Structural changes of mandible after sagittal split osteotomy

Abstract

The object of this study is to observe structural changes of the jaw bone after sagittal split osteotomy. The osteotomy was on mandibles of adult dogs. Time tracing was performed by using two hard tissue labelling agents (tetracycline and calcein) during the experiment.
Microradiograms and labelling findings obtained from horizontally incised large ground sections ranging from the mandibular first molar to the ramus were compared. We obtained the following results:
1. About 15 days after the osteotomy, a new bone formation was observed, extending over a wide range between the interradicular septa of the mandibular first molar and the ramus. However, no new bone formation was found by the buccal surface of the incised extremity. At approximately the same time, a new bone formation began even on the internal surface of the compact bone around the mandibular canal.
2. Starting from the 29 th day after the osteotomy, a new bone formation became inactive in the external wall of compact bone and the interior of the compact bone facing the mandibular canal. Secondly, a new bone formation on the external wall of compact bone disappeared after 90 days through an active resorption. In comparison with this disappearance, a relatively thick bone trabeculae has continued to run apart from the internal wall of compact bone the mandibular canal even after 180 days passed.
3. A new bone formation on the internal wall of compact bone and spongy bone remained to a small degree about 15 days later, and became active after 29 days. After 50 days, the extent of both the incised extremity parts were almost filled with new bone. However, the remodeling began in the new bone after 28 days. As a result, the bone trabeculae consisted of a mixture of compact bone and porous bone. The bone near the alveolar crest showed a compact alignment and the lower part of bone became porous about 180 days later.
4. It was also observed that the remodeling was active in the internal compact bone after 15 days and progressed not only around the incised parts but also to a wide extent in other parts. As a result, the buccal surface of the compact bone near the incised edge was concave. In these procedures, however, the remodeling advanced also in the compact bone.