Thin-plate spline analysis of craniofacial growth in Class I and Class II subjects.

OBJECTIVE To compare the craniofacial growth characteristics of untreated subjects with Class II division 1 malocclusion with those of subjects with normal (Class I) occlusion from the prepubertal through the postpubertal stages of development. MATERIALS AND METHODS The Class II division 1 sample consisted of 17 subjects (11 boys and six girls). The Class I sample also consisted of 17 subjects (13 boys and four girls). Three craniofacial regions (cranial base, maxilla, and mandible) were analyzed on the lateral cephalograms of the subjects in both groups by means of thin-plate spline analysis at T1 (prepubertal) and T2 (postpubertal). Both cross-sectional and longitudinal comparisons were performed on both size and shape differences between the two groups. RESULTS The results showed an increased cranial base angulation as a morphological feature of Class II malocclusion at the prepubertal developmental phase. Maxillary changes in either shape or size were not significant. Subjects with Class II malocclusion exhibited a significant deficiency in the size of the mandible at the completion of active craniofacial growth as compared with Class I subjects. CONCLUSION A significant deficiency in the size of the mandible became apparent in Class II subjects during the circumpubertal period and it was still present at the completion of active craniofacial growth.