| Aim: To study whether the guided bone regeneration (GBR) technique can be used to achieve good bone formation in the defects in the palatal plate, providing a more scientific and effective method for clinical treatment of cleft palate, as well as cell generation and differentiation in palatal bone generation and the formation period and mechanism of the bony framework bridge of the palatal plate, and the effect of collagen-polyglycollic acid on guided regeneration in bony defects in cleft palate. Methods: 1. The collagen solution used in the experiment was the soluble beef tendon collagen, with the main ingredient being type I collagen. The beef tendon was picked and immerged into 70% alcohol solution. 20 min later, under the aseptic condition, the beef tendon was taken out and cut into pieces with a pair of scissors. Then it was placed into 0.5% acetate solution and stirred at intervals at the temperature of 4℃. 48 h later, it was centrifuged (10000r/min) for 1.5 h and then residues were removed. The supernate fluid was salted out with 100g/L NaCl solution. Finally, the precipitated protein was dissolved in 1mmol/L HCl solution at 4℃. The concentration of the prepared collagen protein was 84 g/L (Lowry method). Cross linking: after the commercially available 25% glutaraldehyde was purified by air distillation, the measured final concentration was 11%. The glutaraldehyde solution was dripped into the purified concentrated collagen solution, making the final concentration of glutaraldehyde reach 0.06%. The nonwoven mesh of polyhydroxy-acetic acid fibre 15 μm in diameter was mixed with cross linked collagen and poured into a 24-hole culture plate, mixed to uniformity overnight at 4℃ and placed in the series freeze dryer for 48 h vacuum freeze drying to make the PLGA scaffold embedded in porous collagen, which was rinsed for 7 days in sterile Tris-HCl buffer solution and after natural drying, cross rhBMP 4mg in PLGA and make the rhBMP–2/Co/PLGA membrane sterilized by 60Co radiation for 1-2 h. 2. 8 adult experimental dogs were divided into two groups, with 4 dogs in the experimental group and 4 in the control group. After general anesthesia, the palatal mucosa was cut open to remove the triangular bone plate 4 cm high and 1.5 cm wide and the paranasal mucoperiosteum was cut off. The mucoperiosteum was closed directly with #1 silk thread using interrupted nodal suture in the control group. In the experimental group, the readymade 4×1.5 cm triangular rhBMP-2/Co/ PLGA membrane was cut out and implanted in the bone defect area and the mucoperiosteum was closed with #1 silk thread using interrupted nodal suture. 4, 8, 12 and 24 weeks respectively after the surgical operation, a pair of experimental dogs was euthanized in pairs in the experimental group and control group each. The maxillary bone was observed by the palatal plate coronal position X-ray CT scan. A slice of the palatal specimen 5 cm long and 3 cm wide was cut out and observed after HE dyeing.Results: X-ray CMR imaging after the surgical operation showed a triangular transparent area on the posterior border of the palatal bone plate, slightly increased bone density at the edge of the cleft, a significantly smaller cleft than the removal scope and a blunted tip of the bone defect in the control group. In the experimental group; the transmittance in the bone defect area was slightly higher than that of the original palatal bone plate after 8 weeks, but significantly lower than that in the bone defect area in the control group. The bone density in the bone defect area was uniform from the edge to the center of the defect, but the bone density on the posterior border decreased. The bone density in the defect area increased compared to that after 8 weeks, but there was still a gap in the transmittance compared to that of the normal palatal plate, and the border began to blur. After 24 weeks, the transmittance decreased from the middle posterior border to the interior front of the cleft and the density in the defect area was uniform and significantly...
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