The literature contains evidence that subjects

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1 ORIGINAL ARTICLE Dentofacial growth changes in subjects with untreated I malocclusion from late puberty through young adulthood Tiziano Baccetti, a Franka Stahl, b and James A. McNamara, Jr c Florence, Italy, Rostock, Germany, and Ann Arbor, Mich Introduction: The purpose of this longitudinal study was to compare dentofacial growth changes in untreated subjects with I Division 1 malocclusion with those in subjects with normal () occlusion from late puberty through young adulthood. Methods: The I Division 1 sample consisted of 23 subjects (10 male, 13 female). The sample included 30 subjects (13 male, 17 female). The lateral cephalograms of the subjects in both groups were analyzed at 2 consecutive stages of development: T1, postpubertal observation (cervical vertebral maturation stage 6), and T2, young adulthood stage. The average time between T1 and T2 was 3.5 years. The statistical comparisons of the growth changes in the 2 groups were performed with Mann-Whitney U tests. Results: From late puberty through young adulthood, dentofacial growth in subjects with untreated I malocclusion does not show significant differences when compared with that observed in untreated subjects with normal occlusion. Conclusions: These findings show that I dentoskeletal disharmony does not exhibit significant growth change from late puberty through young adulthood. (Am J Orthod Dentofacial Orthop 2009;135:148-54) The literature contains evidence that subjects with various dentoskeletal disharmonies (eg, I or II dentoskeletal relationships) grow differently from subjects with normal dentoskeletal relationships in both the amount and the direction of growth of the craniofacial structures. 1-8 With regard to I Division 1 malocclusion, several longitudinal studies have demonstrated a significant deficiency in the amount of mandibular growth in untreated Class II subjects with mandibular retrusion when compared with untreated subjects at the circumpubertal period. 1,4,5 These data have offered valid assistance in a Associate professor, Department of Orthodontics, University of Florence, Florence, Italy; Thomas M. Graber Visiting Scholar, Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor. b Research associate, Department of Orthodontics, University of Rostock, Rostock, Germany; postdoctoral scholar, Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor. c Thomas M. and Doris Graber Endowed Professor of Dentistry, Department of Orthodontics and Pediatric Dentistry, School of Dentistry; professor of Cell and Developmental Biology, School of Medicine; research professor, Center for Human Growth and Development, University of Michigan; private practice, Ann Arbor, Mich. Supported by the Max-Kade Foundation and the German Society of Orthodontics, with additional support from the Thomas M. and Doris Graber Endowed Professorship by the University of Michigan. Reprint requests to: Tiziano Baccetti, Università degli Studi di Firenze, Via del Ponte di Mezzo, 46-48, 50127, Firenze, Italy; , t.baccetti@odonto. unifi.it. Submitted, January 2007; revised and accepted, March /$36.00 Copyright 2009 by the American Association of Orthodontists. doi: /j.ajodo planning treatment for patients with I malocclusion and in understanding growth expectations in untreated subjects with this type of disharmony. The growth differences between I and subjects also have pointed to the appropriateness of using subjects with untreated I malocclusions as controls in studies on the effectiveness of I treatment around puberty. 9 Longitudinal investigations on craniofacial growth in patients with untreated I malocclusion so far have focused on prepubertal and pubertal changes. 1-5,10 However, information on postpubertal growth characteristics of I subjects is needed both to evaluate long-term effects of I treatment at puberty and appraise the effects of treatment at a postpubertal stage of development. Several orthopedic treatment approaches to I malocclusion in young adults have been proposed recently (Herbst/multibracket protocol, Jasper jumper, functional appliances) Therefore, our aim in this study was to compare the craniofacial growth features of subjects with untreated I and malocclusions from late puberty through young adulthood. MATERIAL AND METHODS The files of the University of Michigan Growth Study (n 706) and the Denver Growth Study (n 155) were searched for longitudinal records of orthodontically untreated subjects with either I or 148

