Bonding Strength of Universal Adhesives to Laser-Etched Deep and Superficial Dentin.

OBJECTIVE: The effectiveness of laser-etching (LE) on dentin shear bond strength (SBS) of universal adhesives remains unclear. This study aimed to compare the SBS of a nanohybrid composite resin to superficial and deep dentin following application of a contemporary universal adhesive using either self-etch (SE) or LE. MATERIALS AND METHODS: Forty-four extracted human molars were embedded in acrylic blocks and prepared to obtain superficial or deep dentin surfaces (n = 22 each), and then assigned to four groups (n = 11). The Scotchbond Universal Adhesive (SBU) was applied in SE in Groups 1 and 3, while dentin surfaces were conditioned with an Er, Cr:YSGG laser (1.5 W, 20 Hz) before adhesive application in Groups 2 and 4. The nanohybrid composite (Filtek Z550-FZU) was placed and light-cured. SBS was determined with a universal testing machine, while fracture patterns were evaluated under a stereomicroscope, and the results were statistically assessed by either ANOVA or the Kruskal-Wallis test (p < 0.05). RESULTS: Application of universal adhesive using SE and LE did not affect the shear bond strength of nanohybrid composite resin placed after application to superficial and deep dentin (p > 0.05). Evaluation of failure types revealed no difference in failure type distribution between SE and LE groups (p > 0.05). CONCLUSION: Dentin depth and etching technique had no effect on the SBS of composite resin. No difference was found between groups in terms of failure types.