Risk factors associated with incidence and persistence of signs and symptoms of temporomandibular disorders

Objective. To analyze whether gender, self-reported bruxism, and variations in dental occlusion predicted incidence and persistence of temporomandibular disorder (TMD) during a 2-year period. Material and methods. The study population comprised 280 dental students at Umea University in Sweden. The study design was that of a case-control study within a 2-year prospective cohort. The investigation comprised a questionnaire and a clinical examination at enrolment and at 12 and 24 months. Cases (incidence) and controls (no incidence) were identified among those without signs and symptoms of TMD at the start of the study. Cases with 2-year persistence of signs and symptoms of TMD were those with such signs and symptoms at all three examinations. Clinical registrations of baseline variables were used as independent variables. Odds ratio estimates and 95% confidence intervals of the relative risks of being a case or control in relation to baseline registrations were calculated using logistic regression analyses. Results. The analyses revealed that self-reported bruxism and crossbite, respectively increased the risk of the 2-year cumulative incidence and duration of temporomandibular joint (TMJ) signs or symptoms. Female gender was related to an increased risk of developing and maintaining myofascial pain. Signs of mandibular instability increased the risk of maintained TMD signs and symptoms during the observation period. Conclusion. This 2-year prospective observational study indicated that self-reported bruxism and variations in dental occlusion were linked to the incidence and persistence of TMJ signs and symptoms to a higher extent than to myofascial pain.