Effects of 405 nm Diode Laser on Titanium Oxide Bleaching Activation

OBJECTIVE: The objective of this study was to evaluate the effects of a 405 nm diode laser on bleaching reaction of H(2)O(2) and VL-TiO(2) on methylene blue (MB) dye. BACKGROUND DATA: Visible light activating titanium dioxide photocatalyst (VL-TiO(2)) may improve efficacy of hydrogen peroxide (H(2)O(2)) bleaching agents used in dentistry while contributing to their safety by lowering the required concentration of peroxide. METHODS: The experimental solution was prepared with H(2)O(2), VL-TiO(2), MB, and pure water. The final concentration of H(2)O(2) was 3.5% and that of MB was 10 ppm. The experimental solution of 3 mL in a quartz cell was irradiated by a 405 nm diode laser with various powers, duty cycles, and pulse durations for 7 min. RESULTS: In all irradiation conditions, the increase in laser irradiation time gradually decreased the MB concentration. Irradiation by higher output power showed more reduction of MB concentration. Pulse durations as short as 5 ms with duty cycle reduced to 25% did not affect the degree of the reduction in MB concentration compared with continuous wave irradiation at the same average output power. CONCLUSIONS: It was concluded that using 405 nm diode laser, the bleaching effects of VL-TiO(2) depended upon the irradiation time and the average output power, regardless of pulse duration or duty cycle.