RM, Riedel RA and Engst ED (1990) Serial extraction of first premolars - postretention evaluation of stability and relapse Angle Orthodontist 60: 255-262 Little RM, Riedel RA and Stein A (1990) Mandibular arch increase during the mixed dentition: postretention evaluation of stability and relapse American Journal of Orthodontics and Dentofacial Orthopaedics 97: 393-404 Little RM, Wallen TR and Riedel RA (1981) Stability and relapse of mandibular alignment - first premolar extraction cases treated by traditional edgewise orthodontics American Journal of Orthodontics and Dentofacial Orthopaedics 80: 349-365 Littlewood SJ, Millett DT, Doubleday B, Bearn DR and Worthington HV (2006) Orthodontic retention: a systematic review Journal of Orthodontics 33:205-212 Melrose C and Millett DT (1998) Toward a perspective on orthodontic retention American Journal of Orthodontics and Dentofacial Orthopaedics 113: 507-514 NHS Centre for Reviews and Dissemination (1998) Prophylactic removal of third molars: is it justified?

York, University of York National Institute for Clinical Excellence (NICE) (2004) Review of NICE Technology Appraisal Guidance No 1 - Guidance on the removal of wisdom teeth Accessed: 22 February 2012

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Oesterle LJ, Shellhart WC and Henderson S (2001) Enhancing wire-composite bond strength of bonded retainers with wire surface treatment American Journal of Orthodontics and Dentofacial Orthopaedics 119: 625-631 Ormiston JP, Xhuang GJ, Little RM, Decker JD and Seuk GD (2005) Retrospective analysis of long-term stable and unstable orthodontic treatment outcomes American Journal of Orthodontics and Dentofacial Orthopaedics 128: 568-574 Peck S and Peck H (1972) An index for assessing tooth shape deviations as applied to the mandibular incisors American Journal of Orthodontics 61: 384-401 Pratt CA, Hekmat M, Barnard JDW and Zaki GA (1998) Indications for third molar surgery Journal of the Royal College of Surgeons of Edinburgh 43: 105-108 Renkema A-M, Al-Assad S, Bronkhorst E, Weindel S, Katsaros C and Lisson JA (2008) Effectiveness of lingual retainers bonded to the canines in preventing mandibular incisor relapse American Journal of Orthodontics and Dentofacial Orthopaedics 134: 79.e1-179.e8 Rogers MB and Andrews II LJ (2004) A dependable technique for bonding a 3 x 3 retainer American Journal of Orthodontics and Dentofacial Orthopaedics 126: 231-233 Rose E, Frucht S and Jonas IE (2002) Clinical comparison of a multistranded wire and a direct-bonded polyethylene ribbon-reinforced resin composite used for lingual retention Quintessence International 33: 579-583 Rowland H, Hichens L, Williams A, Hills D, Killingback N, Ewings P, Clark S, Ireland AJ and Sandy JR (2007) The effectiveness of Hawley and vacuum-formed retainers: A single-center randomized controlled trial American Journal of Orthodontics and Dentofacial Orthopaedics 132: 730-737 Sadowsky C and Sakols EI (1982) Long term assessment of orthodontic relapse American Journal of Orthodontics and Dentofacial Orthopaedics 82: 456-463 Sadowsky C, Schneider BJ, Begole EA and Tahir E (1994) Long term stability after orthodontic treatment: nonextraction with prolonged retention American Journal of Orthodontics and Dentofacial Orthopaedics 106: 243-249 Sauget E, Covell DA, Boero RP, and Lieber WS (1997) Comparison of occlusal contacts with use of Hawley and clear overlay retainers Angle Orthodontist 67: 223â&#x20AC;&#x201C;230 Shah A (2003) Postretention changes in mandibular crowding: a review of the literature American Journal of Orthodontics and Dentofacial Orthopaedics 124: 298-308 Shah AA, Sandler PJ and Murray AM (2005) How to ... place a lower bonded retainer Journal of Orthodontics 32: 206-210 Sheridan JJ, Ledoux W and McMinn R (1993) Essix retainers: fabrication and supervision for permanent retention Journal of Clinical Orthodontics 27: 37-45 Sheridan JJ, Ledoux W and McMinn R (1994a) Essix appliances: minor tooth movement with divots and windows Journal of Clinical Orthodontics 28: 659-663 Sheridan JJ, Ledoux W and McMinn R (1994b) Essix technology for the fabrication of temporary anterior bridges Journal of Clinical Orthodontics 27: 482-486 Sifakakis I, Pandis N, Eliades T, Makou M, Katsaros C and Bourauel C (2011) In-vitro assessment of the forces generated by lingual fixed retainers.

