This study evaluated the use of mandibular antegonial notch depth as a predictor of facial growth. Serial cephalograms of 40 subjects (20 male, 20 female) from ages 8.5 to over 17 years old were analyzed. A statistically significant negative correlation was found between notch depth and horizontal jaw growth, but the correlation was deemed clinically insignificant. The study concluded that notch depth alone is not a reliable predictor of facial growth for general orthodontic treatment planning. A larger sample size and subjects with more extreme notch depths may have provided stronger correlations.

1. EVALUATTION OF ANTEGONIAL NOTCH
DEPTH FOR GROWTH PREDICTION
Ronald P. Kolodziej, DMD, MS ,a Thomas E. Southard, DDS, MS ,b Karin A.
Southard, DDS, MS ,b John S. Casko, DDS, MS, PhD, c and Jane R. Jakobsen, BS,
Mad
Am J Orthod Dentofacial Orthop 2002;121:357-63
PRESENTEDBY –PRIYA KAWANA
PG 1 ST YEAR STUDENT
DEPARTMENT OF ORTHODONTICS
AND DENTOFACIAL ORTHOPEDICS

2. CONTENTS
 Introduction
 Material and Methods
 Results
 Discussion
 Conclusion
 References

3. INTRODUCTION
 A reliable method of growth prediction would be an invaluable
asset to orthodontists.
 Successful treatment of malocclusions often depends on
appropriate orthopedic intervention to correct underlying skeletal
discrepancies.
 The ability to predict the magnitude and direction of a patient’s
facial growth early in life would enable the clinician to identify
those who require interceptive growth modification and to ensure
that the appropriate treatment can be rendered while growth is
possible.

4.  In addition, the ability to predict facial growth might enable the clinician to
forego unnecessary treatment on patients with skeletal discrepancies whose
growth pattern would probably lead to correction without orthopedic
intervention.
 Similarly; lengthy attempts at orthopedic correction could be avoided in patients
who ultimately would be best treated by surgery.
 Although the ability to predict growth of the entire face would be the most
desirable, accurate prediction of mandibular growth would be of great benefit.
 Maj and Luzi –assessed the changes in several cephalometric parameters on
serial radiographs of patients between the ages of 9 and 13 and used the data to
derive formulas to predict subsequent increases in relative mandibular length
increment.
 They reported that their formulas had a 68 % chance of correctly predicting the
increase within 1.6 mm.

5.  Skieller et al –used multivariate statistical methods to identify 4
morphologic variables that, when assessed on lateral cephalogram
might predict future mandibular rotation(86 % variability).
 Huggare - assessed the morphology of the 1st cervical vertebra as
predictor of mandibular growth and reported a significant
correlation(r=0.68,P< or equal to 0.1) between horizontal
mandibular growth and initial height of the atlas dorsal arch.
 Halazonetics et al-tested the hypothesis that early mandibular
shape might predict the amount and direction of future
mandibular growth.
 Rossouw et al- assessed the validity of frontal sinus as predictor
of mandibular growth.

6.  Aki et al- evaluated the morphology of the mandibular symphysis as a
predictor of the direction of mandibular growth.
 2 studies explored the possibility that mandibular antegonial notch morphology
might predict mandibular growth.
 These studies were based on the findings of Bjork, who reported that
mandibles with a forward growth tendency exhibit a pattern of surface
apposition below the symphysis and surface resorption under the mandibular
angle.
 The opposite pattern occurred in persons with a backward mandibular growth
tendency, leading to concavity on the inferior border of the mandible known as
the antegonial notch.
 Singer et al - attempted to determine if the antegonial notch depth indicated
future mandibular growth direction or potential.

7. MATERIALS AND METHODS
 Iowa Facial Growth Study, a longitudinal study comprising 183 white
subjects.
 92 males and 91 females; 97% of whom are of Northwest European ancestry.
 Serial cephalograms for 20 male and 20 female subjects were randomly
selected.
 None of the subjects had received any orthodontic treatment.
 Each of the 40 sets of cephalograms included radiographs taken when the
subjects were 8.5 years (T1), 12.0 years (T2), and > 17.0 years (T3). The mean
age at T3 was 24.8 years (SD 3.5).

9.  Landmarks corresponding to the method of measuring mandibular
antegonial notch depth as described by Singer et al11 were included in the
regimen.

