| Objects: The mini-implants as anchorage has been used preliminary in the orthodontics. In the clinic, the region where the mini-implants be inserved is usually in the alveolar bone between neighboring teeth, then, the lest mistake in the operation would make the serious injury of the periodontium, especially to periodontal ligament. This study's object was to establish the model of the rabbit's periodontium injured by the mini-implants, to observe the process how the injured tissue would repair, to discuss the probably effect and result about this injury, in the end, hope to give some advice to the clinical operation.Material and Methods: Rabbit's periodontium was the objective in this study.12 health rabbits were choosed to be the simple, divided into 4 groups randomly and every group had 3 rabbits. The rabbits were anesthesia by Diazepam (2ml:10mg)and ketamine(2ml:0.1g), 0.2ml/kg , then were implanted the mini-implants(d=l .2/1.4mm, l=7mm, ZhongBang Cooperation) in the alveolar bone between central incisor of mandible and maxilla. When implanted, the direction of the mini-implants was controlled to contact and injury the rabbit's periodontium, especially to periodontal ligament, then scan the area where inserved the mini-implants by Computerized Tomography in 1.0mm every layer , and utilized three-dimensional reconstruction to observe the mini-implant form different directions in order to confirm the mini-implants had contraction with the teeth roots. If the mini-implants had not contacted with the roots, it was taken off ,and implanted in another direction again. After the implanting operation, The rabbits were breed for a time, their living conditions was recoreded, for example, how long they began to take the food, if the teeth been injuredcame to shake, and so on. The 1, 2, 3, 4group rabbits were put to death in the 1d, 5d, 28d, 50d differently, the alveolar bone of mandible and maxilla that included the teeth were taken out, and the teeth crown were get rid of by high speed turbine engine. They were fixed with 10% glutaraldehyde, decalcified, dehydrated, embedded, chipped, HE stained, then the periodontium how to change and recover was observed by microscope and was recorded in photographs.Result: After the implanting operation, the rabbits began to drink water and took food as soon as came back form the anesthesia, the masticatory movement was normal. The wound on the soft tissue had no infection and the wound of the 2,3,4 groups had recovered successfully. One rabbit died after 10 days, reasons was not clear. Through observation this four groups' pathological section, we could see that: in the first group, the periodontal ligament had been cut off in the injured area and the lamina dura of the corresponding position disappeared, the alveolar bone trabecula was broken, a large number of red blood corpuscles gathered on the below, neutrophil leaked out. In some position the cementum also had been damaged slightly, all this showed that the periodontium had gotten the machinery damaging, the capillary broken and the inflammation cells soaked into. The second group, some part of the periodontal ligament been injured was necrosis, the tissue's structure was smudgy, there was some small chips of the dead bone and some small spots of inflammation in the alveolar bones. Osteoblasts and fibroblasts had come to hyperplasia, it showed that the inflammation and tissue recover was taken place in the same time. The third group, osteoblasts and fibroblasts had come to hyperplasias largely, the new fibrecells appeared in the area where the periodontal ligament was injured, but the fibrecells arranged in disorder, nucleus was larger than normal, and there was small amount inflammation cells around. The new bone trabecula had been appeared, but thin and...
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