Chronic temporomandibular disorders are not necessarily associated with a compromised endogenous analgesic system

Aims: To test whether temporomandibular disorders (TMD) casecontrol differences in conditioned pain modulation (CPM) exist, using a mechanically evoked temporal summation (TS) model. Methods: A series of 10 repetitive, mildly noxious, mechanical stimuli were applied to the fingers of 30 women with TMD, who had a primary diagnosis of masticatory myofascial pain, and 30 age-matched healthy women. The subjects rated the pain intensity caused by the 1st, 5th, and 10th stimuli in the series. To evaluate CPM, the same series of mechanical stimulations were applied with concomitant exposure of the other hand to a painfully cold water bath. Statistical inferences were based on t tests, chi-square tests, or analysis of variance (ANOVA), as appropriate. Results: Pain ratings increased significantly with stimulus repetition (P < .01) and CPM significantly reduced TS of pain (P < .01). Of particular note, both groups showed very similar degrees of CPM, with no significant group difference. Conclusion: Painful TMD is not necessarily associated with a compromised ability to engage the endogenous analgesic system in an experimental setting.