Figure 4.

Averaged mechanobehavior scores in women with bilateral temporomandibular joint (TMJ) disc displacement (+DD) and without (Control) are shown for combined ipsilateral and contralateral TMJs (Iwasaki et al. 2017a). Overall indicates results for time (Day, Night) periods and muscle activity thresholds of 1% to 4%, 5% to 9%, and 10% to 24% of muscle activation required to produce a 20-N bite force. Vertical bars indicate standard errors above and below the mean values and * indicates P < 0.05. In the main, women with bilateral disc displacement had significantly higher mechanobehavior scores during the day and night. However, the findings were contrary to the conventional paradigm of the role of high-magnitude bruxism and clenching in TMJ disc failure. The results showed this type of bruxing and clenching was rare and significant differences between the 2 diagnostic groups were limited to muscle activities required to produce low-magnitude mandibular loads of <5 N.