Healing process after alveolar ridge distraction in sheep.

Abstract

Mandibular augmentation by distraction of the alveolar ridge has been in use for several years. Since 1996, a distraction device that remains in the alveolar ridge after distraction has been used by the Department of Oral and Maxillofacial Surgery of Graz University. The distraction device is transformed into a dental implant after the end of the distraction process and can later be used for prosthetic purposes. We aimed to show the application of the device in this animal experiment and to follow the osseous healing process. Two distraction implants were inserted into the mandibles of 8 sheep. Distraction of 0.5 mm per day was carried out for 8 days. Two sheep were killed 1, 2, 3, and 6 months after distraction, and the dissected mandibles were examined clinically, radiologically, and histologically. After the first month of distraction, only slight radiopacity of the distraction gap was found. This increased steadily up to the third month after distraction. The boundary between the distraction fragments and the gap disappeared gradually. Six months after distraction, a homogeneous fine-meshed spongiosa structure was found in the area of distraction. Histologic examination showed desmoid ossification in the distraction gap and a continued increase in osteoid. After 6 months, mature bone was found. Only in the center was the rebuilding process not complete. Six months after distraction, osseointegration of the implants was shown in the region of the screw thread and distraction cylinder. The healing process corresponded to that found in long bones, but showed only desmal ossification. Osseous integration of the distraction implants was found 6 months after distraction, although the implants were stable 3 months after distraction.