Mechanism design and analysis of a wearable device for rehabilitation of temporomandibular disorder

A wearable device is proposed for the purpose of practical rehabilitation of temporomandibular disorder (TMD). The three-dimensional movement of the jaw is simplified as moving in the two-dimensional sagittal plane. The normal jaw motion is specified in terms of incisor trajectory and condylar trajectory, the former being used to synthesize the mechanism and the latter for the evaluation. A four-bar linkage is designed to meet the requirements, with adjustable links used for achieving a group of the trajectories. The device is symmetric about the middle sagittal plane of the skull and consists of two identical linkages, one at each side of the jaw and its kinematics is simulated in SimMechanics to evaluate both the device design and the man-machine interaction. Lastly, realistic evaluation is done with adding the compliant components in the hybrid system, where the human jaw is modeled by another planar linkage with special attention given to a TMJ that rotates and translates in space.