Purpose: This study examined the shear bond strength of three different adhesive systems to untreated and Nd:YAG laser-treated dentin. Materials and Methods: Sixty freshly extracted noncarious human molars were ground to expose middle dentin, which was polished down to 600 grit. Half of the samples were prepared with an Nd:YAG laser for 20 s at 10 Hz and 80 mJ (laser group); the other half was maintained as a control (control group). Three dentin adhesive systems were applied according to manufacturer’s instructions to the laser-irradiated surfaces and to the control surfaces: Scotchbond Multi-Purpose (SBM), Scotchbond 1 (SB1), and Adper Prompt L-Pop (LP); for SBM and SB1, the dentin surface was etched with 35% phosphoric acid gel for 15 s. A 5-mm-diameter metal ring was used to set the resin composite (Z100), and specimens were stored in water at 37°C for 24 h. Shear bond strength (SBS) was evaluated by means of a universal testing machine with a crosshead speed of 1 mm/min. The results were statistically analyzed with two-way ANOVA and Fisher’s PLSD test (p < 0.05). Results: The bond strength of the control group was significantly higher than that of the laser group (p < 0.05). SBM obtained the highest SBS values in the control group while LP showed the highest in the laser group. Conclusion: Nd:YAG laser irradiation adversely affect adhesion to dentin for all three different dentin adhesive systems tested in this investigation.

Keywords: Nd:YAG laser, dentin, adhesion, shear bond strength, etching