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ď ľ

Little mandibular growth

ď ľ

Considerable growth







Definition  Rationale of growth prediction  Approaches for growth prediction  Growth studies  Classification of methods  Johnston's grid  Template method  Ricketts methods  Computerized prediction  Comparison 

Prediction of growth spurt  Auto correlation analysis  Growth prediction from 1. Antegonial notch 2. Parental data Issues related to growth prediction Current status conclusion 

DEFINITION Kendall and Buckland  “ The process of forecasting the magnitude of statistical variations, at some future point of time”  “Specifying the amount and direction of future growth in the context of a base line or reference point”

Growth prediction & VTO Growth prediction It is a visual plan to forecast the normal growth of the patient ď ľ VTO Anticipated- visualized influences of treatment . It is like a blue print used in building the house. It enables development of alternative treatment plans. ď ľ

Rationale of growth prediction ď ľ

The principal proponents of growth prediction Ricketts and Holdaway have suggested that the major value of the technique is the compilation of all the treatment factors (skeletal tissue ,soft tissue, growth and mechanics) together on paper to see how they inter-relate.

Treatment for growing patient must be directed to the face that is anticipated in the future and not to the one which exists. The plan should  Take advantage of beneficial aspects of growth.  Be able to take care of undesirable effects of continuing growth. 

ď ľ

Once the treatment begins there is a need to continuously monitor the progress. It is done against the VTO forecast. So that if any deviation is there it becomes apparent and necessary modification can be instituted in the mechanics.

To deal with relapse tendencies Even normal growth during adolescence favors relapse in the patient with Class III malocclusion.  Maxillomandibular relationship seen at the end of treatment in a growing child may not be the same at maturity.  Therefore treatment completed with proper facial balance at the age of 12 may prove unsuccessful at the age of 25.

 The

forecast is valuable for orthodontist’s self improvement .

 Source

of problemLack or excess growth. Patient’s lack of cooperation. Unusual physiologic reaction.

According to Hirschfield and Moyers the growth prediction aims for  Future size of a part  Relationship of parts  Timing of growth events  Vectors of growth  Velocity of growth  The effects of orthodontic therapy on any of the above predicted parameters

ď ľ Future

size of a part The prediction of future size, is primarily a problem of predicting future increments which are to be added to the existing size.

ď ľ Relationship

of parts Most important prediction for the clinician is the future relationship of parts, i.e. the future facial pattern. It is the summation of growth of various component of craniofacial complex . Growth prediction is important because growth alters relationships.

ď ľ Timing

of growth events Growth spurts Prediction of growth spurt involves prediction of its onset duration and rate of growth. The thing which makes it further complicated is its variable occurrence.

ď ľ Vectors

of growth Most predictive methods thus far presume a continuation of the pattern first seen. Therefore, the presumption is made that the vectors of growth present at the time of prediction will remain.

ď ľ Velocity

of growth It would be of use to know the future expected rate of growth. Prediction of velocity is most important during the growth spurt.

ď ľ The

effects of orthodontic therapy on any of the above predicted parameters The clinician must always wonder what effects his therapy have on the predicted and actual growth of one specific face. R.E.Moyers

Approaches for growth Prediction 



Hirschfield and Moyers  Theoretical  Regression  Experiential  Time


Science is predictable and reliable. If the prediction consistently gives results which match the actual growth it will become a science ď ľ so we take help from statistics and geometry. Because mathematics is predictable. ď ľ

Theoretical method ď ľ Mathematical

construction of a theoretical model

ď ľ Proving

the hypothesis practically

Regression methods ď ľ

To calculate a value for one variable, called dependent, on the basis of its initial state and the degree of its correlations with one or more independent variables.

A : B :: A’ : B’ A

= S-N length at 10  B = upper face Ht. at 10 Regression equation B= A + 2  A’ = S-N length at 14  B’ = ?

