| Trauma to the chin may cause injury to the articular tissues, resulting in condylar fractures and traumatic arthritis. Ankylosis, fibrous sdhesions and limitation or deviation of jaw opening can occur subsequently to trauma. Previous reports on the injury of TMJ mostly focused on the shape and the function of the TMJ after condylar fractures treated by different motheds. The pathological changes and the biomechanics are poorly understood.In this study, we intended to establish an animal model of indirect injury to both of lamb TMJs. And with this model, pathological changes of the TMJ and changes in the TMJ after condylar fractures treated by different methods were studied. Biomechanics during the impact were also primarily evaluated.Six parts were included in this study.Part 1 Establishment of a new animal model of indirect trauma on the lamb temporomandibular jointsA new designed appatus was used in this study. A cylindered-projectile weighed 0. 845 kg was pushed under the pressure of 10 kg and 25 kg, and the projectile struck on the chin of the lamb. This could simulate the TMJ injuries in the childen. The histological data demonstrated that the impact could produce damages of both of TMJs. Hemarthrosis and destuction of the articular discs and the cartilage of the condylar process and glenoid fossa were observed. The greater force was, the more obvious destruction was found. The changes of the TMJs after indirect trauma are similar to humans. According to the results, conclusions could be drawn that the impact model can be used for the study of TMJs after indirect trauma.Part 2 Histological changes of the lamb temporomandibular joint after indirect traumaThe established animal model was used and the both TMJs of the lambs were observed in this study. 15 lambs were injuried by the cylindered-projectile under the pressure of 10 kg, and another 3 animals were as a control. The experimental group animals were sacrificed at 3 day, 1 week, 2 week, 4 week and 12 weeks. The right and left TMJ wereremoved from the animals, and all the specimens were observed. 3 days later, we could find that all TMJ components showed signs of injury. The synovial membrane was torn up and the cartilage of the condylar process and glenoid fossa was destructed. Hemarthrosis and laceration of the disc and the attachment were also observed. 7 days later, the hemarthrosis was seldomly seen. Effusion was seen in some joints at 2 weeks. At 1 month posttrauma, the severely damaged structure of the two joints in one animal was found. We could find the loss of the disc and the cartilage of the condyle. Effusion also existed. 3 months later, the destructive changes were still there, but we could find the basic structure of the joint. And the results showed that trauma to the chin could result in the irreversible changes in both sides of the TMJ, which changed the internal environment of the joint. Hemarthrosis and destruction of the disc played an important role in the pathogenesis of traumatic diseases in TMJs.Part 3 A comparative study of the histological changes in the TMJ after different treatment of unilateral fractures in the lambsThe histological changes were recorded in the TMJ after different treatment of unilateral fractures. The results demonstrated that the conservative and surgical approachshowed no differences in the symmetry of the face and the function of the mandible. In the conservative group, the condyle could be remodeled. Whatever methods you chose, the destruction of the TMJ was also found. At 3 days posttrauma hemarthrosis could be seen in most of the joints of both groups. Fibrous effusion was seen in a joint of surgery treatment group at 1 month posttrauma. 3 months later, fibrous ankylosis was found in the conservative treatment group. The result showed that the treatment methods could not determine the changes in the joints, and the conservative approach should be the first choice for those not severely dislocated fractured condyles, but the follow-up must be done frequently and some...
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