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Facial growth in males 16 to 20 years of age
Facial growth in males 16 to 20 years of age R. J. Love,* J. M. Murray,** and A. H. Mamandras*** London, Ontario, Canada
Postpubertal craniofacial skeletal and dental changes were examined from lateral cephalograms taken when subjects were 16, 18, and 20 years of age. The sample consisted of males with no previous orthodontic treatment who had Class I skeletal and dental characteristics. Mandibular growth was found to be statistically significant for the age periods of 16 to 18 years and 18 to 20 years. Growth from 16 to 18 years was greater than that from 18 to 20 years. Maxillary and mandibular growth were highly correlated at each age period. However, overall mandibular growth was approximately twice that of overall maxillary growth. Mandibular growth was found to involve an upward and forward rotation, a result of posterior vertical growth exceeding anterior vertical growth. Lower incisors were found to tip lingually with increasing age. Incremental changes in mandibular cephalometric measurements were found to be equivalent when measured from either articulare or condylion, indicating the interchangeability of the landmarks for growth estimates. (AM J ORTHOD DENTOFACORTHOP1990;97:200-6.)
Many studies have been published conceming growth in the prepubertal and pubertal years."" However, longitudinal studies in postpubertal adults have been rare. Postpubertal growth has been shown to produce dramatic alteration in skeletal and dental relationships. ~2 Bjork ~3 studied mandibular • growth in 45 Danish males. Although exact results were not given, Bjork indicated a growth rate of approximately 3 mm per year between the ages of 16 and 17 years, decreasing to no growth between the ages of 21 and 22 years. Behrents, ~4 however, found mandibular growth to be significant past the age of 35 years. Two samples that include data on untreated adults with Class I skeletal and dental relationships are those of the University of Iowa and the Burlington Growth Centre. Studies of the Iowa sample have resulted in a series of articles on facial growth by Bishara and associates, z5~7Studies of the Burlington Research Centre sample have resulted in articles by Woodside ~8and Sinclair and Little.~9 The Iowa and Burlington data indicated that the magnitude of postpubertal craniofacial growth was significant. The data from the Iowa sample included no intervening records between the ages of 17 and 25.5 years. ,6 The sample studied by Sinclair and Little ~9 had no intervening records between the ages of 13 and 20 years. Woodside ~8 studied untreated control subjects only to From the Division of Orthodontics, Faculty of Dentistry, The University of Western Ontario. *Senior Graduate Student. **Clinical Lecturer. ***Associate Professor and Director, Undergraduate Orthodontic Program. 811110440
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the age of 16 years. Data to the age of 20 years incorporated cross-sectional controls and subjects with previous orthodontic treatment. Studies of continuous records of postpubertal Class I skeletal growth cannot be found in the literature. The purposes of this study were to determine postpubertal skeletal and dental changes in males with Class I skeletal and dental patterns and to interpret these changes in a clinical context. METHODS AND MATERIALS
The sample used in this study consisted of 30 patients from the Family and Serial Control Groups of the Burlington Growth Centre. Sample selection was based on the following criteria: (1) white male with no history of orthodontic treatment or extractions, (2) Class I, both skeletally and dentally (i.e., ANB angle < 4 ° and Angle Class I molars), and (3) lateral cephalograms in both habitual occlusion and with mouth wide open, available for the ages of 16 and 20 years. Of the 30 patients selected, 20 had lateral cephalograms taken at the ages of 16, 18, and 20 years, and 10 had lateral cephalograms taken at the ages of 16 and 20 years. All lateral cephalometric landmarks (Fig. 1) used for linear and angular measurements have been described previously. 2°'~' Mandibular measurements from condylion to gnathion, condylion to pogonion, and condylion to gonion were duplicated from articulare and compared by correlation analysis to determine whether the two landmarks could be substituted when mandibular growth increments were being determined.
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t t I
0
J, t t
Ba
t
qccI Plane Go
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Fig. 1. Cephalometriclandmarks and planes. For comparison of maxillary and mandibular growth, two methods were employed. Both used common landmarks from which to measure incremental changes in length. The first method used condylion as a common point. Maxillary length was measured to A point, while mandibular length was measured to gnathion. The second method used sella and the S-N line for measurement of growth of the maxilla and mandible along the functional occlusal plane. Change in maxillary length was measured along the functional occlusal plane from a point formed from the intersection of a perpendicular line from the S-N line at sella and the functional occlusal plane to another perpendicular line from S-N, which contacted the functional occlusal plane after passing through A point. Change in mandibular length was measured from the same posterior reference point (i.e., the intersection of a perpendicular line from sella and the functional occlusal plane to the intersection on the functional occlusal plane of a perpendicular line from S-N to gnathion, Fig. 1). Means and standard deviations were determined for each linear and angular measurement at each age (Table I). In addition, paired t tests were performed for the differences in the means of the measurements for the age ranges 16 to 18, 18 to
20, and 16 to 20 years (Table II). Relationships between the changes in selected measurements were investigated by calculation of correlation coefficients between pairs of measurements. 23 Correlation coefficients were tested for significance with Student t tests. Possible intraexaminer error resulting from landmark selection, tracing, and measurement was determined by random selection of 15 lateral cephalograms, which were retraced and remeasured. Paired t tests were carried out for all linear and. angular measurements. Results indicated that all linear and angular measurements fell within acceptable limits; that is, there was no statistical significance between original and retraced measurements. RESULTS
The values of all cephalometric measurements at the ages of 16, 18, and 20 years are given in Table I. Values for SNA, SNB, and facial axis angles indicated that the sample had a Class I skeletal pattern at all ages examined. All linear measures showed an increase from age 16 to age 20. Lower incisor angulation appeared to be higher than the cephalometric standards described by Downs 24 and Tweed. z5
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Table I. Means and standard deviations of cephalometric measurements for males at ages 16, 18, and 20 years Age 16 yr Measurements
Mean
SNA SNB ANB Facial axis Mandibular plane 1 to mandibular plane Na-ANS ANS -Me Co-A Co-Gn Co-Pog Co-Go Ar°Gn Ar-Pog Ar-Go Go-Gn Go-Pog Occlusal plane (maxilla) Occusal plane (mandible)
82.3 79.5 2.8 90.2 31.0 98.5 57.27 71.71 97.35 127.17 124.83 61.83 119.45 i 17.54 50.84 82.63 82.92 71.11 56.61
20 yr
18 yr
I
SD
Mean
3.8 3.9 1.5 4.3 6.0 6.8 3.11 6.35 4.20 4.60 4.45 4.01 4.44 4.45 3.85 3.47 3.62 4.71 8.70
82.0 79.6 2.4 90.3 30.2 97.7 57.75 72.41 98.33 129.3 ! 127.12 64.20 121.79 119.92 52.79 83.87 84.21 71.69 57.60
SD
Mean
3.6 3.7 1.8 3.8 5.8 6.4 3.42 5.42 4.30 4.00 4.09 3.39 4.13 4.21 3.89 3.78 3.99 3.87 7.67
82.8 80.4 2.4 90.6 29.5 96.8 58.12 73.78 99.51 131.54 129.22 66.02 123.46 121.44 54.33 84.59 84.83 72.42 59.26
[
SD
I
3.8 4.1 ! .7 4.0 5.9 7.0 3.50 6.53 3.95 4.50 4.53 3.57 4.46 4.64 3.59 3.72 3.85 4.49 8.66
Table II. Mean changes and paired t values of cephalometric measurements for males during three
age periods Age period 16-18 yr (n = 20) Measurements
Mean
SNA SNB ANB Facial axis Mandibular plane 1 to mandibular plane Na-ANS ANS-Me Co-A Co-Gn Co-Pog Co-Go Ar-Gn Ar-Pog Ar-Go Go-Gn Go-Pog Occlusal plane (maxilla) Occlusal plane (mandible)
