Nd : YAG laser influence on dentin bond strength of three different adesive systems

Purpose: This study examined the effects of Nd:YAG laser irradiation on the shear bond strength of three different adhesive systems. Materials and Methods: Thirty freshly extracted noncarious human molars were ground to expose middle dentin, which was polished down to 600 grit. Specimens were separated into 6 subgroups (n = 5) and received the following treatments: (C1) Prime&Bond NT as indicated by manufacturer; (C2) Xeno III as indicated by manufacturer; (C3) Tyrian SPE One Step Plus as indicated by manufacturer; (L1) Prime&Bond NT + laser; (L2) Xeno III + laser; (L3) Tyrian SPE One Step Plus + laser. Nd:YAG laser was used in noncontact mode at 15 Hz and 40 mJ for 30 s. A standard 5-mm-diameter composite resin cylinder (Synergy, Coltene) was bonded to the dentinal surface, and specimens were then 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 by two-way ANOVA and the Students t test (p < 0.05). Results: The bond strength of the control group was significantly higher than that of the laser group (p < 0.05). Xeno III obtained the highest SBS values in the laser group, while Prime&Bond NT showed the highest values in the control group. Conclusion: Nd:YAG laser irradiation adversely affected adhesion to dentin for all three different dentin adhesive systems tested in this study.