The class system in place during the Edo (early modern) period in Japan is thought to have included a range of customs that differed between the samurai (ruling class) and commoners. The incidence of caries in the dentition of the samurai was significantly lower than that of commoners. This difference is considered to be due to diet, eating frequency, and tooth care. As to location of the caries, it was found that the incidence of root caries in the samurai was remarkably lower than that in commoners. Root caries does not occur until gingival attachment recedes in an apical direction. The samurai and commoners did not show a significant difference in incidence of periodontal disease, while many samurai dentitions exhibited slick-polished teeth and wedge-shaped defects, which are thought to have been caused by the customary brushing of teeth. Such a custom might have successfully prevented dental caries. Given these findings, we consider that the lower incidence of caries in the samurai, compared with commoners, resulted from the influence of oral hygiene practices that helped to prevent root caries.

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The strict class system in place during the Edo (early modern) period in Japan is thought to have encompassed customs that differed between the samurai (ruling class) and commoners. This study found that in samurai children, deciduous caries occurred only in maxillary incisors at 0.5-2 years of age and did not occur in the mandibular incisors and canines at 3-5 years of age. Conversely, in commoner children, deciduous caries occurred in all maxillary teeth and mandibular molars at 0.5-2 years of age and in all maxillary and mandibular teeth at 3-5 years of age. In commoner children, deciduous caries was seen in tooth types that have a low incidence of deciduous caries in modern Japanese. The present results show that deciduous carious lesions appear earlier and more frequently in the commoner children compared to the samurai children, probably because of differences in lifestyle between the two groups. There was no significant difference in the incidence of enamel hypoplasia in the deciduous dentition between samurai and commoner children, suggesting that the two classes had broadly comparable nutrition. In our previous study using the same skeletal series, similar results between samurai and commoners were found with respect to caries and enamel hypoplasia prevalence of the permanent dentition. Many of the samurai adults had slick polished teeth, which we believe were caused by regular brushing of the teeth in the samurai class. Such a custom might have functioned to prevent dental caries not only in the permanent dentition, but also in the deciduous dentition. Thus, oral hygiene practices in the samurai class are thought to have functioned to prevent dental caries not only in adults but also in children.

The 17 tooth crown traits of the Bunun, one of the aboriginal tribes in Taiwan, were observed and classified, and their frequencies were compared with Sinodonts and Sundadonts defined and classified in East Asian populations by , in order to estimate the genealogical position of the Bunun tribe in East Asia. In the respective comparisons of the 17 traits, the Bunun have considerable resemblance to Sinodonts on shoveling (UI1), double shoveling (UIl) and deflecting wrinkle (LM 1), while on tuberculum dentale (UI2), cusp 5 (UM1) and 4-cusp (LM2), they have considerable resemblance to Sundadonts. Furthermore, cluster analysis and principal co-ordinate analysis based on SMITH's MMDs among the Bunun and other East Asian populations, using all the observed traits, revealed that the Bunun are similar to the Yami (Taiwan aborigine), the North ChinaMongolian and the South Chinese in East Asia, and belong to, if anything, the Sinodonty cluster.Considering the above results and the estimated distribution of Sinodonty and Sundadonty in the past and the present, it cannot be reasoned that Taiwan aborigines had Sinodont characteristics since their ancestors reached Taiwan, but that Sinodontification by Chinese mainlanders has been superimposed on to the native Sundadonty who seem to have come up from the south to Taiwan. The beginning of Sinodontification in Taiwan may have been earlier than in Japan.

Morphological variations of the deciduous dentition are as useful as those of the permanent dentition for determining the biological affinities of human populations. This paper provides material on morphological variations of deciduous teeth of the prehistoric Japanese population from the Late and the Latest Jomon Period (ca. 2000-ca. 300 B.C.). The expression of nonmetric traits of the deciduous teeth in the Jomon sample shows a closer affinity with modern Japanese and Native American samples than with American White, Asiatic Indian, and African samples. However, the frequency of shoveling in deciduous upper incisors in the Jomon sample is lower than those in modern Japanese and Native American samples. The Jomon sample also expresses a much higher frequency of cusp 6 in deciduous lower second molars than seen in modern Japanese, Ainu, and Native American samples. The frequency in the Jomon sample is equal to that in the Australian Aboriginal sample, which shows cusp 6 most frequently among the samples compared. A somewhat low incidence of incisor shoveling in the Jomon sample was also reported in the permanent dentition (Turner [1976] Science 193:911-913, [1979] Am. J. Phys. Anthropol. 51:619-635, [1987] Am. J. Phys. Anthropol. 73:305-321, [1990] Am. J. Phys. Anthropol. 82:295-317; T. Hanihara [1992] Am. J. Phys. Anthropol. 88:163-182, 88:183-196). However, the frequency of cusp 6 in the Jomon sample shows no significant difference from those of Northeast Asian or Native American samples in the permanent dentition (Turner [1987] Am. J. Phys. Anthropol. 73:305-321; T. Hanihara [1992] Am. J. Phys. Anthropol. 88:163-182, 88:183-196). Evidently, some nonmetric traits express an inter-group difference only in the deciduous dentition.