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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.