ABSTRACT
BACKGROUND: Traditional solid bone can not receive satisfied effects in repairing irregular bone defects in oral maxillofacial surgery due to uneven distribution of cells and growth factors. Therefore, it is a research direction to prepare injectable tissue engineering bone.OBJECTIVE: To explore the effects of chitosan/β-tricalcium phosphate/recombinant human bone morphogenetic protein-2(CS/β-TCP/rhBMP-2) composite on mandibular defect repair.DESIGN, TIME AND SETTING: A randomized controlled animal experiment. The experiment was performed atthe animal laboratory, Medical College of Jinnan University from May 2008 to March 2009.MATERIALS: The injectable tissue engineering bone was prepared by using complex of liquid CS and solid β-TCP as scaffold materials, and combined with freeze-dried rhBMP-2.METHODS: Twenty-four New Zealand white rabbits were prepared for double sides mandibular defect models, and randomized into 4 groups: ①CS/p-TCP/rhBMP-2 group: 1 mL CS/β-TCP/rhBMP-2 complex was injected into the defects.②CS/β-TCP group:0.5 mL CS/β-TCP complex was injected into defects. ③Autograft bone group: repairing the defects with sclerotin of the iliac crest.④Blank control group: no implantation. MAIN OUTCOME MEASURES: At weeks 2, 4 and 8 after surgery, the material degradation and new bone formation were evaluated with, haematoxylin-eosin staining, and electron microscope; the bone mineral density was detected by dual energy X-ray absorptiometry (DXA) to determine bone formation rate and quality.RESULTS: ①Gross observation demonstrated that the size and thickness of osteotylus in CS/β-TCP/rhBMP-2 group was equivalent with the autograft group, which were greater than that of the other groups.②Histologicalobservation demonstrated that there were more bone matrixes in the CS/β-TCP/rhBMP-2 group and autograft group than that in the CS/β-TCP group and blank control group at each time points. ③Scanning electron microscope image suggested that at 8 weeks after operation, the bone bed and the materials in CS/β-TCP/rhBMP-2 group were connected with bone, and the gap was diminished. The degradation of the materials was so obvious that the complete structure of materials could not be found. ⑤DXA detection appealed that the bone density of each group was gradually increased with time prolonged. The quantities of bone density in CS/β-TCP/rhBMP-2 group in weeks 2, 4 and 8 were significantly higher than CS/β-TCP group and blankcontrol group (P < 0.05).CONCLUSION: ①CS/β-TCP/rhBMP-2 has good biocompatibility, degradability and the capacity of bone guidance and bone induction. ②CS/β-TCP can be served as a promising carrier for BMP-2, which is a potential degradable biological material for repairing bone defects.