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Craniofacial changes in Class III malocclusion as related to skeletal and dental maturation

Craniofacial changes in Class III malocclusion as related to skeletal and dental maturation



American Journal of Orthodontics and Dentofacial Orthopedics, 2007-08-01, Volume 132, Issue 2, Pages 171.e1-171.e12, Copyright © 2007 American Association of Orthodontists


Introduction: In this large cross-sectional study, we aimed to analyze growth trends in white subjects with Class III malocclusion using both skeletal and dental maturation staging. Methods: The sample consisted of 1091 pretreatment lateral cephalometric records of Class III patients (560 female, 531 male). Cephalometric dentoskeletal measurements were compared at subsequent stages in cervical vertebral maturation and Hellman’s categorization of dental development by means of ANOVA with Bonferroni post-hoc tests in both sexes separately. Results: The findings indicated that, in Class III malocclusion, the pubertal peak in mandibular growth occurs between stages 3 and 4 of cervical vertebral maturation, with average increases in total mandibular length of about 8 and 5.5 mm in Class III boys and girls, respectively. Conclusions: Significant changes in total mandibular length occur until young adulthood (18 years on average), with increases between late maturation stages (4 through 6) that were twice as large as in subjects with normal occlusion for the Class III females, and 3 times as large as in subjects with normal occlusion for the Class III males. Growth trends toward accentuated Class III profile and increased vertical dimension of the face also become apparent at late developmental stages (corresponding with complete eruption of the second and third molars).

In spite of its relatively low prevalence, Class III malocclusion is a challenging orthodontic problem. Information on growth trends in Class III patients is needed for both effective treatment planning and reasonable expectations in terms of stability of treatment outcomes. A better understanding of the amount and direction of growth in Class III patients also comes into play when deciding between orthodontic and surgical approaches to the malocclusion.

Several investigators have attempted to contribute to the knowledge of Class III facial growth trends by assembling groups of orthodontically untreated Class III subjects as control groups when evaluating treatment effects. Investigators evaluating predominantly Asian populations have led the way. Longitudinal data on Class III subjects of European ancestry have become available only within the last decade. The annualized changes as reported in these studies indicate that the rate of maxillary growth in Class III malocclusion during developmental ages is lower than expected for normal subjects (less than 1 mm per year), and that mandibular growth is 3 to 4.5 mm per year. These longitudinal studies were limited in either sample size or observation interval, or both; this unfortunately restricts their applicability to Class III subjects meeting the same inclusion criteria.

Other investigations focused on data collected from many Class III subjects at a single time and used these to make inferences on average craniofacial growth. An example of this type of study is that of Guyer et al, who attempted to characterize Class III patients at various developmental stages by studying lateral cephalograms of 144 Class III children between 5 and 15 years of age. The sample was divided into 4 groups according to chronological age; the authors compared this sample with children with normal occlusions and well-balanced faces (the so-called Bolton standards). The investigators reported that the differences in craniofacial form between Class I and Class III subjects were present in all 4 age groups. Similar results were described by Tollaro et al, who investigated early Class III craniofacial development in untreated European Class III children between the ages of 4 and 6 years with full deciduous dentitions.

The craniofacial characteristics of a sample of 285 white Class III subjects were contrasted with 210 normal controls by Battagel. Boys and girls were examined separately in 4 age groups: 7 to 10 years, 11 to 12 years, 13 to 14 years, and 15 years and older. Class III boys in all age groups had retrusive maxillary positions and protrusive mandibular positions relative to the controls. The girls had a different growth pattern. Relative to the controls, they had more prominent mandibles and more proclined maxillary incisors. The sex differences in Class III malocclusion were highlighted recently by Baccetti et al.

The largest cross-sectional Class III study to date was conducted by Miyajima et al with a sample of 1376 Japanese female subjects, 2.7 to 47.9 years of age. The sample was organized into groups based on the stage of dental development described by Hellman. The maxilla exhibited a retrusive position at an early developmental stage and retained a fairly constant anteroposterior relationship to the cranial base structures with continued development. Likewise, the mandible was protrusive early in development and became increasingly prognathic with age. Recently, Deguchi et al used a large cross-sectional sample (562 subjects) as a control group in a long-term study on the effects of chincup therapy in Asian patients with Class III malocclusion. Three age periods were investigated (8, 13, and 17 years), with no differentiation between boys and girls. Both ANB angle and the Wits appraisal worsened with growth, mainly due to continuous mandibular advancement relative to the maxilla.

