LAUSR

Objective: The shear bond strength (SBS) of composite resin cement and color change to enamel bleached with two different concentrations of hydrogen peroxide (HP) bleaching agents in combination with two different laser applications was evaluated. Materials and Methods: The Er: YAG laser (λ = 2940 nm) and diode laser (λ = 940 nm) were used with the bleaching agent consisting of 40% HP opalescence (Opalescence Xtra Boost, Ulgen, South Jordan, UT, USA) and 35% HP whiteness (Whiteness HP Blue, FGM Dental Products, Joinville, SC, Brazil). Seventy-two human extracted teeth were randomly divided into two groups: For the 40% HP treatment, 36 specimens were divided into three subgroups: (1) HP agent with no laser treatment, (2) HP agent treated with Er: YAG laser, and (3) HP agent treated with diode laser. The same protocol was performed for the 35% HP. The color change was analyzed using the Commission Internationale de l’ Eclairage (CIE) L*a*b* system and surface roughness was analyzed by an atomic force microscope. The specimens were bonded with resin cement and a shear bond test was performed at 0.5 mm/min. The failure surfaces were evaluated using scanning electron microscope analysis. Results: ΔE value of the 40% HP + Er: YAG group was significantly higher than the other groups while diode groups showed the lower SBS values than the control groups (p < 0.05). Conclusions: The Er: YAG laser with 40% HP may be effective for the brighter teeth and the use of Er: YAG laser produced higher adhesion between enamel and resin cement than diode laser.