| Pure titanium and titanium alloys have been widely used as biological materials in medicine currently. Although they have excellent mechanical characters and good biocompatibility, elastic modulus of titanium alloys is still greater than that of bone and teeth. The recent trend in research is to develop low elastic modulusβ-titanium alloys composed of non-toxic and non-allergic elements with excellent mechanical properties. A new titanium alloy, Ti-24Nb-4Zr-7.9Sn (TNZS) which has lower elastic modulus and high strength, has been developed by Institute of Metal Research, Chinese Academy of Sciences. It has been proved to be a kind of well alloy in synthesis.However, there is no one material could match all the requirement of clinical application. During the long period of research, it was observed that titanium and titanium alloys can not form chemical bonds with living bone. A method to solve the problem is to modify metallic surface. Micro-arc oxidation is a good manipuility method for metallic surface treatment. So far, there has not been reported that low elastic modulus alloys treated by MAO internal.In this study, the TNZS alloy was treated by micro-arc oxidation previously, its biocompatibility would be evaluated by cell culture and animal experiments, in order to provide theoretical basis for improving technology of metallic surface treatment and clinical application.Objective:To evaluate the biocompatibility of TNZS treated by micro-arc oxidation.Methods:According to ISO standard(ISO10993-1:1992), the experiments were formulated as below.1. The osteoblasts were isolated from parietal and frontal bones of SD rats and inoculated onto specimens of TNZS,MAO-TNZS and pure titanium.Cell adherence, proliferation and ALP activity were examined. The morphology of the cells was observed by SEM.2. As an important aspect of clinical prediction, insertion experiment in vivo was expected to analyse and assess osteointegration condition and actual clinical effects by microscopical tissue observation and biomechanic study of the interface. Above all, the tibia models of New Zealand rabbits were established in advance, and different implants were designed for experiments in vivo. All animals were sacrificed in 4wk and 26wk respectively. Bone tissues around implants were observed by X-ray, HE microscopy, SEM. Biomechanical stability and interface character were assessed by methods of pull-out tests and SEM scanning.Results:1. MAO-TNZS could accelerate the early adhesion of osteoblasts. In early period, the proliferation and alkaline phosphatase activity of three groups were in a multilayer means. But they were significantly increased on MAO-TNZS than that on TNZS and pure titanium after 7 days'cell culture. SEM showed that osteoblasts on MAO-TNZS spread well and adhered firmly. With the time increasing, the cells proliferated well and secreted matrix.2. The X-ray indicated no bone absorption near the inserted implants;HE and SEM observed no fiber layer around any implants and the implants contacted bone tissue tightly. The synapsis of osteoblasts and fibroblasts stretched to the surface of MAO-TNZS implants, newly-born osteoid tissue appeared faster in MAO-TNZS group than in the others. Pull-out tests indicated that implant-bone bonding power increased with time duration, MAO-TNZS group showed significantly higher bonding power by SPSS analysis than TNZS group and control group at each time period(P<0.05).Conclusion:The TNZS alloy after being micro-arc oxidized could improve the adherence, proliferation and differentiation of osteoblasts, which possesses good biocompatibility. In addition,MAO-TNZS were bioactive and promoted bond tightly to bone tissues which could significantly increase the bonding power between implants and bone tissues. Meanwhile,the new surface could shorten osteointegration periods of dental implants.
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