The cross-sectional study by Battagel gives additional information about the growth characteristics of Class III patients. The author emphasized that the largest increments for mandibular length in the male subjects were at the oldest age interval (15 years and older), indicating peak growth at this late age period. The female samples showed that the maximum changes in facial characteristics occurred between the average ages of 11 and 12 years but continued after age 15. In the control female group at age 14 to 17 years, facial growth had ceased, but development remained active in the Class III group.

Both classical and more recent studies on mandibular growth in normal subjects have shown that mandibular growth decreases significantly after the pubertal peak, and atlases on craniofacial growth show clearly that increases in facial measurements are limited after 15 years of age, particularly in girls. These data suggest that growth trends in Class III malocclusion might differ from those of subjects with normal facial and occlusal developmental patterns, because peak growth occurs rather late, and relatively high rates of growth persist until young adulthood. The significant increase in mandibular length described by Deguchi et al in Class III subjects from 13 through 17 years of age provides additional evidence in this regard.

No previous investigation, however, analyzed a large enough cross-sectional set of white Class III subjects to derive an estimate of growth during the developmental ages in boys and girls separately by using a reliable indicator of skeletal maturity. Recently, the cervical vertebral maturation (CVM) method has gained popularity because of its validity in assessing skeletal maturation during the circumpubertal period and in detecting the growth spurt (interval between cervical stage 3 (CS3) and cervical stage 4 (CS4), according to the most recent version of the method ). Another method for categorization of development during the circumpubertal ages is the appraisal of dental stages according to Hellman, as used in the study by Miyajima et al.

Our aim in this study was to evaluate craniofacial dimensions in Class III subjects at various stages of skeletal maturity as assessed with the CVM method and Hellman’s dental stages. The goal was to estimate the amount of growth at prepubertal, pubertal, and postpubertal ages in a large sample of subjects with Class III disharmony, information that would be valuable for diagnosis and treatment planning for this type of malocclusion.

Material and methods

The parent sample consisted of 1549 pretreatment lateral cephalometric records of white Class III patients collected from 12 private orthodontic practices in Michigan and Ohio, the University of Michigan Graduate Orthodontic Clinic, and the Department of Orthodontics of the University of Florence in Italy.

To be included in the final group, patients had to satisfy all of the following inclusionary criteria: (1) white ancestry; (2) no orthopedic or orthodontic treatment before the cephalogram was taken; (3) diagnosis of Class III malocclusion (anterior crossbite with every attempt to exclude pseudo crossbites, edge-to-edge incisal relationship, accentuated mesial step relationship of the deciduous second molars, and permanent first molar relationship of at least one half cusp Class III); and (4) no congenitally missing or extracted teeth.

The final sample of 1091 subjects with Class III malocclusion met the inclusionary criteria. The sample consisted of 560 females and 531 males. The female age range was 3 years 6 months to 57 years 7 months. The male group ranged from 3 years 3 months to 48 years 5 months.

The lateral cephalograms of the Class III subjects were staged according to the CVM method. It comprises 6 stages (CS) from CS1 through CS6. In white subjects with normal occlusion, the growth spurt occurs between CS3 and CS4. One investigator (B.C.R.) assessed the stages on all patient films. That evaluation was verified by another investigator (T.B.).

Hellman defined 5 main stages of dental development and, within each stage, 3 possible subcategories denoting the eruption status of the tooth in question. Subdivision A describes a completely erupted tooth, clinically present in the mouth. Subdivision B is when the deciduous teeth are shed and the permanent successors begin to erupt. Subdivision C is the beginning of eruption of a molar. In our study, we adapted Hellman’s original method and combined a few of the main categories, because of small sample sizes. The untreated Class III subjects therefore were classified into 5 developmental groups ( Table I ).

Table I
Dental developmental stages
Stage 2A/C Eruption of deciduous molars/permanent incisors and beginning of first molars
Stage 3A Eruption of permanent first molars complete
Stage 3B Eruption of permanent canines and premolars
Stage 3C Beginning of eruption of permanent second molars
Stage 4/5A Eruption of permanent second molars complete/eruption of third molars

The eruption status was not clear in some films in the radiographic sample. A definitive dental developmental stage could be established for 520 of the 560 females and 495 of the 531 males in this study.

Lateral cephalograms were hand traced by using 0.003-in matte acetate and a sharpened 2H lead drafting pencil. All cephalograms were traced by 1 of 2 investigators (B.C.R. and A.L.), and landmark identification was verified by a third (J.A.M.). Any disparities were addressed by retracing the structure. The descriptive cephalometric analysis required the digitization of 71 landmarks on each tracing. A cephalometric analysis including measures adopted from the analyses of Steiner, Jacobson, Ricketts, and McNamara was performed on each tracing.