10.  All pertinent landmarks were recorded with the Accugrid Digitizer
(Numonics Corporation, Montgomeryville, Penn).
 Digitized cephalograms were analyzed by a customized computer
program created with Dentofacial Planner Plus (Dentofacial Software
In Toronto, Ontario, Canada), an integrated cephalometric and facial
imaging software system for orthodontics.
 The program was designed to calculate the linear and angular
cephalometric measurements defined in Table II.

13.  Landmarks from each tracing were digitized, and the linear and angular measurements
were calculated to provide a representation of facial characteristics at T1, T2, and T3.
 Next, to measure growth changes for each subject, the T1 tracing was digitized again, the
T2 tracing was superimposed over the T1 tracing according to the best fit of the anterior
cranial bases when registered on sella, and the T2 landmarks were digitized.
 Similarly, the tracing of the T3 cephalogram was superimposed on the T1 tracing.
 By using the T1 data, a customized program created a horizontal reference line 7° inferior
to the sella-nasion line, with the vertex of the 2 lines at sella. This horizontal line was used
as an arbitrary x-axis.
 The program also created a reference line perpendicular to the x-axis passing through sella
to serve as the y-axis . Thus an x, y coordinate grid based on the T1 tracing was
established.

15.  Measurements on the x, y coordinate grid Positive- if the digitized points were anterior to
the origin along the x-axis or inferior to the origin along the y-axis.
 Measurements Negative -if the digitized points were posterior to the origin along the x-
axis or superior to the origin along the y-axis.
 This method of superimposition combined with the creation of a baseline coordinate
system provided a means of quantifying the growth changes observed between T1 and
T2, T1 and T3, and T2 and T3 for each landmark of interest.
 For each of the 4 landmarks listed in Table II, the changes in the x and y coordinate
values from T1 to T2, T1 to T3, and T2 to T3 were calculated, yielding values
representing the magnitude and direction of displacement for each landmark with growth
during these periods.

16.  Correlation analysis was performed with the SAS statistical software
package (SAS Institute, Inc, Cary, NC) to determine if a relationship
existed between the magnitude of the independent variable (notch
depth) at T1 and the dependent variables (all other cephalometric
measurements) at T1.
 Analyses were similarly performed for the T2 and T3 data.
 Correlation analysis then was performed to determine if a relationship
existed between the magnitude of the notch depth at T1 and the growth
change recorded in the dependent variables from T1 to T2 and T1 to T3.
 Finally, analysis was performed for the notch depth at T2, and the
growth change was recorded in the dependent variables from T2 to T3.

17.  Analyses were performed for the entire sample and separately for each
sex.
 For the present study, the correlation value for clinical significance was
defined as r = 0.70, a value large enough to be viewed favorably by most
researchers.
 In other words, a correlation value of r=0.70 between adolescent antegonial
notch depth and horizontal growth of B-point would mean that antegonial
notch depth explains slightly less than half (0.49) of the variance of horizontal
growth of B-point.

18. RESULTS
 The mean, standard deviation (SD), and range for each cephalometric
parameter and anatomic point examined is for T1, T2, and T3.
 As is evident, the notch depth and y-axis remained relatively constant for
the sample throughout the study.
 On average, the mandibular plane angle (SN-MP) and ANB angle decreased
slightly with growth.
 Maxillary and mandibular anatomic points were displaced downward and
forward.

22. DICUSSION
 The principal finding of this study is that the antegonial notch depth fails to
sufficiently indicate future facial growth to warrant its application as a predictor
for general orthodontic treatment planning in a nonextreme population.
 Although a statistically significant negative correlation exists between the depth of
the mandibular antegonial notch at adolescence and the horizontal growth
displacement of the maxilla and the mandible in a nonextreme patient population,
the correlation is clinically insignificant.
 Singer et al and Lambrechts et al both reported significant differences between
subjects with extremely deep or extremely shallow mandibular antegonial notches
with respect to indicators of mandibular growth direction.

23.  Unfortunately, Lambrechts et al used cross sectional data in their
investigation, and the use of notch depth as a true growth predictor
could not be properly assessed because growth can only be assessed by
comparing at least 2 points in time.
 Singer et al did report some findings based on longitudinal data.
However, they also used a treated sample, which may have influenced
actual growth, and the observation period in that study was relatively
short (mean growth period of subjects 4.3 years) to evaluate the
relationship of notch depth with growth.

