Temporal and regional variation of the tooth size in the Japanese inhabitants based on crown and root-cervix measurements.

时间变化（2，300-O. B. P.）在Aeneolithic Yayoi（2，300 - 1，799 B. P.）的各种牙齿大小中，古坟（公元前1700 - 1300年），中世纪的镰仓（公元前800-700年），现代晚期（130-O. B. P.）对日本列岛的100颗牙齿进行了测量，发现古坟时期的牙齿总尺寸最大，弥生时期次之，古坟时期的牙齿总尺寸最大，弥生时期的牙齿总尺寸最小。另一方面，镰仓时期的总规模是最小的，其次是现代。总齿径最终减小，但并不是不断减小。颞侧复位有增有减，近远中径复位较颊舌径强。牙根颈的缩小程度大于牙冠。上牙比下牙有更强的复位力。有些牙齿比其他牙齿减少更多。牙冠指数和牙根指数（颊舌径/近远中径）的时间变化表明，颊舌径和近远中径的变化率不同。冠-根指数（根颈测量/冠测量）随时间的变化表明牙颈的坚固性逐渐降低，以往对牙齿大小随时间变化的研究主要关注牙齿大小的总体变化，而本研究表明牙列不同部位的牙齿大小随时间变化的方向和速度不同。需要进一步的研究，以澄清在日本列岛的牙齿大小的时间变化的因素。

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.