Center for Evolution and Medicine, Arizona State University, Tempe, AZ, USA.
Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA.
J Anat. 2020 Sep;237(3):529-542. doi: 10.1111/joa.13218. Epub 2020 May 14.
Ontogenetic changes in the human masticatory complex suggest that bite force, a key measure of chewing performance, increases throughout growth and development. Current published bite force values for humans exist for molar and incisal biting, but few studies measure bite forces across all tooth types, or measure bite force potentials in subjects of different ages. In the absence of live data, models of bite force such as the Constrained Lever Model (CLM), are employed to predict bite force at different bite points for adults, but it is unclear whether such a model can accurately predict bite force potentials for juveniles or subadults. This study compares theoretically derived bite forces and live bite force data, and places these within an ontogenetic context in humans. Specifically, we test whether (1) patterns of maximum bite force increase along the tooth row throughout ontogeny, (2) bite force patterns estimated using the CLM match patterns observed from live bite force data, and (3) changes in bite forces along the tooth row and throughout ontogeny are associated with concomitant changes in adductor muscle leverage. Our findings show that maximum bite forces increase throughout ontogeny and change along the tooth row, with the highest forces occurring at the posterior dentition. These findings adhere to the expectations under the CLM and validate the model's utility in predicting bite force values throughout development. Furthermore, adductor muscle leverage values reflect this pattern, with the greatest leverage values occurring at the posterior dentition throughout ontogeny. The CLM informs our study of mammalian chewing mechanics by providing a model of how morphological changes of the masticatory apparatus during ontogeny affect bite force distribution along the tooth row. Furthermore, the decreased bite force magnitudes observed in juveniles and subadults compared with adults suggest that differences in juvenile and subadult diets may partially be due to differences in bite force production potentials.
人类咀嚼复合体的个体发育变化表明，咀嚼效能的关键衡量指标——咬合力，在生长和发育过程中不断增加。目前已经发表了人类磨牙和切牙咬合力的数值，但很少有研究测量所有牙齿类型的咬合力，或测量不同年龄组受试者的咬合力潜力。在没有活体数据的情况下，像约束杠杆模型（CLM）这样的咬合力模型被用来预测成年人在不同咬合点的咬合力，但尚不清楚该模型是否能准确预测青少年或亚成年人的咬合力潜力。本研究比较了理论推导的咬合力和活体咬合力数据，并将其置于人类的个体发育背景中。具体来说，我们检验了以下三个问题：（1）在个体发育过程中，沿牙齿排列的最大咬合力是否呈递增模式；（2）CLM 估计的咬合力模式是否与活体咬合力数据观察到的模式相吻合；（3）沿牙齿排列和整个个体发育过程中咬合力的变化是否与附着肌杠杆的变化有关。我们的研究结果表明，最大咬合力在个体发育过程中不断增加，并沿牙齿排列发生变化，后牙的咬合力最高。这些发现符合 CLM 的预期，并验证了该模型在预测整个发育过程中的咬合力值的有效性。此外，附着肌杠杆值反映了这种模式，整个个体发育过程中后牙的杠杆值最大。CLM 通过提供一个模型，说明了咀嚼器官在个体发育过程中的形态变化如何影响沿牙齿排列的咬合力分布，从而为我们研究哺乳动物咀嚼力学提供了信息。此外，与成年人相比，青少年和亚成年人的咬合力值较低，这表明青少年和亚成年人饮食的差异可能部分是由于咬合力产生潜力的差异。
