Stress analysis in human temporomandibular joint affected by anterior disc displacement during prolonged clenching.

Parafunctional habits, such as prolonged clenching and bruxism, have been associated with dysfunctional overloading in the temporomandibular joint (TMJ). In this study, stress distributions in the TMJ were analysed during prolonged clenching, using three-dimensional finite element (FE) models of the TMJ with and without disc displacement. The aim of this study was to investigate stress distribution of the cartilaginous tissues in the TMJ with and without disc displacement. Finite element models were developed on the basis of magnetic resonance images from two subjects with and without anterior disc displacement. Condylar movements recorded during a 5-min clenching were used as the loading condition for stress analysis. In the asymptomatic model, the highest von Mises stresses were located in the lateral area (4·91 MPa) of the disc surfaces, and after 5-min clenching, the higher stresses were still located at the lateral area (3·65 MPa). In all the cartilaginous tissues, 30-50% of stress reduction occurred during 5-min clenching. In contrast, the von Mises stress in the cartilaginous tissues of the symptomatic model with disc displacement was markedly lower, compared with the asymptomatic model. However, in the condylar cartilage, stress relaxation during clenching was not recognised. Furthermore, relatively high stresses were observed in the retrodiscal tissues throughout clenching. The present results indicate that disc position could be involved in the stress distribution of the TMJ components during prolonged clenching.