The Effect Of Different Mass Concentration Of Alendronate In Hydroxyapatite-alendronate On Rat Critical-sized Calvarial Defect Repairment

Objective:The aim of this experiment was to evaluate the effects of different concentrations of low-released alendronate on repairing of the defects in rats’ calvarias and the relationship between the effect and the concentrations.Method:Twenty healthy Sprague-Dawley rats aged three months of what all male were used in this experiment. Chloral hydrate whose concentration is40g/1was used for anesthesia (10ml/kg). Skin preparation and disinfection were implemented as routin with rat’s being fixed on operation board. Skin and subcutaneous tissue were cut open along the midline from orbital margin to ears trailing edge, so operation field could be observed clearly. Periosteum in operation field was cut off. Four critical full-thickness bone defects were made on each rat’s calvarias with washing of sterile saline. Dura mater should not be spreaded to, and2～3mm distance were left between bone defects and then hydroxyapatite-alendronate what contains different concentrations of alendronate (group A:0mg/g、 group B:1mg/g、group C:2mg/g and group D:4mg/g) were filled in the four bone defects, respectively. Heights of filling materials were kept consistent with surrounding bone tissue. And skin was pulled up so operation incision could be sutured tightly(attached picture). Conventional feeding was implemented after operation and antibiotic was used as routine.5rats randomly selected were killed by overdose anesthesia at2ed week,4th week,8th week and12th week after surgery, and their calvarias were obtained completely with2mm bone tissue surrounding bone defect. Blood and soft tissue were dislodged clearly. Calvarias were kept in paraformaldehyde buffer48h, and then received X-ray test. Image-proplus6.0was used for analyzing the residual area in each defect, and all calvarias were washed12h by tap water. Nitric acid solution was used for removing calcium. And HE staining was producted. Bone regeneration in all groups was compared with pathohistological observation. Percentages of new bone tissue in views were calculated by Image-proplus6.0. Datas in all groups were represented in the form of x±s. Spss13.0sofeware package was used for Analysis of variance of factorial design and univariate analysis of variance. The results are statistically significant based on p<0.05.Result:1. All animals recovered sober completely in1h postoperation, no abnormal conditions appeared and no death or infection. All incision cured and suture fell off in1week after surgery.2. The result of X-ray test showed that no significantly difference among all groups (p>0.05) at the2ed week postoperation, and a statistical difference could be observed at the4th week after operation,group C was better than other groups (p<0.05), while, it gone at the8th and12th week after surgery (p>0.05).3. Little new bone tissue can be observed and the defect was filled with soft tissue at the2ed week postoperation. A portion of fibrous tissue changed into immature bone tissue, and group C was best in the mass of newborn blood vessel at the4th week after operation. Fusion and apearence of imatured bone tissue can be seen, Matured bone tissue could be observed at the8th week after surgery. Reparation continued and remodeling of marrow cavity and cortical bone was in progress at th12th week after surgery. Comparison of the portion of immatured bone in the view indicated a same result as X-ray test. Conclusion:1. There was no significant effect of ALN on the regeneration at the early stage (2ed week postoperation).2. Bone regeneration was most active at the4th week after surgery and the promotion of ALN was most notable at the same time.3. The mass concentration of ALN had a great effect on the regeneration of bone, and2mg/g group was the best one in this experiment.4. Nanohydroxyapatite-Alendronate maybe a candidate material for bone defect regeneration.