Longitudinal outcome of temporomandibular disorders: a 5-year epidemiologic study of muscle disorders defined by research diagnostic criteria for temporomandibular disorders.

AIMS: To investigate the course of myofascial pain defined by Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) over a period of 5 years, and to identify prognostic factors from baseline data.
METHODS: Subjects were 155 consecutive patients and 80 community cases identified from an age-stratified representative population sample; all met the primary selection criterion of reporting pain in the temporomandibular joint (TMJ) or masticatory muscles. The 2 groups were combined to yield a total sample of 235 subjects (50 male, 185 female; mean age = 39 years). Subjects were evaluated at baseline, 1 year, 3 years, and 5 years by trained examiners using standardized, reliable methods. Psychological and behavioral factors were assessed by self report.
RESULTS: According to RDC/TMD criteria, 50 (31%) of the 165 subjects presenting with myofascial pain (MFP) at baseline continued to have their disorder over a period of 5 years; 55 (33%) remitted, and 60 (36%) were recurrent cases. Bivariate statistics and multivariate logistic regression analyses indicated that baseline pain frequency, number of painful palpation sites, and total number of body sites with pain were significant predictors of persistent vs remitted and recurrent cases. No predictors that distinguished remission vs recurrence could be identified. Thirty subjects from the 70 without a diagnosis of MFP at baseline developed a new MFP. A high baseline somatization score (without pain items) was a significant risk factor for onset of MFP.
CONCLUSION: Muscle disorders classified by RDC/TMD are predominantly chronic or fluctuating pain conditions, with a modest probability (31%) of remission.