| Distraction Osteogenesis (DO) is a new surgical technique to reconstruct bone malformation or bone defects by lengthening and widening the bone, by means of exerting certain mechanical force to the bone which is cut but maintained periosteum , soft tissues attachment and blood supply. The bone and soft tissues defect of cleft alveolus were repaired simultaneously by DO technique in our study. The aim of this study is to explore a new approach to repair cleft alveolus (CA), and make it possible for the perfect functional reconstruction of this kind of malformation.A complete cleft(14-16mm wide) was established on the maxilla alveolus arch surgically in the experimental dogs to simulate the cleft alveolus in human beings. The cleft couldn't be recovered automatically because the dimension of the cleft was larger man the thickness of the alveolar bone. Previous studies had shown that thiskind model was stable and reliable. The maxilla plaster models were taken to design and manufacture intraoral tooth-attached distraction devices. The device consists of a screw, bolts with holders to the supporting tooth, and a horizontal bar which is adjustable used to control the moving vector of the distraction three-dimensionally. The device was mounted to the tooth-band .2 weeks after the alveolus bone resection, the tooth-bone complex monofocal transport disc(MTD) were performed by complete horizontal subapical and vertical interdental osteotomy , at the same time the distractor and the arch wire were fixed. The gradual distraction was started after 7 days latency period at the rate of 0.4mm twice a day along the arch wire, till the MTD reached the opposite edge of the CA. The animals were sacrificed at 0,14, 28,63 day after completion of distraction . X-ray禄 regular histology, immunohistochemistry observation were performed.Plain X-ray image showed that there was only a linear gap between the opposite edges of CA and the distraction gap was bridged and new bone was generated along the distraction direction and remodeled .The new bone radiation density was close to normal alveolar bone's gradually. Histology observation and type I , II , III collagen immunohistochemistry stains showed that on the completion day the distraction central zone was filled with fibers , slim and loose bone beams parallel to the distracted vector inserted into fibers from both ends of the distraction gap, within which a lot of fibroblasts and osteoblasts were found. Brown stained type III collagen was found mainly in the central zone. There was a little type I collagen but no stain of type II. On the 14th day, bone beams became thick and weaved with plenty of osteoblasts on the surface, kept growing intothe central zone where there were still some fibers left. Quantities of type I collagen was found and a little typeIII, II collagen can be seen and faint stained. On the 28th day, bone beams remodeled, short and thick and weaved together. Bone formation was active, there were a lot of osteoblasts and osteoclasts and some low-calcified osteoid tissues.There were main type I collagen stains and few type III, II collagen. On the 63rd day, new bone became much maturer and calcium salts deposited largly, mature Harvard's system had formed, new bone structure was similiar to the normal bones. Only the stain of type I collagen was positive, others were negative.The supporting teeth had mean 0.8mm displacement medially. Lightly hyperaemia and blood vessel expansion was seen in the pulp and the periodontal ligments performed hyperplasia in the tension-side and absorption in the stress-side. However, the changes may be reversible with the time going, the pulp and periodontal tissues can gradually recovered its normal structure. The pulp and the periodontal ligments of the anchorage tooth has no change.The results of this study proved that it is possible to get functional reconstruction of cleft alveolus by DO technique. The formation of new bone was mainly intramembrane osteogenesis along the distraction vector. During the different... |
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