In vitro corrosion resistance and in vivo osseointegration testing of new multifunctional beta-type quaternary TiMoZrTa alloys
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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 oC. 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 VSCE, 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).