Design of Jaw Rehabilitation Device for Patients with TMJ Disorder

This paper presents a novel design of a rehabilitation device for patients suffering from jaw opening impairment due to temporomandibular joint (TMJ) disorder and oral fibrosis-inducing conditions.The design of the device is posed as a mechanism synthesis problem through path generation.The path generation is formulated as a multi-objective optimisation to minimise the error between the desired and actual jaw motion profiles and maximise the mechanical advantage.An iterative solution is proposed that follows the ideal jaw profile.A systematic selection of design variables is made, followed by formulating the objective function and identifying appropriate constraints.The optimisation routine uses the steepest descent gradient to find the feasible direction for the objective function and Lagrange multipliers for imposing constraint conditions.Limits on link lengths and coordinates of optimised linkages are imposed based on ergonomic considerations.The paper presents two solutions to achieve the desired objectives: a dual fourbar mechanism covering fourteen precision points and a single fourbar mechanism covering eight precision points.The designed mechanisms are compared for accuracy, and structural analysis is carried out to assess the strength.The solution consisting of a single 4-bar mechanism is found better from the strength and manufacturability point of view.A set of human trials would be required to examine the efficacy of the proposed design.