0.0 0.3 - 0.3 O. I - 1.0 -0.9 0.48 1.02 1.13 2.53 2.44 2.37 2.40 2.26 2.07 1.37 1.32 0.48 1.24
*p < 0.05,
**p < 0.01, ***p < 0.001.
I
18-20 yr (n = 20)
'
Mean
0.12 1.11 2. i 6* 0.31 3.36** 2.88** 3.49** 3.70** 3.64** 5.76"** 6.51 *** 5.57*** 6.75*** 6.91 *** 6.17"** 4.06*** 3.89** 2.06* 2.80*
0.7 0.7 0.0 0.2 -0.5 - 0.8 0.65 0.78 1.18 1.59 1.73 1.67 1.28 1.29 1.26 0.61 0.57 0.95 !.35
1
16-20 yr =
' 3.33** 5.05*** 0.20 0.68 3.60** 2.87** 3.40** 3.85** 3.92*** 6.85*** 6.00*** 5.97*** 6.18"** 5.54*** 5.40*** 3.66** 3.33** 4.80*** 4.52***
3~
Mean 0.5 0.9 -0.4 0.4 - 1.6 - 1.7 0.85 2.07 2.16 4.36 4.39 4.19 4.00 3.90 3.49 1.97 1.91
1.31 2.65
2.53* 4.93*** 2.36* 1.58 8.08*** 4.02*** 4.83*** 7.07*** 7.31"** 9.45*** 10.03"** 9.42*** 9.95*** 9.77*** 10.36"** 6.36*** 6.36*** 6.48*** 7.76***
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Incremental changes in cephalometric values are shown in Table II. Most measures showed highly significant changes in measurement increase for each age period studied. The magnitude of the increases were generally greater from 16 to 18 years than from 18 to 20 years. In some instances the totals of the 16- to 18plus 18- to 20-year increments did not equal the overall (16- to 20-year) increase. This was due to the fact that each of the 16- to 18- and 18- to 20-year totals was derived from samples of 20, while the 16- to 20-year totals were derived from a sample of 30 subjects. Measurements of mandibular lengths (Co-Gn, CoGo, and Go-Gn) indicated that significant growth increments occurred between the age periods from 16 to 18 years and 18 to 20 years (Table II). The maximum and minimum growths (Co-Gn) recorded over the 4year period were 10.2 mm and 1.4 mm, respectively. Nine subjects exhibited mandibular growth in excess of 6 mm. Correlation coefficients calculated for all possible pairs of mandibular growth measurements (Table III) showed the strongest correlations to be between overall length increase (Co-Gn) and ramus length increase (Co-Go), where the correlations reached statistical significance at each age period. The weakest relationships were between ramus length increase (CoGn) and corpus length increase (Go-Gn). These correlations failed to reach statistical significance at any age period. The relationship between overall length increase (Co-Gn) and body length increase (Go-Gn) was intermediate, with correlations reaching statistical significance at 16 to 18 years and at 16 to 20 years. Vertical mandibular growth (Co-Go = 4.19 mm) greatly exceeded horizontal mandibular growth (Go-Gn = 1.97 mm) from 16 to 20 years of age. Growth of the mandible and maxilla (from condylion) is shown in Table IV. Growth of the mandible was greater from 16 to 18 years than from 18 to 20 years, whereas maxillary growth remained relatively constant. Between the ages of 16 and 20 years the mandible outgrew the maxilla by a ratio of approximately 2: 1. When measurements of mandibular and maxillary growth were related to the functional occlusal plane (Table V), a slightly different picture was seen. Mandibular growth remained constant whereas maxillary growth increased from the 16- to 18-year age period to the 18- to 20-year age period. Overall, the mandible still outgrew the maxilla by a ratio of approximately 2: 1, but the increases in both mandible and maxilla were substantially less than those measured from condylion. The mandibular plane angle closed an average of 1.6° over the study period (Table II), as in previous studies? ~,'9 Lower anterior face height (ANS-menton)
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Table III. Correlation coefficients for mandibular
length measurements at three age periods Age period Measurement
16-18 yr (n = 20)
18-20 yr (n = 20)
Co-Gn/Co-Go Co-Gn/Go-Gn Go-Gn/Co-Go
0.69*** 0.58** 0.26
0.70*** 0.24 0.18
I 16-20 yr I (n =30) 0.80*** 0.63*** 0.29
*p < 0.05, **p < 0.01, ***p < 0.001.
Table IV. Co-Gn and Co-A growth for three
age periods Age period
Co-Gn (mm) Co-A (mm) Difference (mm)
16-18 yr (n = 20)
18-20 yr (n = 20)
2.53 1.13 1.40
1.59 1.18 0.41
I
16-20 yr (n = 30) 4.36 2.16 2.20
Table V. Maxillary and mandibular growth
along the occlusal plane for three age periods Age period 16-18 yr (n = 20) Mandible (mm) Maxilla (mm) Difference (mm)
1.24 0.48 0.76
I
18-20yr 01 = 20) 1.34 0.95 0.39
I
{ 16-20 yr } (n = 30) 2.65 1.3 I 1.34
increased 2.07 mm from 16 to 20 years of age while posterior face height (Co-Go) increased 4.36 mm, a rate more than double that of the anterior face height. Lower incisors tipped lingually with respect to the mandibular plane an average of 1.7 ° from 16 to 20 years of age (Table II). Calculation of correlation coefficients for the degree of incisor tipping to overall mandibular length (Co-Gn) and maxillary and mandibular growth measured along the occlusal plane showed that no significant relationship existed between the variables (Table VI). The only significant correlation was shown between incisor tipping and the maxillary-mandibular growth differential from 16 to 18 years of age. Values of correlation coefficients and mean differences in mandibular length increments measured from
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Table VI. Correlation coefficients and mean differences for the comparison of some cephalometric
measurements for three age periods Age period 16-18 yr (n = 20) I
18-20 yr (n = 20)
Measurement to comparison
r
Mean difference
r
Co-Gn/Ar-Gn Co-Go/Ar-Go Co-Pog/Ar-Pog Co-Gn/Co-A Occlusal plane (maxilla/mandible) I-MP/Co-Gn l-MP/occlusal plane (maxilla) l-MP/occlusal plane (mandible) l-MP/occlusal plane (mandible-maxilla)
0.89*** 0.80*** 0.86*** 0.71"** 0.86*** 0.37 0.10 0.22 0.87***
0.12 0.30 0.17 1.39 0.76 -----
0.70*** 0.68*** 0.66*** 0.55* 0.67*** 0.07 0.16 0.19 0.1l
Mean difference 0.31 0.41 0.44 0.41 0.40
16-20 yr (n = 30) Afean
r
difference
0.87*** 0.79*** 0.84*** 0.52** 0.64*** 0.23 0.13 0.30 0.28
0.36 0.70 0.49 2.20*** 1.34"**
*p < 0.05, **p < 0.01, ***p < 0.001.
