Jaw pain and tenderness levels during and after repeated sustained maximum voluntary protrusion.

Eight normal male volunteers performed 4 repeated sustained voluntary isometric protrusive jaw muscle contractions of 25, 50, 75 and 100% of maximum effort. Each contraction was sustained until maximum pain tolerance was reached, and all 4 contractions were completed within a single 120-min experimental period. A 30-min rest period followed each sustained contraction. The following measurements were made before and 1, 2, 3, and 7 days after the experiment: (1) superficial masseter and anterior temporalis muscle pain threshold; (2) maximum active pain-free jaw opening and lateral excursion; and (3) current overall jaw pain level. None of these measurements showed any significant post-experimental changes. Contrary to common clinical belief, these results suggest that in healthy male subjects, significant jaw pain and tenderness following repeated sustained isometric protrusion efforts are difficult to induce.