Statistical analysis

With the sample categorized according to indexes of skeletal maturity (6 stages of CVM) and dental stages (5 stages from Hellman’s original method), descriptive statistics for the cephalometric measurements were calculated for each stage group by sex. The data were analyzed with a commercial social science statistical package (SPSS for Windows, version 12.0, SPSS, Chicago, Ill).

Initially, sex differences were tested by using the Hotelling T 2 test to see whether the differences between the sexes were significant with respect to the cephalometric measurements. The results indicated significant differences and dictated that male and female groups should be analyzed separately, thus confirming previous data. Consequently, 1-way analysis of variance (ANOVA) was used to identify significant differences ( P <.05 and P <.01) between the means for each cephalometric variable in consecutive developmental groups. The Bonferroni correction assisted in the identification of significant differences. In spite of the cross-sectional nature of this study, the terms “increase” and “decrease” will be used in the Results and Discussion sections to depict positive and negative differences, respectively, because these terms are more reader-friendly.

The error of the method for the cephalometric measurements was evaluated by repeating the measures in 100 randomly selected cephalograms. Errors were on average 0.6° for angular measurements and 0.9 mm for linear measurements.

Results

Analysis of CVM stages

In the female subjects, no statistically significant difference for any cephalometric variable was assessed in the transitions from CS1 to CS2 and CS2 to CS3. The comparison between CS3 and CS4 showed significant increases for total mandibular length (Co-Gn), maxillomandibular differential, lower anterior facial height (ANS-Me), and dentoalveolar height at the maxillary molar (U6-PP). The same comparisons were significant for the transition from CS4 to CS5. In addition to the same significant comparisons, during the transition from CS5 to CS6, the increases in upper anterior facial height (N-ANS), extrusion of the maxillary (U1-ANS) and mandibular (L1-Me) incisors, as well as the protrusion of the lower lip in relation to the E-plane (LL-E plane) became significant ( Table II [online, go to www.mosby/AJODO/com ], Figs 1-3 ).

