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INVISALIGN INDIAN DENTAL ACADEMY Leader in continuing dental education

Contents Introduction Kesling’s Setup Essix Retainers - Introduction - Current Retainer Designs - Fabrication - Appliance Delivery - Telephone Supervision - Conclusion Active Tooth Movement With Essix Based Appliance

Invisalign - In a Nutshell - Mechanism of Action - In Detail - Retention and Stability - Advantages - Disadvantages - Summary

INTRODUCTION Movement of teeth without the use of bands, brackets, or wires was described as early as 1945 by Dr Kesling, who reported on the use of a flexible tooth positioning appliance. Later, Nahoum (Vacuum formed dental contour appliance, 1964) and others (Pontiz, 1971; McNamara, 1985) wrote about various types of overlay appliances such as invisible retainers.

Minor tooth movements have also been achieved with a technique developed by Raintree Essix (New Orleans, La). This technique uses clear aligners formed on plaster models of the teeth. The aligners are then modified with “divots,” which create a force to push on the individual teeth, and “windows,” which create the space for teeth to move into. This type of appliance can be effective in correcting mild discrepancies in the alignment of teeth. However, movements are limited to 2 to 3 mm; beyond this range, another impression and a new appliance are needed.

Align Technology, Inc (Santa Clara, Calif), introduced the Invisalign system several years ago. Invisalign takes the principles of Kesling, Nahoum, others, and Raintree Essix even further, using computer-aided-design– computer-aided-manufacture (CAD-CAM) technology combined with laboratory techniques to fabricate a series of custom appliances that are esthetic and removable, and that can move teeth from beginning to end.

Keslings setup The diagnostic setup was first proposed by Kesling in 1945. P.R. Begg does not use tooth positioners, because they are not readily available in Australia. However, Kesling uses a tooth positioner as a finishing appliance on each case. Not only are the tooth positioners the best post treatment retention appliance, but they are the best form of working retainer.

It is possible to obtain more accurate final tooth positions generally and more accurate final occlusal relations with tooth positioners than with any other orthodontic appliance now employed. At the present time, it is impossible to position teeth with arch wires and tooth bands with such final accuracies as can be done with post treatment use of tooth positioners regardless of the particular active orthodontic treatment technique that is used. The tooth positioners, as being described by Kesling in 1945, is a one piece, resilient appliance made from rubber or plastic that fills the free-way space and covers the clinical crowns of the teeth plus the portion of the gingival, both buccal and lingual.

No other appliance has the flexibility to conform to the discrepancy, and yet has the ability to carry the teeth to their desired relations- all with no adjustments required. The skills required of the orthodontist in positioner therapy are those of diagnosis and judgment of the patients willingness or ability to cooperate, not of manual dexterity. The positioner is constructed over a per-determined pattern- the set-up. Teeth that are to be positioned in the patients mouth are removed from the patients model and replaced in the desired positions. The gum area of the set-up is then contoured to normal form after changing the teeth.

The positioner is then formed of an elastic material about the arches in rest position. This results in the upper and lower teeth slightly separated, and the lower arch slightly distal to the upper. Space closure within reason can be accomplished with a tooth positioner, especially spaces manifest during treatment, as in anterior segments. Within limitations the positioners can be used to help maintain or change the amount of anterior overbite.

Labiolingual axial inclination of upper and lower anteriors can be influenced by a positioner, however, these teeth should be uprighted over basal bone as well as possible with appliances. One must be realistic for the correction to be achieved The positioner can achieve the perfection possible in the set up only when that perfection has been approached in the mouth with conventional treatment.


POSITIONER AS A FINISHING APPLIANCEÂ Patients were treated until the correct tooth relations were achieved. Tooth positioner has the ability to quickly achieve the final detailed finishing that is often required. When the positioner is to be used there is no need to place finishing arches or to consider a stage 4. After the teeth have been brought to their approximate final positions with the proper axial inclinations, the positioner will close all spaces, correct slight errors in arch form and develop ideal occlusion as predetermined by the set up.

The control model made at the time of the appliance were removed, was duplicated and the teeth were cut from the model and repositioned in the set up. In the set up all the spaces have been closed, arch form has been corrected and the normal amount of anterior over bite has been created along with text book normal occlusion in the posterior segment. Tooth positioner was fabricated over the setup. The patient then exercised into the positioner four hours a day and wore it while sleeping. Results desired by the set up were achieved in two weeks. At that time the exercise wearing was reduced to three hours a day. After four months, the patient just wore the positioner at night as a retainer.

