The repair of critical-size defects with porous hydroxyapatite/polyamide nanocomposite: an experimental study in rabbit mandibles

This study was conducted to evaluate the healing of critical-size surgical defects after implantation of porous nano-hydroxyapatite/polyamide composite (nHA/PA) blocks based on a bilateral mandible model using adult New Zealand white rabbits. 15 rabbits were divided randomly into three groups according to the observation period: 4, 12 and 24 weeks. The defects on one side were implanted with nHA/PA blocks and the contralateral defects were kept empty as blank controls. A combination of macroscopic, radiographic, histological and histomorphometric studies were performed up to 24 weeks postoperatively and compared with normal healing. Large amounts of callus and active osteoblasts were found in the pore structure after 4 weeks of implantation, and the defects were completely occupied by neo-bone with density comparable with that of host bone at 24 weeks. Significant difference was found between nHA/PA groups and blank controls regarding X-ray opacity over the whole period and bone parameters at 4 weeks postoperation (P < 0.05). The porous nHA/PA composite promotes bone formation over the extension of the defect, particularly in the early stage. Porous nHA/PA offers interesting potential for maxillofacial reconstructive procedures in load-free areas.