Surface Characterization of Micro-Arc-Oxidized Titanium Doping with Bismuth Compounds

Objectives: Peri-implantitis is a bacterial infection participating complication which would cause late failure of implants. Recent studies focus on developing the surface treatment which would create an anti-bacteria feature on the titanium implant. Bismuth (III) compound have been used for more than 200 years to treat ailments such as syphilis, diarrhea resulting from bacterial infections, and peptic ulcers caused by Helicobacter pylori. The aim of this study is to characterize the surface feature of bismuth doped micro-arc oxidized (MAO) titania layer which have an anti-bacteria potential on the titanium implant. Methods: ASTM grade 2 titanium discs (12mm in diameter, 1mm in thickness) were mechanically grinded and chemical polished. The electrolyte was composed of 0.2M calcium acetate, 0.04M b-glycerol phosphate disodium (AO), and supperadditions of 0.01M bismuth acetate (BA) or bismuth nitride (BN). The disk was anodized by a DC power supply under a constant current density of 70mA/cm² to achieve the final voltage of 280V with a platinum cathode and continued for 3 minutes under stirrer at 25 degree Celsius. After cleaning, the surface features were characterized by surface roughness, Scanning Electron Microscopy, X-ray Diffraction (XRD), and X-ray Photoelectron Microscopy(XPS). Results: Bismuth doped MAO samples possess the same roughness, morphology, and Ca/P ratio similar to AO. The surface oxide structure is mainly anatase by thin-film XRD. By XPS, Ti-OH and TiO are also detected other than the majority oxides TiO₂. The surface concentration of bismuth is 2.3at%, 6.2 at% and the depth is detected <50 nm and <100 nm for BA and BN respectively. Bismuth was doped as Bi⁰: Metal, Bi⁺³: Bi₂O₃, and Bi⁺⁵: Ti₂Bi₂O₇ on surfaces by MAO. Conclusions: Our results suggest that bismuth can be doped into titania layer when preparing titanium implant by MAO for anti-bacterial purpose consideration. This research was granted by China Medical University CMU97-300.