Morphological differences in the craniofacial structure between Japanese and Caucasian girls with Class II division 1 malocclusions

The craniofacial features of 49 Japanese and 75 British Caucasian girls with Class II division 1 malocclusions were evaluated from lateral cephalometric radiographs, and the morphological differences between both races were examined. The subjects' ages ranged from 11 years 1 month to 12 years 11 months. The mean values of 13 linear and 13 angular cephalometric parameters were compared. The Japanese Class II division 1 sample had a significantly shorter anterior cranial base length (S-N; P < 0.001) and a more obtuse articular angle (S-Ar-Go; P < 0.001). Analysis of the dentoalveolar components in Japanese subjects showed more proclined lower incisors (L1/Go-Me; P < 0.05) and a steeper occlusal plane (Occ.P/S-N; P < 0.01) relative to those of Caucasians. The short anterior cranial base length and excessive vertical development in the Japanese population might be common racial morphological features, but the main reason for the Class II division 1 skeletal disharmony in both races was different; it was caused by the anteriorly positioned maxilla in Caucasians and the backward rotated mandible in the Japanese.