Abstract: Objective To study the effects of oral fluoride-containing environment on titanium surface oxide film properties and corrosion behaviors. Methods The pure titanium samples were immersed in artificial saliva with different fluorine concentrations, and the fluorine-free artificial saliva was used as the control group. The test samples and soaking solutions after 7 days were collected, and the titanium surface oxide film compositions were analyzed by X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion behaviors of pure titanium samples in artificial saliva of different groups. The quantities of titanium ion release in soaking solutions of different groups were detected by inductively coupled plasma optical emission spectrometer (ICP-OES). Results The analysis of XPS survey spectra showed that the contents of titanium and oxygen element on the titanium surface gradually decreased with the increase of fluorine concentration, whereas the content of fluorine element increased correspondingly. The analysis of XPS high resolution spectra showed that the content of TiO2 on the titanium surface decreased with the increase of fluorine concentration. According to the Nyquist plots, Bode-phase diagrams and equivalent circuit fitting data obtained by EIS test, the corrosion resistance of titanium oxide film decreased with the increase of fluorine concentration, and the corrosion behavior of titanium increased gradually. ICP-OES revealed a significant increase of titanium ion release as the concentration of fluoride increased. Conclusions The oral fluoride-containing environment can damage the titanium surface oxide film, accelerate the corrosion behavior, and in turn, induce the release of titanium ion. This effect is enhanced with the increase of fluorine concentration.

Key words: Fluoride, Titanium, Surface oxide film, Corrosion