0. Madam Pittsburgh, Pa.

.S., and V. Sassouni, D.D.S., MS.,

I n order to be more efficient in their therapeutic approach to maloc- clusion, orthodontists have long been interested in the possibility of predicting changes in their young patients that will occur through the simple process of aging. Very sophisticated statistical tools are available to describe the changing aspect of the direction of growth. In some such growth studies,l for instance, the theory of “stochastic process” and Warkow chains” has been proposed. In spite of this sophistication of the probabilistic approach to the changes occurring in the growing child, one may still raise the pragmatic question of what changes are of interest to the orthodontists: Changes in occlusion! Changes in esthetics? The first question is probably not salient, since most malocclusions are not self- correcting ; the second type of prediction, then, is the important one.

Since esthetic changes have been shown to be accurately measured by the changes in soft-tissue profile,z and since most growth and prediction studies are based on the skeleton,3-5 a legitimate question concerns the validity of skeletal changes as a prediction of esthetic changes. In an attempt to answer this ques- tion, Subtelny6 studied the growth of both skeletal and soft-tissue profiles ; however, since only the means were given, accuracy of prediction could not be measured from his data. Other authors have studied either one profile or the other without measuring the relationship between them75 8 or have compared the two profiles merely at one point in time. g Those authors, furthermore, did not investigate whether or not the profile changes were different among various facial types.

The present report is concerned with the difference in growth of the soft- tissue and skeletal profiles, measuring also the effect of sex and facial type. The predictability of the changes is also reported here.

Materials and methods

Sample. Thirty-five semilongitudinal series from “Heredity and Growth” (Xassouni) and sixteen longitudinal series from Denver’s “Child Research

From the Department of Orthodontics, School of Dental Medicine, University of Pittsburgh.

3

84 Mauchamp and Sassouni Am. J. Orthod. July 1973

Gl-Gl'

Fig. 1.

Council” were utilized. All children were of Caucasian descent, with no pathoses, and they had been selected in accordance with[ the following criteria: natural lip seal, all teeth present, and normal dental occlusion.

In order to group the children according to the vertical facial classification described by Sassouni,10-12 an index proposed by Manos13 was utilized (gonial angle + 5 x palatal-mandibular angle). When grouping had been done, the number of series in each cell was as follows:

0 8 0. B. 10 6 N. 8 5 D. B. 11 12

The male normal group was not large enough and was therefore disregarded for the rest of the study.

Measurements. Cephalometric roentgenograms were traced. Landmarks and planes were then obtained following the description proposed by Krogman and SassounP: optic plane, glabella, subnasale, and pogonion. Passing through the three points, lines parallel to the optic plane were traced, intersecting with the

VoEume 54 Number 1 Growth md pre&ctio?z of profiles

1’ I I I

t Skeletal minus Soft Tissue

Femole Normal

Individual __ Mean ----

h I I I I 1 I , I I I I I

8 10 12 14 16 18

Fig. 2.

skeletal or soft-tissue profile, and establishing three corresponding points : glabella prime, pogonion prime, and subnasale prime (Fig. I).

Six measurements were takeire : soft-tissue thickness at glabella ( Gl-Cl’) , at subnasale ( Sn-Sn’) , and at pogonion (Pog-Peg’) 4-G ; soft-tissue angle (Gl’-Sn- Peg’), skeletal angle (Gl-Sn’-Peg), and the difference between those two angles (skeletal angle minus the soft-tissue angle). In addition, increase in fat was recorded by the change in channel on the Wetzell grid, and direction of growth of the mandibIe was measured by the difference between the horizontal and the vertical increases, using the optic plane as a horizontal.

Analysis. For each group and measurement, the individual curves were traced. (See Fig. 2 for one of the measurements.) At each year the interpolated values were used and averaged in order to obtain a mean growth curve. The standard deviations were also measured as descriptive statistics. Finally, the values were combined to give both a total female and a total male sample. These, along with their means, were shown on a graph, in turn, to illustrate the sex effect.

