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The Dental Aesthetic Index (DAI) is an orthodontic index based on socially defined aesthetic standards. The primary aim of this study was to compare the prevalence of malocclusion using the DAI among three ethnic groups of Asian origin; Japanese, Chinese in Taiwan and Native Americans with white Americans. A secondary goal was to consider the possibility that genetic factors might be the cause of the characteristics of malocclusion in the ethnic groups of Asian origin. Malocclusion was evaluated in 1029 Japanese and 176 Chinese in Taiwan students utilising the DAI, and the findings were compared with those of Native Americans and white Americans. The DAI values of Japanese and Native Americans were significantly higher than those of Chinese in Taiwan and white Americans. The mean DAI values showed no common tendency among the three ethnic groups. The characteristics of malocclusion in each ethnic group were also evaluated by analysis of each of the 10 DAI component scores. The results revealed common characteristics of malocclusion in the three ethnic groups of Asian origin using white Americans as the standard. The findings in the present study suggest the possibility that genetic factors might have an influence on the characteristics of malocclusion.

Differences in the dental arch and palate among Taiwan Aboriginals were investigated and compared with Taiwanese and Japanese. Plaster models were taken from 315 Taiwan Aboriginal adults, 185 Taiwanese and 426 Japanese between 1979 and 1989, and various dimensions were measured. There were no clear differences in the characteristics of the dental arch and palate between Taiwan Aboriginal tribes. However, they were found to differ from those of Taiwanese and Japanese. In a dendrogram constructed from a cluster analysis, two major clusters were found. Among males, the first cluster contained Paiwan and Rukai, the second contained Japanese, Taiwanese, Ami and Bunun. Among females, the first contained Japanese, Taiwanese, Rukai and Paiwan, the second contained Ami and Bunun. The Ami were close to Bunun and the Paiwan were close to Rukai among both males and females. These results indicate that Ami and Bunun, and Paiwan and Rukai, respectively, have close affinities.