Statement of problem: It is unclear whether patients with temporomandibular disorders (TMD) who report high levels of bruxism have more severe signs and symptoms of TMD and more advanced tooth wear than patients with TMD who report lower levels of bruxism.
Purpose: The purpose of this study was to determine whether there was a significant association between tooth wear, the parafunctional oral habit of bruxism, temporomandibular joint (TMJ) pain, and muscle pain severity in a TMD population.
Material and methods: A total of 84 subjects previously diagnosed with TMD, according to the Research Diagnostic Criteria for TMD (RDC/TMD) and who met 10 specific inclusion/exclusion criteria underwent a thorough multiaxial examination and classification recommended by the National Institute of Dental and Craniofacial Research (NIDCR). Measurement of tooth wear facets by use of a 4-point scale were graded in 10 zones on mandibular casts. One calibrated examiner performed all scoring. Bruxism was assessed in a standardized pretreatment questionnaire and in the dental history and interview (RDC/TMD) to indicate how frequently (0 = never to 3 = very often) subjects performed a list of oral habits, which included bruxism. The Kappa reliability coefficient (range from: -1.0 to 1.0) was used to correct for chance agreement, and was computed for each of the 10 study sites designated for rating. Subjects were also compared for muscle and joint pain. Muscle pain was a summed measure derived from the dental examination findings (range 0 to 20), calculated from the presence or absence of pain induced by palpation of 20 predetermined muscle sites. Similarly, joint pain was a summed measure of the presence or absence of pain in the TMJs induced by palpation of the joints on the outer surface and in the external auditory canal in 5 different positions of the mandible. A Pearson product-moment correlation was used to compute the summed severity of tooth wear and the subjects' age. Analysis of covariance was used to determine whether the number of wear facets was significantly higher in patients with TMD who reported a history of bruxism, compared with patients with TMD who reported no or minimal bruxism, after controlling for the effect of age. Multivariate analysis of variance was used to determine whether the number of painful muscles of mastication and joint sites on standardized examination were significantly higher in patients with TMD with a history of bruxism (alpha=.05).
Results: In the population tested, tooth wear was modestly correlated with age (r =.40, P<.001). Of the 84 subjects studied, 11.9% reported no bruxing activity, 32.1% reported some or occasional bruxing activity, and 47.6% had frequent bruxism activity; the remaining 8.4% were eliminated from analysis because they provided inconsistent responses. Bruxism activity was not correlated with muscle pain on palpation and was inversely associated with TMJ pain on palpation. Tooth wear was not significantly correlated with bruxism, TMJ pain, or muscle pain.
Conclusions: In this TMD population, tooth wear factors did not differentiate patients with bruxism from those without. The amount of bruxism activity was not associated with more severe muscle pain and was associated with less pain in the TMJ on palpation.