A case-control study of temporomandibular disorders: symptomatic disc displacement.

This case-control study was designed to investigate the risk factors for disc displacement (DD) without myofascial pain (MFP). The study population included 59 cases with DD without MFP, selected in two hospital dental clinics, and 100 concurrent controls selected in one of these clinics. The association with DD was evaluated for bruxism, head-neck trauma, orthodontic treatment, and sociodemographic characteristics by using unconditional logistic regression. In the multivariate analysis, excluding psychological factors, an association was found between DD and clenching-grinding (OR=3.57; 95% CI: 1.27-9.98). This association persisted when anxiety (OR=3.07; 95% CI: 1.08-8.70) or depression (OR=4.02; 95% CI: 1.43-11.31) was included in the model. A positive association was noted between orthodontic treatment and DD (OR=3.10; 95% CI: 1.06-9.65). The effect between orthodontic treatment and DD remained and increased with the inclusion of anxiety (OR=3.65; 95% CI: 1.15-11.61) or depression (OR=3.20; 95% CI: 1.06-9.65). A high level of anxiety (OR=2.40; 95% CI: 1.01-5.73), was positively related to DD. We concluded that clenching combined with grinding, and orthodontic treatment are factors related to DD. The interpretation of these associations, however, requires caution because of the inclusion of prevalent cases.