Effects of Functionally Graded Hydroxyapatite for Large Mandibular Defects in Adult Rabbits

Abstract

Objectives: As an alternative to autograft harvesting, we develop a functionally graded hydroxyapatite (fg-HAp) to induce bone regeneration within extensive bone defects. The functionally graded crystallinity from the inside layer to the surface layer of the fg-HAp promotes bone remodeling and replacement. We evaluate the effects of fg-HAp alone and in combination with fibroblast growth factor (bFGF) on bone regeneration within a bone defect in a rabbit mandible. Methods: The bone defect in the rabbit mandible was 12 x 9 x 3.5 mm in size. For the control group, no material was added to the defect. The experimental groups consisted of fg-HAp alone and fg-HAp combined with 5μg of bFGF. At 2, 4 and 8 weeks after implantation, we excised the mandibles and performed histomorphometrical analysis. Results: The fg-HAp resorption and replacement with new bone occurred fastest at the lingual portion of the defect. The fg-HAp maintained the mandibular outline and was absorbed by multinucleated giant cells. Blood vessel infiltration into the framework of fg-HAp was also observed. Adding 5μg of bFGF did not accelerate bone regeneration. The fg-HAp fragment was observed at the buccal portion of the defect. Excavated bone healing was observed only in the control group. Conclusions: The fg-HAp is an effective substrate for bone regeneration in critically sized bone defects.