Since three factors were involved (sex, facial type, and age), a three-way analysis of variance for unequal cell frequencies using weighted means was computed for each one of the six measurements. This analysis gave each factor effect after neutralization of the other two factors as well as their interaction :

Analysis of variance

Sex P < 0.0001 Facial type P < 0.1252 Age P < 0.7664

Sex-age P < 0.9958 Facial type-age P < 1.0

86 Maucha,mp awl Sassouni Am. J. Orthod. July 1973

180 -

178 -

176 -

174 -

Skeletal Convexity

Total Female Sample

.I / ._.-.-

./ / /' -.-. --

- I I I 1 I I I I I 0 3 12 14 16 18

C I I I I I , I I I I I I I

- Skeletal Convexity Skeletal Convexity

180 - 180 - Total Male Sample Total Male Sample

Open Open Bite - Bite - Deep Bite ----- Deep Bite ----- Mean - Mean -

178 -

176 -

IIll II I I I I I I IIll 1 III Ill I \ \

0 4 8 8 10 10 12 12 14 14 16 16 18 18

Figs. 3 and 4.

The effect of direction of mandibular growth and the increase in fat on the different measurements was measured by partial correlation, neutralizing the time factor, since the time elapsed between two observations was not always constant.

SKELETAL PROFILE (FIGS. 3 AND 4). There was no difference in skeletal profile between the different facial type groups. The female skeletal profile was straighter by 2 to 3 degrees (depending on age) than the male skeletal profile. The skeletal convexity decreased during aging; that is, the profile straightened by 1.5 degrees in males and 4 degrees in females. The statistical analysis, as shown albove, revealed only a significant sex effect.

Growth and prediction of profiles

8 8 10 10 12 12 14 14 Subteiny d ___ Subteiny d ___ Present Study 6 - __ Present Study 6 - __

9 9 --- ---

Skeletal Convexity

Fig. 5.

Because of a large dispersion of the individual curves, the analysis of variance was unable to show age effect. Bs found in this study, the decrease in convexity during aging is less than the 6 degrees found by Subtelny, but both findings were in general agreement with those of Lande.15 The Subtelny study, however, did not reveal the strong sex effect found here, which can only be ex- plained by his analysis, or by the use of different landmarks. The values in the present study, as shown in Fig. 5, are slightly larger than those in Subtelny’s study because of the use of glabella instead of nasion.

The correlation between direction of growth of the mandible and skeletal profile change was very low (0.17 in females and 0.04 in males). This finding is contradictory to the general contention concerning the effect of mandibular growth on the profile.

Sex

~0~~ ,

P < 0.0181 Sex-age P < 0.9990 Facial type P < 0.2809 &ire P < 0.9983

F&ai type-age P < 1.0

SOFT-TISSUE PROFILE (FIGS. 6 AND 7). There was no difference between the different facial types for the soft-tissue profile, either graphically or statistical- ly. The age effect also was minimal, and the only positive finding was the straighter profile of females as compared to males. This sexual dimorphism, however, is not as strong as for the skeletal profile.

The findings here are very similar to those of Subtelny, as shown in Fig. 8; the latter, however, does not reveal the sex effect. The increase in soft-tissue convexity, as shown by Pelton and E1asser7 in their study, was contradictory

88 Mauch~mnp and Xnssouni Am. J. Orthod. July 1973

172 _ Soft Tissue Convexity

Total Female Sample

0 6 8 lo l2 l4 l6 ‘* I I I , I I , , I , , , ,

172 _ Soft Tissue Convexity

Total Mole Somple

Open Bite - 170 _ Deep Bile ----

Mean ----

0 7 8 10 12 14 16 18

Figs. 6 and 7.

to either Subtelny’s findings or ours, which may be explained by the cross-

sectional sample utilized by those authors. SKELETAL CONVEXITY MINUS SOFT-TISSUE CONVEXITY (FIG. 9). Females had

an earlier increase in the difference between the two convexities than the males had, but for the over-all increase the two groups were very similar (4 degrees total increase). This confirms the previous findings on skeletal and soft-tissue profile where the skeletal convexity decreased by 4 degrees and the soft-tissue convexity remained stable.

POGOIVION (FIG. 10). The amount of soft-tissue growth at pogonion was 1 mm. in females and 3 mm. in males. This increase is slightly larger than that found by Subtelny, but closer to the data of Bowker.

The soft-tissue thickness, being larger in open-bite than in deep-bite patients,

Growth and prediciion of profiles

Soft Tissue Convexity

Pelton and Elsosser d-. Present Study b-,

$ --- -r--- P-- 0 8

I ,,I I, I I I I I I

14- Skeletal Minus Soft Tissue

Total Sample

I- 4 6; I,, , , , , , , , , , I]

8 10 12 14 16 18

Figs. 8 and 9.

therefore was not contributory to the dished-in appearance of persons with deep-bite.

