TMJ Modeling

The masticatory region is an important human motion system that is essential for basic human tasks like mastication, speech or swallowing. An association between temporomandibular disorders (TMD) and high temporomandibular joint (TMJ) stress has been suggested, but in vivo joint force measurements are not feasible to directly test this assumption. Consequently, biomechanical computer simulation remains as one of a few means to investigate this complex system. To thoroughly examine orofacial biomechanics, we developed a novel, dynamic computer model of the masticatory system.

The temporomandibular joint discs were modeled as FEM and four axial springs mimic the biomechanics of the TMJ capsule. Since attaching the axial springs to a single node of the FEM would lead to unstable and incorrect simulation results, we used a distributed FEM attachment, spreading out the applied force over appr. 20 nodes per ligament. To speed up simulations, articular cartilage was modelled as an Elastic Foundation (EF) contact model.

The model is validated using high-resolution MRI data for protrusion and opening that were collected from the same volunteer. Joint stresses for a clenching task as well as protrusive and opening movements are computed. Simulations resulted in mandibular positions as well as disc positions and shapes that agree well with the MRI data. The model computes reasonable disc stress patterns for dynamic tasks. Moreover, to the best of our knowledge this model presents the first ever contact model using a combination of EF layers and a FEM body, which results in a clear decrease in computation time.