Optical Effects of Experimental Light-Activated Bleaching Procedures

Abstract

The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures. The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching. Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy. Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis. The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.