PROCEDURE The cast is cut using a fretsaw blade to separate individual teeth. A horizontal cut is made three mm apical to gingival margin. Vertical cuts are made to separate individual teeth and the individual teeth are set in desire position using red wax.

USES 1. In visualizing and testing the effect of

complex tooth movements and extractions on the occlusion. 2. The patient can be motivated by simulating the various corrective positions on the cast. 3. Tooth size – arch length discrepancies can be visualized by means of a setup.

Essix Retainers (1993) INTRODUCTION Orthodontists' concept of retention is moving toward the idea that teeth will move unless retained indefinitely. However, permanent retention implies permanent supervision, and that is where reality clashes with stability. An orthodontic practice basically consists of treatment of active cases, which consume the most time and generate the most income, and supervision of retention cases, which takes less time and produces minimal, if any, income. This balance has been workable because, in due course, retention patients either are dismissed with wishes of good luck or simply fade away.

When permanent retention is emphasized, the equilibrium is upset. As an example, if 200 patients per year are given permanent retainers and seen twice a year, after 10 years this will add up to 4,000 retention appointments per year. At 10 minutes per visit, that would take up about three months' worth of appointments. The cornerstone of Essix permanent retention is the complete delegation of responsibility to the patient.

Patient before and after placement of Essix retainers

Essix retainers have nothing to adjust; the only thing that could be done on a recall visit would be to check the patient's compliance and listen to any comments. Telephone supervision is a time-andmoney-saving service to our patients and is sincerely appreciated.

Current Retainer Designs Fixed retainers must be systematically monitored, not only for displacement, but for hygiene problems that can be induced by the accumulation of plaque and calculus. Although well-aligned teeth should be easier to clean, the presence of a bonded retainer makes cleaning more difficult. Removable appliances don't interfere with hygiene, but are at best only adequate retention mechanisms.

The Hawley-type retainer, which dates from the 1920s, was originally used to move teeth, not for retention. The retaining component for the anterior teeth— a point contact of wire on the labial surface and a mass of acrylic approximating the lingual cervix— is insufficient. When the appliance becomes loose, the mechanical constraints are lessened and the teeth can shift. In addition, most of the acrylic simply anchors wire elements that are not critical to the essence of retention— the stabilization of the teeth.

Clear, full-arch, vacuum-formed plastic devices are only marginally esthetic, are removable, and are difficult to work with. As in Hawley-type retainers, the bulk of the appliance is distal to the cuspids, covering and retaining posterior teeth. These buccal sections tend to fracture, make the appliance bulky, and are usually the cause of complaints of awkwardness of bite. The limitations of conventional mechanisms, which may be adequate for limited retention, explain some of the dismal results that have been achieved with permanent retention. These devices are too bulky or unhygienic for the long term, and sooner or later the patient's enthusiasm wanes.

• • • • • •

Essix thermoplastic copolyester retainers change the rules of permanent retention. They are a thinner, but stronger, cuspid-to-cuspid version of the full-arch, vacuum-formed devices. Advantages include: The ability to supervise without office visits. Absolute stability of the anterior teeth. Durability and ease of cleaning. Low cost and ease of fabrication. Minimal bulk and thickness (.015"). The brilliant appearance of the teeth caused by light reflection. If compliance with permanent retention is to be achieved, the orthodontist must provide duplicate retainers. Essix retainers can be produced in the office for only a few dollars each, and the cost to the patient, with a replacement retainer included, is about one-third that of a conventional


Since only the anterior teeth are retained, a universal perforated plastic tray works well for both arches. Vinyl polysiloxane is the impression material of choice. A combination of the light and heavy (putty) types is preferred.

Heavy and light vinyl polysiloxane impression materials in Universal perforated plastic tray. Impression has been cut distal to cuspids with scalpel.

Pour the impression with a high-quality die stone that has been mixed in a vacuum spatulator. If the undercuts gingival to the contact points are extreme, creating three-cornered spaces, they must be reduced to a more normal contour. It is imperative that adequate undercuts remain to insure a positive fit of the appliance. Apply a coating of a separating medium before thermoforming.

A pressure-type thermoforming unit such as a Biostar is superior to a suction device in recording the critical interproximal undercuts. Essix 0.75mm (0.030") thermoplastic copolyester is mandatory for the fabrication of Essix retainers. Thinner, 0.5mm material is too flimsy, while thicker, 1 mm material lacks flexibility. Copolyester, unlike polycarbonates, does not require heat treatment before thermoforming. It is much stronger, clearer, and resistant to abrasion than acrylic sheet, and thus produces thinner yet sturdier appliances. During the thermoforming, the thickness of the plastic is reduced from .030" to .015".

