Osteoarthrosis in TMJ is known to accompany characteristic features of the craniofacial malformation and malocclusion. In order to explain the mechanism that brings about the typical mandibular changes relating to the frequent clinical symptom, i.e., the limited mouth opening in TMJ patients. The present study investigated the mandibular morphology of the rabbit, also intentional TMJ osteoarthrosis was performed on the TMJ of the rabbits and their morphological changes were observed. A total of 12 New Zealand house rabbits weighing an average of 3 kgwere used and all left side joints were surgically meniscectomized and right side joints were used as controls. The rabbits were sacrificed in one week, two weeks, one month, three months and 5 months after the menisectomy, and the removed TMJs were examined by histological and radiographical methods and analyzed statistically. It was found that the mandibular morphology caused by osteoarthritis in the TMJ was characterized by the decrease in size of the ascending ramus, posterior ramus bowing, deep antegonial notch and thickening of the cortex in inferior and posterior borders of the mandible, that the similar features were also observed in the rabbit mandible. When the menisectomy was performed in the unilateral side of rabbit TMJ, the mandibular changes including the increased depth of antegonial notch and posterior ramus bowing occurred only on the affected side. These data suggested that the limitation of the mandibular movement and altered masticatory pattern by meniscectomy affects the structural remodeling of the mandible and TMJ likely the TMJ osteoarthrosis

The primary growth center (MdPGC) of human fetal mandible was conspicuously distinguished in the soft X-ray view of fetal mandibles.1) As the peripheral adaptive growth of mandible advanced during the postnatal period, the MdPGC became overshadowed by condensed cortical bone. However, in the well-processed radiograms of adult mandible a condensed radiopaque image, measuring 0.5-1.0 cm in diameter, can be observed below the apex of first premolar. In this study we aimed to trace a sclerotic sequela of mandibular primary growth center during postnatal period. Panoramic radiograms of two hundreds adults and soft X-ray views of thirty dry mandible were analyzed by statistical methods. The adult MdPGC was clearly distinguishable from the mental foramen. The area of MdPGC was seldom changed in the older persons, even in the edentulous mandibles. Additionally, the benign lesions of odontogenic cysts and tumors hardly destroyed the original structure of MdPGC, while the malignant tumors of squamous cell carcinoma and metastatic cancer rapidly destroyed and resolved the radiopaque area of the MdPGC.