Biocompatibility Evaluation Of A Newly Developed Titanium Alloy Implant

Objective and background:The materials used for medical applications especially for dental and orthopedic implants should possess excellent biocompatibility, corrosion resistance in body environment, and superior mechanical properties, wear resistance, and nontoxicity. Commercially pure titanium(cp-Ti) and Ti-6Al-4V alloy have been widely applied in dental implant because of their good corrosion resistance and biocompatibility. And it has been reported that the long-term survival rate of titanium implants is as high as 94.5%, 89% and 82% after 5, 10, and 16 years respectively.Despite the success in the use of traditional titanium and its alloys, some drawbacks still exist. Their strength and wear resistance are relatively low, and the friction coefficients are higher in comparison with other metals. Among these drawbacks the high Young’s modulus of the Ti-6Al-4V(110Gpa) and cp-Ti(100GPa) was thought to be a main one. Compared to bone tissue(10-40GPa) the great difference between the implant material and bone can induce stress shielding, which is a process that occurs when the forces exerted on a member with prosthesis are different from the forces applied to a normal limb. This difference induces the loss of bone density, leading to bone atrophy and implant loosening. Besides, for Ti-6Al-4V, the release of both Al and V ions has been found to be associated with long-term health problems, such as Alzheimer disease, peripheral neuropathy and osteomalacia.To avoid vanadium toxicity, in the 1980 s, V-free titanium alloys such as Ti-5Al-2.5Fe(ISO 5832-10) and Ti-6Al-7Nb(ISO 5832-11) were developed, as second-generation titanium alloys for biomedical uses, exhibiting mechanical properties similar to Ti-6Al-4V. In recent years, scientists are devoted to developing new Titanium alloys with low Young’s modulus and free of toxic elements. β-phase Ti alloys are preferred to be used as bioimplant materials, and they are formed by incorporating β-stabilizing elements such as Nb, Zr, Ta, Mo, Pd and Mn. These elements decrease elastic modulus and have not caused adverse effect in vitro and in vivo. Ti-10Ta-10 Nb, Ti-35Nb-2Ta-3Zr and Ti-13Nb-13 Zr have been introduced with low Yong’s modulus and excellent biocompatibility. Among these new titanium alloys, Ti-35Nb-5Ta-7Zr alloy showed the low Young’s modulus(55GPa) and Ti-24Nb-4Zr-7.9Sn alloy possesses the lower Young’s modulus(42 GPa),the Young’s modulus of Ti-35Nb-4Sn alloy was about 40 GPa which is closest to that of human cortical bone’s.In this study, we introduced a new Titanium alloy Ti-Nb-Zr-Ta-Si, with a low Young’s modulus and high strength. To date, there is no characterization of osteoblasts functions on this new alloy. Our aim was to evaluate the influence of Ti-Nb-Zr-Ta-Si alloy on osteoblast cell’s behavior compared to cp-Ti. And the alloy with regard to bone anchorage and osseointegration performance were also been evaluated. Methods:SEM was used to observe surface morphology of the samples. MG-63 cells were co-cultured with samples, after 24 h, cells were stained on samples and SEM was used to observe cells’ morphology; after 4 h, DAPI staining was used to qualitatively detect adhesion cells amount of each group; at 1, 4, 7 day CCK-8 was used to assess cell proliferation; at 1,3,7 day intracellular ALP activity were determined and ALP levels were normalized to the total protein content of cells; through Real-Time PCR the relative expression levels of Osterix, COLΙ and OCN were assayed at 1, 3, 7 day. In vivo, samples were inserted into rabbits’ femurs, after 4, 8, 12 weeks the bone-bonding ability were evaluated through pull-out test. Conclusion:1.The new Ti-Nb-Zr-Ta-Si alloy can promote cells adhesion, proliferation and differentiation compared to cp-Ti;2.The in vivo study showed that the new Ti-Nb-Zr-Ta-Si alloy accelerated bone formation in the early stages.