2 American Journal of Orthodontics and Dentofacial Orthopedics Volume 135, Number 2 Baccetti, Stahl, and McNamara 149 Table I. Descriptive statistics for age, sex, and observation intervals I (10 m, 13 f) (13 m, 17 f) Age at T1 (CS 6) (y) Age at T2 (young adulthood) (y) T2-T1 interval (y) m, Male; f, female. malocclusion. Lateral cephalograms of good quality at 2 consecutive developmental intervals, corresponding to the postpubertal stage in cervical vertebral maturation (T1, CS6) and young adulthood (T2, approximately 3.5 years after T1), were available for all selected subjects. 16 All subjects were of European- American ancestry (white) and had no craniofacial abnormalities or tooth anomalies in number or eruption (supernumeraries, congenitally missing teeth, impacted canines). Subjects with I Division 1 malocclusion were diagnosed according to the following signs on the lateral cephalograms at T1: full-cusp I molar relationship, excessive overjet ( 5 mm), and ANB angle 4. Subjects with occlusion were selected according to a molar relationship at T1, normal overjet (2-4 mm), and ANB angle between 0 and 3. Demographic data for the 2 groups are given in Table I. Cephalograms were traced by an investigator (F.S.) and verified for landmark location, anatomic contours, and tracing superimpositions by a second (J.A.M.). Any disagreements were resolved by retracing the landmark or structure to the satisfaction of both observers. A customized digitization regimen and analysis from Dentofacial Planner (Dentofacial Software, Toronto, Ontario, Canada) was used for all cephalograms examined in this study. The cephalometric analysis required the digitization of 77 landmarks and 4 fiducial markers. The customized cephalometric analysis containing measurements from the analyses of Steiner, 17 Jacobson, 18 Ricketts, 19 and McNamara 20 was used, generating 33 variables 11 angular and 22 linear for each tracing. All sets of cephalograms were traced at the same time. A preliminary tracing was made for each film in the series, with particular attention paid to tracing the outlines of the maxilla and the mandible, including the mandibular condyle. Then each set of consecutive films was checked thoroughly, beginning with the second and third films in the series. Fiducial markers were placed in the maxilla and the mandible on the third tracing and then transferred to the second tracings in each subject s cephalometric series, based on superimposition of internal maxillary or mandibular structures. The locations of the fiducial markers were then transferred to the first and subsequently the fourth through sixth films similarly. The maxillae were superimposed along the palatal plane by registering on the bony internal details of the maxilla superior to the incisors and the superior and inferior surfaces of the hard palate. Fiducial markers were placed in the anterior and posterior parts of the maxilla along the palatal plane. This superimposition described the movement of the maxillary dentition relative to the maxilla. The mandibles were superimposed posteriorly on the outline of the mandibular canal. Anteriorly, they were superimposed on the anterior contour of the chin and the bony structures of the symphysis. A fiducial marker was placed in the center of the symphysis and another in the body of the mandible near the gonial angle. This superimposition facilitated measuring the movement of the mandibular dentition relative to the mandible. The magnifications of the 2 data sets were different; the lateral cephalograms from the University of Michigan study had a magnification of 12.9%, and those from the Denver study had a magnification of 4%. Therefore, the lateral cephalograms from the 2 studies were corrected to match an 8% enlargement factor. Twenty-four lateral cephalograms randomly chosen from all observations were retraced and redigitized to calculate method errors with Dahlberg s formula. 21 The errors for linear measurements ranged from 0.4 (overjet) to 0.9 mm (pogonion to nasion perpendicular); the errors for angular measurements varied from 0.4 (ANB) to 1.5 (interincisal angle). The assessment of the stages in cervical vertebral maturation on lateral cephalograms for each subject was performed by 1 investigator (T.B.) and verified by a second (J.A.M.). 16 Any disagreements were resolved to the satisfaction of both observers. Statistical analysis Descriptive statistics of craniofacial measurements in the I and samples at T1 and T2 were calculated, as well as the between-stage changes. The Kolmogorov-Smirnov test showed lack of normality of distribution for several measurements. Therefore, nonparametric statistics with Mann-Whitney U tests were used. The following comparisons were made: (1) starting forms between I and samples at T1, (2) final forms between I and samples at