condylion and articulare are given in Table VI. Most of the mean differences were not statistically significant, and all correlation coefficients were highly significant (p < 0.001) for all age periods. These results indicated that condylion and articulare may be used interchangeably to record incremental mandibular length changes, at least from 16 to 20 years of age. DISCUSSION
The findings of this study on mandibular growth and maxillomandibular relationships provide further information about craniofacial changes in postpubertal adolescents and adults to supplement data already published from previous investigations.~4"~s'2s2s Values found for mandibular length (Co-Gn) were less than those reported at equivalent ages by Woodsidefl 8 possibly because of a difference in radiographic technique (i.e., lateral cephalogram versus 45 ° lateral oblique). In contrast, data from this study show that the Burlington sample exhibits greater mandibular lengths than the samples of either Behrents '4 or Bishara and Jakobsen.~7 These differences may be due to sample selection or inherent sample variability, although it is quite possible that they are a result of variable radiographic enlargement factors. Cephalometric standards, such as those published by Riolo et al.,2° Bishara,,5 and Behrents, ~4may have more than one enlargement factor because of changes in equipment or technique over the course of the study, making data comparisons within and between studies inaccurate. It is apparent from the data (Table II) that significant changes occur in the craniofacial skeleton after the age
of 16. Statistical significance was achieved for all linear dimensions measured at each age period. Overall mandibular length (Co-Gn) increased an average of 4.36 mm over the 4-year study period (Table II). The increase was much larger than that determined by Behrents ~ in his study of 84 boys at the age of 17 years and 39 men at the age of 83 years. Behrents found statistically significant mandibular length increases up to the age of 35 years and nonsignificant changes after the age of 40 years. The average increase in mandibular length from age 17 to age 83 was 2.7 mm. Mandibular length in our study exceeded that in Behrents' study (3.4 mm at age 18 and 3.8 mm at age 20). In Behrents' sample, however, 23% of the subjects had Class II malocclusion. Results reported by Buschang et al. 29 indicated that the inclusion of Class II malocclusions would certainly reduce the mandibular length found at each age but would not affect incremental values between ages. Mandibular growth was twice the amount of maxillary growth, whether measured fro m condylion or along the occlusal plane. More mandibular growth occurred between the ages of 16 and 18 years than between 18 and 20, whereas maxillary growth was constant in both age periods. A steady rate of maxillary growth has been previously noted by Linder-Aronson et al. 3° MitanP ~ found synchronicity in the timing and rate of maxillary and mandibular growth in 60% of his sample of 30 children. Similarly, Jamison et alfl 2 found that the maxillary-mandibular relationship remained constant between the ages of 8 and 17 years. The high correlation coefficients for maxillary and mandibular
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incremental changes in this study also indicated a relationship between maxillary and mandibular growth rates. Such a relationship would be expected when a balanced facial pattern is maintained. The mandibular plane angle closed 1.6 ° between the ages of 16 and 20 years. This is in agreement with the findings of Bjork and Skieller, 33 Bishara, 15 Behrents, '4 and Sinclair and Little ~9 but disagrees with the findings of Forsberg. 28 Forsberg found that the mandibular plane angle increased 0.26" in men from the age of 24.9 years to the age of 35.2 years. Upward and forward rotation was a constant finding in this investigation; 26 of 30 persons showed a reduction in the mandibular plane angle, whereas in 4 persons the mandibular plane angle remained constant. The reduction in mandibular plane angle occurred despite a concomitant increase in anterior face height. It appears most likely that this reduction was the result of the differential increase between posterior and anterior face height (4.19 and 2.92 mm, respectively) over the study period. Greater posterior vertical growth would result in a lowering of the gonion region and subsequent upward and forward mandibular rotation. The greater rate of growth in posterior face height compared to anterior face height in postpubertal samples can be seen in the data of other longitudinal studies. 14.16.19.34The greater rate of posterior versus anterior growth appears to be a reversal of the trend seen before and during puberty in which anterior face height increases more rapidly than posterior face height) 6'~9 Lavergne and Gasson J5 and Isaacson et al. 36 concluded mandibular rotation was a result of disproportionate growth. Lavergne and Gasson 35 found a high degree of upward and forward rotation when mandibular growth exceeded maxillary growth, a situation that was found in all but two of the subjects in this study. The decrease in lower incisor angulation to the mandibular plane does not appear to be a universal occurrence and is probably sample specific. Bjork and Skieller 33 and Perera 37 found lower incisor angulation to be functionally stable, the angulation remaining constant. Forsberg 28 and Behrents '4 found lower incisors proclined with increasing age. Retroclination of lower incisors would result in loss of arch length and subsequent crowding. This possibility coincides with what is seen clinically in many posttreatment orthodontic cases. In this study, change in incisor angulation was not correlated with growth of the mandible or of the maxilla (Table VI) but showed a high correlation with the maxillomandibular growth differential from age 16 to age 18. The low correlations overall and between the ages of 18 and 20 leave some doubt whether differential jaw growth causes lingual tipping of incisors.
The cause is probably multifactorial in nature, with differential growth one of the factors. Incisor inclination at the age of 16 (Table I) was greater than that given as a cephalometric norm by Downs 2~ and Tweed. 25 However, the lower incisor angulation found in this study was in agreement with the findings of other investigations. ~5.~9.2o Measurements of mandibular linear incremental changes from condylion and articulare were found to be equivalent. It may be impossible to locate condylion on lateral cephalograms taken with teeth in occlusion, and very few lateral cephalograms are taken with the mouth wide open. Although this study did not measure positional changes in articulare the data support the conclusions of Agronin and Kokich 38 that remodeling or displacement of arficulare is reflected in changes in the glenoid fossa. SUMMARY AND CONCLUSIONS
1. Cephalometric measurements at each age indicated that the Class I skeletal pattern was maintained throughout the study period. Comparison of mandibular length measurements to norms from other studies revealed significant differences, which may be attributable to sample dissimilarity, radiographic enlargement, or both. 2. The rate of change of mandibular measurements was significant at each age interval. However, a much greater rate of change was seen from 16 to 18 years than from 18 to 20 years. Growth rates for this study did not agree with some previous studies. 3. Mandibular growth was greater than maxillary growth at each age interval when measured by either of two methods. A larger differential was seen from 16 to 18 years than from 18 to 20 years. Despite the fact that the magnitude of maxillary and mandibular growth after the age of 16 years did not approach previously reported pubertal levels, growth of both jaws was significant and may need to be assessed in orthodontic treatment planning. 4. The mandibular plane angle was significantly reduced, indicating a upward and forward rotational growth pattern. Forward rotation was thought to be brought about by disproportionate anteroposterior vertical growth. 5. Lower incisors were found to retrocline with increasing age. The degree of tipping was not found to be consistently related to maxillary or mandibular growth or to the difference between them. However, these results indicate that orthodontically treated patients retention may be advisable for extended periods of time, perhaps to the age of 20 years and beyond in male patients.
