| Objective: Through the method of removing the rabbit incisors after grinding gradually, we established the rabbit incisors defect model, and we implanted titanium screws immediately in the tooth sockets, the gaps between implant and bone would be filled with the zoledronic acid-nano-hydroxyapatite complex, which made the titanium screw acquire initial retention. We try to find the affection to osseointegration by zoledronic acid local application after immediate implanting of titanium screw in rabbit fresh tooth socket.Methods: 1 Preparation of the zoledronic acid-nano-hydroxyapatite complex Refering to the experimental method of Gao Y and Yoshinaria M: 2mg of zoledronic acid was dissolved into 10 ml 0.9% sodium chloride, then the nano-hydroxyapatite particles was soaked in the solution for 24 h.2 The experimental animal models and grouping Select 9 New Zealand white rabbits which have the characteristics as follows : healthy, 6-month-old, male and with the weight of about 2.5- 3.0kg. After adaptive feeding for 7 days, they were randomly divided into two groups, 6 in the experimental group, and 3 in the control group. Every week, maxillary and mandibular incisors would be drill off 2-3mm under local anesthesia with 2% lidocaine. This procedure should be repeated for four times. Then after anesthesia by using the chloral hydrate solution(3ml/kg), the rabbits were fixed on the table separately, kept mouth opening, disinfected oral and surgical scope with lodine cotton ball, separated the gums with probe, waggled teeth slowly to loose, held the incisors with needle holder, removed off the maxillary and mandibular incisors slowly along the arc of the rabbit incisors.3 Titanium screw implantIn each tooth socket of the maxillary and mandibular incisors, we immediately implant Φ2.0mm×10.0mm titanium screw, and then we filled the gap between the titanium screw and the bone with zoledronic acidnano-hydroxyapatite complex for the experimental group, and the nano-hydroxyapatite for the control group, the initial stabilization was harvested in both group. At last, the rabbits gums was sutured tightly in each group, and the rabbits were sent into the cage. After the operation, the rabbits were given intramuscular injected with gentamicin for forty thousand units everyday within 7 days to prevent infection.4 The observation The animals were sacrificed randomly after 4,8,12 weeks respectively(experimental group 2, control group 1). We generally observed the maxillary and mandibular titanium screws to confirm whether they were loose off or not, and whether there were infection or not around the implants. X-ray was used to observe the mineral density of bone around the implants, and then the gray values of bone both in the experimental group and the control group were calculated, statistical methods were used to compare the differences between experimental and control groups. After the removal of titanium screws in the maxillary and mandibular tissue, we made sections and stained them using HE staining, and observed the bone remodeling under the light microscopy of bone remodeling. At the same time, we calculate the osteoblast index(OBI) with the multifunctional true color cell image analysis and management system, and compare the OBI differences using the statistical methods of the experimental group and the control group.Results: 1 Somatoscopy: Both in the experimental group and the control group, the animals were all normal in the aspect of spirit, diet, activity. And their wound were well healed, without purulent infection and fistula, with the normal color of mucosa and no implant exposure. 2 The general observation: In the experimental group, after 4 weeks, the titanium screws were stable, no screw falling-off. There were loose bone tissue surrounding the titanium screws, while in the control group, the titanium screws were some loose, but without falling-off, and there were gaps between the titanium screws and the surrounding bone tissue. And for the 8 weeks and 12 weeks, the titanium screws in the both groups showed no loose and falling-off, and with certain retention force, the titanium screws were surrounded by bone tissue closely.3 X-ray observation: The titanium screws of each specimen are in place, and the nano-hydroxyapatite around the titanium screws were gradually absorbed and replaced by bone tissue as time expand, moreover, the bone tissue density were raised gradually.4 The analysis of the bone density: Using statistical analysis software for X-ray gray values,the results showed that in 3 periods(in 4, 8, 12 weeks), the gray values of the bone tissue around the titanium screws were higher in the experimental group than that in the control group,and it is statistically significant(P<0.05).5 Histopathology observation: In 4th, 8th and 12 th week after surgery,the new bone tissue was better matured in the experimental group, and the tabular new bone was formed earlier. The bone trabecula were arranged orderly and with the high degree of calcification, and between the bone trabecula, many capillaries and a number of osteoblast and osteocyte were also observed. Compared to the experimental group, the new bone was formed slower, and the bone trabecula were fewer and calcification degree was lower in the control group, many capillaries and fewer osteoblast and osteocyte.6 The bone morphometry analysis: SPSS13.0 was used to statistical analyze the OBI on the 4th week, the result showed that the OBI in the experimental group was higher than that of the control group, P <0.05, and the difference is statistically significant.Conclusion: 1 Through the method of removing the rabbit incisors after a gradual grinding procedure, we can establish a secure and reliable animal model for tooth implant, and also provide a new way for the immediately implant animal model. 2 Topical application of zoledronic acid can inhibit the bone resorption and promote the bone formation, and therefor enhance the successful rate of tooth implant. |
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