Kinematic analysis of power-law relationship between jaw movement velocity and curvature

With respects to skillful human motions such as arm movements during writing or reaching, invariant relationship between kinematic parameters indicates a strategy of the movement execution. The aim of present study was to propose a method for identifying the invariant characteristics of human jaw movement kinematics. The method estimated constraints on formation of masticatory movement trajectory in terms of slope of linear relationship between speed and radius of curvature. The analysis was applied to compare the constraining factors on formation of the masticatory jaw movement paths between children and adults. The masticatory movements of five female adults and five female children with good occlusion were monitored using a 3D tracking device. The radius of curvature of the movement paths highly correlated with the tangential velocity (Adults, mean r(2)=0.81; Children, mean r(2)=0.77). The mean of slopes of the linear relationship for the children (0.47) was significantly higher than that for the adults (0.36) (P<0.01). Based on these findings, it is suggested that the proposed motion analysis is capable of distinguishing the underlying kinematic properties of the children's masticatory jaw movements from those of the adults.