BACKGROUND: Nano-hydroxyapatite (Nano-HA) has been shown to be a good choice of bone repair material owing to its salts composition consistent with natural bone and its scaffold structure homothetic to natural bone structure. OBJECTIVE: To investigate the feasibility of nano-HA in repair of jaw bone defect in rabbits. DESIGN, TIME AND SETTING: Materials-based animal experimental observation was performed at Laboratory Animal Center of Jiamusi University and Beijing Ji Shui Tan Hospital between January 2003 and June 2005. MATERIALS: Neutralization reaction of calcium biphosphate and calcium hydroxide was used to construct the system. The reactants were managed to be cotloidal by reaction control and using appropriate nucleating agents. Acerata HA crystal obtained under different conditions was sintered to obtain the nano-HA granule with a diameter of 1-56 nm. METHODS: Twenty-four healthy Chinese Harbin rabbits were randomly and evenly divided into an experimental group and a control group. After anesthesia, a penetrating 1.5 cm x1.5 cm defect was made with the GX micro-drill at the mandibular edge in each rabbit. Nano-HA was implanted in defects of the experimental group, and common HA was used in the control group. Antibiotics were used for 5 days afterwards. MAIN OUTCOME MEASURES: Change in bone mineral density after implantation of nano-HA. RESULTS: After repair of bone defect, the bone mineral density in the expedmental group increased gradually to a normal level and tended to be stable; whereas it was gradually decreased in the control group. There was significant difference between the experimental and control groups (P < 0.01). CONCLUSION: Nano-HA can promote new bone maturation, and this material produces favorable results in repair of bone defects.

BACKGROUND: To repair bone defect, histocompatibility, growing characteristics, biodegradation and repairing mechanism of nanometer need to be further studied in clinic. OBJECTIVE: To observe the growing characteristics and histocompatibility of nano-hydroxyapatite (Nano-HA) for repairing jaw defect of rabbits.DESIGN: Randomized grouping animal study.SETTING: Beijing Jishuitan Hospital and Stomatology College of Jiamusi University.MATERIALS: A total of 24 New Zealand rabbits, either gender, weighing 2.5-3.5 kg, were provided by Animal Experimental Center of Jiamusi University. The animal experiment had got confirmed consent from local ethic committee. Nano-HA was provided by Material Engineering College of Jiamusi University and dealt with routine hyperthermia/hypertension sterilization. In addition, hydroxyapatite was provided by Wuhan Industry University, and the diameter was 1.0-2.0 μm.METHODS: The experiment was carried out in the Experimental Animal Center of Jiamusi University from November 2001 to May 2006. All rabbits were randomly divided into experimental group and control group with 12 in each group. Bone defect in the diameter of 1.0 cm was produced on body of mandible. Nano-HA was used to repair the bone defect of rabbits in the experimental group, while hydroxyapatite was used to repair the bone defect of rabbits in the control group. At 1, 4, 8 and 12 weeks after operation, all rabbits were sacrificed. In addition, medical imaging analysis system was used to analyze generative quantity of tissue in the two groups; meanwhile, histological quality and quantity were also analyzed so as to observe histocompatibility and newborn osteogenesis. MAIN OUTCOME MEASURES: Histocompatibility and newborn osteogenesis.RESULTS: With the time passing by, the amount of repairing materials was decreased because of the combination with newborn tissue into bone in bone defect-repaired region in the experimental group. When it was closed to normal bone, the amount was stable. However, bony callus was not able to grow in materials in the control group. Results of correlation analysis demonstrated that materials were negatively straight-line correlation with newborn bone (r = -0.912 0, P < 0.01). During the repairing procedure of bone defect, newborn bone was closely correlative with Nano-HA; while, with the increase of newborn bone, the amount of repairing materials was decreased because of the combination with newborn tissue into bone.CONCLUSION: Nano-HA can combine with newborn bone tissue so as to rapidly generate bone, while it has an excellent biocompatibility.