下顎枝垂直骨切りによる下顎枝延長に関する実験的研究 : 近位骨片と顎関節に及ぼす影響
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概要
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The postoperative findings of the unilateral vertical ramus elongation using intraoral vertical ramus osteotomy (IVRO) were studied experimentally. Adult Japanese monkeys (macaca fuscata) were used for the experiments. Changes of the postoperative proximal segment of the monkeys including their TMJs were examined radiographicaliy and histopathologicaliy. Thirteen Japanese monkeys with permanent teeth were used. Study groups were made up of a sham group (4 animals), an experimental group (8 animals) and a control (1 animal). Bilateral IVRO was performed on the animals of the experimental group. After osteotomy, metal splints were cemented to the left lower molar teeth to elongate the rami 10mm vertically. The animals of the sham group underwent only osteotomy, and the rami were not elongated. The control animal did not undergo any operations. The following results were obtained. 1. Postoperative occlusion of the sham group and the experimental group was as stable as the occlusion at the time of operation. In the experimental group, relapses were not observed during 12 postoperative months in spite of 10mm of elongation. 2. Radiographically, the left proximal segment of the experimental group monkeys were rotated backward immediately after the operation until the 1st postoperative month. This backward rotation decreased after the 3rd postoperative month and returned to the preoperative position after the 6th postoperative month. 3. Histopathologically, the cartilaginous layer of the mandibular condyle was thick from the center to the rear at the 1st postoperative month at the elongated side of the experimental group. This thickness decreased at the 3rd postoperative month. Bleeding, which was probably due to the stress of IVRO, was observed in the superior joint cavity until the 3rd postoperative month. In the no-elongated side of the experimental group, the thickness of the cartilaginous layer of the mandibular condyle had become thinner than in the elongated side, and adhesions were observed between the articular disk and joint surface until the 3rd month. Degenerative changes were not found in any of the groups. After the 6th postoperative month, the histopathological findings of the TMJ of the experimental group and the sham groups were similar to those of the control. These results suggest that the effect of unilateral vertical ramus elongation using IVRO for the proximal segment and for the TMJ did not continue for a long time, because of production of a more functional articular disk-condyle relationship by repositioning of the proximal segment and the condyle and/or remodeling of the condyle.
- 九州歯科学会の論文
- 2000-02-25