ABSTRACT
Objective To evaluate the bonding condition of hydroxyapatite (HA)/zirconia ( ZrO2 ) composite and bone interface and the ability of HA/ZrO2 in repair of bone defects.Methods Bone defect models were established in the lumbar vertebral body of 24 Beagle dogs and were implanted with HA/ZrO2 gradient composite (Group A ),HA/ZrO2 unilayer composite (Group B ),pure ZrO2 (Group C) and pure HA (Group D) successively.Dogs were sacrificed and lumbar vertebral specimens were harvested 6,12,16 weeks postoperatively and before the sacrifice at postoperative 6 and 12 weeks,the dogs were intramuscularly administered of quadracycline for fluorescence labeling.The interface bonding and repair of bone defects were observed through X-ray films,histomorphology and biomechanical test.Results The X-ray films displayed that the Group A achieved more formation of osteotylus and better repair of bone defects with the extension of the implantation period,followed by the Groups B and D and that the Group C had relatively worse results.Histomorphology study showed that the fluorescence labeling was enhanced gradually from 6 to 12 weeks in the Group A,with its growth from the edge of the implanted material to the inner part and its tight adhesion to the material,indicating active osteogenesis and massive bone formation.While the fluorescence labeling of the Groups B,C and D centered in the edge of implanted materials without presence in the material inner part.The mineralization rate of the four materials at 6 and 12 weeks had significant differences ( P ＜ 0.05).Synostosis rates at 6,12 and 16 weeks were the highest in the Group A,with the rate of up to (90.26 ±3.82) ％ at 16 weeks (P ＜0.05 ).Biomechanical test showed the maximum shear strengths at 6,12,16 weeks in the Group A were (2.64±0.16) MPa,(2.95 ±0.19) MPa and (3.45 ±0.23) MPa respectively (P＜0.05).Conclusion HA/ZrO2gradient biocomposite bonds well with the bone and possesses good repair ability for bone defects and hence is an ideal novel material for bone defect reconstruction.