Characteristics of Osteogenesis Around Dental Implants Inserted into Vascularized Bone Grafts and Free Bone Grafts in Mandible of Dogs

Abstract

The objective of this study was to investigate the characteristics of osteogenesis around dental implants in both vascularized and nonvascularized bone grafts. Vascularized bone grafts were nourished by inferior alveolar vessels providing medullary blood flow to the mandibles of adult dogs. Titanium implants were placed into the bone grafts and normal mandibles. The time course of osteogenesis around the implants was observed histologically from 2 to 24 weeks after operation. Specimers stained with Stevenel's blue and Van Gieson-picrofuchsin stains and fluorescently labeled specimens were examined with a confocal laser scanning microscope. Implant-bone contact rates were determined.In vascularized bone grafts, new bone formation was evident all around the implants at 2 weeks postoperatively. New bone became compact with the passage of time. These processes of new bone formation were similar to those of normal mandibles.In cortical bone of vascularized bone grafts, bone resorption was recognized. However, bone remodeling was found at an early stage, suggesting that implants could be placed into vascularized bone grafts immediately after the primary operation.In nonvascularized bone grafts, bone resorption and remodeling occurred from the outside of cortical bone. New bone formation around implants was found at 8 weeks postoperatively. The implant apex was encapsulated by fibrous tissue at 24 weeks postoperatively. The results suggest that simultaneous implantation with free bone grafting requires a long time for bony linkage and that encapsulation of implants by fibrous tissue may occur in nonvascularized bone grafts.