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6. M a n d i b u l a r i n c r e m e n t a l c h a n g e s m e a s u r e d f r o m a r t i c u l a r e w e r e e q u i v a l e n t to t h o s e m e a s u r e d f r o m c o n dylion. The two landmarks could be used interchangea b l y for g r o w t h d e t e r m i n a t i o n s . We wish to thank Drs. F. Mader, P. QuigIey, R. Thompson, J. Wanklin for their help in this project and Susan Minelli and Aura Hidalgo for typing the manuscript.
REFERENCES 1. Meredith H. Serial study of change in a mandibular dimension during childhood and adolescence. Growth 1961;25:229-42. 2. Bergerson EO. The directions of facial growth from infancy to adulthood. Angle Orthod 1966;36:18-43. 3. Bergerson EO. The male adolescent growth spurt: its prediction and relation to skeletal maturation. Angle Orthod 1972;42:31938. 4. Hunter CJ. The correlation of facial growth with body height and skeletal maturation at adolescence. Angle Orthod 1966; 36:44-54. 5. Savara BS, Tracy WE. Norms of size and annual increments for five anatomical measures of the mandible in boys from three to sixteen years of age. Arch Oral Biol 1967;12:469-86. 6. Odegaard J. Growth of the mandible studied with the aid of metal implant. AM J ORTttOD 1970;57:145-57. 7. RickettsRM. Aprincipalofarcialgrowthofthemandible. Angle Orthod 1972;42:368-86. 8. Cross JJ. Facial growth: before, during, and following orthodontic treatment. AM J OR'ntOD 1977;71:68-78. 9. Matthews RJ, Ware WH. Longitudinal mandibular growth in children with tantalum implants. AM J ORTttOD 1978;74:633-55. I0. Bishara SE, Jamison JE, Peterson LC, DeKock WH. Longitudinal changes in standing height and mandibular parameters between the ages of 8 and 17 years. AM J ORntOD 1981;80:11535. 11. Lewis AB, Roche AF, Wagner B. Growth of the mandible during pubescence. Angle Orthod 1982;52:325-42. 12. Singer J. Posttreatment change: a reality. AM J OR'ntOD 1975;67:277-89. 13. Bjork A. Variations in the growth pattern of the human mandible: longitudinal radiographic study by the implant method. J Dent Res 1963;42:400-11. 14. Behrents RG. An atlas of growth in the aging craniofacial skeleton. Monograph 18. Ann Arbor, Michigan: University of Michigan Center for Human Growth and Development, 1985. 15. Bishara SE. Longitudinal cephalometric standards from 5 years of age to adulthood. A.',t J OR'trOD 1982;79:35-44. 16. Bishara SE, Peterson LC, Bishara E. Changes in facial dimensions and relationships between the ages of 5 and 25 years. AM J ORTttOD 1984;85:238-52. 17. Bishara SE, Jakobsen JR. Longitudinal changes in three normal facial types. AM J OR'ntOD 1985;88:466-502. 18. Woodside DG. Distance, velocity and relative growth rate standards for mandibular growth for Canadian males and females aged three to twenty years [American Board of Orthodontics thesis]. St. Louis: Library of American Association of Orthodontists, 1969. 19. Sinclair PM, Little RM. Dentofacial maturation of untreated normals. A.',t J ORTiIOD 1985;88:146-56.
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20. Riolo ML, Moyers RE, McNamara JA, tIunter WS. An atlas of craniofaeial growth: cephalometric standards from the University School Growth Study, the University of Michigan. Monograph 2. Ann Arbor, Michigan: University of Michigan Center for Human Growth and Development, 1974. 21. Behrcnts RG. Growth in the aging craniofacial skeleton. Monograph 17. Ann Arbor, Michigan: University of Michigan Center for ttuman Growth and Development, 1985. 22. Popovich F, Thompson GW. Craniofacial templates for orthodontic case analysis. In: Clark JW, ed. Clinical dentistry; vol. 2. New York: Harper and Row, 1983:1-24. 23. Snedecor GW, Cochran WG. Statistical methods. Iowa City: Iowa State University Press, 1971. 24. Downs WB. The role of cephalometrics in orthodontic case analysis and diagnosis. AM J ORTItOD 1948;38:i62-82. 25. Tweed C. Clinical orthodontics. Vol 1. St. Louis: CV Mosby, 1966. 26. Bjork A, Palling M. Adolescent age changes in sagittal jaw relation, alveolar prognathy, and incisal angulation. Acta Odontol Scand 1955;12:201-32. 27. Christie TE. Cephalometric patterns of adults with normal occlusion. Angle Orthod 1977;47:i28-35. 28. Forsberg CM. Facial morphology and aging: a longitudinal cephalometric investigation of young adults. Eur J Orthod 1979; 1:1523. 29. Buschang PH, Tanguay R, Turkewicz J, Demirjian A, La Palme L. A polynomial approach to craniofacial growth: description and comparison of adolescent males with normal occlusion and those with untreated Class 11 malocclusion. AM J OR'rnODDENTOFACORTItOP 1986;90:437-42. 30. Linder-Aronson S, Woodside DG, Daigle DJ. A longitudinal study of the growth in length of the maxilla in boys between ages 6-20 years. Trans Eur Soe Orthod 1976;169-79. 31. Mitani H. Occlusal and craniofacial growth changes during pubetty. AM J ORTItOD 1977;72:76-84. 32. Jamison JE, Bishara SE, Peterson LC, Kremenak CR. Longitudinal changes in the maxilla and the maxillary-mandibular relationship between 8 and 17 years of age. AM J OR'moP 1982;82:217-30. 33. Bjork A, Skieller V. Facial development'and tooth eruption: an implant study at the age of puberty. AM J ORTItOD 1972;62:33983. 34. Knott V. Growth of the mandible relative to a cranial base line. Angle Orthod 1973;43:305-13. 35. Lavergne J, Gasson N. A metal implant study of mandibular rotation. Angle Orthod 1976;46:144-50. 36. Isaacson RJ, Zapfel RJ, Worms FW, Bevis RR, Speidel TM. Some effects of mandibular growth on the dental occlusion and profile. Angle Orthod 1977;47:97-106. 37. Perera PSG. Rotational growth and incisor compensation. Angle Otthod 1987;57:39..49. 38. Agronin KJ, Kokich VG. Displacement of the glenoid fossa: a cephalometric evaluation of growth during treatment. AM J ORTIIOD DENTOFACORTIIOP 1987;91:42-8. Reprint requests to: Dr. A.H. Mamandras Division of Orthodontics Faculty of Dentistry The University of Western Ontario London, Ontario, Canada N6A 5C1
Postpubertal craniofacial skeletal and dental changes were examined from lateral cephalograms taken when subjects were 16, 18, and 20 years of age. The sample consisted of males with no previous orthodontic treatment who had Class I skeletal and dental characteristics. Mandibular growth was found to be statistically significant for the age periods of 16 to 18 years and 18 to 20 years. Growth from 16 to 18 years was greater than that from 18 to 20 years. Maxillary and mandibular growth were highly correlated at each age period. However, overall mandibular growth was approximately twice that of overall maxillary growth. Mandibular growth was found to involve an upward and forward rotation, a result of posterior vertical growth exceeding anterior vertical growth. Lower incisors were found to tip lingually with increasing age. Incremental changes in mandibular cephalometric measurements were found to be equivalent when measured from either articulare or condylion, indicating the interchangeability of the landmarks for growth estimates. (AM J ORTHOD DENTOFACORTHOP1990;97:200-6.)
