**3. Conclusion**

456 Contemporary Approach to Dental Caries

Fig. 7. Relation with percentage of root caries surfaces per tooth surface and mean CEJ-AC

mm±SD (number of tooth surfaces )

Without root caries With root caries

Distal 2.9±1.3(423) 3.6±1.9(23) 0.045 Buccal 3.5±2.0(404) 4.3±3.1(3) 0.490 Mesial 3.0±1.3(405) 3.4±1.4(9) 0.224 Palatal 3.6±1.3(477) 4.00(1) --------

Distal 3.3±1.7(311) 3.9±1.2(27) 0.010 Buccal 3.8±2.0(359) 4.3±2.1(16) 0.367 Mesial 3.0±1.4(367) 4.3±1.6(24) < 0.001 Palatal 4.4±2.1(397) 5.4±1.8(17) 0.011

Distal 2.7±1.5(617) 3.6±1.5(32) 0.001 Buccal 4.0±2.1(569) 6.0±2.8(10) 0.013 Mesial 2.6±1.4(618) 3.9±2.8(10) 0.126 Lingual 3.0±1.4(511) -------- (0) --------

Distal 3.1±1.8(453) 4.0±2.0(36) 0.002 Buccal 4.1±2.3(453) 5.7±2.4(39) < 0.001 Mesial 2.9±1.6(471) 4.6±1.9(27) < 0.001 Lingual 3.7±1.6(504) 4.3±1.1(16) 0.192

Table 3. Mean CEJ-AC distance per tooth surface by the presence of root caries.

*p*-value 1

Tooth type Mean CEJ-AC distance per tooth surface

distance per tooth surface.

Upper premolar

Upper molar

Lower premolar

Lower molar

1 Mann-Whitney test

We investigated the relationship between caries and periodontal disease in the people of the Yayoi period. The Yayoi, who dominated the Japanese archipelago around the 5th C B.C., are the direct ancestors of the modern Japanese and were the first people to engage in rice cultivation in Japan.

The people in the Yayoi period had a high prevalence of root caries, and the rate of dental caries, is suggested to be due to changes in dietary habits that occurred concomitant with the development of agriculture. On the other hand, tooth wear and compensatory physiologic growth of the abraded tooth are reduced with a rice diet, and alveolar bone loss occurs due to periodontitis. This results in increased exposure of the root surface, which is thought to result in root caries.