Drawbacks The assumption within the method that the equation remain constant over the whole time period. ď ľ An individual whose growth is to be predicted in clinical practice may not even be a member of the population upon which the regression equation is based. ď ľ

Experiential method ď ľ

It is based on the clinical experience of a single investigator who attempts to quantify his observations of practice in such a way that they can be used by others. E.g. Ricketts forecast

Drawbacks  Theoretical


base is shaky on two

– The assumption must be made that the individual being predicted will behave as the mean of a population of which he is a not a member – The morphology of the mandible and other parts is a clue to the future growth of the face

Time-series methods ď ľ Problem

solving through applied mathematics ď ľ Time-series is considered to be composed of four parts : 1. Trend or long-term movement 2. Oscillations about a trend 3. Cyclic or periodic events 4. Random (unsystematic) components

Bjork :  Longitudinal  Metric  Structural.


is evaluated over a specified period to determine the pattern of growth.  Annual cephalograms  Serial cephs are used to predict the growth trend & future growth

ď ľ

This concept was clinically applied by Tweed on his growing patients.

ď ľ

Facial cephalograms are taken 12 to 18 months apart to evaluate the skeletal facial changes & then the pt. is classified into one of the three categories.

TYPE A  Growth of the middle. and lower face proceeds in unison.  Changes in the vertical and horizontal dimensions being approximately equal. TYPE B  Middle Face grows downward and forward more ,rapidly than the lower face. This type of growth is predominantly in a vertical direction. TYPE C  Lower face develops at a faster rate than the middle face.

ď ľ

Tweed's basic assumption was that the growth pattern would remain constant.

ď ľ

HOWEVER the pattern and rate of growth in one period is not similar to that occurring in a subsequent period in any given individual.

Metric Approach It aims at prediction of future growth on the basis of existing facial morphology ď ľ Measuring different structures on a single x-ray film. Then relating these measurements to future growth. ď ľ

 Important

aspect - coefficient of correlation – r  It signifies the strength of relationship  r = 0.8 < for clinical use  But coefficient of correlation of facial dimension when related to future growth does not exceed 0.4 – 0.5

 Correlation

B/W face at 12 yr and residual growth - Bjork Study on Swedish boys following them over the age of 12-20yr present with a very low correlation.  Making matter more difficult is the pubertal spurt.  The ultimate growth in the length of the mandible cannot be assessed from its size before puberty

Structural method  Developed

by Bjork from Superimpositions on metallic implants.  consists of recognizing specific structural features in the mandible that indicate future growth trends.  Predicts extremes of growth patterns more accurately.

Bjork listed seven areas on cephalogram 1. The inclination of the condyle 2. The curvature of the mandibular canal 3. Inclination of the symphysis. 4. Shape of the lower border of mandible. 5. The interincisal angle 6. interpremolar or molar angles are also more acute in forward rotators. 7. The anterior lower face height.

Rossouw, Lombard, Harris 1991  Postulated that the large frontal sinus goes hand in hand with the abnormally large mandible  Correlation for mandibular lengths with the large frontal sinus size is found out to be(0.480)  Orthodontics or surgery?  No correlation with pattern.

Growth studies The numeric standards on which the present day growth predictions are based are derived from 3 major studies reports.  Bolton-Brush Growth study  Burlington Growth study  Michigan Growth study 

These studies are carried out longitudinally over hundreds of samples and the data is organized to provide the picture of normal or average changes. ď ľ Present day templates are formed by treating this information graphically. ď ľ

Bolton-Brush growth study ď ľ

ď ľ

Longitudinal study of over 4000 subjects from birth to adult hood. Started in 1929 under B.H.Brodbent at case reserve university in Ohio.

Records taken include1. Lat. Ceph. 2. P.A. Ceph 3. hand wrist x-ray 4. Dental casts 5. Nutritional medical health status  NO SUBDIVISIONS  All records are currently housed in Bolton –Brush growth study center. 

Burlington Growth study  Prospective

longitudinal study started in 1952 in Burlington Canada under R.E.Moyers of university of Toronto  1258 children participated  Records collected annually from age 3 to 18 year.

