Bite-force endurance in patients with temporomandibular joint osteoarthrosis and internal derangement

The aim of this study was to investigate the potential clinical relevance of testing bite force endurance in patients with articular temporomandibular disorders. The endurance of a 50 N bite force was measured in 51 patients with painful temporomandibular joint disorders. The results were compared to those of a control group of 20 subjects. The force exerted was sustained until this task could not be continued because of intolerable pain or fatigue. The endurance test was repeated following therapy. Testing bite force endurance could be reliably carried out (paired t-test not significant, product-moment correlation coefficient 0.87). The mean endurance time in the patient group was significantly different from that of the control group (t = 7.43, df = 69, P < 0.01). The 95% confidence intervals for patients and controls did not show any overlap. No difference in endurance time between diagnostic subgroups could be detected (F = 1.30, df = 4,46, P < 0.28). Following treatment, all patients showed a significant increase of endurance time (t = 8.09, df = 50, P < 0.01) and reported a decrease in post-test pain. The mean difference between pre- and post-treatment endurance was 60s. Subjects of the control group stopped the biting effort predominantly because of muscle fatigue. By contrast, the main reason of the patients to cease the effort was TMJ pain. The results of this study indicate that the discriminatory power of the test is sufficient to justify its utility as a complementary tool in assessing the functional capacity of the masticatory system.