Store the cast in the patient's model box in case it is needed for future construction of duplicate retainers. Cut the retainer from the plastic sheet and trim the edges to the proper form with a curved pair of Mayo scissors. Essix retainer cut away from plastic sheet and trimmed with curved Mayo scissors

Pay particular attention to these details: • Do not scallop the labial flange of the retainer to conform to the cervical line. Extend it 2-3mm into the labial gingiva, and trim it to make a gentle, continuous curve.

Labial contour of upper and lower Essix retainers

• Trim the lower lingual flange similarly. Trim the upper lingual flange in a straight line across the palate, from cuspid to cuspid. If chairside adjustment is necessary, trim with a scissor, ligature cutter, or scalpel.

Palatal contour of upper Essix retainer

• Cut a small space at each cuspid between the gingival margin and the distogingival edge of the appliance, allowing the patient to remove the appliance with a fingernail along the long axis of the incisors.

Space cut at distogingival margin of cuspid to allow removal of retainer with fingernail

Appliance Delivery Essix retainers can be placed the same day fixed appliances are removed. The vinyl polysiloxane impression is taken immediately after debonding. Minor incisor rotations can be corrected by altering the cast, since the teeth will be slightly mobile. In no case, however, should more than two days elapse between appliance removal and retainer delivery.

Furthermore, if the patient does not brux, the retainers should last for years. With heavy bruxing, retainers need to be replaced once or twice a year, but that is still an attractive alternative to irreversible dental attrition. A single-arch Essix retainer should be worn 24 hours a day (except for cleaning) for two weeks, and then at night only.

If both upper and lower retainers are placed, the patient should wear the lower during the day and the upper at night for four weeks, then both at night only. The material is so thin that accommodation to speaking and eating is not a problem. The retainers should be cleaned with a soapy cottontip swab; brushing with toothpaste dulls their brilliance. If the patient chews gum, a brand that does not stick to dental appliances should be recommended. For caries control, we prescribe a fluoride rinse every night and a fluoride gel once a week. The retainers make excellent delivery trays.

Attractive, soft retainer cases can be used instead of the hard, bulky plastic types, since Essix retainers are nearly impervious to fracture or distortion. Soft cases do not interfere with the line of jeans or business clothes, and the clinician's address and phone number can be printed on the cases to aid in recovery if they are lost.

A. Soft cloth Essix retainer case usually preferred by adults. B. More colorful case preferred by adolescents.

Telephone Supervision Patients are routinely contacted by phone to confirm appointments; retention monitoring is merely an extension of this procedure. The task can be delegated to a staff member with a personable telephone manner. Calls should be made when it is most convenient for the patient— home or work, daytime or evening. Calls can be scheduled 30 days after delivery of retainers, and every four to six months thereafter.

Conclusion Essix retainers have proven quite versatile. Their flexibility and positioner effect make them an alternative to spring retainers in correcting minor tooth movements. They can be used to reduce occlusal forces Essix retainer placed on upper arch from the opposing arch to reduce occlusal forces against lower arch during air-rotor when moving posterior stripping mechanics. teeth with air-rotor stripping mechanics.

They can serve as a temporary bridge for a missing anterior tooth, when thermoformed over a pontic placed in the edentulous space on the cast. They can also act as night guards for bruxism and as bite planes-to relieve bracket impingement until the bite can be opened.

The use of Essix retainers, in combination with telephone monitoring, opens the way to a practical, patientfriendly method of true permanent retention.

ACTIVE TOOTH MOVEMENT WITH ESSIX BASED APPLIANCE Sheridan has described two methods for moving teeth. One, by the use of windows and divots whereby minor tooth malalignments, such as bucco-lingual and mesio-distal malpositions and rotations. (JCO 1994) Secondly, with the help of thermosealing. (JCO 1995)

Trimmed working cast for thermoforming Essix retainer.

Cutting window in thermoformed appliance with acrylic bur Finishing window border with scalpel

The Divoter: precision thermoforming tool

Heating shaft of Divoter

Monitoring inside of appliance for divot depth

Removing residual plastic debris from heating shaft prior to use

A. Incisal placement of divot produces more tipping. B. Gingival placement produces more bodily movement

A. Distal placement of divot produces mesial rotation. B. Mesial placement produces distal rotation.

Mesial contact point of lateral incisor locked within Essix appliance while divot induces facial rotation of out-of-line distal surface.