Many studies have been published conceming growth in the prepubertal and pubertal years."" However, longitudinal studies in postpubertal adults have been rare. Postpubertal growth has been shown to produce dramatic alteration in skeletal and dental relationships. ~2 Bjork ~3 studied mandibular • growth in 45 Danish males. Although exact results were not given, Bjork indicated a growth rate of approximately 3 mm per year between the ages of 16 and 17 years, decreasing to no growth between the ages of 21 and 22 years. Behrents, ~4 however, found mandibular growth to be significant past the age of 35 years. Two samples that include data on untreated adults with Class I skeletal and dental relationships are those of the University of Iowa and the Burlington Growth Centre. Studies of the Iowa sample have resulted in a series of articles on facial growth by Bishara and associates, z5~7Studies of the Burlington Research Centre sample have resulted in articles by Woodside ~8and Sinclair and Little.~9 The Iowa and Burlington data indicated that the magnitude of postpubertal craniofacial growth was significant. The data from the Iowa sample included no intervening records between the ages of 17 and 25.5 years. ,6 The sample studied by Sinclair and Little ~9 had no intervening records between the ages of 13 and 20 years. Woodside ~8 studied untreated control subjects only to From the Division of Orthodontics, Faculty of Dentistry, The University of Western Ontario. *Senior Graduate Student. **Clinical Lecturer. ***Associate Professor and Director, Undergraduate Orthodontic Program. 811110440
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the age of 16 years. Data to the age of 20 years incorporated cross-sectional controls and subjects with previous orthodontic treatment. Studies of continuous records of postpubertal Class I skeletal growth cannot be found in the literature. The purposes of this study were to determine postpubertal skeletal and dental changes in males with Class I skeletal and dental patterns and to interpret these changes in a clinical context. METHODS AND MATERIALS
The sample used in this study consisted of 30 patients from the Family and Serial Control Groups of the Burlington Growth Centre. Sample selection was based on the following criteria: (1) white male with no history of orthodontic treatment or extractions, (2) Class I, both skeletally and dentally (i.e., ANB angle < 4 ° and Angle Class I molars), and (3) lateral cephalograms in both habitual occlusion and with mouth wide open, available for the ages of 16 and 20 years. Of the 30 patients selected, 20 had lateral cephalograms taken at the ages of 16, 18, and 20 years, and 10 had lateral cephalograms taken at the ages of 16 and 20 years. All lateral cephalometric landmarks (Fig. 1) used for linear and angular measurements have been described previously. 2°'~' Mandibular measurements from condylion to gnathion, condylion to pogonion, and condylion to gonion were duplicated from articulare and compared by correlation analysis to determine whether the two landmarks could be substituted when mandibular growth increments were being determined.
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]Vumbcr 3
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t t I
0
J, t t
Ba
t
qccI Plane Go
M
Fig. 1. Cephalometriclandmarks and planes. For comparison of maxillary and mandibular growth, two methods were employed. Both used common landmarks from which to measure incremental changes in length. The first method used condylion as a common point. Maxillary length was measured to A point, while mandibular length was measured to gnathion. The second method used sella and the S-N line for measurement of growth of the maxilla and mandible along the functional occlusal plane. Change in maxillary length was measured along the functional occlusal plane from a point formed from the intersection of a perpendicular line from the S-N line at sella and the functional occlusal plane to another perpendicular line from S-N, which contacted the functional occlusal plane after passing through A point. Change in mandibular length was measured from the same posterior reference point (i.e., the intersection of a perpendicular line from sella and the functional occlusal plane to the intersection on the functional occlusal plane of a perpendicular line from S-N to gnathion, Fig. 1). Means and standard deviations were determined for each linear and angular measurement at each age (Table I). In addition, paired t tests were performed for the differences in the means of the measurements for the age ranges 16 to 18, 18 to
20, and 16 to 20 years (Table II). Relationships between the changes in selected measurements were investigated by calculation of correlation coefficients between pairs of measurements. 23 Correlation coefficients were tested for significance with Student t tests. Possible intraexaminer error resulting from landmark selection, tracing, and measurement was determined by random selection of 15 lateral cephalograms, which were retraced and remeasured. Paired t tests were carried out for all linear and. angular measurements. Results indicated that all linear and angular measurements fell within acceptable limits; that is, there was no statistical significance between original and retraced measurements. RESULTS
The values of all cephalometric measurements at the ages of 16, 18, and 20 years are given in Table I. Values for SNA, SNB, and facial axis angles indicated that the sample had a Class I skeletal pattern at all ages examined. All linear measures showed an increase from age 16 to age 20. Lower incisor angulation appeared to be higher than the cephalometric standards described by Downs 24 and Tweed. z5
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Table I. Means and standard deviations of cephalometric measurements for males at ages 16, 18, and 20 years Age 16 yr Measurements
Mean
SNA SNB ANB Facial axis Mandibular plane 1 to mandibular plane Na-ANS ANS -Me Co-A Co-Gn Co-Pog Co-Go Ar°Gn Ar-Pog Ar-Go Go-Gn Go-Pog Occlusal plane (maxilla) Occusal plane (mandible)
82.3 79.5 2.8 90.2 31.0 98.5 57.27 71.71 97.35 127.17 124.83 61.83 119.45 i 17.54 50.84 82.63 82.92 71.11 56.61
20 yr
18 yr
I
SD
Mean
3.8 3.9 1.5 4.3 6.0 6.8 3.11 6.35 4.20 4.60 4.45 4.01 4.44 4.45 3.85 3.47 3.62 4.71 8.70
82.0 79.6 2.4 90.3 30.2 97.7 57.75 72.41 98.33 129.3 ! 127.12 64.20 121.79 119.92 52.79 83.87 84.21 71.69 57.60
SD
Mean
3.6 3.7 1.8 3.8 5.8 6.4 3.42 5.42 4.30 4.00 4.09 3.39 4.13 4.21 3.89 3.78 3.99 3.87 7.67
82.8 80.4 2.4 90.6 29.5 96.8 58.12 73.78 99.51 131.54 129.22 66.02 123.46 121.44 54.33 84.59 84.83 72.42 59.26
[
SD
I
3.8 4.1 ! .7 4.0 5.9 7.0 3.50 6.53 3.95 4.50 4.53 3.57 4.46 4.64 3.59 3.72 3.85 4.49 8.66
Table II. Mean changes and paired t values of cephalometric measurements for males during three
age periods Age period 16-18 yr (n = 20) Measurements
Mean
SNA SNB ANB Facial axis Mandibular plane 1 to mandibular plane Na-ANS ANS-Me Co-A Co-Gn Co-Pog Co-Go Ar-Gn Ar-Pog Ar-Go Go-Gn Go-Pog Occlusal plane (maxilla) Occlusal plane (mandible)
