[A morphological study of the cranial base and dentofacial structure of Japanese with Angle Class II, div. 1 malocclusion--as compared with American white with Angle Class II, div. 1 malocclusion].

The purpose of this study was to clarify the morphological differences of Angle class II, div. 1 malocclusion between Japanese and American Caucasians by comparing their cranial base and dentofacial morphology. Materials were lateral cephalograms of 61 Japanese (30 males: mean age 12y3m and 31 females: mean age 12y10m) and 67 American Caucasians (27 males: mean age 13y6m and 40 females: mean age 13y) with Angle class II, div. 1 permanent dentition. Results were as follows: 1. The anterior cranial base length in Japanese with Angle class II, div. 1 malocclusion was significantly shorter than that of American Caucasians. 2. The maxillary length in Japanese with Angle class II, div. 1 malocclusion was significantly shorter than that of American Caucasians. 3. Less than SNA, less than SNB and less than ANB showed no significant difference between Japanese and American Caucasians with Angle class II, div. 1 malocclusion. 4. The whole mandibular length in Angle class II, div. 1 malocclusion of Japanese males and American males showed no significant difference. But the mandibular body length of Angle class II, div. 1 malocclusion in Japanese females was significantly shorter than that of American ones. 5. No significant difference was observed in gonial angle when the two groups were studied. 6. As compared with American Caucasians, the backward rotation of the mandible was evidently observed in Japanese with Angle class II, div. 1 malocclusion.