SUBNASALE (FIG. 11) _ The amount of soft-tissue growth at subnasa!e was more significant, being 3 mm. in females and 4 mm. in males. The same facial type effect as for pogonion was found here, possibly because of the requirement of natural lip seal in the sample selection (which meant more soft-tissue material if the lower face height were large).

The change in channel on the Wetzell grid and the soft-tissue growth at

90 Mauchamp and Xassouni Am. J. Orthod. JUZ2/ 1973

JF--r Soft Tissue Thikness at Pogonion

’ lb ’ 1; ’ lb ’ lk ’ 1: ’ Subtelnv d - Bowker d- Present Study 6---.

0 10 0 --- e--,-. - P-.- -

I I III III IllI I

Soft Tissue Thikness at Subnasale

16 -

14 -

12 -

I I III II I I I I I I

6 8 10 12 14 l8 0 11 Subtelny d - Present d - - 0 ---- Study f-16

Figs. 10 and 11.

either pogonion or subnasale had a very low correlation \r = 0.16 for subnasale and pogonion in males).

Prediction

Predictability was measured by deviations of individual curves from the aver- age curve, bringing all individual curves to the mean value at the original year (9 and 13 for the first type of prediction, every year in the yearly prediction).

2’ , ,,’ ,’ I I ,’ ,I’ 176

172

I--

l

170 Soft Tissue Gonvexity

Camporison of Predictability between Skeletal and Soft Tissue Convexity at one year for males

0 12 Meon Trend -.- ; t Mean of absalutedeviation fmm mean trend a ; Range __ _ _

I , I I

180 - Skeletal Convexity

178 __--

176

174

172

170 c Soft Tissue Convexity c _--- 168 __---- *_-- =l.Lllml

166 164 -- 162 I -_-_ -- -I

1 I I I / 9 14 13 17

0 Predictability of Skel. and Soft Tissue convexity from 9 to 14 and 13 to 17 in Males

13 Mean Trend - ; +Maon of absolutedeviation fmm meun trend4 ;Ronge- - - _

Figs. 12 and 13.

The changes in skeletal convexity were more predictable than in soft- tissue convexity, and even more so for the annual prediction than for ages 9 to 14 (Figs. 13 and 14). However, the difference in ability to predict those changes using skeletal or soft-tissue profile was not very great, for that matter, even decreasing the advantage of the skeletal profile.

The fact that the soft-tissue profile did not change in a significant way during

92 Mauchamp and Sassouni Am. J. Orthod. J2LZ1/ 1973

I I I I I _ Skeletal Convexity

I I I I I 1 I .

17 I’ Soft Tissue Convexity I’

172 - I’ 1’

168 -

164- ‘\ ‘\ \ t \ I I I I I I I I 8 I I

10 I

12 14 1 ,

16 18

0 Comporisoon of Predictability between Skeletal and Soft Tissue Convexity at One Year for Femofes

14 Mean Trend - ; +Meanofobsolutedwiation fmm mean trend4 ; Range---.

I I I 184 - Skeletal Convexity *a’ *-

__-* _* 182 __*- -

180 -

178 -

176 ---_ - ---__

---__ -- 174 -___ - --.

Soft Tissue Convexity ,r’ 172 :- -

__-- __--

__-- 170 -

168 -

166 - -.__ --_. --._ __ 164 --__

I --__ -

-_ --__

0 15

1 1 -*. I I

9 I

14 :13 17 Predictability of Skel. ond Soft Tissue convexity change from 9 to 14 ond 13 to 17 in Females

Mean Trend - ;+ Mean of absolute deviation fmm mean trend4 ;Range- _- - .

Figs. 14 and 15.

aging, at least on an average basis, may raise the question of validity of qualita- tive growth prediction. Even the changes occurring in the skeletal profile were characterized by variability, and the attempt made here to reduce this biologic variation was not successful. The further contention that more straightening of the profile occurred with horizontal mandibular growth was not verified

Growth and p~rediction af profiles

here, which casts further doubt on the validity of predictive methods for facial changes based on mandibular growth.

onclusions

1. Four measurements showed increasing values from the ages of 7’ to 18 years : Pogonion, 2 mm. ; subnasale, 4 mm. ; skeletal convexity, 4 degrees; and skeletal-minus-soft-tissue convexity, 4 degrees. Soft-tissue convexity alone showed a stationary state during aging. All these findings agreed with those of Subtelny and Bowker but were contradictory to the findings on soft-tissue convexity made by Pelton and Elsasser.