0.0 0.3 - 0.3 O. I - 1.0 -0.9 0.48 1.02 1.13 2.53 2.44 2.37 2.40 2.26 2.07 1.37 1.32 0.48 1.24
*p < 0.05,
**p < 0.01, ***p < 0.001.
I
18-20 yr (n = 20)
'
Mean
0.12 1.11 2. i 6* 0.31 3.36** 2.88** 3.49** 3.70** 3.64** 5.76"** 6.51 *** 5.57*** 6.75*** 6.91 *** 6.17"** 4.06*** 3.89** 2.06* 2.80*
0.7 0.7 0.0 0.2 -0.5 - 0.8 0.65 0.78 1.18 1.59 1.73 1.67 1.28 1.29 1.26 0.61 0.57 0.95 !.35
1
16-20 yr =
' 3.33** 5.05*** 0.20 0.68 3.60** 2.87** 3.40** 3.85** 3.92*** 6.85*** 6.00*** 5.97*** 6.18"** 5.54*** 5.40*** 3.66** 3.33** 4.80*** 4.52***
3~
Mean 0.5 0.9 -0.4 0.4 - 1.6 - 1.7 0.85 2.07 2.16 4.36 4.39 4.19 4.00 3.90 3.49 1.97 1.91
1.31 2.65
2.53* 4.93*** 2.36* 1.58 8.08*** 4.02*** 4.83*** 7.07*** 7.31"** 9.45*** 10.03"** 9.42*** 9.95*** 9.77*** 10.36"** 6.36*** 6.36*** 6.48*** 7.76***
Volume 97 Number 3
Incremental changes in cephalometric values are shown in Table II. Most measures showed highly significant changes in measurement increase for each age period studied. The magnitude of the increases were generally greater from 16 to 18 years than from 18 to 20 years. In some instances the totals of the 16- to 18plus 18- to 20-year increments did not equal the overall (16- to 20-year) increase. This was due to the fact that each of the 16- to 18- and 18- to 20-year totals was derived from samples of 20, while the 16- to 20-year totals were derived from a sample of 30 subjects. Measurements of mandibular lengths (Co-Gn, CoGo, and Go-Gn) indicated that significant growth increments occurred between the age periods from 16 to 18 years and 18 to 20 years (Table II). The maximum and minimum growths (Co-Gn) recorded over the 4year period were 10.2 mm and 1.4 mm, respectively. Nine subjects exhibited mandibular growth in excess of 6 mm. Correlation coefficients calculated for all possible pairs of mandibular growth measurements (Table III) showed the strongest correlations to be between overall length increase (Co-Gn) and ramus length increase (Co-Go), where the correlations reached statistical significance at each age period. The weakest relationships were between ramus length increase (CoGn) and corpus length increase (Go-Gn). These correlations failed to reach statistical significance at any age period. The relationship between overall length increase (Co-Gn) and body length increase (Go-Gn) was intermediate, with correlations reaching statistical significance at 16 to 18 years and at 16 to 20 years. Vertical mandibular growth (Co-Go = 4.19 mm) greatly exceeded horizontal mandibular growth (Go-Gn = 1.97 mm) from 16 to 20 years of age. Growth of the mandible and maxilla (from condylion) is shown in Table IV. Growth of the mandible was greater from 16 to 18 years than from 18 to 20 years, whereas maxillary growth remained relatively constant. Between the ages of 16 and 20 years the mandible outgrew the maxilla by a ratio of approximately 2: 1. When measurements of mandibular and maxillary growth were related to the functional occlusal plane (Table V), a slightly different picture was seen. Mandibular growth remained constant whereas maxillary growth increased from the 16- to 18-year age period to the 18- to 20-year age period. Overall, the mandible still outgrew the maxilla by a ratio of approximately 2: 1, but the increases in both mandible and maxilla were substantially less than those measured from condylion. The mandibular plane angle closed an average of 1.6° over the study period (Table II), as in previous studies? ~,'9 Lower anterior face height (ANS-menton)
Facial growth ill males
203
Table III. Correlation coefficients for mandibular
length measurements at three age periods Age period Measurement
16-18 yr (n = 20)
18-20 yr (n = 20)
Co-Gn/Co-Go Co-Gn/Go-Gn Go-Gn/Co-Go
0.69*** 0.58** 0.26
0.70*** 0.24 0.18
I 16-20 yr I (n =30) 0.80*** 0.63*** 0.29
*p < 0.05, **p < 0.01, ***p < 0.001.
Table IV. Co-Gn and Co-A growth for three
age periods Age period
Co-Gn (mm) Co-A (mm) Difference (mm)
16-18 yr (n = 20)
18-20 yr (n = 20)
2.53 1.13 1.40
1.59 1.18 0.41
I
16-20 yr (n = 30) 4.36 2.16 2.20
Table V. Maxillary and mandibular growth
along the occlusal plane for three age periods Age period 16-18 yr (n = 20) Mandible (mm) Maxilla (mm) Difference (mm)
1.24 0.48 0.76
I
18-20yr 01 = 20) 1.34 0.95 0.39
I
{ 16-20 yr } (n = 30) 2.65 1.3 I 1.34
increased 2.07 mm from 16 to 20 years of age while posterior face height (Co-Go) increased 4.36 mm, a rate more than double that of the anterior face height. Lower incisors tipped lingually with respect to the mandibular plane an average of 1.7 ° from 16 to 20 years of age (Table II). Calculation of correlation coefficients for the degree of incisor tipping to overall mandibular length (Co-Gn) and maxillary and mandibular growth measured along the occlusal plane showed that no significant relationship existed between the variables (Table VI). The only significant correlation was shown between incisor tipping and the maxillary-mandibular growth differential from 16 to 18 years of age. Values of correlation coefficients and mean differences in mandibular length increments measured from
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Am. J. Orthod. Dentofac. Orthop. March 1990
Table VI. Correlation coefficients and mean differences for the comparison of some cephalometric
measurements for three age periods Age period 16-18 yr (n = 20) I
18-20 yr (n = 20)
Measurement to comparison
r
Mean difference
r
Co-Gn/Ar-Gn Co-Go/Ar-Go Co-Pog/Ar-Pog Co-Gn/Co-A Occlusal plane (maxilla/mandible) I-MP/Co-Gn l-MP/occlusal plane (maxilla) l-MP/occlusal plane (mandible) l-MP/occlusal plane (mandible-maxilla)
0.89*** 0.80*** 0.86*** 0.71"** 0.86*** 0.37 0.10 0.22 0.87***
0.12 0.30 0.17 1.39 0.76 -----
0.70*** 0.68*** 0.66*** 0.55* 0.67*** 0.07 0.16 0.19 0.1l
Mean difference 0.31 0.41 0.44 0.41 0.40
16-20 yr (n = 30) Afean
r
difference
0.87*** 0.79*** 0.84*** 0.52** 0.64*** 0.23 0.13 0.30 0.28
0.36 0.70 0.49 2.20*** 1.34"**
*p < 0.05, **p < 0.01, ***p < 0.001.
