Objectives: To investigate the electrochemical mechanism of Ti-6Al-4V alloy in acidic artificial saliva with NaF and/or bovine albumin (BA).
Methods: The electrochemical behavior of Ti-6Al-4V alloy was investigated using electrochemical impedance spectroscopy (EIS) measurements at the open circuit potentials. The electrolytes used included artificial saliva with 0-0.5% NaF, with 0.1% NaF+0.01-0.5% BA, and with 0.01-0.5% BA at pH 5 and 37 degrees C. One-way ANOVA was used to analyze the influence of NaF and BA concentration on the polarization resistance (Rp) obtained from the EIS data. Surface chemical analyses were performed with X-ray photoelectron spectroscopy.
Results: The impedance was mainly characterized by the resistance and capacitance of a protective TiO2-based passive film on Ti-6Al-4V alloy when NaF concentration was low (< or = 0.01%). When NaF concentration was higher than 0.1%, the impedance was characterized by two capacitive and one inductive effects, which were related to the metal's charge transfer reaction and the decayed TiO2-based oxide film (capacitive effects), and the relaxation of the adsorbed Ti-F complex compound (inductive effect). The addition of 0.01-0.5% BA in 0.1% NaF-containing artificial saliva significantly increased the impedance of Ti-6Al-4V alloy compared to that without BA addition (p < 0.001). The presence of BA in fluoride-free artificial saliva had no influence on the electrochemical impedance of Ti-6Al-4V alloy (p > 0.05).
Significance: The EIS measurement technique is suitable for the study of the electrochemical behavior of dental alloy. The electrochemical mechanism of Ti-6Al-4V alloy in artificial saliva is related to the fluoride and bovine albumin concentration.