The influence of time, facial side, and location on pain-pressure thresholds in chronic myogenous temporomandibular disorder.

This study examined masseter and temporalis pain-pressure thresholds in 29 patients with chronic bilateral myogenous temporomandibular disorder and in 11 controls. Patients with evidence of temporomandibular joint pathosis were omitted. The influence of time, facial side, muscle site, and side of greatest spontaneous pain on pain-pressure thresholds was measured. No significant pain-pressure threshold differences were found between the more and less painful sides, as indicated by the patients, which lends support to theories of centrally mediated pain. Mean pain-pressure thresholds in patients differed over the four sessions, which is consistent with recent reports of fluctuating levels of pain in patients with temporomandibular disorders. Additional findings included significant pain-pressure threshold differences among muscle sites in patients and controls, and lower patient pain-pressure thresholds relative to controls. Within- and between-session reliability was adequate for patients (r = .85 and r = .75, respectively) and controls (r = .90 and r = .75, respectively).