24.  Finally, the samples of Singer et al and Lambrechts et al consisted
exclusively of subjects with extreme morphology (notch depths 3.0 mm or
1.0 mm), not necessarily representing the general population a clinician
would encounter.
 The present study, by design, assessed the actual growth of the mandible in
relation to antegonial notch depth in an untreated random sample of white
subjects.
 For all anatomic points studied, a moderate negative correlation was found
between adolescent notch depth and horizontal jaw growth (from
adolescence to adulthood), while prepubescent notch depth showed a weak
correlation with all future growth.

25.  This is not surprising, however, because for any given prediction, the success
rate decreases as the time between the prediction and the predicted event
increases.
 This would explain why a prediction at prepubescence would be less likely to
predict growth through adulthood, but it does not account for the weak
relationship observed when prepubescent notch depth was correlated with
growth from prepubescence to adolescence.
 After comparing growth changes from pretreatment to post retention between
deep-notched and shallow-notched groups, Singer et al reported no significant
difference between the groups for changes in ANB value.
 This agrees with the findings of the present study, which show no significant
correlation between notch depth and growth changes in ANB.

26.  In the present study, a larger sample size would have been desirable to increase
statistical power.
 The need for complete sets of radiographs representing prepubescence,
adolescence, and adulthood greatly limited the number of subjects available for
the investigation.
 A larger sample would also have allowed us to study correlations for a subset
of patients whose notch depths were extreme (3.0 mm or 1.0 mm).
 It is reasonable to speculate that a sample consisting exclusively of subjects
with extreme magnitudes of notch depth similar to those described by Singer et
al11 would yield stronger and perhaps clinically significant.
correlations.Therefore, in the present random, nonbiased sample, the depth of
the antegonial notch cannot be considered to be a valid predictor of mandibular
growth for treatment planning purposes.

27. CONCLUSION
 A statistically significant (P < or equal to .05) negative relationship exists
between mandibular antegonial notch depth (measured at age 12) and subsequent
horizontal jaw growth in a random, nonbiased sample of untreated subjects.
 As notch depth decreased, more horizontal jaw growth was observed. Conversely,
as notch depth increased, less horizontal jaw growth was observed, but the
strength of this relationship was weak.
 Previous investigators have proposed that antegonial notch depth, when extreme
in magnitude, might be used to predict facial growth.
 We concluded that antegonial notch depth fails to sufficiently indicate future
facial growth to warrant its application as a growth predictor in a nonextreme
population.

28. CRITICAL APPRAISAL
 The study was done on white subjects so cannot be generalized.
 A larger sample size would have been desirable to increase statistical
power.
 Sample consisting exclusively of subjects with extreme magnitudes of
notch depth s would yield stronger and perhaps clinically significant.

29. REFERENCES
 Maj G, Luzi C. Longitudinal study of mandibular growth between nine and thirteen
years as a basis for an attempt of its prediction. Angle Orthod 1964;34:220-30.
 Skieller V, Bjork A, Linde-Hansen T. Prediction of mandibular growth rotation
evaluated from a longitudinal implant sample. Am J Orthod 1984;86:359-70
 Huggare J. The first cervical vertebra as an indicator of mandibular growth. Eur J
Orthod 1989;11:10-6
 Huggare JÅV, Cooke MS. Head posture and cervico vertebral anatomy as
mandibular growth predictors. Eur J Orthod 1994; 16:175-80.
 Halazonetis DJ, Shapiro E, Gheewalla RK, Clark RE. Quantitative description of the
shape of the mandible. Am J Orthod Dentofacial Orthop 1991;99:49-56.
 Rossouw PE, Lombard CJ, Harris AMP. The frontal sinus and mandibular growth
prediction. Am J Orthod Dentofacial Orthop 1991;100:542-6. 10.
 Aki T, Nanda RS, Currier GF, Nanda SK. Assessment of symphysis morphology as a
predictor of the direction of mandibular growth. Am J Orthod Dentofacial Orthop
1994;106:60-9. Tor

30.  Singer CP, Mamandras AH, Hunter WS. The depth of the mandibular antegonial
notch as an indicator of mandibular growth potential. Am J Orthod
Dentofacial Orthop 1987;91:117- 24.
 Lambrechts AHD, Harris AMP, Rossouw PE, Stander I. Dimensional differences
in the craniofacial morphologies of groups with deep and shallow mandibular
antegonial notching. Angle Orthod 1996;66:265-72. 13.
 Bjork A. Prediction of mandibular growth rotation. Am J Orthod 1969;55:585-
99. 14. Bjork A. The use of metallic implants in the study of facial growth in
children: method and application. Am J Phys Anthropol 1969;29:243-54. 15.