动物造模,实验性牙槽突裂模型 z-bio 2021-12-28 472

　　Background: Congenital cleft alveolar is a deformity caused by the unfused original palate within 4-12 weeks of pregnancy. The purpose of alveolar crack repair is to establish the bone continuity of the alveolar ridge of the maxilla. Seal the nose and mouth spread, creating a good anatomy for oral restoration. The application of autologous bone, allogeneic bone and xenogeneic bone graft materials and various tissue engineering bone substitute materials for alveolar cleft bone grafting. Optimizing the quality of existing bone graft materials and finding new and better bone substitute materials is the key to improving clinical efficacy. Experimental testing of various graft materials requires the establishment of an appropriate biological model in advance to conduct experimental research and evaluate the clinical effects of bone formation and healing. Animal models that simulate alveolar cracks are considered appropriate experimental models for clinical intervention trials. Several animal models have been used to detect alveolar fissure bone graft materials including mice, rats, rabbits, cats, dogs, pigs, goats, sheep and monkeys. The development of alveolar clefts in experimental animals can be achieved, whether it is the process of intrauterine embryonic development caused by surgery or congenital. Compared with large models, including rabbits, rodent models have inherent limitations. Rodents have smaller long bones, more fragile cortex, and do not show bone remodeling in the cortex. Rabbits are not aggressive, easy to observe, and have a faster time for pregnancy and maturity. The bone histology of rabbits is not very similar to human bone. The literature reports the similarity of bone density and fracture toughness between rabbits and humans. Compared with primates and rodents, rabbits exhibit rapid bone metabolism and bone turnover rates, mainly cortical remodeling. In order to correctly simulate the human in vivo environment, the rabbit model is an animal model suitable for experimental research on alveolar cristae. Because rabbits are reproducible, precise, easy to handle internally, relatively easy to anesthetize, provide a large enough area for testing and can withstand surgical trauma of the appropriate size.

　　Method: Micro-focus CT (micro-CT) imaging investigation: Through the micro-CT imaging of the rabbit skull, an imaging analysis of the bone anatomy was obtained to evaluate the feasibility of the alveolar crack and the plan of the crack operation. Use cross-sectional slices and 3D reconstruction for image evaluation.

　　Congenital Cleft Alveolar Surgery and MicroCT Imaging: Surgery was performed on the head of a dead rabbit. Approval by the animal ethics committee is not required, because this procedure was performed on an animal that was sacrificed, and this animal was used in another animal test project. The split surgery was performed according to the proposed procedure. Postoperative micro-focus CT (Micro-CT) assesses rabbit skull defects.

　　In vivo alveolar cleft formation: animals, anesthesia and feeding 30 minutes before the experiment, the rabbits were anesthetized with xylazine hydrochloride 5mg/kg intramuscularly. The veterinarian sedated, anesthetized and took care of the animals according to the methods already used. During the study period, the animals were kept in single cages, and the animals were kept and observed according to a unified agreement until the end of the experiment.

　　New Zealand rabbit internal alveolar cleft surgery (n = 16) maxillary alveolar surgery site preparation: rabbit supine position surgery under aseptic conditions. A linear mucosal incision of about 2 cm is made on the outside of the left central incisor. Curved along the tooth, extending to the distal cheek corner of the left central incisor, and then extending to the gingival edge of the left central incision of the midline nipple face. Peel away the gums and soft tissues to expose the maxillary alveolar and central incisor periodontal attachment. Subsequently, the skin flaps expose the nostrils under the periosteum. Use a curved periosteal dissector to protect and improve the nasal mucosa without puncturing the nasal mucosa. Using a rotating instrument with a round cemented carbide dental drill, perform a lateral osteotomy on the outer curve of the left central incisor to form a window that reveals the root of the central incisor. Use a small tooth elevator to gently dislocate the central incisor to the side wall, and then use a veterinary extraction forceps to extract it. Further osteotomy surgery to remove the upper and lower bone plates with rongeurs to expose the nasal mucosa without damaging the mucosa. The bone wax is then applied to the defected bone wall to approximate the oral mucosa. Suture the inside and outside with absorbable sutures. The central part of the wound is open, forming a pocket that can overlook the bone defect. Finally, the defects are filled with oxidized cellulose. The nasal mucosa remained intact throughout the operation. The animals were allowed 8 weeks to repair the defect and form the maxillary alveolar defect. The second stage adopts the same surgical preparation and strict operation to expose the alveolar bone defect for bone grafting. A proximal incision was made to separate the oral cavity at the defect site of the alveolar bone. Expose the bone defect and fix the bone wall with a dental drill. Rabbits were fed soft feed directly after surgery.

　　Cone beam CT of alveolar cleft after surgery: 8 weeks after the modelling, the rabbit skull was imaged with cone beam CT.

　　Result: New Zealand white rabbit skull bone survey: the occlusion of the upper jaw anterior teeth of New Zealand rabbits, two pairs of central incisors and double appendage palatal incisors. The central incisor is protruding and semicircular in shape, and the accessory palatal incisor is small, accounting for about half of the length of the central incisor. A central incisor was taken out to examine the skull, and it was found that the protruding teeth passed through the maxilla below the nostril, leaving a thin layer of bone to separate the alveolar fossa from the nasal mucosa. The removed central incisor alveolar socket forms a sac-like cavity of 7-8 mm, which is an ideal model for the study of alveolar clefts. Once the upper and lower bone plates are removed, a continuous defect is created, simulating a common congenital alveolar cleft patient.

　　Congenital alveolar cleft surgery and micro-CT imaging: A simulation study of rabbit skull alveolar cleft surgery shows the feasibility of creating a defect of an appropriate size. This defect can easily be extended to the nasal mucosa to simulate a real clinical defect. It is easy to close the soft tissue and suture the mucosa. The three-dimensional view of the defect shows a triangular alveolar fissure defect with a width of 8 mm. Simulate the clinical manifestations of patients with alveolar fissure defects.

　　Creating surgical alveolar clefts in New Zealand rabbits: The operation time for each rabbit is between 15 and 30 minutes, and all procedures can be performed during ketamine anesthesia without tracheal intubation. In a few cases, additional injections of ketamine are required. The bleeding was mild, and these animals were active and behaved very well immediately after the operation. The animals started eating on the first day after the operation. The animals eat freely throughout the study period. All rabbits survived 8 weeks postoperatively until they were sacrificed.

　　Postoperative alveolar crack CT: After 8 weeks of healing, a computerized tomography scan was performed on an animal. The three-dimensional image of the defect site shows a triangular alveolar fissure defect with a width of 8 mm. Extend the nose to the defect site and verify the depth of the alveolar socket.

　　Conclusion: A simple and predictable clinical trial of a rabbit model of alveolar cracking. Tissue engineering bone substitute materials can be established based on existing anatomical structures. In the extraction of the central incisor, the extraction socket is modified by extending it to the nasal mucosa, and the application of simple bone wax and oxidized cellulose materials during the repair period of the cleft palate avoids the rapid formation of bone and the filling of the defect. Allow 8 weeks of healing to produce a predictable size defect, which can be used for subsequent transplantation procedures.