Table II
Descriptive statistics and comparison of craniofacial measurements at subsequent stages in CVM (CS)
Females CS1 (n = 167) CS2 (n = 51) CS3 (n = 60) CS4 (n = 85) CS5 (n = 90) CS6 (n = 107) 1 vs 2 2 vs 3 3 vs 4 4 vs 5 5 vs 6
mean age: 8 y 2 mo mean age: 10 y 8 mo mean age: 11 y 8 mo mean age: 12 y 10 mo mean age: 14 y 1 mo mean age: 17 y 2 mo
X SD X SD X SD X SD X SD X SD
Cranial base
SNFH (°) 8.9 2.9 9.5 2.7 8.6 3.1 9.8 2.8 9.2 3 9.1 2.9 NS NS NS NS NS
S-N (mm) 67.9 3.5 68.5 3.5 70.2 4.3 71.1 3.4 71.5 3.6 72.4 3.6 NS NS NS NS NS
Cranial flexure (°) 121.8 5.4 122 4.9 123.1 5.2 122.9 5.4 123.2 5.5 123 5.6 NS NS NS NS NS
Maxillary skeletal
SNA angle (°) 80.3 3.3 80.2 3.9 80 4.6 79.8 3.1 81 3.9 80.7 3.6 NS NS NS NS NS
PtA to NaPerp (mm) −0.7 2.6 −0.3 3.6 −1.4 3.5 −0.5 3.2 0.2 3.7 −0.4 3.7 NS NS NS NS NS
PP-FH (°) −0.5 3.2 −1.1 3.2 −0.1 4.1 −1 3.3 −0.4 2.9 0.5 3.9 NS NS NS NS NS
Co-Pt A (mm) 82.1 4.5 83.3 4.6 86.3 5.9 88.7 5.2 90.5 5.1 90.4 4.7 NS NS NS NS NS
Mandibular skeletal
SNB angle (°) 79.4 3.2 79.9 3.5 79.8 3.7 79.7 3.1 80.9 3.7 81.2 3.6 NS NS NS NS NS
Pog-Na Perp (mm) 0.4 1.2 0.9 1.4 1.4 2.5 1.5 1.6 1.5 1.8 2.4 1.8 NS NS NS NS NS
Facial angle (°) 88.5 2.9 90 3.5 89.1 3 90.3 3 90.9 3 91.4 3.4 NS NS NS NS NS
Co-Gn (mm) 106.4 6.3 109.4 6.5 113.3 7.7 118.8 7.8 122.7 6.7 126.7 6.2 NS NS
Maxillary/mandibular
MPA (°) 25.9 4.3 24.7 5 25.7 4.9 26.9 5.6 25.8 5.4 25.7 5.6 NS NS NS NS NS
ANB angle (°) 0.9 2.2 0.3 2 0.2 2.7 0.1 2 0.1 2.2 −0.5 3 NS NS NS NS NS
Wits (mm) −4.2 2.5 −4.6 2.4 −4.9 2.8 −5 2.8 −5.1 2.9 −5.7 4.1 NS NS NS NS NS
Mx-Md diff (mm) 24.4 3.9 26.1 3.5 27.1 3.9 30.1 4.3 32.3 4.6 36.3 4.6 NS NS
Molar relation (mm) −3.9 1.7 −4.1 1.8 −4.2 2 −5.1 1.5 −5.5 1.9 −6.1 2.5 NS NS NS NS NS
Vertical
Nasion to ANS (mm) 47.2 3.8 48.4 3.2 50.4 3.6 52.2 3.1 53.2 3.4 55.1 3.7 NS NS NS NS
ANS to Me (mm) 60.3 4.6 60.8 5 62.6 4.7 66.3 5.6 68.4 5.7 71.2 5.9 NS NS
UFH/LAFH ratio 82.4 7.2 83.2 7.9 83.9 6.4 82.5 7.2 80.9 7.3 80.4 7.9 NS NS NS NS NS
U1-ANS (mm) 24.5 2.7 25 2.8 25.6 3 27.8 3.6 25.5 2.9 29.6 3.1 NS NS NS NS
U6-PP (mm) 18.3 2 19.4 2.2 19.8 2.2 22 2 23.6 2.2 25.5 2.4 NS NS
L1-Me (mm) 36.2 2.4 36.3 2.3 37.5 2.8 38.9 2.6 40 3 41.3 3.2 NS NS NS NS
Dentoalveolar
U1-Pt A (mm) 1.1 2.7 2.2 2.4 2.9 1.9 3.3 2.3 4.3 2.4 4 2.9 NS NS NS NS NS
U1-SN (°) 100.3 9 103.3 8.5 105 5.6 103.3 5.4 106.3 6.5 105 7.2 NS NS NS NS NS
IMPA (°) 88.2 7 87.6 6.7 88 8.4 84 6.3 85.8 7.6 83.9 8.3 NS NS NS NS NS
FMIA (°) 65.9 6.9 67.7 6.9 66.3 8.8 68.9 6.9 68.4 8.1 70.4 8.4 NS NS NS NS NS
L1-A Pog (mm) 3 1.9 2.8 2 3.3 2.7 2.8 2.4 3.5 2.6 3.2 2.6 NS NS NS NS NS
Interincisal angle (°) 136.6 11.7 134.9 11.2 132.6 8.8 135.9 9.2 132.9 11.7 136.3 10.8 NS NS NS NS NS
Soft tissue
UL-E plane (mm) −4 2.3 −4.3 1.8 −5.1 2.3 −5.5 2.6 −6.4 2.7 −8.0 2.9 NS NS NS NS NS
