Pressure pain thresholds fluctuate with, but do not usefully predict, the clinical course of painful temporomandibular disorder

Central sensitization elicits pain hypersensitivity and is thought to be causally implicated in painful temporomandibular disorder (TMD). This causal inference is based on cross-sectional evidence that people with TMD have greater sensitivity than controls to noxious stimuli. We tested this inference in the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) prospective cohort study of 3258 adults with no lifetime history of TMD when enrolled (visit 1). During 5 years of follow-up, 1 group labeled "persistent TMD cases" (n=72) developed first-onset TMD by visit 2 that persisted ⩾ 6 months until visit 3. Another group labeled "transient TMD cases" (n=75) developed first-onset TMD at visit 2, which resolved by visit 3. Randomly sampled "controls" (n=126) remained TMD-free throughout all 3 visits. At each visit, pressure pain thresholds (PPTs) were measured by algometry at 10 cranial and bodily sites. In persistent TMD case patients, mean PPTs reduced 43 kPa (P<.0001) between visits 1 and 2 and thereafter did not change significantly. In transient TMD case patients, mean PPTs reduced 41 kPa (P<.001) between visits 1 and 2, and then increased 20 kPa (P<.001) by visit 3. These patterns were similar after excluding cranial sites symptomatic for TMD. Importantly, visit 1 PPTs had no clinically useful prognostic value in predicting first-onset TMD (odds ratio [OR]=1.07, P=.15). Among first-onset case patients, visit 2 PPTs were modest predictors of persistent TMD (OR=1.36, P=.002). In this longitudinal study, PPTs reduced when TMD developed then rebounded when TMD resolved. However, premorbid PPTs poorly predicted TMD incidence, countering the hypothesis that PPTs signify mechanisms causing first-onset TMD.