| Residual Ridge Resorption (RRR) as the result of tooth missing caused by many etiological factors, will lead to the difficulties of prosthetic restoration, implants planting and will influence the patient's quality of life, mental health in different level, because it not only reduce the height of alveolar ridge, but also reduce the width of it. So the prevention of residual alveolar ridge bone absorption has the vital significance. There are some studies related to the treatment such as autogenous bone graft, allograft bone graft, immediate dental implants, osteo-promotion by the GTR, etal. However, reports related to relevant local drug treatment is relatively few. Simvastatin is clinically used to reduce blood cholesterol since Mundy first found that statins could promote the expression of osteoblast and simulate bone formation in vivo in rodents. Researches about statin treatment of fractures and promote bone defect repair, prevention osteoporosis are increasing.Since statins have liver selectivity, drug utilization rate is only 2.4% in circulation after oral administration, the dose reaching to the target tissue is far less than the dose inducing bone formation. There are some weakness for local injection such as repeated in large doses. The preliminary research results show that it exists some faults when single PLGA as drug carrier such as hydrophilic of PLGA, weak ability of cell adsorption, acidic degradation products, local PH decline cause aseptic inflammation faults. Considering the human tissue consisting of inorganic and organic compound ingredients, therefore from the angle of biomimetic, inorganic and organic compound biological material as the simvastatin drug carrier will be better. In this study, the possibility of preventive effect of simvastatin carried by calcium phosphate cement/poly (lactide-co- glycolide) (CPC/PLGA) on RRR was explored, we establish Residual Ridge Resorption (RRR) animal model firstly after extraction of lower incisors in Wistar rat, in this way, it can provide some scientific theory for the clinical application of simvastatin carried by CPC/PLGA scaffold materials in future.50 Wistar male rats were chosed and divided into experimental group and control group randomly, each group had 25 rats in this experiment. In experimental group, the simvastatin/CPC/PLGA scaffold was implanted into the tooth socket, and the CPC/PLGA scaffold was implanted in control group immediately after extraction of lower incisors. General observation of local healing of tooth socket, 1,2,4,8,12weeks later, 5 rats were killed by heart perfusion using of 4%paraformaldehyde in experimental and control group respectively and then samples were collected. Relative width of residual alveolar ridge were determined by caliper and relative length of residual alveolar ridge were measured by using Image- Pro Plus 6.0 analysis software after soft X-ray testing, all the data managed with software SPSS17.0 (P<0.05). Then histopathological changes of the samples were observed by HE and the effect of bone repair were evaluated.Experimental results show that tooth socket healing well without obvious inflammation, the relative length and width of residual ridge in experimental group was higher than that of control group significantly after 2w,4w,8w,12w days of implantation (P<0.05). Histological experimental results showed that experimental group in the rate and quality of new bone formation were better than control group. The inflammation in tissue was lighter than single PLGA as drug carrier. CPC/PLGA was relatively safe and feasible in clinical application because there were not any adverse reactions, such as hypersensitivity or poisoning in the process of experiment.This study is the first to verify that the scaffold with slow-release ability such as simvastatin/CPC/PLGA can increase the healing of extraction socket and prevent the RRR, and show preventive effect of simvastatin on RRR and promote bone repair in tooth socket with the techniques of soft x-ray and histology.
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