LL-E plane (mm) −0.7 2.4 −1 2.2 −1.6 2.7 −2.1 2.5 −2.4 3 −4 2.9 NS NS NS NS
Nasolabial angle (°) 112.4 12.8 112.8 11.8 112.2 14.9 111 12.2 109.7 12.3 109.8 12 NS NS NS NS NS
Cranial base
SNFH (°) 8.3 2.7 8.2 3.6 8.5 3.1 9.2 2.5 8.6 2.7 7.7 3.5 NS NS NS NS NS
S-N (mm) 71.2 3.6 71.8 3.5 71.8 3.6 73.7 3.6 76 3.9 77.3 4.2 NS NS NS NS NS
Cranial flexure (°) 121 4.7 121.1 5.4 122.1 4.8 122.3 4.6 122.9 5.2 121.8 6 NS NS NS NS NS
Maxillary skeletal
SNA angle (°) 80.2 3.7 80.5 3.6 79.3 4.5 81 3.5 81.8 4.6 81.1 4.4 NS NS NS NS NS
PtA to NaPerp (mm) −1.4 2.8 −1.3 2.8 −2.3 4.2 −0.8 3.2 −0.3 4.4 −1.5 4.6 NS NS NS NS NS
PP-FH (°) −0.5 3.2 −0.2 2.8 0.3 3.4 0.0 3.2 0.8 3.5 0.9 4.4 NS NS NS NS NS
Co-Pt A (mm) 84.8 4.6 86.1 5 87.8 4.8 89.1 4.1 92.3 6.3 94.1 5.6 NS NS NS NS NS
Mandibular skeletal
SNB angle (°) 79.5 3.5 80 3.2 79.4 3.2 80 3.1 80.5 3.8 82.4 4.5 NS NS NS NS NS
Pog-Na perp (mm) 0.3 1.2 0.7 0.9 0.8 1.3 1.2 1.6 1.3 1.3 2.9 2.1 NS NS NS NS
Facial angle (°) 88 2.9 88.5 2.6 88.4 2.7 89.9 2.8 89.7 3.7 91.4 4 NS NS NS NS NS
Co-Gn (mm) 111.3 6.2 114.4 6.6 116.5 7.3 124.2 5.9 130.5 6.5 137.7 8.4 NS NS
Maxillary/mandibular
MPA (°) 26.5 4.5 26.5 5 27.5 4.5 27.2 4.5 27.2 5.4 25.4 6.1 NS NS NS NS NS
ANB angle (°) 0.7 2.2 0.5 2.3 −0.1 2.7 0.9 2.5 1.2 2.5 −1.3 2.8 NS NS NS NS
Wits (mm) −4.4 2.4 −4.6 2.6 −5.3 2.7 −4.4 3 −3.7 3.7 −5.9 4.5 NS NS NS NS
Mx-Md diff (mm) 25.3 3.8 27.3 3.8 29.3 4.1 32 4.1 32.2 4 41 6 NS NS NS
Molar relation (mm) −3.8 1.7 −4.1 1.9 −4.4 2.2 −6.1 3 −6.4 1.9 −6.9 3.6 NS NS NS NS
Vertical
Nasion to ANS (mm) 48.4 3.4 50.4 4.9 51.9 4.2 55.9 3.3 57 3.6 58.7 4.3 NS NS NS NS
ANS to Me (mm) 62.6 4.9 64.9 5.2 66.9 5.5 71 5.5 74.7 6.8 77.6 6.6 NS NS NS
UFH/LAFH ratio 81.3 6.8 81.4 7.5 81.3 7.9 82.3 6.9 80.1 6.8 78.7 7.6 NS NS NS NS NS
U1-ANS (mm) 25.6 2.9 26.8 3.1 27.6 3.4 29.3 2.9 30.2 3.5 31.2 3.5 NS NS NS NS NS
U6-PP (mm) 19.1 2.3 20.7 2.8 21.9 2.8 23.9 2.5 25.8 2.9 27.9 3.2 NS NS NS
L1-Me (mm) 37.9 2.6 39 2.5 39.6 3 42.1 3.1 44.1 3.3 45.6 3.3 NS NS NS
Dentoalveolar
U1-Pt A (mm) 0.7 2.4 1.7 2.6 2.3 2.3 3.6 2.5 3.8 2.6 4.4 2.1 NS NS NS NS NS
U1-SN (°) 99.7 8.8 102.1 6.9 102.4 6.4 103.9 6.3 105.1 6.4 106.1 7.9 NS NS NS NS NS
IMPA (°) 87.3 6.3 86.2 7.3 85.8 6 85.9 7.3 85.3 7.1 83.6 6.9 NS NS NS NS NS
FMIA (°) 66.2 6.3 67.3 6.8 66.7 6.2 66.9 8.2 67.4 7.6 71 7.7 NS NS NS NS NS
L1-A Pog (mm) 3.1 1.7 3.3 2 3.6 2.2 3.6 2.5 3.3 2.4 3.7 2.9 NS NS NS NS NS
Interincisal angle (°) 138.2 11.6 137 10.2 135.8 8.7 133.8 9.8 133.7 9.3 137.2 10.4 NS NS NS NS NS
Soft tissue
UL-E plane (mm) −3.3 2.2 −4.1 2.4 −4.3 2.7 −5 2.7 −6.3 2.7 −8.1 3.4 NS NS NS NS NS
LL-E plane (mm) 0.1 2.3 −1 2.4 −0.7 3.2 −1.3 2.9 −1.9 3.4 −4 2.9 NS NS NS NS
Nasolabial angle (°) 112.4 12.7 114.2 15.5 114.5 12.5 116.2 9.8 111.6 9.7 106.7 12.8 NS NS NS NS NS
NS , Not significant; X , mean; Mx , maxillary; Md , mandibular; diff , difference.

