Electrochemical and biocompatibility examinations of high-pressure torsion processed titanium and Ti-13Nb-13Zr alloy

Abstract

The purpose of this study was to estimate the electrochemical behavior and biocompatibility of ultrafine-grained (UFG) commercially pure titanium (CPTi) and Ti-13Nb-13Zr (TNZ) alloy obtained by high-pressure torsion process. Electrochemical behavior of materials in artificial saliva at 37 degrees C was evaluated by potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS), and the obtained results indicated that UFG TNZ alloy showed corrosion current density (j(corr)=53 +/- 5 nA cm(-2)) which was 2 times lower compared to coarse-grained (CG) TNZ alloy (j(corr)=110 +/- 12 nA cm(-2)) and higher corrosion resistance, while UFG CPTi and CPTi showed approximately the same corrosion rate (mean j(corr) approximate to 38-40 nA cm(-2)). Static immersion test in artificial saliva, performed in this study, showed that the released ion concentrations from UFG materials were more than 10 times lower than the permitted concentration (the highest released Ti ion concentration from UFG CPTi and UFG TNZ alloy was 1.12 and 1.28 ppb, respectively, while permitted concentration was 15.5 ppb). The in vitro cytotoxicity tests, as the initial phase of the biocompatibility evaluation, showed that the fraction of surviving cells in all examined materials was much higher compared to the control sample and hence demonstrated absence of cytotoxicity and an increase of fibroblast cells adhesion on UFG materials surfaces. UFG CPTi and UFG TNZ alloy can be considered as promising materials for applications in dentistry due to high corrosion resistance and outstanding biocompatibility which were shown in this study.