75.3 Friday, Jan. 6 Mandibular helical axis during feeding in non-human primates IRIARTE-DIAZ, J*; TERHUNE, C.E.; ROSS, C.F.; University of Chicago; Duke University; University of Chicago email@example.com
Teeth trajectories are often used for the study of mandibular movement. These trajectories, however, depend on the location of the reference point and their interpretation can be equivocal. In contrast, the finite helical axis (FHA) is a mathematical model that completely describes the movement of a rigid body. Previous studies have shown that the FHA is located inferior to the mandibular condyle and that it varies continually through the gape cycle. In humans, the position and orientation of the FHA varies primarily during the closing phases, with little fluctuation of the FHA during the opening phases. Few data are available regarding the position and/or orientation of the FHA in non-human primates and it remains unclear to what extent the paths of FHA during mastication in other taxa are similar to or different from those documented for humans. Here we present data on the rigid-body kinematics of three species of primates (Cebus, Macaca and Papio) obtained by measuring the three-dimensional position of mandibular and cranial markers during feeding using high-speed, high-resolution video recordings. Similar to humans, the location of the FHA in these primates was below the mandibular condyle. FHA orientation, however, changed throughout the whole gape cycle, with substantial changes during both closing and opening phases. Differences in mandibular movement during feeding between human and non-human primates, as well as differences among non-human primates species are expected to reflect differences in morphology of the temporomandibular joint and differences in patterns of muscle activation.