The role of stress, occlusion, and condyle position in TMJ dysfunction-pain.

Lateral transcranial TMJ radiographs are duplicable within +/- 0.2 mm and are cross-sectional views of the lateral third of the condyle and fossa. The innate asymmetry of humans, when the right and left sides of the fossa and condyle are compared, was clinically insignificant. Tomograms are not indicated because they lack appropriate resolution and detail to evaluate qualitative bone changes; and because they are not an in-office procedure, the condylar position in the fossa is completely unreliable. A correlation was reported between condylar position in the fossa and TMJ dysfunction in over 320 patients. This observation suggests that a new definition of centric relation is indicated, a definition that differentiates whether it is functional or dysfunctional. The criterion is the correlation between the occlusal findings and the condylar position in the fossa as recorded by the lateral TMJ radiographs (when the teeth are in maximum occlusion). Stress response was found to be greater in males than in females (in all vertebrates, including humans); therefore stress cannot be a direct cause of craniomandibular pain since more women have the disorder. It was concluded that stress is an indirect contributing factor that usually works through the medium of clenching. The role of the neuromuscular mechanism in craniomandibular pain was discussed. Proprioception reflex activity forms the basis for muscle length, mandibular positional sense, as well as masticatory function. Occlusal disharmonies increase noxious input to the neuromuscular system, as well as stress-induced clenching, causing increased muscle activity and spasm-pain. Condylar displacement also contributes to TMJ dysfunction-pain, depending on its direction. Anterior condylar displacement can initially affect the muscles by inducing overfunctional response in the proprioceptive system. Posterior condylar displacement usually results in an intrajoint response consisting of a disk derangement, reciprocal clicking, possible anterior disk dislocation, possible pathologic swallowing pattern, and noxious stimulation to the proprioceptive system. These factors contribute to subsequent trismus, muscle spasm and pain, and long-term pathologic remodeling of the joint. A detailed history is necessary to evaluate the role of stress. The physical occlusal findings are correlated with the condylar displacement observed in the TMJ radiographs to diagnose and plan corrective treatment.