Modeling of the effect of friction in the temporomandibular joint on displacement of its disc during prolonged clenching

Purpose: The effect of the frictional coefficient in the temporomandibular joint on the disc during prolonged clenching was examined. Materials and Methods: For this purpose, a finite element model of the temporomandibular joint based on magnetic resonance images from a volunteer subject was used. Muscle forces applied for clenching were used as a loading condition for stress analysis during 10 minutes. With respect to the frictional coefficient between articular surfaces, 3 different values ranging from μ = 0.001 to μ = 0.1 were established. Results: At the onset of clenching, large stresses were found in the central and lateral part of the intermediate zone in the disc, and its stress distribution was not markedly changed during 10 minutes of clenching. In the retrodiscal tissue, stress relaxation occurred during the first 2 minutes of clenching. When the frictional coefficient between articular surfaces increased, the anterior, lateral, and central points in the disc moved further forward. At the end of 10 minutes of clenching, the disc showed a more anterior position as the frictional coefficient increased. Conclusion: This result indicates that increase of the frictional coefficient between the articular surfaces may be a major cause for the onset of the disc displacement.