Etiology Study On Abnormal Occlusal Contacts In Temporomandibular Disorders

The earliest etiologic and therapeusiology theories proposed for temporomandibular disorders(TMDs) was the suggestion that abnormal occlusal contacts were essential. Occlusion has great importance to the reconstruction of temporomandibular joint and the functions of nerves and muscles. The load of TMJ directly come from biting force. And the mode of mandibular movement is the reflection of the coordination between nerves and muscle functions, as well as TMJ conditions. Because of limitation of the knowledge in occlusion and TMD, the classification of occlusion are mainly based on morphology, while the criterions for diagnosis and treatment effects are based on symptoms and signs.The study was undertaken to analysis with occlusions and mandibular movement in TMD patients and asymptomatic volunteers, and in order to find the relationships between malocclusion and the characteristics of mandibular movements. The purpose of this study was to observe TMD patients' occlusal contacts and its effects to the patients' symptoms.The study showed that abnormal occlusion in vertical direction was significancly correlated with TMD symptoms, and the risks of getting pain and click increased 2.69 times. Abnormal occlusion in vertical direction was not only the results of losing teeth, but also the results of malocclusion. Occlusaltherapies should restore the fluent occlusal curves.Studys on the pathways of mandibular border movements showed that intercuspal position (ICP) is the top point of border movement. Only when the teeth contact cusp-to-fossa steadily with their counterparts can the mandible arrived to the highest position. Moving forward is a important way for muscles to adapt to anatomic structures of occlusion and joints. The incapability for the mandible to get highest position would result in abnormal joint and muscle functions.The stability of occlusal pathway during masticatory movement was poorer in TMD patients than in asymptom volunteers, In coronal direction, the shapes of the occlusal pathway were affected by mesial-distal occlusal characteristics. While there were no significant difference between occlusion, the shape and the stability of occlusal pathway during masticatory movement and the symptoms of TMD patients. Occlusion did not affect occlusal pathway during masticatory movement significantly for there were multiple factors affecting mandibular movements, in which the compensation of masticatory muscles and stomatognathic system were of much importance.Occlusal adjustment can increase occclusal contact points and contact areas, which could relieve the pain obviously. The results showed that improving occlusal contacts by occlusal adjustment could ease the pain caused by chronic TMD. While occlusal guidance has no significant relationship with pain of TMD patients.Characters of disc anterior displacement and uncentral position of condyle in fossa might relate to joint structure remodeling. Prolonging courses did notalways result in the changing of disc's position. Whether abnormal occlusal contact resulted in abnormal stress in temporomandibular jiont(TMJ ) and the degenerative changes in articular disc and condyle need to be farther studied.In conclusion, occlusal contact relationships in vertical direction had great significance in physiology and pathology for stomatognathic systems. Because of functional compensation of masticatory muscles and TMJ reconstruction, occlusal guidance had little effects to functions of the stomatognathic systems. Abnormal occlusion and change of occlusal contact characters did not infulence jaw movement significantly.