| By traction of the two segments after the osteotomy, the two bone segments was moved to the contrary direction. Osteogenesis is realized between the bone segments and the bone is lengthened or broadened. This technique is called distraction osteogenesis(DO). The destination of the study was to explore the feasibility of 2-Dimensional palate bone distraction osteogenesis. By distraction osteogenesis, the soft and bone tissue defects of the canine cleft palate model were rehabilitated, and the palate bone was lengthened and the velopharyngeal insuffence was ameliorated at the same time. The results of the study can offer experimental evidence to the treatment of cleft palate and velopharyngeal insuffence by DO. The objects were to provide a new treatment method and to realize the functional restore for the congenital cleft palate.We designed and manufactured a titanium and external 2-Dimensional distractor for hard palate according to the principle of mechanical movement and distraction osteogenesis. The distraction appliance are composed of anchorage, fixation of bone segments and 2-Dimensional movement appliance. At the first experiment, a midline hard cleft palate model was created artificially in a vitro canine skull. The surgery and distraction were simulated on the model to close the cleft palate and lengthen the palate. The destination of the second experiment was to explore the feasibility of lengthening the hard palate. The palate osteoectomy by"n"shape was performed on canines, and the 2-Dimensional distraction appliance was installed at the same time. After the interval period of 12 days, the distraction was carried out with the frequency of 2 times a day and with the rate 0.8mm everyday. After the distraction period of 15 days, the distraction was maintained for 10 weeks, and then the animals were performed euthanasia for observation. At the third experiment, seven dogs range from 1-1.5 years were underwent 8â…¹25mm2 palate osteoectomy to produce artificial canine cleft palate model. They were assigned randomly to two groups. The 2 dogs without treatment was experimental control group. They were performed euthanasia after 8 weeks. The experimental group contained 5 dogs that were installed distractor at the same time of the palate osteoectomy. After the interval period of 12 days, the distraction was carried out with the frequency of 2 times a day. The arrowy turnplate was rotated firstly with the rate of one circle once, and then the horizontal turnplate was rotated with the rate of half circle once. At everyday, the hard palate can be lengthened approximately 0.8mm and distracted medially approximately 0.4mm, and the cleft was shortened 0.8mm. The cleft was closed after 13 days of distraction. Then, the arrowy turnplate was rotated with the same rate to lengthen the palate. The distraction was finished on the fifteenth day. The distraction was maintained for 10 weeks, and then the animals were performed euthanasia for observation of general specimen and tissue response.The shape and width of the cleft palate kept almost the same as it was made on control dogs. It showed that artificial canine cleft palate model is suited to the study of the cleft palate restore. At the second experiment, the palate mucosa of two bone segments had healed. It can be found at the 3D CT reconstruction that the new bone is formed at the arrowy distraction area, and almost had been ossificated. The bone density of new bone is similar with normal bone. The bone transport disc had been obviously lengthened. At the third experiment, the canine cleft palate disappeared after the maintenance period at the experiment group. The palate mucosa between the cleft margin had inosculated by the compress effect of the distractor. It can be found at the 3D CT reconstruction that the new bone is formed at the arrowy and horizontal distraction area, and almost had been ossificated. The bone density of new bone is similar with normal bone. The bone transport disc had been obviously moved to the center of the cleft and lengthened. However, slightly absorption can be found at the cleft margin. New bone is slightly higher than the normal bone.Histological study showed the new bone was formed by the aggradation and calcification of bone matrix from the distraction direction. The New bone trabeculaes arrayed in parallel from the distraction direction. The New bone trabeculaes were thicker and denser, and had calcified and matured. They formed uniform matured multi-layors bone structure. The active bone rebuild cound be found, there were many osteoblasts and osteoclasts around the bone trabeculaes. Mature Harverd's system had formed.It can be concluded from the study that the designed 2-Dimensional distraction device can be used to stably and successfully distract palate bone to close cleft palate and lengthen soft palate in canine. The results of the study showed that it is possible to restore the cleft palate and lengthen the palate at the same time by the DO technique. It is a new method to realize functional restoration of cleft palate and velopharyngeal incompetence.
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