Records consisted of  Medical history  periodontal evaluation  6 cephalometric radiographs  Hand wrist x-ray  dental casts  I.O. x-rays Entire material is currently housed in Burlington growth center university of Toronto

 Burlington

data has subdivisions on the bases of sex and growth pattern  vertical  horizontal  average subjects selected had ideal occlusion

Michigan Growth study Study was done on the students of elementary & sec. school under the university of Michigan.  Published by Riolo et al. in 1974 

Data was obtained from untreated subjects with normal occlusion an admixture of cl I & cl II relationship  So it represent normative rather than ideal standards. 

classification  

 

 

 

Based on average values individualized prediction short range long range manual Computerized Templates Geometric construction

Golden proportions - Prediction of ideal

Johnston’s forecast grid  Developed

by L.E. Johnston in 1975  Based on the addition of mean increments of growth by direct superimposition on a printed grid  The validity of this grid was tested in a series of 5 years forecast on 32 individuals.(7.5 – 12.5 yr)

The land marks used are :  S–N plane as a reference plane  Point A  Point B  Point M  Posterior Nasal Spine  Tip of nose

ď ľ

Vectors for A, B and M are inbuilt into the grid and are derived from the templates prepared by Harries and associates and the behavior of N and P was patterned after reports by Ricketts

Starting age , Years of prediction , Sex

Tracing of landmarks is superimposed along S-N and registered at S

The points are then advanced downward and forward one unit per year

Soft tissue is traced by shifting the grid back 0.3 mm/year


Shortcomings a

moderate flattening of the profile and occlusal plane,  a slight mesial drift of M.  Apart from the points A and B other landmarks have little application

ď ľ age

or sex non specific. ď ľ facial pattern - all patients will grow the same amount and direction.

Template Method Template is the graphic equivalent of tables of means and deviations in various age groups ď ľ It provides visual representation of growth patterns and permits visual comparison with normals ď ľ

Baum – 1952 First to develop cephalometric templates based on down’s analysis he developed a set of 4 transparencies to be laid directly on the cephalogram

The serial cephalometric radiographs obtained during the Burlington, Michigan and Bolton growth studies have been treated statistically to allow their use in growth prediction.

 There

are 2 types of templates :

– Schematic template – Anatomically complete template

Schematic template The schematic templates show the changing position of selected landmarks with age on a single template ď ľ The "track'' produced by each landmark was averaged over many individuals to produce a normative ''picture" of growth in a given population. ď ľ

Burlington templates  Popovich

and Thompson propose method of growth prediction based on Burlington templates.  It uses the tracings at the ages of 4,6,8,10,12,14,17,20  Registered on S-N LINE  reference plane used is cranio -occlusal line drawn 22* to S-N line

ď ľ

Description of movements of points throughout growth is integrally related to the particular frame of reference from which movement is observed.

 Static

aspect – demonstrate degree of balance or imbalance and its location  Dynamic aspect – projects degree of change anticipated without treatment

6 sets of templates are available  Vertical grower male-female  Avg. grower male female  Horizontal grower




the lateral templates are used to determine the growth pattern to which individual compares most closely. Appropriate template is selected considering the age and anterior cranial base length Superimposing the template and individual cephalogram, future magnitude and direction of growth is estimated.

Anatomically complete template  Based

on Bolton growth study data.  Age-specific  A reference template is selected so that the lengths of anterior cranial base are same  The growth is predicted by advancing the template ages from the reference templates

Anatomic templates

Ricketts Growth Prediction  Growth

Estimation from facial pattern- 1957  Cephalometric Synthesis-1961  Short-range VTO  Long-range VTO - 1972

Growth Estimation from facial pattern - 1957 ď ľ

ď ľ

Ricketts suggested that facial form was to a large degree determined by the position of the chin. Chin position determines the form of face.

ď ľ Chin

position was mainly influenced by 3 factors 1. Changes in the cranial base 2. Condylar position 3. Condylar growth in amount and direction upward + forward - brachycephalic upward + backwardâ&#x20AC;&#x201C; dolicocephalic

Determinants of chin position 

Cranial base flexion

Condylar positioning forward/backward 

Condylar growthAmount/direction 

Summation of total changes

CEPHALOMETRIC ANALYSIS AND SYNTHESIS Analysis  Characterize the condition  Compare the condition with norms  Classify  Communicate

Synthesis Use in treatment planning ď ľ Static

synthesis- non growing

ď ľ Dynamic

synthesis- growing

Static synthesis Estimation is done about movement of the teeth and changes in lips.  The lower incisor is positioned normal to the APo  The upper incisor is then adjusted to it with normal overbite and overjet  The necessary anchorage can be envisioned by movement of the posterior teeth 

 The

Dynamic Synthesis

– Growth of the chin - foremost consideration – Cranial areas are employed for basal references

 

Step 1- cranial behavior –insignificant step 2 -Chin behavior

 Estimate

based on direction and magnitude of growth of Y-axis  Class II case -Y axis open about one degree during a two year period  class III case -Y axis closed one degree  2.5 – 3.0 mm / Yr – linear growth

Step 3 - Maxilla behavior Point A and the anterior nasal spine usually drop vertically about one- third the total facial height increase during treatment. point A is modified by  extraoral traction  intermaxillary elastics when accompanied by torquing action to the upper incisor teeth. 