American Journal of Orthodontics and Dentofacial Orthopaedics 139: 44-48 Sinclair PM and Little RM (1983) Maturation of untreated normal occlusions American Journal of Orthodontics and Dentofacial Orthopaedics 83: 114-123

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Southard TE, Behrents RG and Tolley EA (1989) The anterior component of force Part 1: Measurement and distribution American Journal of Orthodontics and Dentofacial Orthopaedics 96: 493-500 Southard TE, Behrents RG and Tolley EA (1990) The anterior component of force Part 2: Relationship with dental malalignment American Journal of Orthodontics and Dentofacial Orthopaedics 97: 41-44 Southard TE, Southard KA and Tolley EA (1992) Periodontal force: a potential cause of relapse American Journal of Orthodontics and Dentofacial Orthopaedics 101: 221-227 Stratton CS and Burkland GA (1993) The effect of maxillary retainers on the clarity of speech Journal of Clinical Orthodontics 27: 338-340 Surbeck BT, Ă&#x2026;rtun J, Hawkins NR, and Leroux (1998) Associations between initial, posttreatment, and postretention alignment of maxillary anterior teeth American Journal of Orthodontics and Dentofacial Orthopaedics 113: 186-195 Taner TU, Haydar B, Kavuklu I and Korkmaz A (2000) Short-term effects of fiberotomy on relapse of anterior crowding American Journal of Orthodontics and Dentofacial Orthopaedics 118: 617-623 Thickett E and Power S 2010 A randomized clinical trial of thermoplastic retainer wear European Journal of Orthodontics 32: 1-5 Tuverson DL (1980) Anterior interocclusal relations American Journal of Orthodontics 78: 361-393 Vaden JL, Harris EF and Zeigler Gardner RL (1997) Relapse revisited American Journal of Orthodontics and Dentofacial Orthopaedics 111 543-553 Valiathan M and Hughes E (2010) Results of a survey-based study to identify common retention practices in the United States American Journal of Orthodontics and Dentofacial Orthopaedics 137: 170-177 Walkow TM and Peck S (2002) Dental arch width in Class II Division 2 deep-bite malocclusion American Journal of Orthodontics and Dentofacial Orthopaedics 122: 608-613 Yavari J, Shrout MK, Russell CM, Haas AJ and Hamilton EH (2000) Relapse in Angle Class II Division 1 Malocclusion treated by tandem mechanics without extraction of permanent teeth: A retrospective analysis American Journal of Orthodontics and Dentofacial Orthopaedics 118: 34-42 Zachrisson BU (1997) Important aspects of long-term stability Journal of Clinical Orthodontics 31: 562-583

Useful related references not referred to in this chapter Ă&#x2026;rtun J, Krogstad O and Little RM (1990) Stability of mandibular incisors following excessive proclination: a study in adults with surgically treated mandibular prognathism Angle Orthodontist 60: 99-106 Kennedy DB, Joondeph DR, Osterberg SK and Little RM (1983) The effect of extraction and orthodontic treatment on dentoalveolar support American Journal of Orthodontics and Dentofacial Orthopaedics 84: 183-190 Lake SL, McNeill RW, Little RM and West RA (1981) Surgical mandibular advancement: a cephalometric analysis of treatment response American Journal of Orthodontics and Dentofacial Orthopaedics 80: 376-394 Little RM (1990) Stability and relapse of dental arch alignment British Journal of Orthodontics 17: 235-241

STABILITY AND RETENTION EXCELLENCE IN ORTHODONTICS 2012

Lopez-Gavito G, Wallen TR, Little RM and Joondeph DR (1985) Anterior open-bite malocclusion: a longitudinal 10-year postretention evaluation of orthodontically treated patients American Journal of Orthodontics and Dentofacial Orthopaedics 87: 175-186 McReynolds DC and Little RM (1991) Mandibular second premolar extraction - postretention evaluation of stability and relapse Angle Orthodontist 61: 133-144 Shields TE, Little RM and Chapko MK (1985) Stability and relapse of mandibular anterior alignment: a cephalometric appraisal of first premolar extraction cases treated by traditional edgewise orthodontics American Journal of Orthodontics and Dentofacial Orthopaedics 87: 27-38 Sinclair PM and Little RM (1985) Dentofacial maturation of untreated normals American Journal of Orthodontics and Dentofacial Orthopaedics 88: 146-56

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