|Budget Amount *help
¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 2000 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1999 : ¥700,000 (Direct Cost : ¥700,000)
Temporal variations(2,300-O.B.P.) of the various tooth sizes of the Aeneolithic Yayoi(2,300-1,799 B.P.), Protohistoric Kofun(1,700-1,300 B.P.), Medieval Kamakura (800-700 B.P.), and Late Modern period(130-O.B.P.) in the Japanese archipelago were investigated, using not only the maximum diameter of crown but also a new measurement of root-cervix uninfluenced by tooth attrition.
Total tooth size in the Kofun period is the biggest, and the size in the Yayoi period is the next biggest. On the other hand, the total size in the Kamakura peroid is the smallest, and the next smallest period is the modern. The total tooth size reduced finally, but the size did not reduce constantly. There were some increase and some reducton in the temporal reduction.
In general, mesiodistal diameters have stronger reduction than buccolingual diameters. The tooth root-cervix reduced stronger than tooth crown. Upper teeth has stronger reduction than lower teeth. Some teeth has more reduction than other teeth. Thus is was made clear that different parts of the dentition have different reduction rates.
Temporal change of crown index and root index(buccolingual diameter/mesiodistal diameter)indicated that changing rate of buccolingual diameter and mesiodistal diameter are different. Temporal variation of crown-root index(root-cervix measurement /crown measurement) made it clear that robustness of the tooth cervix reduced gradually.
Though old studies of the temporal change of the tooth size paid attention to the total change of the tooth size, this study suggested that different parts of the dentition have different direction and rate of temporal change. Further research will be required in order to clarify the factor of the temporal change of the tooth size in the Japanese archipelago.