A prospective investigation over two decades on signs and symptoms of temporomandibular disorders and associated variables. A final summary.

The aim of this summary of a longitudinal investigation on temporomandibular disorders (TMD) was to present the prevalence figures of signs and symptoms of TMD and certain other examined variables, and the correlations between these variables, over a 20-year period. Originally, 402 randomly selected 7-, 11-, and 15-year-olds were examined clinically and by means of a questionnaire. The same examination procedure was repeated three times: after 4-5 years and after 10 and 20 years, respectively. Signs and symptoms of TMD were mainly mild, but common already in childhood. They increased up to young adulthood, after which they leveled out. Progression to severe pain and dysfunction was rare, and spontaneous recovery from more pronounced symptoms was also rare. Significant correlations between reported bruxism and TMD symptoms were found, and a baseline report of tooth-grinding was a predictor of TMD treatment during the 20 years covered by the investigation. Occlusal factors were only weakly associated with TMD signs and symptoms. However, a lateral forced bite between the retruded contact position (RCP) and the intercuspal contact position (ICP) and a unilateral crossbite deserve further consideration as possible local risk factors for development of TMD. In conclusion, a substantial fluctuation of TMD signs and symptoms was observed in this sample of Swedish subjects followed for 20 years from childhood to adult. The demand for TMD treatment was low at all examinations, while the estimated treatment need was larger. One-third of subjects who had some kind of orthodontic treatment did not run a higher risk of developing TMD later in life.