Morphometric estimation of torsional stiffness and strength in primate mandibles

In comparative studies of masticatory function and mandibular biomechanics, the mediolateral dimension of the postcanine corpus (corpus breadth) is commonly utilized as a measure of torsional stiffness from which relative torsional strength is inferred. The use of this dimension entails certain assumptions about corpus shape and cortical bone distribution that are invalid. When corpus breadth is related to an appropriate, empirically supported measure of torsional strength, it is revealed that this dimension has limited utility for inference of biomechanical competence under torsion. The use of linear dimensions to infer structural adaptations to specific loading regimes is problematic given that bone tissue is not optimally deployed to minimize strain levels arising from isolated loads. For the inference of the masticatory biomechanical environment, the more reasonable approach is to consider overall size of the corpus (i.e., cross-sectional area) for inference of intra- and inter-specific differences in masticatory forces.