Aims: This experiment study was undertaken to evaluate the differences, in bone response to various grafts.

Methods: Ninety, 3.5 months New Zeland white rabbits, weighing 4kg, were divided randomly in 6 groups of 15 animals. Under anesthesia, a 4.5mm hole was drilled in the 2 posteriors femoral condyles of each rabbit, in totaling 180 condyles. Holes were filled with various grafts as follow: Group I-autograft, Group II-xenograft (Lubboc®), Group III-allograft DBM (Grafton®), Group IV-substitute calcium sulfate (Osteoset®), Group V-substitute calcium phosphate hydroxyapatite (Ceraform®), Group VI- was used control. After the implantation, the animals were sacrificed at 1, 3 and 6 months intervals tissue samples from the implanted areas were processed for histological evaluation.

Results: Group I: At 1 month, autologous grafts were lined with activated osteoblasts and osteoclasts. Lamellar bone and cartilage were evident. Neoangiogenesis was prominent. At 3, 6 months defects were filled with mature bone. Group II: Lubboc® displayed moderate (1 month) to intense (3 months) remodeling activity and pronounced neoangiogenesis. At 3 months, endochondral osteogenesis and lamellar bone production were more prominent. At 6 months graft material was significantly restricted and lamellar had considerably replaced woven bone. Group III: Grafton® putty was present at 1, 3 months. There were few osteoblasts and numerous multinuclaeated cells rimming implant surfaces. Endochondral ossification foci, new bone formation and neovascularisation were observed (1, 3 months). At 6 months DBM fibers were absent. Lamellar and woven bone was evident. Group IV: At 1 month new bone (mostly woven) was present, lined with activated osteoblast and few osteoclasts. Endochondral ossification and angiogenesis were evident. At 3, 6 months bone remodeling was augmented, and Osteoset® graft was diminished. Complete closure of defects was observed, at 6 months. Group V: Ceraform® exhibited almost the same properties as Osteoset®. However, endochondral osteopoiesis and bone remodeling were less intense. Additionally, after 6 months, Ceraform® was still evident. Group VI: The defect areas were clearly observed at 1, 3 months.

Conclusion: Autografts are the most effective graft materials. Although Lubboc® is not totally resorbed, it seems to induce lamellar bone synthesis stronger than Grafton®. Bone substitutes are inferior to allografts.