Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
PLoS One. 2013 Jul 23;8(7):e69990. doi: 10.1371/journal.pone.0069990. Print 2013.
Most of the morphological features recognized in hominin teeth, particularly the topography of the occlusal surface, are generally interpreted as an evolutionary functional adaptation for mechanical food processing. In this respect, we can also expect that the general architecture of a tooth reflects a response to withstand the high stresses produced during masticatory loadings. Here we use an engineering approach, finite element analysis (FEA), with an advanced loading concept derived from individual occlusal wear information to evaluate whether some dental traits usually found in hominin and extant great ape molars, such as the trigonid crest, the entoconid-hypoconulid crest and the protostylid have important biomechanical implications. For this purpose, FEA was applied to 3D digital models of three Gorillagorilla lower second molars (M2) differing in wear stages. Our results show that in unworn and slightly worn M2s tensile stresses concentrate in the grooves of the occlusal surface. In such condition, the trigonid and the entoconid-hypoconulid crests act to reinforce the crown locally against stresses produced along the mesiodistal groove. Similarly, the protostylid is shaped like a buttress to suffer the high tensile stresses concentrated in the deep buccal groove. These dental traits are less functional in the worn M2, because tensile stresses decrease physiologically in the crown with progressing wear due to the enlargement of antagonistic contact areas and changes in loading direction from oblique to nearly parallel direction to the dental axis. This suggests that the wear process might have a crucial influence in the evolution and structural adaptation of molars enabling to endure bite stresses and reduce tooth failure throughout the lifetime of an individual.
人类牙齿中大多数形态特征，特别是咬合面的形貌，通常被解释为机械加工食物的进化功能适应。在这方面，我们也可以预期，牙齿的总体结构反映了对咀嚼负荷产生的高应力的承受能力。在这里，我们使用工程方法，有限元分析（FEA），结合从个体咬合磨损信息得出的先进加载概念，来评估通常在人类和现生大型猿类臼齿中发现的一些牙齿特征，如三角嵴、尖牙-后尖牙嵴和原尖嵴，是否具有重要的生物力学意义。为此，我们将 FEA 应用于三个不同磨损阶段的大猩猩下第二臼齿（M2）的 3D 数字模型。我们的结果表明，在未磨损和轻度磨损的 M2 中，拉伸应力集中在咬合面的凹槽中。在这种情况下，三角嵴和尖牙-后尖牙嵴起到局部增强牙冠的作用，以抵抗沿近远中凹槽产生的应力。同样，原尖嵴的形状像一个扶壁，以承受集中在深颊侧凹槽中的高拉伸应力。这些牙齿特征在磨损的 M2 中不太起作用，因为随着磨损的进展，牙冠中的拉伸应力会生理性地减小，这是由于拮抗接触面积的增大和加载方向从斜向变为几乎平行于牙轴。这表明，磨损过程可能对臼齿的进化和结构适应具有关键影响，使其能够在个体的一生中承受咬合应力并减少牙齿失效。
