Effects of the placement of endosseous implants in vascularized bone grafts on bone union in beagle dogs

Recently, reconstructive surgery with revascularized osteocutaneous flaps has been used to restore function in patients with bone defects caused by surgery for oral cancer. However, few basic studies have addressed problems such as the union of bone segments after osteotomy, the effects of dental implant placement on blood flow, and bone formation at the bone:implant interface in grafted bone. Nine adult beagle dogs were divided into three groups of three dogs each. Each group received osteotomized vascularized tibial grafts, osteotomized tibial grafts with implants (implants placed in contralateral limbs as control), or simple (non-vascularized) tibial grafts. The development of bone around the implants was studied by histological examination, contact micro-radiography (CMR), and fluorescent bone labeling. In the dogs receiving osteotomized vascularized tibial grafts, bone bridging was confirmed at both the medial and distal junctions of the bone segments after 4 weeks. Additional newly formed bone was observed after 8 weeks, and bone union at the surface of the segments was completed after 12 weeks. In contrast, bone formation was clearly delayed in dogs receiving simple (non-vascularized) tibial grafts. Histologically, no difference in bone union was evident between limbs with dental implants in tibial bone and control limbs without implants, suggesting that implant placement does not negatively affect revascularization. Fluorescent bone labeling technique confirmed high vascularity of the vascularized tibial bone grafts but not of the simple (non-vascularized) tibial bone grafts early after the procedure. Our results suggest that osseointegration occurred around dental implants placed at the same time as reconstruction with osteotomized vascularized bone grafts in this animal model.