The clinical significance of median occlusal position.

The harmony of the occlusal components of the teeth, mandibular joint and muscles, were investigated in 180 human subjects by clinical, dental articulator, radiographic and electrodiagnostic methods. Significant correlations were found between disharmony of these components at median occlusal position (MOP), and with pain-dysfunction of the masticatory system. Using the standardized stimuli of opening the jaw wide and snapping it shut automatically into MOP, temporalis and masseter muscle co-ordination and somesthetic reflex effects were quantified. The interval from tooth contact (s) to reinstitution of EMG activity (x), and the EMG silent-period duration (SP), were prolonged in the patients but returned to within the control range with elimination of the pain-dysfunction. Muscle incoordination with mandibular dysfunction was prevalent in the patients, and the incidence of osteoarthritis was greatest in those with persistent symptoms. The hypothesis was supported that disharmony of MOP exists in pain-dysfunction patients--while successful occlusal therapy leads to the restoration of the harmony within the biologic range. This implies physiological significance to this hitherto clinically neglected occlusal position.