Teeth setup

22* to mandibular plane 1 mm ahead of A-Pog


GROWTH PRINCIPLE A normal human mandible grows by vertical apposition at the ramus on a curve or arc, which is a segment of a circle. The radius of this circle is determined by using the distance from mental protuberance (Pm) to point Eva.

ď ľ Ricketts,1972

it has been proved by the studies that some form of bending of mandible occurs during growth which is orderly and in a form of an arc of a circle. This principle can be used as a working hypothesis for growth projection of a mandible .

New planes and points of reference  Condylar axis  Corpus axis  Pt Pm  Pt Xi  Pt Eva  Pt Mu  Pt TR

Pt Xi

ď ľ Pt

Xi represents the center of ramus

Pt PM & Pt Dc

ď ľ

PM is a stress center & located in dense cortical bone

Condylar axis and Corpus axis

ď ľ

Attempt to overcome surface variation and to determine central or internal structural

 The

cortical “core” of the mandible, is recognized using Pm, Xi and Dc points.  since all these points and planes are drawn for particular pt., the prediction is individualized.

After this experiments were undertaken to determine a method by which the form and size of the mandible, after a five-year growth interval, could be predicted with use of only the first x-ray as a reference. ď ľ The size increases and form alterations were available from the computer ď ľ

Not enough bending

Excessive bending

ď ľ It

was thought that perhaps the stress lines of the mandible would reveal its hidden secrets.

ď ľA

mandible, alleged to be 850 years old, which had been given to Ricketts by the late William B. Down. ď ľ Mandible clearly showed the pattern of stress lines

convergence of stress lines at the  protuberance menti  Base of coronoid process on lateral side  Y-shaped bony prominence on medial side – Pt Eva

Pt Eva Pt Eva almost exactly coincides with the forking of the stress lines on the internal and outer table of the ramus. ď ľ nutritive foramina Growth center ? ď ľ

ď ľ

When the size increase of the mandible as determined in the computer study was incrementally added to the arc at the sigmoid notch, it was found that the predicted mandible was almost absolutely correct in size and form when compared with the final composite.

‘K’ factors


be used over the period of not more than 2-3 year.  Prediction of chin by constructing the chin acc. To patients own mandibular line..  it uses patients existing growth pattern And provides the ‘safety factor’.

Basic planes and points

SEQUENCE  Cranial base prediction  Mandibular growth prediction  Maxillary prediction  Occlusal plane prediction  Dentition  Soft tissue

Cranial base prediction ď ľ Cranial

base flexion is ignored ď ľ length increments- 1 mm / yr Take a clue from Spheno-occipetal synchondrosis

Cranial base prediction

 Nasion

& Basion – 1 mm/yr

Mandibular growth prediction Rotation & lengthening  Rotation – Direction of effective growth is determined The mandibular plane is influenced accordingly  Lengtheningcondyle-1 mm/yr body -2 mm/yr

Mandibular growth prediction


ď ľ Rotated

about Ba

Condylar axis and corpus axis

Condylar axis – 1 mm/yr  Corpus axis – 2 mm/yr 

Symphysis construction

Maxillary prediction 1/3 rd of total facial ht increase is due to upper face Ht increase ď ľ Pt A is influenced by tooth movement treatment mechanics is given consideration while relocating it ď ľ

Maxillary prediction

ď ľ Mark

1 with Me

Point A changes 1 3


Occlusal plane

ď ľ

Half of lower facial Ht. increase is attributed to either dentition and new occlusal plane is constructed

Lower incisor

ď ľ 22*

to mandibular plane ď ľ +1 mm to A-Pog

Mandibular molar



Lips , chin

Completed final prediction

Computer prediction Computer is essentially a tool of analysis and not a method of analysis. ď ľ Computers are programmed to use equations based on manual methods ď ľ computer technology facilitates testing and applying more complex formulas to growth prediction. ď ľ

