Effect of ultraviolet ray on tooth bleaching using titanium dioxide photocatalyst

Purpose: The purpose of this study was to evaluate the effect of ultraviolet ray (UV) on tooth bleaching using titanium dioxide photo catalyst in vitro . Materials and Methods: Hematoporphyrin-stained paper (HSP) and artificially discolored bovine teeth (BT) were bleached by an in-office bleaching material containing low concertation of hydrogen peroxide and titanium dioxide photocatalyst. For the bleaching, light irradiation was performed at wavelengths of 265, 310, 365, 405, and 450 nm for HSP, and 265, 300, and 405+470 nm for BT. Before and after bleaching, color was measured to obtain CIE L*a*b* values. The color differences (ΔE) were calculated and were statistically analyzed. Results: In the HSP experiment, the 265 and 310 nm groups showed a remarkable bleaching effect and ΔE of the 310 nm group was statistically the highest ( p < 0.05). In the BT experiment, ΔE of the 265 nm group was statistically the highest followed by 300 nm, then 405+470 nm groups ( p < 0.05). Conclusion: UV-C (265 nm) and UV-B (300 and 310 nm) showed high bleaching effect with an in-office bleaching material containing low concentration of hydrogen peroxide and titanium dioxide photocatalyst. 20 Ten were bleached in each ( 10). After light irradiation, the bleaching material was removed. Before and after the bleaching procedure, a photograph was taken with a digital camera and the color of the HSP surface was measured by a CIE XYZ camera (RC500, PaPaLaB, Hamamatsu, Japan) and CIE L*a*b* values were obtained. The color difference (ΔE) was calculated using the following equation.