Temporomandibular disorder (TMD) is the collective term for a number of functional disorders of the head and neck region. The main symptoms of TMD are pain and dysfunction of the muscles of mastication and/or temporomandibular joints (TMJs). The etiology of TMD is now believed to be multifactorial due to the heterogeneity of TMDs. The dental occlusion is suspected to be an etiologic factor. Originally described as playing a role ranging from a primary causative factor to a cofactor, it is now considered to play a rather insignificant part in the development of dysfunction in the temporomandibular system.
Aim: To investigate the relationship between occlusal parameters and the signs and symptoms of TMDs in population- based subjects. General occlusion-related variables as well as static and dynamic contact relationships in the posterior region were analyzed for this purpose.
Materials and methods: Five hundred and fifty eight subjects aged 20 to 49 years with at least 20 remaining teeth were evaluated for contact relationships between the dental arches in static and dynamic occlusion and for malocclusion (project affiliated with the Study of Health in Pomerania baseline study, SHIP0). Clinical TMJ function analysis was also performed on each subject. Bivariate relationships were examined using the chi-square test, correlation analysis, and multivariate models.
Results: Of all the subjects, 5.7% had pure anterior canine guidance and 4.2% had hyperbalancing occlusal contact. Occlusal guidance patterns were not associated with TMD signs and symptoms. Likewise, no occlusal parameter was associated with signs and symptoms of TMDs (self-reported pain). Patients with no occlusal contact or only unilateral occlusal contact in the posterior region (3.6%) showed a tendency for a higher rate of tenderness of the TMJ (P = 0.055). Those with an inverted maxillary central incisor exhibited a significantly higher rate of TMJ tenderness (P = 0.02) and a tendency for a higher rate of tenderness of the masticatory muscles (P = 0.065). The following associations were found for tenderness of the TMJ (results adjusted for age, sex, and marital status; significance level P = 0.05): vertical bite/Angle Class II/2 malocclusion (cover bite): odds ratio (OR) = 2.3 (1.4-3.8); no occlusal contact or only unilateral occlusal contact in the posterior region: OR = 3.9 (1.3-11.3); bruxism: OR = 1.6 (0.9-2.7). Reciprocal clicking of the TMJ (TMJ sounds) was significantly associated with a loss of posterior support (right side: P = 0.021; left side: P = 0.041). These associations were no longer significant in the multivariate analysis of the longitudinal data.
Conclusions: Subjects with a loss of posterior support due to missing teeth or the absence of occlusal contact in maximum intercuspation had a higher incidence of TMJ sounds and tenderness. Angle Class II/2 malocclusion (cover bite) in the maxillary anterior region was associated with tenderness on palpation of the TMJ and masticatory muscles. Except for cover bite, there was a low prevalence of all occlusal parameters with significant associations with TMD signs and symptoms. Although cross-sectional data analysis revealed associations between TMD and occlusal factors, causality of these relationships cannot be assumed.