3 150 Baccetti, Stahl, and McNamara American Journal of Orthodontics and Dentofacial Orthopedics February 2009 Table II. Descriptive statistics and statistical comparisons for cephalometric measurements in I and subjects at T1 (CS6) I Cephalometric measure Difference P value Cranial base NSBa ( ) * Maxillary skeletal Co-Pt A (mm) SNA ( ) Pt A to nasion perp (mm) Mandibular skeletal Co-Gn (mm) Co-Go (mm) * SNB ( ) Pg to nasion perp (mm) * Maxillary/mandibular Wits (mm) Max/mand diff (mm) ANB ( ) Vertical skeletal FH to palatal plane ( ) FH to mandibular plane ( ) ArGoMe ( ) CoGoMe ( ) N to ANS (mm) ANS to Me (mm) Interdental Overbite (mm) Overjet (mm) Interincisal angle ( ) Molar relationship (mm) Maxillary dentoalveolar U1 to Pt A vertical (mm) U1 to FH ( ) Mandibular dentoalveolar. L1 to Pt A-pogonion (mm) * L1 to mandibular plane ( ) *P 0.05; P 0.01; P T2, and (3) between-stage changes (T2-T1) in I vs samples. RESULTS Descriptive statistics for the cephalometric measurements in I and subjects at T1 and T2 are given in Tables II and III. Results of the statistical comparisons between I and subjects on the changes for all cephalometric variables during the observation interval and the T1 to T2 changes are shown in Table IV. In the comparison of starting forms between Class II and samples at T1 (Table II), the measurement of cranial base flexure was significantly greater in subjects with I malocclusion. There were no statistically significant differences between the 2 study groups with regard to maxillary skeletal and dentoalveolar measures. Significant differences were found for mandibular dimensions, both for condylion-gnathion and condylion-gonion. The mandible was significantly retruded in I subjects when related to the anterior cranial base. This difference was also reflected by the significantly greater intermaxillary sagittal discrepancy (Wits appraisal, maxillomandibular differential, and ANB angle) in the I sample. No significant differences were found for vertical skeletal relationships. As expected on the basis of the inclusion criteria, overjet was significantly greater and molar relationship was significantly smaller in subjects with I malocclusion. The mandibular incisors were significantly retruded in the I sample when compared with the sample.

4 American Journal of Orthodontics and Dentofacial Orthopedics Volume 135, Number 2 Baccetti, Stahl, and McNamara 151 Table III. Descriptive statistics and statistical comparisons for cephalometric measurements in I and subjects at T2 (young adulthood) I Cephalometric measures Difference P value Cranial base NSBa ( ) * Maxillary skeletal Co-Pt A (mm) SNA ( ) Pt A to nasion perp (mm) Mandibular skeletal Co-Gn (mm) Co-Go (mm) * SNB ( ) Pg to nasion perp (mm) * Maxillary/mandibular Wits (mm) Max/mand diff (mm) ANB ( ) Vertical skeletal FH to palatal plane ( ) FH to mandibular plane ( ) ArGoMe ( ) CoGoMe ( ) N to ANS (mm) ANS to Me (mm) Interdental Overbite (mm) Overjet (mm) Interincisal angle ( ) Molar relationship (mm) Maxillary dentoalveolar U1 to Pt A vertical (mm) * U1 to FH ( ) Mandibular dentoalveolar. L1 to Pt A-pogonion (mm) * L1 to mandibular plane ( ) *P 0.05; P 0.01; P In the comparison of the final forms between the I and samples at T2 (Table III), all differences that were statistically significant at T1 were so at T2, with the addition of 1 significant difference: the maxillary incisors were more protruded in the Class II sample. In the comparison of between-stage changes (T2- T1) in the I vs the samples (Table IV), no significant differences were found. DISCUSSION I malocclusion is a common clinical problem in dentofacial orthopedics; this disharmony occurs in about a quarter to a third of the North American white population In contrast with this prevalence, only a few studies have investigated craniofacial growth features of orthodontically untreated subjects with I dentoskeletal disharmony. This information is important in terms of growth expectations in patients observed at an early developmental phase and for the evaluation of treatment outcomes in growing patients. Only 4 major longitudinal studies have described the growth changes in the dentofacial region of untreated I subjects compared with untreated subjects with normal occlusion. 1,4,5,10 Bishara et al 10 observed the growth trends in I malocclusion from the deciduous through the permanent dentitions with average ages of 5 years at the start and 12.2 years after treatment. They did not report significant differences between I and samples (with the exception of upper lip protrusion). However, the most severe patients were excluded from the I group, and the