In 1970s Ricketts introduced his method of computer analysis based on his vast clinical experience. ď ľ Initially the computer forecast was based on the pattern extension method proposed by Ricketts. ď ľ

Rocky Mountain Data System Rocky mountain Data systems (RMDS) ď ľ In conjunction with the early investigations of Ricketts, Rocky mountain co. designed a computerized cephalometric analysis, to quantify craniofacial characteristics in more detail. ď ľ The computer growth forecast method is essentially similar to the Ricketts method with some modifications.

Modifications Individual growth curves are used for the mandible, maxilla, and soft tissue rather than using the same increments for every age group ď ľ Abnormal growth predicted with RMDS data bank ď ľ

Growth curves Individual growth curves are based on national/ethnic groups (e.g.: Growth curves for German children, Japanese Children).  They show relative amounts of normal cranial growth at various ages for particular race. 3 types  Upper face  Lower face  Soft tissue 

Growth curves

ď ľ

The RMDS computer performs growth predictions by combining these growth curves with average linier and directional change for approximately 200 cephalometric landmarks

Computerized ceph. analysis

Modules. ď ľ A module is defined as the average amount of growth observed for the average American Caucasian patient in a unit time ď ľ For each cephalometric landmark the amount of change in position per module of growth, and the direction of change per module are known.


ď ľ

The computer will determine the amount of modules which elapsed during the period being forecasted.

ď ľ

The change for each point - direction - amount per module is known. it is multiplied by the number of modules. The result is a computer growth forecast without treatment.

Abnormal class III patterns

ď ľ

Consistent type emerged which grew excessively in mandible and less in cranial base than predicted.

Study reveled that patients differs from normals in –  Abnormally forward location of porion.  Forward position of ramus.  Downward deflection of cranial base.  Class III molars. .

Predictor measurements

ď ľ Proportionately

increased growth in mandible than the cranial base.

These predictor measurements are used to get insight as to which PT. would require early ortho treatment , conventional one ,or surgical correction after the growth is complete. ď ľ Subjects with mandibular prognathism who can be properly treated by orthodontic tooth movement alone can be distinguished from subjects with mandibular prognathism that requires orthognathic surgery. ď ľ

Four methods of growth forecasting were compared by Schulof & Bagha 1975 – Johnston forecast grid – Ave. increments from sella-nasion – Ricketts short-range prediction – Computer forecast (coupling of Ricketts short –long range prediction)

Results JOHNSTON GRID  Least accurate  64 % accurate for Point A  70 % accurate on Pogonion  It was accurate as any for predicting the nose The basic objection to this method is that it applies growth rates of one age group to another

AVERAGE INCREMENTS ď ľ Improvement over the Johnston grid at both Pogonion and point A

RICKETTS SHORT-RANGE PREDICTION METHOD  Less error than Johnston grid or average increments  Some of the smaller over-all error was due to the fact that point CC, the origin of this growth prediction, is closer to Pogonion than to Sella  10 to 20 percent improvement over average increments

RMDS COMPUTER PROGRAM  Most accurate of the four methods  21% more accurate than Ricketts  56% more accurate than Johnston grid

Its main strength lies in recognizing and predicting the growth of unusual face patterns . Which are the main problem areas of treatment. ď ľ In this area the computer prediction accuracy improved to 90 % ď ľ

Growth is not only Statistics ,it’s a biological process. Growth prediction should not over look important biological phenomena occurring during growth because we are treating a child not a cephalometric tracing.  One such much talked about, biological phenomenon is growth spurt. 

Prediction of growth spurt How Often Does It Occur? ď ľ Bjork's 1963 study Out of the 45 boys evaluated only 11 individuals (less than 25%) had what Can be described as a discernible pubertal growth accentuation.

What is the Magnitude' of the Spurt?

Bjork's findings 1.



There was a significant acceleration in condylar growth in less than 25% of the samples. The magnitude, duration and timing of the spurt varied widely even in this selected sub-sample of 11 subjects. There was no relationship between the intensity of the growth and its direction.


