Dysfunctional temporomandibular joint and muscle pain

TLDR: The occlusal stability in centric relation was found to be of extreme importance for muscle harmony during swallowing, and electromyographic evidence of muscle balance in rest position could be obtained in more than one-half of the patients in spite of Occlusal interference and temporomandibular joint pain.

Abstract: The relationship between occlusal disharmony and pain in the temporomandibular joint and adjacent muscles was tested clinically and electromyographically before and after occlusal adjustment on 32 patients. Various degrees of bruxism associated with psychic tension and occlusal interferences were observed in all of the patients. Clinically, all patients experienced relief of the pain and discomfort after complete occlusal adjustment. Electromyographically, a harmonious and well-synchronized contraction pattern of the temporal and masseter muscles was recorded after the adjustment. Any type of occlusal interference was found to trigger muscle spasms and pain, but the most consistent and significant interference was a discrepancy between centric relation and centric occlusion. The muscle disharmony was displayed electromyographically mainly in swallowing. The second most significant occlusal disharmony was balancing side interference. The balancing side contact had to be lighter than the working side contacts to establish a harmonious masticatory pattern. The patients' symptoms subsided without altering the vertical dimension. A close correlation was observed between the clinical and electromyographic recordings of occlusal interferences and muscle disharmony. However, electromyographic evidence of muscle balance in rest position could be obtained in more than one-half of the patients in spite of occlusal interference and temporomandibular joint pain. Masticatory contacts were seldom observed posterior to centric occlusion. However, the occlusal contacts in swallowing apparently occurred between centric occlusion and centric relation. The occlusal stability in centric relation was found to be of extreme importance for muscle harmony during swallowing. Rest position determined by conventional clinical methods did not always correspond to minimal, harmonious muscle activity electromyographically. A slight opening from the clinically determined rest position often facilitated the recording of an even, minimal contraction of the temporal and masseter muscles. The mandible could be opened from this position about 1/2 inch further (a resting range) without eliciting any increased muscle activity from these muscles.