5 152 Baccetti, Stahl, and McNamara American Journal of Orthodontics and Dentofacial Orthopedics February 2009 Table IV. Changes between T1 and T2 (CS6 and young adulthood stage) in I vs subjects and statistical comparisons (differences in growth changes are not significant) I Cephalometric measure Difference P value Cranial base NSBa ( ) Maxillary skeletal Co-Pt A (mm) SNA ( ) Pt A to nasion perp (mm) Mandibular skeletal Co-Gn (mm) Co-Go (mm) SNB ( ) Pg to nasion perp (mm) Maxillary/mandibular Wits (mm) Max/mand diff (mm) ANB ( ) Vertical skeletal FH to palatal plane ( ) FH to mandibular plane ( ) ArGoMe ( ) CoGoMe ( ) N to ANS (mm) ANS to Me (mm) Interdental Overbite (mm) Overjet (mm) Interincisal angle ( ) Molar relationship (mm) Maxillary dentoalveolar U1 to Pt A vertical (mm) U1 to FH ( ) U1 horizontal (mm) U1 vertical (mm) U6 horizontal (mm) U6 vertical (mm) Mandibular dentoalveolar L1 to Pt A-pogonion (mm) L1 to mandibular plane ( ) L1 horizontal (mm) L1 vertical (mm) L6 horizontal (mm) L6 vertical (mm) analysis of growth changes ended at an average age of 12.2 years, when active growth is far from completed. The other 3 investigations on the same topic found significant differences in growth changes between I and subjects. 1,4,5 Stahl et al 5 reported a significant deficiency in mandibular growth in I subjects at the growth spurt (interval CS3-CS4), which was maintained at the postpubertal observation (CS6). These studies showed that I dentoskeletal disharmony does not tend to self-correct with growth and worsens with the deficiency in mandibular dimensions. On the basis of these findings, the use of untreated I controls in studies on the effectiveness of dentofacial orthopedics on mandibular growth during the circumpubertal period was recommended. 5 A characteristic common to all studies on growth in untreated I Division 1 malocclusion is that they end at either puberty or a postpubertal stage (CS6, approximately 2 years after the adolescent growth spurt 5 ). Information is needed about the growth char-

6 American Journal of Orthodontics and Dentofacial Orthopedics Volume 135, Number 2 Baccetti, Stahl, and McNamara 153 acteristics of subjects with I malocclusion observed longitudinally after the circumpubertal period, because nonsurgical I treatment can be performed also during late adolescence and young adulthood. For instance, Ruf and Pancherz 11,12,15 used the Herbst appliance in I subjects well after the pubertal growth spurt. These studies on Herbst appliance use in postpubertal patients show that dentoalveolar effects predominate over remaining growth effects. Unfortunately, the classic North American growth studies do not provide information on specific postpubertal dentoskeletal changes in I subjects. Even recall studies include so few I subjects that untreated I malocclusions could not be differentiated from untreated malocclusions in the appraisal of possible growth changes in the early adulthood. Our aim in this study was to compare the longitudinal craniofacial growth changes in untreated subjects with I Division 1 malocclusion with those in subjects with normal occlusion from a late postpubertal stage of development (CS6) through young adulthood. 16 The combined analyses of both the University of Michigan and the Denver studies enabled us to collect 23 I subjects and 30 subjects to be analyzed from late puberty into young adulthood. The average age of our sample ( years) corresponds to the time during which clinicians accomplish either postpubertal treatment of I malocclusion or postpubertal assessment of outcomes of previous therapy At the beginning of the observation period (CS6), the I subjects were characterized by obtuse cranial base angle, retruded mandible, deficiencies in the linear measurements of mandibular length and mandibular ramus height, excessive value for the Wits appraisal, and retroclined mandibular incisors, in addition to the occlusal features of I Division 1 malocclusion (excessive overjet and distal molar relationship). These results are consistent with the findings of previous studies. 1,3,5 Almost 50% of the variables we found to be significant, however, had a P value between 0.05 and Borderline significance for several cephalometric variables must be viewed with caution. All these characteristics were maintained fully at T2 (approximately 3.5 years after T1; average age, 19 years). No significant differences between I and subjects were found with regard to the growth changes from late puberty through young adulthood. Furthermore, the amount of growth in I subjects from late puberty into young adulthood was minimal. In terms of absolute values, average growth changes during the observed interval were between 0 and 1.2 mm (mandibular length). Some considerations can be derived from these findings. First, the lack of significant differences in growth trends between the I and groups after puberty indicates that the use of untreated I controls in studies on the effectiveness of dentofacial orthopedics performed after the circumpubertal period (or during early adulthood) is not mandatory. Both I and subjects can serve as adequate controls for the appraisal of orthopedic interventions in those with I malocclusions after active growth. 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