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

本研究采用牙冠最大径和不受牙齿磨损影响的牙根颈径的新测量方法，研究了从绳文初期（约10，000 - 6，000 BP）到现代日本居民牙齿大小的时间和区域变化.从Aeneolithic弥生时代（约2，300 - 1，700 BP）到现代的移民群体比本地群体（如Jomonese和Ainu）拥有更大的牙齿。2.移民的弥生人或古坟人在移民群体中牙齿最大。弥生或古坟的牙齿尺寸最终向现代时期减小，但时间上的减小伴随着一些波动.新石器时代的日本人和本地弥生人的牙齿大小显示出一些减少到最近的阿伊努人在本地组。最有趣的结果是绳文时代长期的时间变化。在绳纹初期-早中期-晚中期-末期（约10，000 - 2，300 BP），牙齿的大小随时间而增加。绳纹时代的时间变化与同一时期全球性的牙齿减少趋势相反。近远中径与颊舌径、冠径与根颈径在变化方面存在一定差异。另一方面，第三磨牙与另一磨牙的比例显示出暂时的减少，而这种减少可能与一般牙齿大小的暂时增加相反。为了弄清绳文时代的特殊变化的因素，需要进一步的研究。

Temporal and regional variations of the various tooth sizes from the Initial Jomon period (about 10,000-6,000 BP) to the modern period in the Japanese inhabitants were investigated, using not only the maximum diameter of tooth crown but also a new measurement of tooth root-cervix uninfluenced by tooth attrition.1. The migrant group from the Aeneolithic Yayoi period (about 2,300-1,700 BP) to the modern period has larger teeth than the native group such as the Jomonese and the Ainu.2. The migrant Yayoi population or the protohistoric Kofun population has the largest teeth in the migrant group. The Yayoi or Kofun tooth size finally decreases toward the modern period, but the temporal decrease is accompanied with some fluctuations.3. The tooth sizes of the Neolithic Jomonese and the native Yayoi population show some reduction toward the recent Ainu in the native group.4. The most interesting result is a temporal change in a long term of the Jomon period. A temporal increase of the general tooth size was observed in the Initial-Early-Middle-Late-Final Jomon period (about 10,000-2,300 BP). The temporal change in the Jomon period shows an opposite change to the tooth reduction of a global tendency in the same period. There are some differences of the changing aspects between mesiodistal diameters and buccolingual diameters, and between crown diameters and root-cervix diameters. On the other hand, a temporal reduction of the ratio of the third molar to the other molar was shown, while the reduction might be contrary to the temporal increase of the general tooth size. Further research will be required in order to clarify the factor of the peculiar change in the Jomon period.