Temporomandibular disorders and bruxism. Part I.

Correct functioning of the entire stomatognathic system is achieved by a compatible relationship of all its parts. Four determinants, by their mutual harmonious activity, dictate the function of the entire system: the teeth, periodontium with supporting structure, muscles, temporomandibular joint (TMJ) and CNS. In such a complex system a disorder of any integrative part causes disturbances also in other parts of the system. Changed functions can arise through organic disorder, and also iatrogenically by inadequate conservative, prosthetic, surgical or orthodontic therapy. For this reason it is often difficult to recognise the primary cause. The first responses of the system to the disorder are adaptive mechanisms which occur within one or more integrative parts, and depending on their intensity and duration symptoms grow more prominent. Tissue response can be ortho- or parafunctional. Attempts are made to exclude psychoemotional influences and the obstacle eliminated by either abrasion, clenching or grinding of the teeth. If the obstacle is not eliminated by abrasion, the cause of such functional disorder becomes the trigger for parafunctional activity. From a review of the relevant literature it can be concluded that parafunctional activity is caused by changed occlusion, with determined psychological habits of the patient and specific tissue response of the stomatognathic system. Therefore, therapy of these disorders is made more difficult and includes a multidisciplinary approach.