Background: Studies on the association between malocclusion and temporomandibular joint disorder (TMD) have reported conflicting results.

Objectives: To determine the impact of malocclusion and orthodontic treatment on symptoms of TMD.

Methods: At 12 years, 195 subjects fulfilled a questionnaire regarding TMD symptoms and participated in an oral examination including preparation of dental casts. The study was repeated at ages 15 and 32. The occlusions were assessed by applying the Peer Assessment Rating (PAR) Index. Associations between the changes in PAR scores and TMD symptoms were analysed with the chi-square test. A multivariable logistic regression was used to calculate the odds ratios (OR) and 95% confidence intervals (CI) of TMD symptoms at 32 years predicted by sex, occlusal traits and orthodontic treatment history.

Results: One in three subjects (29%) was orthodontically treated. Sex was associated with more self-reported headaches by females at 32 years (OR 2.4, 95% CI 1.05-5.4; p = .038). At all time points, any crossbite was significantly associated with greater odds for self-reported temporomandibular joint (TMJ) sounds at 32 years (OR 3.5, 95% CI 1.1-11.6; p = .037). More specifically, association occurred with posterior crossbite (OR 3.3, 95% CI 1.1-9.9; p = .030). At 12 and 15 years, boys whose PAR score increased were more likely to develop TMD symptoms (p = .039). Orthodontic treatment had no impact on the number of symptoms.

Conclusions: Presence of crossbite may increase the risk of self-reported TMJ sounds. Also, longitudinal changes in occlusion may have an association with TMD symptoms while orthodontic treatment is not associated with the number of symptoms.