condylion and articulare are given in Table VI. Most of the mean differences were not statistically significant, and all correlation coefficients were highly significant (p < 0.001) for all age periods. These results indicated that condylion and articulare may be used interchangeably to record incremental mandibular length changes, at least from 16 to 20 years of age. DISCUSSION
The findings of this study on mandibular growth and maxillomandibular relationships provide further information about craniofacial changes in postpubertal adolescents and adults to supplement data already published from previous investigations.~4"~s'2s2s Values found for mandibular length (Co-Gn) were less than those reported at equivalent ages by Woodsidefl 8 possibly because of a difference in radiographic technique (i.e., lateral cephalogram versus 45 ° lateral oblique). In contrast, data from this study show that the Burlington sample exhibits greater mandibular lengths than the samples of either Behrents '4 or Bishara and Jakobsen.~7 These differences may be due to sample selection or inherent sample variability, although it is quite possible that they are a result of variable radiographic enlargement factors. Cephalometric standards, such as those published by Riolo et al.,2° Bishara,,5 and Behrents, ~4may have more than one enlargement factor because of changes in equipment or technique over the course of the study, making data comparisons within and between studies inaccurate. It is apparent from the data (Table II) that significant changes occur in the craniofacial skeleton after the age
of 16. Statistical significance was achieved for all linear dimensions measured at each age period. Overall mandibular length (Co-Gn) increased an average of 4.36 mm over the 4-year study period (Table II). The increase was much larger than that determined by Behrents ~ in his study of 84 boys at the age of 17 years and 39 men at the age of 83 years. Behrents found statistically significant mandibular length increases up to the age of 35 years and nonsignificant changes after the age of 40 years. The average increase in mandibular length from age 17 to age 83 was 2.7 mm. Mandibular length in our study exceeded that in Behrents' study (3.4 mm at age 18 and 3.8 mm at age 20). In Behrents' sample, however, 23% of the subjects had Class II malocclusion. Results reported by Buschang et al. 29 indicated that the inclusion of Class II malocclusions would certainly reduce the mandibular length found at each age but would not affect incremental values between ages. Mandibular growth was twice the amount of maxillary growth, whether measured fro m condylion or along the occlusal plane. More mandibular growth occurred between the ages of 16 and 18 years than between 18 and 20, whereas maxillary growth was constant in both age periods. A steady rate of maxillary growth has been previously noted by Linder-Aronson et al. 3° MitanP ~ found synchronicity in the timing and rate of maxillary and mandibular growth in 60% of his sample of 30 children. Similarly, Jamison et alfl 2 found that the maxillary-mandibular relationship remained constant between the ages of 8 and 17 years. The high correlation coefficients for maxillary and mandibular
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Number 3
incremental changes in this study also indicated a relationship between maxillary and mandibular growth rates. Such a relationship would be expected when a balanced facial pattern is maintained. The mandibular plane angle closed 1.6 ° between the ages of 16 and 20 years. This is in agreement with the findings of Bjork and Skieller, 33 Bishara, 15 Behrents, '4 and Sinclair and Little ~9 but disagrees with the findings of Forsberg. 28 Forsberg found that the mandibular plane angle increased 0.26" in men from the age of 24.9 years to the age of 35.2 years. Upward and forward rotation was a constant finding in this investigation; 26 of 30 persons showed a reduction in the mandibular plane angle, whereas in 4 persons the mandibular plane angle remained constant. The reduction in mandibular plane angle occurred despite a concomitant increase in anterior face height. It appears most likely that this reduction was the result of the differential increase between posterior and anterior face height (4.19 and 2.92 mm, respectively) over the study period. Greater posterior vertical growth would result in a lowering of the gonion region and subsequent upward and forward mandibular rotation. The greater rate of growth in posterior face height compared to anterior face height in postpubertal samples can be seen in the data of other longitudinal studies. 14.16.19.34The greater rate of posterior versus anterior growth appears to be a reversal of the trend seen before and during puberty in which anterior face height increases more rapidly than posterior face height) 6'~9 Lavergne and Gasson J5 and Isaacson et al. 36 concluded mandibular rotation was a result of disproportionate growth. Lavergne and Gasson 35 found a high degree of upward and forward rotation when mandibular growth exceeded maxillary growth, a situation that was found in all but two of the subjects in this study. The decrease in lower incisor angulation to the mandibular plane does not appear to be a universal occurrence and is probably sample specific. Bjork and Skieller 33 and Perera 37 found lower incisor angulation to be functionally stable, the angulation remaining constant. Forsberg 28 and Behrents '4 found lower incisors proclined with increasing age. Retroclination of lower incisors would result in loss of arch length and subsequent crowding. This possibility coincides with what is seen clinically in many posttreatment orthodontic cases. In this study, change in incisor angulation was not correlated with growth of the mandible or of the maxilla (Table VI) but showed a high correlation with the maxillomandibular growth differential from age 16 to age 18. The low correlations overall and between the ages of 18 and 20 leave some doubt whether differential jaw growth causes lingual tipping of incisors.
The cause is probably multifactorial in nature, with differential growth one of the factors. Incisor inclination at the age of 16 (Table I) was greater than that given as a cephalometric norm by Downs 2~ and Tweed. 25 However, the lower incisor angulation found in this study was in agreement with the findings of other investigations. ~5.~9.2o Measurements of mandibular linear incremental changes from condylion and articulare were found to be equivalent. It may be impossible to locate condylion on lateral cephalograms taken with teeth in occlusion, and very few lateral cephalograms are taken with the mouth wide open. Although this study did not measure positional changes in articulare the data support the conclusions of Agronin and Kokich 38 that remodeling or displacement of arficulare is reflected in changes in the glenoid fossa. SUMMARY AND CONCLUSIONS
1. Cephalometric measurements at each age indicated that the Class I skeletal pattern was maintained throughout the study period. Comparison of mandibular length measurements to norms from other studies revealed significant differences, which may be attributable to sample dissimilarity, radiographic enlargement, or both. 2. The rate of change of mandibular measurements was significant at each age interval. However, a much greater rate of change was seen from 16 to 18 years than from 18 to 20 years. Growth rates for this study did not agree with some previous studies. 3. Mandibular growth was greater than maxillary growth at each age interval when measured by either of two methods. A larger differential was seen from 16 to 18 years than from 18 to 20 years. Despite the fact that the magnitude of maxillary and mandibular growth after the age of 16 years did not approach previously reported pubertal levels, growth of both jaws was significant and may need to be assessed in orthodontic treatment planning. 4. The mandibular plane angle was significantly reduced, indicating a upward and forward rotational growth pattern. Forward rotation was thought to be brought about by disproportionate anteroposterior vertical growth. 5. Lower incisors were found to retrocline with increasing age. The degree of tipping was not found to be consistently related to maxillary or mandibular growth or to the difference between them. However, these results indicate that orthodontically treated patients retention may be advisable for extended periods of time, perhaps to the age of 20 years and beyond in male patients.
