3-D simulation of the occlusion in the human evolution

这项研究有两个方面。一个是通过磨牙的三维测量来分析咬合的修复，另一个是通过对化石和现存古人类下颌骨和牙齿的观察来研究不同人群的咬合类型。基于对化石和现存古人类下颌骨和牙齿的观察。(1)人类磨牙具有复杂的三维结构。通过对这些结构的测量，可以追踪特定种群的咬合机制。本研究使用激光三维测量系统（Kashimura Co.Ltd.）对化石人类臼齿进行无磨耗测量。原始人和类人猿的尖端位置设计有一个基本的区别。现代人类的牙齿相对较小，但在人类谱系中有较高的尖牙。咬合表比其他类人猿大。采用三维变形技术对磨损严重的磨牙进行修复。给出了磨牙冠的49个（7X7）节点的三维坐标，得到了充分的结果。(2)骨结构位于咬合的基底。对公元前1万~公元前300年现代日本人的祖先绳纹人的下颌骨进行了CT扫描分析。该人群颊皮质骨较厚。这意味着从舌侧到颊侧在牙齿上有很大的矢量或力。这种定向力也解释了这个种群的严重磨损。在南太平洋人群中也调查了闭塞类型，他们被认为在现代人类中具有理想闭塞。结果表明，美拉尼西亚人普遍存在边对边咬合，密克罗尼西亚人的咬合类型与日本人相似。

This research is two fold. One is on the restoration of the occlusion analyzed by the 3-D measurement of molars, and the other is the investigation of the types of occlusion in various populations based on the observation of the mandible and teeth of fossil and extant hominoids.based on the observation of the mandible and teeth of fossil and extant hominoids.(1) Human molars have three-dimensionally complicated structures. Mechanism of occlusion of a certain population can be traced by the measurement of these structures. This research deals with fossil human molars without attrition with the use of laser 3-D measurement system (Kashimura Co.Ltd.) There is a basic difference of the positional design of cusps between hominoids and anthropoid apes. Modern humans have relatively small teeth but high cusps in the homo lineage. Occlusal table proper is larger than other hominoids. Restoration of the molar crown from the heavily worn molar was tried with the use of 3-D morphing technique. Three-dimensional coordinates of the 49 (7X7) nodes of the matrix were given to the worn molar crown and the sufficient results were obtained.(2) Bony structures lie on the basement of occlusion. The mandibles of Jomon people, ancestors of modern Japanese from BC 10,000 to 300, were analyzed by the CT scanning. Buccal cortical bone was thick in this population. This implies large vector or force working on the teeth from lingual to buccal side. Heavy attrition in this population is also explained by this directional force. Type of occlusion were also investigated in the South Pacific populations who are thought to have idealistic occlusion among modern humans. Results suggested that edge-to-edge occlusion was popular in Melanesian population and that the type of occlusion in Micronesians was similar to Japanese one.