Effect of Diode Laser Irradiation on Tooth Bleaching Agent

Objectives: The purpose of this study was to evaluate the bleaching effect of 35% hydrogen peroxide bleach in combination with an 810 nm diode laser and indocyanine green (ICG), whose absorption peak is around 810 nm.
Methods: Fifty extracted bovine incisors were divided into five groups and subjected to bleaching treatment. The labial enamel was flattened to obtain a specimen with surface area of 5 mm x 5 mm. Artificial staining of samples was performed using black tea extract. ICG was pre-mixed with urea powder (ICG/urea). The 35% hydrogen peroxide (H₂O₂) was blended with pure urea or ICG/urea at a weight ratio of 1:4. The bleaching gropes were designed as follows:
Group 1: 5 min treatment, Urea/ H₂O₂
Group 2: 1 min treatment time, Urea/ H₂O₂, laser irradiation (1 min)
Group 3: 1 min treatment, ICG/urea/ H₂O₂ , laser irradiation (1 min)
Group 4: 5 min treatment, ICG/urea/ H₂O₂, laser irradiation (1 min) left for 4 min
Group 5: 5 min treatment, ICG/urea/ H₂O₂, left for 4 min, followed by laser irradiation (1 min)

The laser irradiation was performed using an 810-nm diode laser system (Sheep810, UNITAC CO., LTD, Onomichi, Japan) at a wavelength of 810 at 1 W of power. L*a*b* values were recorded before and after bleaching and the colour difference (ΔE) was statistically analyzed (P < 0.05).
Results: Group 3 exhibited significantly increased ΔE when compared to Group 1 and 2.
Group 4 showed the highest ΔE value, while there was no difference between Group 4 and 5.
Conclusions: H₂O₂-based bleaching using 810 nm diode laser irradiation with ICG showed a high bleaching effect.