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Love, .._:Murray, atzd Mamandras
6. M a n d i b u l a r i n c r e m e n t a l c h a n g e s m e a s u r e d f r o m a r t i c u l a r e w e r e e q u i v a l e n t to t h o s e m e a s u r e d f r o m c o n dylion. The two landmarks could be used interchangea b l y for g r o w t h d e t e r m i n a t i o n s . We wish to thank Drs. F. Mader, P. QuigIey, R. Thompson, J. Wanklin for their help in this project and Susan Minelli and Aura Hidalgo for typing the manuscript.
REFERENCES 1. Meredith H. Serial study of change in a mandibular dimension during childhood and adolescence. Growth 1961;25:229-42. 2. Bergerson EO. The directions of facial growth from infancy to adulthood. Angle Orthod 1966;36:18-43. 3. Bergerson EO. The male adolescent growth spurt: its prediction and relation to skeletal maturation. Angle Orthod 1972;42:31938. 4. Hunter CJ. The correlation of facial growth with body height and skeletal maturation at adolescence. Angle Orthod 1966; 36:44-54. 5. Savara BS, Tracy WE. Norms of size and annual increments for five anatomical measures of the mandible in boys from three to sixteen years of age. Arch Oral Biol 1967;12:469-86. 6. Odegaard J. Growth of the mandible studied with the aid of metal implant. AM J ORTttOD 1970;57:145-57. 7. RickettsRM. Aprincipalofarcialgrowthofthemandible. Angle Orthod 1972;42:368-86. 8. Cross JJ. Facial growth: before, during, and following orthodontic treatment. AM J OR'ntOD 1977;71:68-78. 9. Matthews RJ, Ware WH. Longitudinal mandibular growth in children with tantalum implants. AM J ORTttOD 1978;74:633-55. I0. Bishara SE, Jamison JE, Peterson LC, DeKock WH. Longitudinal changes in standing height and mandibular parameters between the ages of 8 and 17 years. AM J ORntOD 1981;80:11535. 11. Lewis AB, Roche AF, Wagner B. Growth of the mandible during pubescence. Angle Orthod 1982;52:325-42. 12. Singer J. Posttreatment change: a reality. AM J OR'ntOD 1975;67:277-89. 13. Bjork A. Variations in the growth pattern of the human mandible: longitudinal radiographic study by the implant method. J Dent Res 1963;42:400-11. 14. Behrents RG. An atlas of growth in the aging craniofacial skeleton. Monograph 18. Ann Arbor, Michigan: University of Michigan Center for Human Growth and Development, 1985. 15. Bishara SE. Longitudinal cephalometric standards from 5 years of age to adulthood. A.',t J OR'trOD 1982;79:35-44. 16. Bishara SE, Peterson LC, Bishara E. Changes in facial dimensions and relationships between the ages of 5 and 25 years. AM J ORTttOD 1984;85:238-52. 17. Bishara SE, Jakobsen JR. Longitudinal changes in three normal facial types. AM J OR'ntOD 1985;88:466-502. 18. Woodside DG. Distance, velocity and relative growth rate standards for mandibular growth for Canadian males and females aged three to twenty years [American Board of Orthodontics thesis]. St. Louis: Library of American Association of Orthodontists, 1969. 19. Sinclair PM, Little RM. Dentofacial maturation of untreated normals. A.',t J ORTiIOD 1985;88:146-56.
Am. J. Orthod. Dentofac. Orthop. March 1990
20. Riolo ML, Moyers RE, McNamara JA, tIunter WS. An atlas of craniofaeial growth: cephalometric standards from the University School Growth Study, the University of Michigan. Monograph 2. Ann Arbor, Michigan: University of Michigan Center for Human Growth and Development, 1974. 21. Behrcnts RG. Growth in the aging craniofacial skeleton. Monograph 17. Ann Arbor, Michigan: University of Michigan Center for ttuman Growth and Development, 1985. 22. Popovich F, Thompson GW. Craniofacial templates for orthodontic case analysis. In: Clark JW, ed. Clinical dentistry; vol. 2. New York: Harper and Row, 1983:1-24. 23. Snedecor GW, Cochran WG. Statistical methods. Iowa City: Iowa State University Press, 1971. 24. Downs WB. The role of cephalometrics in orthodontic case analysis and diagnosis. AM J ORTItOD 1948;38:i62-82. 25. Tweed C. Clinical orthodontics. Vol 1. St. Louis: CV Mosby, 1966. 26. Bjork A, Palling M. Adolescent age changes in sagittal jaw relation, alveolar prognathy, and incisal angulation. Acta Odontol Scand 1955;12:201-32. 27. Christie TE. Cephalometric patterns of adults with normal occlusion. Angle Orthod 1977;47:i28-35. 28. Forsberg CM. Facial morphology and aging: a longitudinal cephalometric investigation of young adults. Eur J Orthod 1979; 1:1523. 29. Buschang PH, Tanguay R, Turkewicz J, Demirjian A, La Palme L. A polynomial approach to craniofacial growth: description and comparison of adolescent males with normal occlusion and those with untreated Class 11 malocclusion. AM J OR'rnODDENTOFACORTItOP 1986;90:437-42. 30. Linder-Aronson S, Woodside DG, Daigle DJ. A longitudinal study of the growth in length of the maxilla in boys between ages 6-20 years. Trans Eur Soe Orthod 1976;169-79. 31. Mitani H. Occlusal and craniofacial growth changes during pubetty. AM J ORTItOD 1977;72:76-84. 32. Jamison JE, Bishara SE, Peterson LC, Kremenak CR. Longitudinal changes in the maxilla and the maxillary-mandibular relationship between 8 and 17 years of age. AM J OR'moP 1982;82:217-30. 33. Bjork A, Skieller V. Facial development'and tooth eruption: an implant study at the age of puberty. AM J ORTItOD 1972;62:33983. 34. Knott V. Growth of the mandible relative to a cranial base line. Angle Orthod 1973;43:305-13. 35. Lavergne J, Gasson N. A metal implant study of mandibular rotation. Angle Orthod 1976;46:144-50. 36. Isaacson RJ, Zapfel RJ, Worms FW, Bevis RR, Speidel TM. Some effects of mandibular growth on the dental occlusion and profile. Angle Orthod 1977;47:97-106. 37. Perera PSG. Rotational growth and incisor compensation. Angle Otthod 1987;57:39..49. 38. Agronin KJ, Kokich VG. Displacement of the glenoid fossa: a cephalometric evaluation of growth during treatment. AM J ORTIIOD DENTOFACORTIIOP 1987;91:42-8. Reprint requests to: Dr. A.H. Mamandras Division of Orthodontics Faculty of Dentistry The University of Western Ontario London, Ontario, Canada N6A 5C1