Temporomandibular disorders and functional occlusion after orthodontic treatment: results of two long-term studies.

The prevalence of temporomandibular (TM) disorders and the status of the functional occlusion in former orthodontic patients many years after treatment were evaluated in two independent clinical studies. In each study, the former orthodontic patients were compared to similar groups of adults with untreated Class I and Class II malocclusions. Both studies reported similar findings with regard to TM disorders; there was no statistically significant difference (p greater than 0.05) between the orthodontic and control groups in either study. The illinois study found a high prevalence of nonfunctional (balancing) contacts in both groups, while the Eastman study found a somewhat lower prevalence. Differences for most of the occlusal parameters between the orthodontic and control groups were not statistically significant in either study. The findings for these two studies are similar and suggest that orthodontic treatment performed during adolescence does not generally increase or decrease the risk of developing TM disorders in later life.