Pathological Study Of Influence Of Unilateral Mastication To TMJs

Object This study evaluated the histological response of the temporomandibular joint's condylar and disk following one side posterior teeth extraction in miniature rats. Material and Method 80 Wiaster write rats (one month of age) were divided into two experiment groups and two control groups. Each group had twenty rats. All the experiment rats were extracted right maxillary molars, and after the extraction all the experiment and control animals were fed under equal condition. One experiment and control group animals were killed after 4 weeks and the other groups were killed after 8 weeks. The temporomandibular joint of experiment and control animals, functional and non-functional sides were observed by means of light microscope and scanning electron microscope. Result Missing one side posterior teeth have great influence on two side TMJs. We found that obvious degenerative changes were common in all TMJs of the experimental rats, and the both side TMJs' changes had no significant differences. The pathologic changes included condylar surface became rough, some had big fibroid straps forming on the surface. Collagenous fibers disordered, and there were irregular fissures forming. Chondrocytes proliferated, and the volume of the cells decreased. Surface material was damaged in some area, so that the fiber under it could be seen. Condyle trabeculea widened. Disks became thin, especially at the middle line. Disks' surface also became rough, collagenous fibers disordered or abrupted,and irregular fissures formed between fibers. Disk's surface material was damaged , and the fibers under it also could be seen. One specimen's disk adhered to condylar at the middle region. One specimen's middle line perforated. The TMJs' changes were similar between 8 weeks group and 4 weeks group. Conclusion: The result of this experiment confirms that occlusal disturbance can cause degenerative change of the TMJs, thus we think occlusal disturbance as one importance cause of temporomandibular joint disorder syndrome.