Standing height Autocorrelation analysis (Bishara)  Analysis compares growth profile of various facial parameters to that of standing height b/w 8 – 15 yrs of age  Correlation is below 0.5  Mandibular length in girls had a clinically significant correlation with the timing of changes in standing height (r = 0.83 )

The findings Growth profile of height was significantly different from that of mandibular length and relationship ď ľ Autocorrelation analysis have little predictive value in determining the growth profile of any of the mandibular parameters - except for Ar-Pog for females. ď ľ

Clinical implications Timings and magnitude of facial changes and mandibular length in particular cannot be predicted from standing Ht. or skeletal maturation. ď ľ However significant mandibular changes in size and relationship take place during adolescence. ď ľ Starting treatment of A-P discrepancies without waiting for pubertal spurt ď ľ

Antegonial notch - an indication of mandibular growth potential: Prominent mandibular antegonial notch is a commonly reported finding in subjects with arrested growth of the mandibular condyles. ď ľ Singer and Hunter 1987, The craniofacial characteristics of individuals with deep mandibular antegonial notch, compared with those of shallow notch by the use of longitudinal lateral cephalometric radiographs. ď ľ

They concluded that,  Deep notch subjects had a more retrusive mandible with  Shorter corpus,  Less ramus height  Greater gonial angle than did shallow notch subjects.

The results suggests that ď ľ deep mandibular antegonial notch is indicative of a diminished mandibular growth potential and a vertically directed mandibular growth pattern.

The growth of the mandibular condyle fails to contribute to the lowering of the mandible, ď ľ masseter and medial pterygoid, continue to grow and cause the bone in the region of the angle to grow downward ď ľ A relative tension is generated between the angle and the muscle sling such that bone deposition occurs in the area under the angle posterior to the notch. ď ľ

PARENTAL DATA TO PREDICT THE GROWTH SUZUKI ET AL 1991  There is a similarity between the facial form and features of an offspring and that of his parents.  If the face of a young offspring resembles the face of either parent, it usually continues to resemble that parent.  The phenotype of facial appearance does not change with growth.

ď ľ

Coefficients of correlation of craniofacial forms ranged b/w 0.5-0.9 and they increased from childhood to adulthood.

ď ľ

Suzuki et al. by studying 1700 cephalogram deduced, correlation coefficients to develop prediction models (in the form of a mathematical equation) to predict the individual growth of children, based on data relating to their parents.

Current status of growth prediction Current data on which norms used in growth prediction are based is sample specific. More the individual resembles this sample group, more accurate is the prediction. Ideally separate growth standards should be established for sexes, racial groups, facial patterns ect. But available data sets are too small to allow this kind of division. ď ľ

All 3 major studies BOLTON, BURLINGTON, MICHIGAN are carried out on whites of north European descent. growth prediction is based on avg. changes, but pt. may not have avg. amount or direction of growth. so our ability to predict facial growth is poorest for the very patients who need it most.

In country like India. With various ethnic origins, multi racial, multicultural population growth prediction simply does not work. Because that much ‘Purity’ of the population does not exist.  Growth prediction based on mean values projects mean forecast which will be applicable for most in a population but it may not be the case with your own patient. 

Clinical decision making In severe skeletal discrepancies prediction is not much of a challenge. One can assume that the existing growth pattern prevails. And orthopedic correction should be included in the treatment plan. Average skeletal discrepancy For the majority of cases, future growth is less predictable. â&#x20AC;&#x153; worst case scenario â&#x20AC;&#x153;

CONCLUSION The overall changes in the size and relationship of the human face in 20 year period From childhood to adulthood are, In general difficult to accurately predict for an individual. This is because the changes are under the influence of the combined and complex effects of the hard to predict, genomic, and environmental factors. ď ľ The situation is rendered even more complex because we are using a two dimensional image to predict a three dimensional multifunctional object. ď ľ


ď ľ

Because of the uncertainties involved in predicting growth ,orthodontic treatment becomes a game of strategy against nature. However The Goal of growth prediction is to reduce the clinicians ignorance of the future. The best can be done ,is to base the treatment planning in the existing facial pattern allowing for average growth changes for the group to which patient belongs. With the knowledge and better understanding of growth prediction, we can be skilled and better equipped to intervene during growth process. Leader in continuing dental education

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