2022 Volume 35 Issue 2 Pages 111-118
Purpose : When dental implants made of titanium or titanium alloy are implanted in the oral cavity, there is a concern that discoloration or corrosion may occur due to exposure to fluoride. This study aimed to compare the discoloration and ion release behavior of commercially pure titanium and titanium alloys in fluoride-containing solutions and to clarify the mechanism by which titanium is corroded by fluoride using surface analysis.
Method : As specimens, commercially pure titanium (TI), Ti-6Al-4V (TAV), and Ti-7Nb-6Al (TNB) were mirror-polished. The polished specimens were immersed in saline solutions with or without sodium fluoride (NAF and SAL). Corrosion was evaluated based on the color difference (ΔE＊ab), reduction of glossiness (Gs (20°)), and concentration of metal ions released into the NAF and SAL solutions. In addition, surface analysis was performed on certain specimens using X-ray photoelectron spectroscopy (XPS).
Results : There was no indication of corrosion on the specimens immersed in SAL from the ΔE＊ab value, Gs (20°) decrease, and concentration of released metal ions. TAV and TNB immersed in NAF showed larger ΔE＊ab and concentration of released metal ions than TI. The XPS analysis revealed that oxidation progressed in all specimens immersed in NAF. In addition, TiO2 and V2O5 were detected on TAV, and TiO2 and Nb2O5 were detected on TNB. Al was not detected on the surfaces of either TAV or TNB.
Conclusion : TI, TAV, and TNB specimens showed superior corrosion resistance in SAL but low resistance in NAF. TAV and TNB showed lower corrosion resistance to fluoride than TI in NAF. After immersion in NAF, passive films covered the surfaces of TAV and TNB but no Al2O3 was detected.
