Berthaume Michael A, Dumont Elizabeth R, Godfrey Laurie R, Grosse Ian R
Medical and Biological Research Group, Department of Mechanical Engineering, University of Hull, Kingston upon Hull HU6 7RX, UK Department of Anthropology, University of Massachusetts, Amherst, MA 01003, USA
Department of Biology, University of Massachusetts, Amherst, MA 01003, USA.
J R Soc Interface. 2014 Dec 6;11(101):20140965. doi: 10.1098/rsif.2014.0965.
Teeth are often assumed to be optimal for their function, which allows researchers to derive dietary signatures from tooth shape. Most tooth shape analyses normalize for tooth size, potentially masking the relationship between relative food item size and tooth shape. Here, we model how relative food item size may affect optimal tooth cusp radius of curvature (RoC) during the fracture of brittle food items using a parametric finite-element (FE) model of a four-cusped molar. Morphospaces were created for four different food item sizes by altering cusp RoCs to determine whether optimal tooth shape changed as food item size changed. The morphospaces were also used to investigate whether variation in efficiency metrics (i.e. stresses, energy and optimality) changed as food item size changed. We found that optimal tooth shape changed as food item size changed, but that all optimal morphologies were similar, with one dull cusp that promoted high stresses in the food item and three cusps that acted to stabilize the food item. There were also positive relationships between food item size and the coefficients of variation for stresses in food item and optimality, and negative relationships between food item size and the coefficients of variation for stresses in the enamel and strain energy absorbed by the food item. These results suggest that relative food item size may play a role in selecting for optimal tooth shape, and the magnitude of these selective forces may change depending on food item size and which efficiency metric is being selected.
牙齿通常被认为在其功能方面是最优的，这使得研究人员能够从牙齿形状中推断出饮食特征。大多数牙齿形状分析会对牙齿大小进行标准化，这可能会掩盖相对食物大小与牙齿形状之间的关系。在这里，我们使用四尖臼齿的参数化有限元（FE）模型，模拟了相对食物大小在脆性食物破碎过程中如何影响最佳牙尖曲率半径（RoC）。通过改变牙尖RoC为四种不同的食物大小创建形态空间，以确定最佳牙齿形状是否随食物大小的变化而改变。这些形态空间还用于研究效率指标（即应力、能量和最优性）的变化是否随食物大小的变化而改变。我们发现，最佳牙齿形状随食物大小的变化而改变，但所有最佳形态都相似，有一个钝尖会在食物中产生高应力，还有三个尖用于稳定食物。食物大小与食物中应力的变异系数和最优性之间也存在正相关关系，而食物大小与牙釉质中应力的变异系数和食物吸收的应变能之间存在负相关关系。这些结果表明，相对食物大小可能在选择最佳牙齿形状方面发挥作用，并且这些选择力的大小可能会根据食物大小和所选择的效率指标而改变。
