Morphological relationship between the mandible and teeth : its functional and evolutionary significance

为了研究下颌骨内发育的牙列何时、如何以及在多大程度上与下颌骨外部生长相关，进行了一系列的三项对比研究。首先，对史前日本人和现代日本人进行了人口间的比较。其次，对两种脑猿类灵长类动物(狒狒和日本猴)进行了性别比较。最后，对包括现代人在内的四个灵长类物种进行了物种间比较。通过以上研究，提出了以下几点建议：1)前牙相对较大的前牙，是现代日本和雄性相较于绳索和雌性相伴的较高前体的共同来源。2)正中牙和尖牙隐窝在下颌发育过程中的分布格局存在种间和种间差异，其原因是发育牙和下颌可利用空间的大小平衡。3)下颌联合的物种特异性特征，包括倾斜度，在很大程度上与成年犬的大小无关，其物种间差异在整个生长过程中一直保持不变。因此，这些结果表明了解发育中牙齿的空间状况对解释下颌骨形态的重要性。

To examine when, how, and to what extent the developing dentition within the mandible is interrelated with external mandibular growth, a series of three comparative studies were undertaken. First, an interpopulation comparison was made between prehistoric Jomon and modern Japanese. Second, sex comparisons were conducted in two cercopithecine primates(hamadryas baboon and Japanese monkey). Finally, interspecies comparisons were carried out among four primate species including modern humans. Through the above studies, some suggestions were made : 1) the relatively large size of the anterior teeth is indicated as the common source of the high anterior corpi of the modern Japanese and the male baboons relative to the Jomon and the female baboons, respectively. 2) both interpopulation and interspecies differences in the placement patterns of the incisor and canine crypts within the developing mandible can be accounted for by the size balance between the developing teeth and mandibular available space. 3) species-specific characteristics of the mandibular symphysis, including the inclination, are largely independent of the adult canine size, and its interspecies differences are consistently maintained throughout growth. The results thus indicate the importance of understanding the spatial conditions of the developing teeth in interpreting mandibular morphology.