Craniofacial morphology and adolescent facial growth in Pierre Robin sequence.

INTRODUCTION: The purpose of this research was to analyze craniofacial morphology and adolescent facial growth in subjects with Pierre Robin sequence (PRS). The research was conducted at the Center for Craniofacial Care and Research at The Hospital for Sick Children, Toronto, Ontario, Canada, and the Burlington Facial Growth Research Center, Faculty of Dentistry, University of Toronto. METHODS: Longitudinal lateral cephalometric tracings of 34 Caucasian subjects with nonsyndromic PRS were compared with those of unaffected control subjects, matched for age, sex, and ethnicity, and representing the range of occlusions in an untreated population. Cephalometric measurements were obtained before orthodontic treatment (age, 11.8 years) and after orthodontic treatment but before any surgical treatment (age, 16.6 years). Between-group differences of craniofacial measurements were analyzed with paired t-tests, and longitudinal growth differences were analyzed with analysis of variance (ANOVA) adjusted for the growth interval. RESULTS: Significant differences were noted, with the PRS group showing smaller cranial base length, shorter maxillary and mandibular lengths, increased palatal and mandibular plane inclinations, and more open mandibular flexure. Mandibular body length and height were smaller as were ramal length and width, anterior basal thickness, and chin thickness. The ramus-to-body ratio was greater. With growth, greater gains in anterior face and symphyseal height were seen, but the mandible showed less closure of its internal flexure. The maxilla and the mandible remained retrusive during adolescent growth, and the maxilla became more retrognathic. Mandibular morphologic differences persisted in spite of additionally adjusting for cranial base length in the analysis. CONCLUSIONS: Subjects with PRS had reduced cranial base and maxillary and mandibular lengths. Mandibular deficiency was most pronounced in the body. Due to bimaxillary retrognathism, the maxillomandibular dysplasia was not significant. A vertical growth pattern worsened the profile. There was no evidence of adolescent mandibular catch-up growth.

Comparison of facial morphology in two populations with complete unilateral cleft lip and palate from two different centers.

OBJECTIVE: To identify differences in craniofacial morphology of two populations with a history of complete unilateral cleft lip and palate (UCLP) treated under different protocols. DESIGN: Retrospective longitudinal cohort study. SETTING: Cleft Center of the University of Nijmegen, The Netherlands, and the Cleft Lip and Palate Program, The Hospital for Sick Children, Toronto, Canada. SUBJECTS: Nineteen patients (16 male, 3 female) from Nijmegen and 19 patients (16 male, 3 female) from Toronto. Each patient was matched for sex and age with a patient from the other group. The mean ages at which lateral cephalometric radiographs were available for the Nijmegen group were 5.5, 9.9, and 18.3 years, while for the Toronto group these were available at mean ages of 5.3, 10.1, and 18.3 years, respectively. Eighteen patients from the Nijmegen group received an alveolar bone graft at a mean age of 9.5 years (range 8.2 to 13.5 years). None of the patients from Toronto received bone grafts. MAIN OUTCOME MEASURES: Eighteen cephalometric variables per radiograph were calculated at each time registration, using Dentofacial Planner cephalometric software. Statistical evaluation was performed with repeated-measures analysis of variance. RESULTS: No differences were seen in the maxillary measurements. The patients in the Toronto group had significantly larger mandibles at all three time registrations. CONCLUSIONS: The Nijmegen and Toronto protocols resulted in similar maxillary projections in patients with UCLP. Comparison of data from other studies supports the contention that the larger profile convexity of the Nijmegen group is a reflection of a genetically determined smaller mandibular size in the Dutch population.

Mandibular morphology and growth with and without hypodontia in subjects with Pierre Robin sequence.

INTRODUCTION: Mandibular micrognathia is the hallmark of Pierre Robin sequence (PRS). A high prevalence of mandibular hypodontia has been reported in subjects with PRS. The hypothesis of this study is that the morphology of the mandible in subjects with PRS and mandibular hypodontia is different from that in subjects with PRS but without mandibular hypodontia. METHODS: The study was conducted at the craniofacial center of The Hospital for Sick Children in Toronto. The study sample comprised 16 caucasian children with nonsyndromic PRS (7 boys, 9 girls) with mandibular hypodontia and 18 white children with nonsyndromic PRS (6 boys, 12 girls) without hypodontia. Longitudinal lateral cephalograms were available before orthodontic treatment (T1; mean age, 11.7 years) and after orthodontic treatment but before orthognathic surgery (T2; mean age, 16.6 years). A new, customized cephalometric analysis with additional landmarks and measurements to study mandibular morphology was performed. Differences in measurements were studied by using analysis of variance adjusted for age and sex. RESULTS: Cephalometric measurements were smaller in the group with mandibular hypodontia at T1: mandibular length (3.36 mm, P = .04), ramal length (2.78 mm, P = .04), posterior facial height (3.97 mm, P = .03), and mandibular molar eruption (1.96 mm, P = .02). At T2, the differences increased: mandibular length (4.56 mm, P = .02), ramal length (4.04 mm, P = .002), posterior facial height (5.98 mm, P = .001), and mandibular molar eruption (2.08 mm, P = .04). Comparison of growth increments between the 2 groups from T1 to T2 showed a greater cranial base deflection increment in the group with mandibular hypodontia (0.88 degrees, P = .02) and a larger posterior facial height increment in the group without mandibular hypodontia (2.02 mm, P = .04). CONCLUSIONS: Children with nonsyndromic PRS with mandibular hypodontia had smaller mandibles than children with nonsyndromic PRS and normal complements of mandibular teeth. Their patterns of growth did not improve during adolescence, and the magnitude of differences increased.

Predisposing factors to formation of cleft lip and palate: inherited craniofacial skeletal morphology.

OBJECTIVE: To identify inherited craniofacial morphologic features in individuals at high risk for cleft of the lip, cleft palate, or both. SUBJECTS: Twins without cleft from 33 pairs of monozygotic twins discordant for cleft lip, cleft palate, or both were studied. There were 17 males and 16 females of Caucasian origin, ranging from 3 to 18 years (15 with cleft lip and palate [CLP], 10 with cleft lip [CL], and 8 with cleft palate [CP]), collected from five craniofacial centers (United States and Canada). DESIGN: The twin without cleft (noncleft) from each set was compared with an age- and sex-matched control individual from the Burlington Growth Centre, Toronto, Ontario. Posteroanterior and lateral cephalograms were traced and digitized using a computer custom analysis. Descriptive statistics, Student's t tests, and analysis of variance were used to test 40 variables in a pilot study comparing the noncleft twin groups with the controls. Preliminary analysis permitted pooling of the CLP and CL groups (n = 25). To minimize false-positive significance, only 14 variables (from the maxillofacial area) were tested. RESULTS: Using the raw probabilities, eight variables showed significant differences between the pooled noncleft CLP and CL (CL[P]) twin group and the controls. However, when the level of significance was adjusted, only four (nasal width [p < .01], cranial base length [p < .05], cranial base width/length ratio [p < .001], and maxillary width/length ratio [p < .05]) were significantly different. No significant differences were confirmed between the noncleft CP twin group and the controls. CONCLUSIONS: The noncleft member of a discordant monozygotic pair has a number of facial characteristics that differ from the general population. These may predispose to the formation of a cleft lip or palate and may result from a deficiency or distortion of the mesenchyme that forms the craniofacial structures.