Effect of laser-activated bleaching with 445, 915, and 970nm diode lasers on enamel color change: an in vitro study

 Considering the increasing use of esthetic treatments, one of which is bleaching treatment, choosing the different wavelengths and parameters for this treatment can help in choosing the best treatment. Based on this, this study aimed to investigate bleaching with three wavelengths of 445nm, 915nm, and 970 nm on the amount of teeth discoloration. In this study, 77 human permanent teeth without caries were selected and randomly divided into 7 groups as control, 445 nm (1 and 1.5 W and time 20 seconds), 915 nm (2 and 2.5 W and time 30 seconds) and 970 nm (1.5 and 2 W and time 30 seconds). The bleaching gel used was 40% hydrogen peroxide bleaching gel(Ultradent-Opalescence, USA). All groups were subjected to laser irradiation with a 0.5 cm2 area with continuous wave mode radiation at a distance of 1 mm from the bleaching gel. Before starting the study, all the samples were subjected to calorimetry using a spectrophotometer. After bleaching with the said wavelengths, Color change data on the CIE L * a * b* system was analyzed statistically by the one-way ANOVA and Tukey’s HSD test. Based on the findings, ΔE was positive in all groups. The highest amount was in the 445nm 1.5w group and the lowest was seen in the control group and then in the 970nm 2w group (P<0.05). The highest dispersion of color change is related to the 445nm 1.5w group (P<0.05). In general, the results showed that the use of 445nm diode laser 1.5w (ΔE=12) and 970nm diode laser 2w (ΔE=37.5) was the most and least effective in teeth bleaching, respectively. According to the results of the present Invitro study, the 445 nm laser with a power of 1.5 watts had the most effect in changing tooth color, and the 970 nm group with a power of 2 watts showed the least effect.