Divot-induced moments create torquing couple

Incisal cap produces pure root torque

Case 1. A. Incisor alignment before treatment. B. After four months of wearing Essix appliance with successive 1mm divots.

Case 2. A. Incisor alignment after debonding. B. After two weeks of Essix appliance with 1mm divot to align lower right lateral incisor.

By thermosealing we can selectively increase the thickness of the appliance either anteriorly or posteriorly by incorporating layer of composite or light cure acrylic between two sheet of the Essix plastic. By thermosealing we can use Essix appliance as a bite plane, habit breaking appliance, molar uprighting appliance or space maintainer.

A. Essix plastic sheets with light-cured acrylic between them. B. Plastic sheets thermosealed to encapsulate acrylic layer

Full-arch working cast made to Essix standards

Base sheet with center section and peripheral excess cut away

Prying distal ends of base appliance with thin-bladed instrument to remove it from cast

Anterior section of base appliance cut away, and remainder of appliance replaced on cast

Bead of light-cured acrylic applied to palatal area of base appliance

Heat Gun used to prepare base appliance for second thermosealing

Base and second plastic sheets thermosealed with light-cured acrylic between them

Bulk of plastic cut away with acrylic disk

Finished "full Essix" appliance after trimming

Barrier wire tacked to base appliance

Light-cured acrylic placed in palatal area and covering base of wire barrier

Finished habit appliance after trimming

Active element of uprighting spring tacked to cast with composite. Retentive element of spring placed on base appliance

Palatal acrylic covering retentive element of uprighting spring

Finished molar uprighting appliance after trimming

Thermosealed rigid plastic bar between two abutment teeth

Finished space maintainer after trimming

Finished bite plane after trimming

Drs. Rinchuse and Rinchuse successfully used Essix based appliance to carry out active tooth movements for correcting single tooth anterior cross bite and lingually displaced canine (using finger springs), and aligning ectopically positioned canine (using bonded bracket, metal attachments to the appliance and various elastics) and for expansion of maxilla (using a hybrid Essix-nickel titanium removable palatal expander).

INVISALIGN IN A NUTSHELL Align Technology, Inc. developed Invisalign appliance for orthodontic tooth movement in the USA in 1998. This appliance was the first orthodontic treatment method to be based solely on 3-D digital technology. Through the use of computer programmes that can manipulate 3-D images of individual malocclusions, a series of algorithmic stages is produced which can move the teeth in a series of precise movements (0.15 – 0.25 mm), or stages.

Invisalign braces are a new revolutionary way to straighten teeth without metal. A series of clear, removable aligners are used to gradually straighten teeth, without metal or wires. Aligners are made of clear, strong medical grade plastic that is virtually invisible when worn. Aligners look similar to clear tooth-whitening trays, but are custom-made for a better fit to move teeth. Some dentists have referred to Invisalign braces as "contact lenses for teeth."

MECHANISM OF ACTION Like brackets and archwires, Invisalign braces move teeth through the appropriate placement of controlled force on the teeth. The principal difference is that Invisalign braces not only control forces, but also control the timing of the force application. At each stage, only certain teeth are allowed to move, and these movements are determined by the orthodontic treatment plan for that particular stage. This results in an efficient force delivery system.

HOW DOES INVISALIGN WORK? You wear each set of aligners for about 2 weeks, removing them only to eat, drink, brush, and floss. As you replace each aligner with the next in the series, your teeth will move – little by little, week by week – until they have straightened to the final position your dentist has prescribed. You’ll visit your dentist about once every 6 weeks to ensure that your treatment is progressing as planned. Total treatment time averages 9-15 months and the average number of aligners worn during treatment is between 18 and 30, but both will vary from case to case.

INVISALIGN IN DETAIL For each patient, the orthodontist submits a set of polyvinyl siloxane impressions, a centric occlusion bite registration, a panoramic radiograph, a lateral cephalometric radiograph, and photographs to Align Technology.

Vinyl polysiloxane, - considered the most accurate of impression materials, - has excellent elastic recovery, - minimal permanent deformation, and - superior tear strength. Impressions can be stored for as long as a week without significant loss of accuracy and can be disinfected and repoured multiple times. The material is available in several viscosities that bond to one another, allowing flexibility in impression technique.

