| Objectives To prepare concentration gradient of strontium-doped brushite coatings on titanium alloy implant anchorage by two steps electrochemical and establish osteoporosis model in rats. To observe the osseointegration of coating implant anchorages in osteoporotic rats, which to find the best content of strontium of the strontium-brushite coatings and provide a new idea for the surface modification methods and clinical applications of implants.Methods 1 The surface modification of medical titanium alloy(Ti-6Al-4V, TC4) was studied through two steps electrochemical to prepare strontium-brushite coatings on titanium alloy, which the mole fraction of strontium-doped was 5%, 10%, 15% and 20%. The chemical compositions of coatings was tested by X-ray diffractometer(XRD), and the concentration of strontium doped was examed by X-ray fluorescence spectrometer(XRF). Field emission scanning electron microscopy(SEM) was used to examine micro morphology of the strontium-doped brushite coatings. The biocompatibility of strontium-brushite coatings was judged preliminarily by hemolysis rate that was tested by hemolysis test in vitro. 2 Totally 36 female SD rats were selected as the osteoporosis model and divided into 4 groups: OVX0% group, OVX5% group, OVX10% group, OVX15% group, and 9 normal rats were set up in the control group. The corresponding implant anchorages were placed in the right tibia and the number of it was two, then loaded the implant anchorages interactive one week later. The immunofluorescence staining selected tetracycline hydrochloride and calcein, which was performed on different occasions before the rats had been killed. Produce the implant anchorage and alveolar bone tissue sections after 2, 4, 8 weeks implant loading. Recorded the observation results of immunofluorescence staining and methylthionine chloride along with acid fuchsin straining, and then calculated the rate of bone implant contact and mineral apposition. To took the statistical analysis by SPSS17.0 system.Results 1 The concentration gradient of strontium-brushite coatings were successfully prepared on titanium alloy by two steps electrochemical deposition and the coatings were dense and had multi gaps. According to test results, the calculation of strontium concentration was done under Sr /(Sr+Ga) molar ratio, which showed that the preparation of strontium-doped titanium substrate concentr-ation of 5%, 10%, 15%, 20% of strontiumbrushite coating was successful, detecting hemolysis rates were less than 5% and in line with the corresponding requirements of medical materials(P<5%). 2 The mobility degree of the implant anchorages coated with strontium-brushite coating were zero and the bone implant contact rate and mineral apposition rate of these coating implants were significantly higher than that of OVX0% group(P<0.05). There was no difference between OVX10% group and OVX15% group(P > 0.05), but showed significant difference compared with control group, OVX0% group and OVX5% group(P<0.05). The bone implant contact rate of control group had significant difference with other groups(P<0.05) after 2 weeks implants loading. The bone implant contact rate of control group and OVX10% group after 4 weeks implants loading had significant difference with other groups(P<0.05). After 8 weeks implants loading the bone implant contact rate of OVX10% group had significant difference with other groups(P<0.05).Conclusions 1 The process of two steps electrochemical deposition can be used for prepared the concentration gradient of strontium-doped brushite coating on the surface of titanium alloy and this method showed a good biocompatibility. 2 The surface modification method of titanium alloy with strontium-brushite coating could effectively enhanced the effect of osseointegration and the stability of the implant anchorage. 3 10% and 15% strontium-brushite coating had a good effect on the promotion of implant anchorage's osseointegration in osteoporotic rats, and the effect of 10% strontium-brushite coating was the best. |
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