A comparative study of Caucasian and Japanese mandibular clinical arch forms

The purpose of this study was to clarify morphological differences between Caucasian and Japanese mandibular clinical arch forms in Class I, II, and I II malocclusions. The study included 60 Class I, 50 Class II, and 50 Class m cases from each ethnic group. The most facial portion of 13 proximal cont act areas was digitized from photocopied images of the mandibular dental ar ches. Clinical bracket points were calculated for each tooth based on mandi bular tooth thickness data. Four linear and 2 proportional measurements wer e taken. The dental arches were classified into square, ovoid, and tapered forms to determine and compare the frequency distributions between the 2 et hnic groups. The Caucasian population had a statistically significant decre ased arch width and increased arch depth compared with the Japanese populat ion. When the subjects were regrouped by arch form, no statistically signif icant difference in arch dimension was observed between the 2 ethnic groups in any of the arch form samples. Our results suggest that there is no sing le arch form specific to any of the Angle classifications or ethnic groups. It appears to be the frequency of a particular arch form that varies among Angle classifications or ethnic groups.