Effects of disc displacement on stress distributions in temporomandibular joint

To investigate stress distributions on temporomandibular joint (TMJ) with different disc displacements through numerical simulation. A three-dimensional finite element model of normal TMJ including the mandible, teeth, discs and articular cartilage was established according to CT images of a volunteer with asymptomatic joints. Based on the model, four corresponding models with the anterior, posterior, lateral and medial displacement of the disc were developed. Contact elements were considered to simulate the interaction between the discs and articular cartilages of the condyle and the temporal bone. Cable elements were used to simulate the ligaments and attachments of the disc. The muscle forces and boundary conditions corresponding to the centric occlusions were applied on the models. The maximum compressive stress occurred at the intermediate zone due to the anterior displacement of the disc, which was as high as 3.23 MPa. The model with the posterior, lateral and medial displacements of the disc had higher stresses than the model with the anterior displacement of the disc and healthy TMJ model. The stresses at the back of the articular eminences in four models with disc displacements were much higher than those in healthy TMJ model. However, the effects of disc displacements on the stresses of the condyles were not obvious. Disc displacements could cause higher stresses in the discs and at the back of the articular eminences, especially in the model with the posterior, lateral and medial displacements of the disc, which was likely to cause damage to TMJ structure and function.