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Over the last decade, new titanium alloys are developed in different areas of implantology. The aim of this study was to characterize a new Ti-Al-Nb-Ta-Mo based alloy, with high potential for being used as a biomedical implant. The evaluation of Ti-6Al-2Nb-2Ta-1Mo was performed both in vitro (by monitoring its corrosion resistance in Hank's Balanced Salt Solution, HBSS) and in vivo (by evaluating the osseointegration following rabbit tibia implantation), by comparison with titanium and Ti-6Al-7Nb alloy. Electrochemical impedance spectroscopy (EIS) data showed high impedance values for all titanium samples after 1 week immersion times in HBSS at 37 o C. According to EIS analysis, the corrosion resistance of the Ti-6Al-2Nb-2Ta-1Mo alloy immersed in HBSS was higher compared to the standard cp-Ti or with the Ti-6Al-7Nb alloy. In addition, a higher degree of osseointegration was achieved by the Ti-6Al-2Nb-2Ta-1Mo alloy, thus probing that a higher resistance to electrochemical corrosion provided enhanced protection to the implant surface against biodegradation, thus positively affecting the qualitative and quantitative evolution of bone tissue repair.

The present study explores the in vitro and in vivo responses of new multifunctional quaternary beta-type TiMoZrTa alloys designed for biomedical implantation. The electrochemical resistance to corrosion of the alloys was investigated in vitro, using linear potentiodynamic polarization (LPP) and electrochemical impedance spectroscopy (EIS) tests in acidified physiological saline solution at 37 o C. The pH was adjusted to 4.0 by adding lactic acid in order to simulate the hypoxia stress condition that may occur in the healing process of fractures. The biomaterial alloys spontaneously formed a passivation oxide film on their surfaces, which remained stable for polarizations up to +1.0 V SCE , and became more resistant with the increased amount of Ta in the alloy composition. The animal tests of the quaternary Ti-20Mo-7Zr-xTa alloys showed adequate biocompatibility as a tibial implant. Among them, the 15% Ta-alloy implant showed the best osseointegration according to the results of the biochemical, histological and computed tomography characterizations, and can be considered as a potential biomaterial with low elastic modulus (43.6 GPa).

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