**1. Introduction**

446 Contemporary Approach to Dental Caries

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children and clinical characteristics. Eur Arch Paediatr Dent. Vol. 12, No. 1, (Feb,

The people of the Yayoi period were the first wet-rice agriculturalists in Japan, and the people of modern Japan are the direct descendents of the Yayoi people. They dominated the Japanese archipelago from the 5th C B.C. to 3rd C A.D. The remains of the Yayoi people have been excavated from several sites in western Japan. It has been proposed that the Yayoi originated in East Asia, based on the morphologic characteristics of the skull and teeth (Hanihara, 1993), as well as genetic evidence(Omoto & Saitou, 1997) . Agriculture practices during the Yayoi period in Japan closely resembled those in southern China and Korea. Based on these findings, the Yayoi people are believed to have been migrants from the Asian continent who introduced wet-rice agriculture to the Japanese islands (Temple, 2010).

Previous studies of ancient populations have revealed a close relationship between oral disease and subsistence patterns (Eshed *et al.*, 2006). In Japan, the incidence of carious teeth among Yayoi period agriculturalists was found to be higher than that among huntergatherers from the preceding Jomon period (Temple & Larsen, 2007). Temple and Larsen (Temple & Larsen, 2007) reported that dietary and behavioral variations among the people of the Yayoi period during the transition to an agriculture-based society precipitated an increase in the frequency of carious teeth, as well as variations in carious tooth frequency, based on geographic location and sex.

 Most of the carious lesions in ancient populations occurred at or near the cemento-enamel junction–alveolar crest (CEJ–AC). (Hildebolt *et al.*, 1988, Kerr *et al.*, 1988, Lunt, 1974, Moore & Corbett, 1971, Moore & Corbett, 1975, Varrela, 1991, Vodanovic *et al.*, 2005) These lesions appear to be associated with an exposed root surface caused by alveolar bone recession, although a definitive conclusion has not been reached. Exposure of the root surface is a prerequisite for carious lesions of the root, and alveolar bone loss is a major cause of such exposure. Therefore, root caries may occur as a result of alveolar bone loss.

Using multiple sets of remains from the Yayoi period, we investigated carious disease(Haraga, 2006) and alveolar bone loss(Uekubo, 2006) among the Yayoi people. Moreover, we identify the factors associated with root caries, and examine the relationship between root caries and alveolar bone loss(Otani *et al.*, 2009). Our findings may be useful for investigating the pathology of root caries in relation to the Yayoi diet.

Caries and Periodontal Disease in Rice-Cultivating Yayoi People of Ancient Japan 449

teeth using a periodontal probe. Up to four tooth surfaces (distal, buccal, mesial, and lingual/palatal) were examined, and the measurements are expressed in millimeters. For tilted teeth, we measured the vertical distance. Teeth with a fractured alveolar crest or that were missing were excluded from the analysis. Teeth were also excluded if the alveolar bone on the buccal side was lost due to physiologic fenestration or a lesion in the root apex.

The distribution and site characteristics of dental caries previously identified in a Yayoi population using the aforementioned procedure. We examined 5010 teeth, 941 teeth were classified as antemortem teeth, and 998 teeth were classified as postmortal loss (Otani *et al.*, 2009) (Table 1). The number of teeth in each individual ranged from a minimum of 2 to a maximum of 32, with an average of 19.5. The total number of carious teeth was 883, for a cares ratio of 17.6%. The percent of individuals with caries was 79.1%, and the percent of

Our analyses indicated that among the Yayoi people, most caries occurred in the root area, particularly on the approximal surface of the tooth root (Haraga, 2006). Moreover, Figure 3 shows the distribution of caries by tooth surface. When categorized into 3 groups, namely occlusal, , the occlusal surface percentage was 10.4%, the crown and root were compared, the crown ratio was 37.4% and the root ratio was 52.2%. When Caries location was classified into 9 tooth surfaces as follows: occlusal surface, crown buccal surface, crown lingual surface, crown approximal surface, root buccal surface, root lingual surface, and root

Fig. 2. Caries in Yayoi people

individuals with root caries was 65.8%

**2.2 Distribution of dental caries in Yayoi people** 