P <.05;

P <.01.

Average differences between CVM stages for midfacial length in Class III subjects.
Fig 1
Average differences between CVM stages for midfacial length in Class III subjects.

Average differences between CVM stages for mandibular length in Class III subjects.
Fig 2
Average differences between CVM stages for mandibular length in Class III subjects.

Average differences between CVM stages for lower anterior facial height in Class III subjects.
Fig 3
Average differences between CVM stages for lower anterior facial height in Class III subjects.

As with the female groups, no statistically significant difference for any cephalometric variable was assessed in the males in the transitions from CS1 to CS2 and CS2 to CS3. The comparison between CS3 and CS4 showed significant increases for total mandibular length (Co-Gn), maxillomandibular differential, upper and lower anterior facial heights (N-ANS and ANS-Me), and dentoalveolar height at the maxillary molar (U6-PP) and mandibular incisor (L1-Me). A significant decrease was recorded for the molar relationship. During the transition from CS4 to CS5, significant increases were found for total mandibular length (Co-Gn), upper and lower anterior facial heights (N-ANS and ANS-Me), and dentoalveolar height at the maxillary molar (U6-PP) and mandibular incisor (L1-Me). The transition from CS5 to CS6 showed significant increases in the position of the chin in relation to nasion perpendicular (Pog-Na perp), Co-Gn, maxillomandibular differential, and protrusion of the lower lip relative to the E-plane. The decreases in ANB angle and Wits appraisal were significant as well when CS5 was compared with CS6 ( Table II , Figs 1-3 ).

Analysis of dental stages

In the female subjects, the comparison between stages 2A/2C and 3A showed significant increases for length of the anterior cranial base (S-N), total mandibular length (Co-Gn), upper anterior facial height (N-ANS), and dentoalveolar height at the maxillary molar (U6-PP) and mandibular incisor (L1-Me). A significant sagittal advancement of the maxillary incisors (U1- Pt A) along with their proclination (U1-SN), and a significant reduction of the interincisal angle were found in this initial interval. The same comparisons were significant for the transition from stage 3A to stage 3B, with the addition of significant increases in the sagittal position of the chin in relation to nasion perpendicular, maxillomandibular differential, lower anterior facial height (ANS-Me), and dentoalveolar height of the maxillary incisor (U1-ANS). The differences in the inclination of the maxillary incisors to S-N and in the interincisal angle were not significant during this interval. During the transition from stage 3B to stage 3C, the increases in total mandibular length (Co-Gn), maxillomandibular differential, molar relationship, and upper anterior facial height (N-ANS) were all significant. In the transition from 3C through 4A/5A, significant increases were recorded for Co-Gn, maxillomandibular differential, and lower anterior facial height (ANS-Me). Significant differences were found also for dentoalveolar height at the maxillary incisor (U1-ANS), maxillary molar (U6-PP), and mandibular incisor (L1-Me) ( Table III [online, go to www.mosby/AJODO/com ], Figs 4-6 ).

