Dentin bond strengths of four adhesion strategies after thermal fatigue and 6-month water storage

Statement of Problem: The stability of current dental adhesives after artificial aging may depend on the adhesion strategy. Purpose: To evaluate the effect of thermal fatigue and water storage on the dentin microtensile bond strengths (μTBS) of four adhesion strategies. Materials and Methods: Forty-eight human molars were assigned to four dentin adhesives: FL-OptiBond FL (Kerr Corporation, Orange, CA, USA); SOLO-OptiBond SOLO Plus (Kerr Corporation); XTR-OptiBond XTR (Kerr Corporation); and AIO-OptiBond All-in-One (Kerr Corporation). Teeth were restored with a hybrid composite, and sectioned to obtained bonded beams. For each adhesive, one-third of the central and peripheral beams were assigned to one of three aging conditions: (1) kept in distilled water for 24 hours (24h); (2) thermocycled (TC) for 20,000 cycles; and (3) stored in distilled water for 6 months (6M). Beams were tested in tension mode. Statistical analysis (p < 0.05) was computed using Analysis of Variance and Fisher's Least Significant Difference post hoc test. Results: The highest mean μTBS for 24h, TC, and 6M were obtained with XTR, but only the 6M mean μTBS were significantly higher than those of the other three adhesives. For FL, mean μTBS decreased significantly from 24h to TC. For SOLO, mean μTBS remained stable over the three aging conditions. Mean μTBS for AIO decreased significantly from 24h to 6M. Conclusion: The self-etch adhesives XTR and AIO performed similarly or better than the etch-and-rinse adhesives FL and SOLO for all three testing conditions. Their aging stability seems to be material-dependent. CLINICAL SIGNIFICANCE The dentin bonding ability of the newest self-etch adhesives has improved compared with other similar materials, including etch-and-rinse adhesives. Adhesives that contain a hydrophobic resin (FL and XTR) tend to be more stable in water storage.