Photocatalytic antibacterial effect of TiO₂ film formed on Ti and TiAg exposed to Lactobacillus acidophilus

When irradiated under near-ultraviolet (UV) light, TiO₂ exhibits strong bactericidal activity. The TiO₂ photocatalyst would be effective on orthodontic appliances after its antibacterial effect on the carcinogenic microorganism Lactobacillus acidophilus is evaluated. To compare the antibacterial effect of two crystalline forms of TiO₂, rutile and anatase, thermal oxidation and anodic oxidation were employed to form each structure, respectively. The antibacterial effect of TiO₂ film on TiAg was also compared with that on Ti. Bacterial solutions were pipetted onto the TiO₂-coated specimen and illuminated with UVA (2 x 15 W, black light, 356 nm) up to 100 min and the reaction solutions were incubated to count the colony-forming units. The antibacterial activity of the coated specimens was similar to that of the uncoated group. The antibacterial activity of the coated specimens of TiAg was not different from that of Ti. TiO₂ coatings formed on both Ti and TiAg specimens did not exhibit cytotoxicity on the L-929 cells of mice.