Table III
Descriptive statistics and comparison of craniofacial measurements at subsequent stages in dental development
Females 2A/2C (n = 35) 3A (n = 189) 3B (n = 69) 3C (n = 64) 4A/5A (n = 162) 2A/2C vs 3A 3A vs 3B 3B vs 3C 3C vs 4A/5A
X SD X SD X SD X SD X SD
Cranial base
SNFH (°) 8.5 2.8 9 2.9 9.7 2.6 8.5 2.9 9.4 2.9 NS NS NS NS
S-N (mm) 65.6 2.9 68.5 3.6 70.1 3.4 71.4 3.6 72.4 3.4 NS NS
Cranial flexure (°) 120.5 5 122.5 5.3 122.4 4.3 121.5 5.4 123.6 5.9 NS NS NS NS
Maxillary skeletal
SNA angle (°) 80.7 3.3 80.2 3.7 79.8 3.1 80.9 3.8 80.7 3.8 NS NS NS NS
PtA to NaPerp (mm) −0.7 2.5 −0.8 2.9 −0.5 3.2 −0.7 3.4 0.1 3.7 NS NS NS NS
PP-FH (°) −0.9 3.5 −0.4 3.4 −0.9 3.3 0.6 3.7 −0.1 3.4 NS NS NS NS
Co-Pt A (mm) 80 4 82.4 4.6 84.4 4.9 86.5 4.8 88.1 4.6 NS NS NS NS
Mandibular skeletal
SNB angle (°) 79.2 3 79.5 3.5 79.7 3.1 80.9 3.6 80.9 3.7 NS NS NS NS
Pog-Na Perp (mm) −0.2 1.2 0.6 1.2 1.4 1.4 1.8 2.2 2 1.8 NS NS NS
Facial angle (°) 87.6 2.8 88.9 3.1 90.2 2.9 90.4 3.5 91.3 3.3 NS NS NS NS
Co-Gn (mm) 101.6 5 108.3 6.2 115.7 7.6 120.3 6.1 126.6 7.1
Maxillary/mandibular
MPA (°) 27.9 4.1 25.4 4.7 26.8 5.1 26.3 5.7 25.6 5.3 NS NS NS NS
ANB angle (°) 1.5 2 0.7 2.2 0.2 1.8 0 2.7 −0.1 2.8 NS NS NS NS
Wits (mm) −4.2 2.1 −4.3 2.7 −5.2 3.3 −5.3 3.3 −5.4 3.7 NS NS NS NS
Mx-Md diff (mm) 22.6 3.2 25.1 3.8 29.8 4.6 31.9 4.8 34.5 5.3 NS
Molar relation (mm) −4.1 1.7 −3.9 1.7 −4.7 2 −5.8 1.8 −5.7 2.4 NS NS NS
Vertical
Nasion to ANS (mm) 44.8 3 48.1 3.5 51.3 3.5 53.5 3.7 54.5 3.7 NS
ANS to Me (mm) 59.5 4.7 60.7 4.9 65.5 5.4 66.8 5.7 70.5 5.9 NS NS
UFH/LAFH ratio 79.6 6.5 83.2 7.6 81.7 6.8 83.4 7.1 80.4 7.5 NS NS NS NS
U1-ANS (mm) 23.6 2.7 24.8 2.9 27.4 3.1 27.6 3.2 29.3 3.1 NS NS
U6-PP (mm) 17.2 1.5 18.8 2.1 21.4 3.6 22.6 2.4 24.8 2.5 NS
L1-Me (mm) 34.9 2.1 36.7 2.5 38 2.8 39.4 3.1 41.1 3 NS
Dentoalveolar
U1-Pt A (mm) −0.8 2.2 1.7 2.6 3.1 1.9 3.8 2.8 4.2 2.6 NS NS
U1-SN (°) 94.5 9.6 102.5 8.1 103.6 5.5 105.6 6.7 105.2 6.9 NS NS NS
IMPA (°) 86.6 5.7 88.8 6.8 84.6 7.6 84.9 8.2 84.7 7.8 NS NS NS NS
FMIA (°) 65.5 6.3 6.8 6.7 68.6 7.2 68.8 9.7 69.6 8 NS NS NS NS
L1-A Pog (mm) 2.2 1.8 3.2 1.9 2.9 2.3 3 2.9 3.3 2.6 NS NS NS NS
Interincisal angle (°) 142.5 10.5 134.3 10.7 135.2 8.8 134.6 12.7 135 10.7 NS NS NS
Soft tissue
UL-E plane (mm) −4.1 2.6 −4.1 2.1 −5.1 2.3 −6.6 3.1 −7.6 2.8 NS NS NS NS
LL-E plane (mm) −1 2.3 −0.7 2.4 −1.8 2.3 −1.8 3.1 −3.5 3.1 NS NS NS
Nasolabial angle (°) 114.1 12.9 112.8 12.6 112.5 10.8 110.5 11.2 109 12.7 NS NS NS NS
Cranial base
SNFH (°) 7.2 4.6 8.3 2.7 9.2 2.6 9 3.2 8.2 3.2 NS NS NS NS
S-N (mm) 68.7 3 70.7 3.5 73.1 3.6 74.6 3 76.6 4.3 NS NS
Cranial flexure (°) 120.5 4.7 121 4.9 121.7 4.4 121.7 5.4 122.3 5.5 NS NS NS NS
Maxillary skeletal
SNA angle (°) 79.6 3.4 80.2 3.8 80.5 4 80.8 3.6 81 4.4 NS NS NS NS
PtA to NaPerp (mm) −2.7 2.5 −1.4 2.9 −0.4 3.4 −0.3 3.7 −1 4.5 NS NS NS NS
PP-FH (°) 0.4 3.1 −0.4 3.3 −0.2 2.8 −0.2 3.3 0.6 4.1 NS NS NS NS
Co-Pt A (mm) 82 3.9 84.9 4.6 90.1 4.7 92.6 4.2 95.7 5.8 NS
Mandibular skeletal
SNB angle (°) 79.3 3.9 79.6 3.4 79.6 3.2 79.9 3.5 81.4 4.2 NS NS NS NS
Pog-Na Perp (mm) −0.1 1.3 0.5 1.1 1.2 1.6 1.2 1.9 2.3 2 NS NS NS NS
Facial angle (°) 86.3 3.2 88.2 2.6 89.4 3 89.5 3 90.6 3.7 NS NS NS NS
Co-Gn (mm) 105.6 5.2 110.6 5.7 121.3 6.3 124.8 5.8 133.7 9.2
Maxillary/mandibular
MPA (°) 28 3.5 26.3 4.6 27.8 5.5 27.2 4.6 26.2 5.7 NS NS NS NS
ANB angle (°) 0.3 2.3 0.7 2.3 0.9 2.5 0.8 2.2 −0.4 2.8 NS NS NS NS
Wits (mm) −3.9 2.6 −4.4 2.3 −4.7 2.8 −4.2 2.8 −5.1 4.2 NS NS NS NS
Mx-Md Diff (mm) 23.7 4.2 25.7 3.4 31.3 3.8 32.2 3.8 38 6.4 NS NS
Molar relation (mm) −4.2 1.5 −3.7 1.9 −5.2 1.8 −5.4 2.2 −6.4 3.2 NS NS NS
Vertical
Nasion to ANS (mm) 46.5 5.1 49.2 3.7 53.7 3.5 55.4 3.9 57.8 4 NS
ANS to Me (mm) 61.1 4.5 62.9 4.3 69.9 5.7 71.7 5.1 76.3 6.9 NS
UFH/LAFH ratio 80.5 9.1 82.1 7 80.2 6.8 80.6 8.1 79 7.5 NS NS NS NS
U1-ANS (mm) 24 2.6 25.7 2.6 29.3 3 29.7 2.5 30.9 3.5 NS NS NS
U6-PP (mm) 18.1 2.3 19.4 2.1 23.2 2.4 24.5 2.4 26.9 3.2 NS NS
L1-Me (mm) 36.7 2.1 38.2 2.4 41.2 3.2 42.1 2.7 44.8 3.5 NS NS
Dentoalveolar
U1-Pt A (mm) −0.8 2.3 1 2.3 3 2.3 4 2.2 4.3 2.8 NS NS
U1-SN (°) 94.8 11.2 101.1 7.6 103 5.8 104.7 5.7 105.8 7.1 NS NS NS
IMPA (°) 82.4 6.6 85.7 6.5 84.6 6.4 85.2 6.9 84.6 7.1 NS NS NS NS
FMIA (°) 69.5 6.5 66.1 6.4 67.6 7.5 65.6 8 67.2 7.7 NS NS NS
L1-A Pog (mm) 1.9 1.6 3.2 1.8 3.4 2.5 3.8 2.7 3.7 2.6 NS NS NS NS
Interincisal angle (°) 147.6 13.8 136.8 10.3 135.4 8.7 131.9 8.8 135.2 9.9 NS NS NS
Soft tissue
UL-E plane (mm) −3.8 2.6 −3.6 2.3 −4.4 3 −5.7 2.4 −7.4 3.6 NS NS NS NS
LL-E plane (mm) −0.8 2.8 −0.2 2.3 −1 3.2 −1.8 2.8 −3.5 3.4 NS NS NS
Nasolabial angle (°) 109.5 18.6 114.1 13.2 115.2 11.4 113 9.1 110.8 11.7 NS NS NS NS
NS , Not significant; X , mean; Mx , maxillary; Md , mandibular; diff , difference.

