Model-based analysis of jaw-movement kinematics using jerk-optimal criterion: simulation of human chewing cycles.

Large intra- and/or inter-individual variability in human masticatory motor behaviors may reduce objectivity in assessing normality/abnormality for jaw movements. Analytical simulation by kinematic modeling based on a universally accepted objective criterion is a potentially useful clinical tool for credible diagnostic quantification of jaw motion. This study aimed to test whether a minimum-jerk (maximum-smoothness) model could accurately simulate the kinematics in each separate gum-chewing cycle of 10 healthy adults, and if so, to examine whether simulation errors reflected an extent of abnormality for chewing movements for 10 patients caused by temporomandibular joint disorders (TMD). The model predicted the lower incisor-point movements of the control group with reasonable accuracy. Overall, the prediction errors for the patients group were greater than the control group, demonstrating that prediction errors for jaw opening velocity were sensitive to the criteria for joint disorders. It was concluded that the present simulation emerged as being capable of scaling the not so smooth masticatory jaw movements performed in the presence of TMD.