Credibility of morphologic and psychologic theories of TMJ pain-dysfunction aetiology

An evaluation of the morphologic and psychologic theories of the aetiology of TMJ pain-dysfunction can be revealing if made without resorting too much to scientific experimental results, because the interpretation of results as well as the questions asked are largely dependent on a prior commitment to one of the theories. Accepting that the TMJ pain-dysfunction became a common disease after the industrial revolution gives reason to look for a causative factor connected with it. Both an increase of psychologic stress and a change of dental morphology and function appear as possible factors, but only the latter has factual evidence. The lack of functional wear disturbs the unconscious swallow reflex but apparently not mastication. This suggests that retrusive interferences are a necessary but not always sufficient condition for the initiation of the TMJ pain-dysfunction. Psychologic factors are contributory, they can cause tooth clenching and perhaps grinding, but there seems to be no reason other than interferences from occlusion for that taking place eccentrically. Thus psychogenic tooth clenching and grinding do not seem to be pathogenic without the morphologic factor.