2. From the graphic interpretation, the sex effect was significant for all measurements. For soft-tissue, there was a larger thickness in males and an earlier spurt in females; for convexity, there was a straighter profile in females than in males. The difference between the two convexities was increasing by an equal amount in both sexes, although it occurred earlier in females. From the analysis of variance, the sex effect was significant for all the measurements ex- cept subnasale,

3. The facial-type effect was significant for soft-tissue thickness, with larger values shown in skeletal open-bites than in skeletal deep-bites.

4. The direction of growth at gnathion did not reveal any relationship to change in profile convexity between two consecutive observations.

5. The increase in fat as measured by channels on the Wetzell grid was not significantly related to the increase in soft-tissue thickness.

6. The changes occurring in the soft-tissue profile are as predictable as the changes in the skeletal profile when made over a 4-year period, which is not true when prediction is made on a l-year span.

ummary

A study was undertaken to measure the effect of aging on the skeletal profile, the soft-tissue profile, and their relationship (soft-tissue thickness), also measuring the effect of facial type, mandibular growth, and increase in fat on the dependent variable. Fifty-one longitudinal series were used for this purpose, and the data were treated statistically as well as graphically. Aging had an effect on all measurements except soft-tissue profile ; there was also a sex effect shown by the straighter profile in females. Facial type, direction of mandibular growth, and increase in fat were unsuccessfully manipulated.

An attempt to measure the predictability of the changes occurring in the skeletal or soft-tissue profile was also made. The two profiles appeared to be equally predictable on a long age span.

This study supplements Subtelny’s findings with a different treatment of the data, an estimation of variability, and a measurement of the effect of different variates.

REFERENCES

1. Chiang, C. L.: Introduction to stochastic processes in biostatistics, New York, 1968, John Wiley & Sons, pp. 45-69.

2. McFarland, 0. W.: A study on the influence of skeletal changes due to orthodontic

94 Maucharnp and Sassouni Am. J. Orthod. July 1973

treatment on facial esthetics, Thesis, University of Pittsburgh, School of Dental Medicine, Pittsburgh, 1969.

3. Brodie, A. G.: On the growth pattern of the human head from the third month to the eighth year of life, Am. J. Anthropol. 68: 209, 1941.

4. BjGrk, A.: The face in profile, Lund, 1947, Berlingska Boktryckeriat. 5. Nanda, R. S.: Growth changes in skeletal facial profile and their significance in orthodontic

diagnosis, AM. J. ORTHOD. 59: 501, 1971. 6. Subtelny, J. D.: A longitudinal study of soft tissue facial structures and their profile

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among 6,829 white individuals, according to age and sex, Angle Orthod. 25: 199, 1955. 8. Bowker, W. D., and Meredith, H. V.: A metric analysis of the facial profile, Angle

Orthod. 29: 149, 1959. 9. Merrifield, L. L.: The profile line as an aid in criticaly evaluating facial esthetics,

AM. J. ORTHOD. 52: 804, 1966. 10. Sassouni, V.: A roentgenographic cephalometric analysis of cephalo-facie-dental relation-

ships, AX J. ORTHOD. 41: 735-764, 1955. 11. Sassouni, V.: The face in five dimensions, ed. 2, Morgantown, W. Va., 1962, University

of West Virginia Publications. 12. Sassouni, V., and Nanda, S. V.: Analysis of dentofacial vertical proportions, AX. J.

ORTHOD. 50: 801-823, 1964. 13. Manes, W. S.: A three-dimensional roentgenographic study of vertical facial types

(open-bite and deep-bite skeletal pattern), Thesis, University of Pittsburgh, School of Dental Medicine, Pittsburgh, 1969.

14. Krogman, W. M., and Sassouni, V. : A syllabus in roentgenographic cephalometry, Philadelphia, 1957, Philadelphia Center for Research in Child Growth.

15. Lande, M. J.: Growth behavior of the human facial profile as revealed by serial cephalometrio roentgenology, Angle Orthod. 22: 78, 1952.