Guided Tissue Regeneration Membrane Enhance Bone Formation During Distraction Osteogenesis In Rabbits

Background and objective:Distraction osteogenesis (DO) is the process of bone lenghthening by gradual mechanical distracton. It was first described in the field of orthopaedics, and then developed into daily surgical practice for the treatment of different craniofacial anomalies. There are many factors that influence the quality of bone formation during distraction osteogenesis, usually the formation of fibrous tissues at the distraction gap may result from the accumulation of rapidly migrating fibroblasts at the site of an osteotomy, and then influence the bone formation by decreasing the number of osteoblasts. The guided tissue regeneration membrane (GTRM) could theoretically prevent fibroblasts from entering the distraction gap, allowing the osteotomy site to be fillde with only osteogenic cells to enhance the bone formation in distraction zone. Therefore,in this study we firstly establish the mandibular distraction osteogenesis model in rabbits, and then research the ability of guided tissue regeneration membrane in bone formation during distraction osteogenesis. The results of this study will provide valuable informations for GTRM to accelerate callus formation and shorten treatment period during distraction osteogenesis, and lay the foundation for eventual clinical application.Methods:1.Creation of the mandibular distraction osteogenesis model in rabbit (control group):Twenty white New Zealand rabbits were peformed osteotomy in the left mandible and then interal distraction device was positioned and fixed on the mandible. Five days after osteotomy, distraction was carried out at a rate of0.8mm every day(twice a day,0.4mm at8a.m.and8p.m.)for ten days, to produce a distraction gap of approximaately8mm. After distraction was completed, the distraction was left in situ, and went into the consolidation phase. Half of animal randomly chosen from each group were sacrificed at the end of week2and6throughout the consolidation phase. The right mandibular samples were taken out for X-ray and histology examinations.2.The GTRM used in distraction osteogenesis (experimental group):Twenty white New Zealand rabbits were peformed osteotomy in the left mandible and then interal distraction device was positioned and fixed on the mandible with the GTRM inside wrapped around the distraction zone, then came to the process in accordance with method one. Half of animal randomly chosen from each group were sacrificed at the end of week2and6throughout the consolidation phase. The right mandibular samples were taken out for X-ray and histology examinations.3.The distracted mandibles were removed and processed for radiographic,and then measured the bone mineral density (BMD). Eight serial sections of each specimen were made for HE staining and were observed the thickness,number and arrangement direction of the trabecular as well as the number and density of osteoblast in the light. Image analysis software was used to analyze bone histomorphometry. Eight discrete sections were measured for each specimens, and the mean measurement results of the speciments were the parameter values. The bone volumes in the newly formed cortical bone area and in the cancellous boen area of the distraction zones were measured.4.Statistical analysis:All data are expressde as menas±tandard errors in all independent experiments. Statistical differences among groups were evaluated by t-test. p<0.05was considered statistically significant. Results:1.The animals tolerated the surgical procedures and distraction well. Diet,feces and urine were normal, and the mandibular deviation occurred at the end of the distraction. Radiological and histological study confirmed osteogenesis in gaps in animal models. The mandibular were extended in accordance with the intended target. 2.Radiological and histological study confirmed that the group of GTRM (the experimental group) showed better bone formation than the control group. Results of statistical analysis on bone mineral density and histomrorphometry showed the same as the result mentioned above.(p<0.05)Conclusion:1.Our experiments establishde a feasibility,repeatability and steadily modle of rabbits unilateral mandibular distraction osteogenesis by the reformed interal distactors. It was appropriate for large quantities of animal experiments and lay the foundation for eventual clinical application combined with cytokine and material witch promoted bone formation.2.GTRM can more effectively promote new bone formation and mineralization during mandibular distraction osteogenesis under radiographic and histological examinations,suggesting that GTRM is an effective method to promote the mandibular distraction osteogenesis.