Bone healing at distraction implants after alveolar distraction in dogs

Objectives: A new distraction device-distraction implant(DI), which has dual functions of distractor and implant, has been developed to augment alveolar ridge. We aimed to evaluate the application of this device and to follow the bone healing process. Methods: All mandibular premolars were extracted for 5 adult dogs. Two months later, a box-shaped osteotomy of the edentulous alveolar ridge was carried out, and two distraction implants were installed simultaneously. After a 7-day latency period, the transport segment was distracted at a rate of 1mm/day for 8 days. After distraction , the distraction implants were left to integrate into the bone.The specimens were obtained 5, 8, 12weeks after consolidation, and prepared for radiologic, histologic and histomorphometric analyses. Results: The ridges were augmented an average of 6.92±1.03mm. Radiographic examination showed a radiolucence was still seen in the distraction gap 5 weeks after distraction, but the radiopacity of the regenerated bone increased steadily up , to 12 weeks after distraction, the boundry between the distraction gap and native mandible disappeared. Histologic examination showed woven bone was seen 5weeks after distraction in the sites lateral to the macro-thread of DIs, while collagen fiber was seen around the micro-threaded regions of distraction screw of DIs. Signs of lamellar ossification were seen in distracted area occassionally 8weeks later, and loose woven osteoid was found around the micro-thread sites. 12 weeks later, osseintegration of the whole DI was shown, but the remodeling of bone was still continuous. Conclusions: Th results of this experiment suggest that simutaneously osteointegration of DI and distraction osteogenesis of alveolar ridge is possible. Using this type of distraction device to augment alveolar ridge vertically is a beneficial method.