| Objective: After removal of rabbit’s maxillary and mandibular incisors, each socket was filled with mixtures of nano silver-nano hydroxyapatite or nano hydroxyapatite alone respectively, and Simultaneously, one titanium screw would be implanted into the socket. It was observed the osteointegration between implant and bone tissue around, and analyzed the effect of nano silver and nano hydroxyapatite mixture in immediate implant.Methods:1 Group: Nine healthy adult New Zealand rabbits, male and female, were randomly divided into 2 groups, one group of 6 rabbits as the experimental group, while other 3 as control group. In the experimental group, each socket was filled with mixture of nano silver and nano hydroxyapatite immediately after tooth extraction, then one titanium screw was implanted into it; while in the control group, the socket was only filled with nano hydroxyapatite and titanium screw. Animals would be killed at 4th, 8th, and 12 th week respectively, which 2 experimental rabbits and 1 controlled rabbit for each time.2 Preparation of nano silver and nano hydroxyapatite mixture: 1% of nano silver and nano hydroxyapatite mixture was prepared by mixing of 10 g nano hydroxyapatite powder and 0.1g nano silver powder together.3 Grind off rabbit’s 4 incisors in both maxilla and mandible: in order to extract incisor successfully, it should be grind off gradually first. The procedure as follows would be repeated once a week, and kept for four weeks; under local anesthesia, half of the labial crown would be grind off by cooling of 0.9% sodium chloride drop.4 Bone graft and immediate implant: After gradual grinding was completed, rabbit’s maxillary and mandibular incisors were extracted one by one. In experimental group, filled each socket with mixture of nano silver and nano hydroxyapatite which blended with some 0.9% sodium chloride firstly, then inserted a titanium screw in it, sutured gingiva to cover the screw, and douched suture area with sterile saline. Same procedure for control group but the sockets would be filled with nano hydroxyapatite only and screws.5 Results observation: Animals were killed respectively by air embolism method at 4 weeks,8 weeks and 12 weeks after operation. Speciments of maxilla and mandible were harvest immediately. Generally observation was recorded to whether titanium screws became loose or fell off, and the situation of bone tissue around them; Torque test was to test screw bone integrate strength. X-ray examination was to find how the osseous tissue around screw regenerated, and osseointegration between titanium screw and surrounding bone tissue; Bone density were measured by the gray value of regenerated osseous tissue around screw, and analyzed by statistical analysis software; Histological analysis was made by observing HE sections.Results:1 General observation: No screw which became loose or fell off was founded in experimental group, each titanium screw was tightly encysted by bone tissue around; In contrast, screws became some loose in control group at 4th week, but did not fall off. While there was a gap existed between titanium screw and surrounding bone.2 X-ray observation: All titanium screws were still in specimens, and the density of bone around screws increased with the increase of time. Bone density in experimental group were higher than that in control group at 4th,8th and 12 th week after operation.3 Torque test: Torque test was made at the same time point of 4th, 8th, 12 th weeks after operation. Implant bone integrate strength in experimental group was higher than that in control group, the results shows significantly different, and were statistically significant(P < 0.05).4 Bone density analysis: The gray value of X-ray gray were analyzed and analysis statistically by statistical analysis software. Results showed that, at the same time point of 4th, 8th, 12 th weeks after operation, gray value of regenerated osseous tissue around screw in experimental group was higher than that in control group, the results were significantly different, and were statistically significant(P < 0.05).5 Histologic analysis: At the same time point, osteogenesis in experimental group show occurred some earlier, the regenerated osseous tissue had more maturity, a large amount of osteoblast and osteocyte could be found, bone trabecula was dense, with a high degree of calcification; Relatively, control group had less osteoblast, less dense bone trabecular, and a lower degree of calcification. In addition, no inflammatory cell infiltration could be found in HE staining in experimental group at 4th, 8th and 12 th week. However, in control group at 4th week, large amount of inflammatory cell infiltration, and a few inflammatory existed at 8th week after operation.Conclusion:1 In condition of immediate implant, filling the sockets with mixture of nano silver and nano hydroxyapatite,or only with nano hydroxyapatite can both contribute to the bone regeneration and osseointegration between titanium screw and bone tissue around.2 Compared with using nano hydroxyapatite alone for bone graft, using mixture of nano silver and nano hydroxyapatite has better antibacterial activity, biological compatibility and osteoinductive ability, which may accelerate osseointegration and promote osteogenesis. |
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