Dental Condition of Two Tribes of Taiwan Aborigines-Ami and Atayal

Abstract

This is a study of dental and oral conditions of Taiwan aborigines from the epidemiological and anthropological points of view. A total of 166 Ami and 128 Atayal adolescents were included from their original living area, the Hwa-Lien Hsin and Wa-Lai District, Taiwan, Republic of China. Oral examination was done carefully and caries incidence, periodontal index, and Angle's Classification combined with OFI were included. After that, hydrocolloid impressions were taken, and dental casts were immediately made. The mesiodistal and buccloingual crown diameters and also the arch depth and width were measured using a sliding caliper. Dental morphological traits, such as shovel-shaped incisors, Carabelli's cusp, protostylid, and upper and lower molar groove patterns were observed and classified, and the results are given with statistical analysis. The aborigines have a quite low incidence of dental caries and periodontal disease which may be related to their dietary habits, good oral hygiene, and good dental occlusion. With regard to the differences between the Ami and Atayal, most of the date show no statistical significance except in the dental occlusion. The Atayal's occlusion is better than that of the differences of genetics or other factors. There are no sex differences in all the date in the dental survey, but there are sex differences in both the misiodistal and buccolingual crown diameters of both the Ami and Atayal tribes (the tooth crown of the male subjects is invariably broader and larger than that of females). In the dental arch dimensions, most of the data show no sex diffreence, except in the breadth of the upper and lower dental arch of the Atayal. Anthropologically, there are no statistical differences, in mesiodistal and buccolingual crown diameters and most of the data of dental arch dimesions, but there is a difference in arch depth in Ami and Atayal adolescents. The Atayal have a deeper dental arch than do the Ami. As for dental morphologi, the Taiwan aborigines have a high frequency of shovel-shaped incisors and Carabelli's trait but a relatively low frequency of protostylid. There are no definite differences between races in the occlusal pattern of maxillary first molars, but there are differences in the maxillary second molars. The usual pattern is 4-- for the upper first and second molars of the Taiwan aborigines as well as for thedibular occlusal pattern, the first molar tends to follow the primitive "dryopithecus" pattern of 5 cusps and Y configuration, but in the second molar there are varying degrees of departure from Y5 to the more advanced +4 pattern with +5 and Y4 as intermediates.