The impressions are poured up in dental plaster and then placed in a tray and encased with epoxy and urethane. The tray is placed into a destructive scanner; the scanner’s rotating blade makes numerous passes over the epoxy-encased models, removing a thin layer with each pass.


A computer linked with the scanner then assembles the scanned information to create a 3dimensional rendering of the models.

After the bite has been established, the Invisalign virtual orthodontic technician (VOT) uses software to “cut� the virtual models and separate the teeth, allowing them to be moved individually. A virtual gingiva is placed along the gingival line of the clinical crown to serve as the margin for the manufacturing of the aligners.

Cutters separate teeth

Placement of virtual gingiva

The orthodontist’s prescription is followed in positioning the teeth and the bite to proper alignment virtually on the computer with the company’s Treat software (Align Technology, Santa Clara, Calif). Once the final setup has been done, tooth movements are staged so that there are no occlusal and interproximal interferences, and the velocity of the movements is within the criteria set by the company. The number of stages necessary depends on the amount and complexity of the movement. The VOT can now send the data to the referring orthodontist so that he or she can check the proposed treatment (referred to as ClinCheck) the Invisalign Web site.

When the orthodontist has approved the treatment plan, the aligners will be manufactured so that the movements seen on the computer screen can be transferred clinically to the patient. The computer images are converted to physical models by using a process called stereolithography. These models are then used to fabricate the aligners on a Biostar pressure molding machine (Great Lakes Orthodontic Products, Tonawanda, NY).

Stereolithography machines

Stereolithography models


Align Technology engineers have formulated a proprietary material for use in the aligners. The aligners are trimmed and laser-etched with the patient’s initials, case number, aligner number, and arch (upper or lower). They are then disinfected, packaged, and shipped to the doctor’s office. The entire process of making the Invisalign aligners is a marvel of modern technology. Without the aid of computers and technologically advanced machinery, it would be impossible to fabricate aligners in such large numbers and with such great accuracy.

Fabricating these aligners in an orthodontic office would be a very time-consuming and labor-intensive process that probably would not be practical for everyday treatment. The Invisalign technique gives patients an esthetic choice in their orthodontic treatment that all orthodontists can easily implement in their offices.

RETENTION & STABILITY At present, retention protocol with this appliance is similar to that used with other types of appliances. Usually the final appliance or a thicker version (0.04 inch) of it is worn full time for six months, followed by night time wear indefinitely.

ADVANTAGES 1. You can straighten your teeth without

anyone knowing. 2. An Invisalign patient can eat and drink anything while being treated along with being able to brush and floss normally to maintain good oral hygiene. This is not possible while wearing traditional braces. 3. Another advantage is that the teeth can be bleached with the appliance at the beginning of, and during treatment.

4. Invisalign braces are comfortable. There are no metal brackets or wires to cause mouth irritation. 5. No metal or wires also means you spend less time in the doctor's chair getting adjustments and in some cases a patient only needs to see the dentist half as often as with traditional braces.

DISADVANTAGES 1. Only relatively small magnitudes of change are

possible because of the technical difficulty of evenly dividing larger overall movements into small precise stages manually. 2. Most people experience temporary, minor discomfort for a few days at the beginning of each new stage of treatment. This is normal and is typically described as a feeling of pressure. It is a sign that the Invisalign braces are working sequentially moving your teeth to their final destination. This discomfort typically goes away a couple of days after you insert the new Aligner in the series.

3. Like all orthodontic treatments, Invisalign braces may temporarily affect the speech of some people, and you may have a slight lisp for a day or two. However, as your tongue gets used to having Aligners in your mouth, any lisp or minor speech impediment caused by the Aligners should disappear. 4. Open bite.

SUMMARY A new system of orthodontic tooth movement using established methods for minor correction to achieve greater magnitudes of correction has been introduced. The major advantage of the system is the esthetic, hygiene, low discomfort and removable nature of the appliance.

The current limitations are in terms of case selection, increased cost, experience required for computer treatment planning, difficulty obtaining certain tooth movements, and the lack of potential in teeth involving mixed dentition or impacted teeth. The clinician must have an in-depth understanding of biomechanics, biology, periodontal concerns, and optimal therapeutic occlusion achieved during orthodontic treatment to successfully plan and use this appliance.

In future, we may see the replacement of PVS impressions with emerging intraoral scanning devices and the recording of treatment changes or modifications immediately in a digital format. Adding the other 3 D compartments (skeletal, facial, jaw movement and animation to the surface map of the teeth) will greatly enhance the diagnostic and treatment capabilities of this new appliance.

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