P <.05;

P <.01.

Average differences between dental stages for midfacial length in Class III subjects.
Fig 4
Average differences between dental stages for midfacial length in Class III subjects.

Average differences between dental stages for mandibular length in Class III subjects.
Fig 5
Average differences between dental stages for mandibular length in Class III subjects.

Average differences between dental stages for lower anterior facial height in Class III subjects.
Fig 6
Average differences between dental stages for lower anterior facial height in Class III subjects.

In the males, there were a few statistically significant differences in the transition from stage 2A/2C to stage 3A: significant increases in Co-Gn, upper anterior facial height (N-ANS), sagittal advancement of the maxillary incisors (U1- Pt A) with their proclination (U1-SN), and a significant reduction of the interincisal angle. Many significant differences were found between stages 3A and 3B: increases in the length of anterior cranial base (S-N), Co-Gn, maxillomandibular differential, and molar relationship. The comparison between stage 2A/2C with stage 3A also showed significant increases for upper and lower anterior facial heights (N-ANS and ANS-Me), in distance of the maxillary molar from the palatal plane (U6-PP), and in dentoalveolar height at the mandibular incisor (L1-Me), and a significant proclination of the maxillary incisors (U1-ANS and U1-Pt A). During the transition from stage 3B to stage 3C, only the increases in total mandibular length (Co-Gn) and lower anterior facial height (ANS-Me) were significant. In the transition from 3C through 4A/5A, significant increases were recorded for Co-Gn, maxillomandibular differential, and upper and lower anterior facial height (N-ANS and ANS-Me). Significant differences were found also for dentoalveolar height at the maxillary molar (U6-PP) and mandibular incisor (L1-Me). The sagittal position of the lower lip relative to the E-plane also showed significant increases ( Table III , Figs 4-6 ).

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