Objectives . This study evaluated the immediate and 6-month term resin–dentin bond strength of different hydrophilicity primers bonded to acid-etched dentin saturated with water or ethanol.

Materials and methods . Flat dentin surfaces from extracted human third molars were obtained 2 mm above the cement–enamel junction on deep-coronal. The surfaces were acid-etched, left moist and saturated with water (water wet-bonding) or ethanol (ethanol wet-bonding). Two consecutives coats of each experimental primer 35/65% (v/v) HEMA/EtOH or Bis-GMA/EtOH, were then applied to both water-and-ethanol-saturated dentin surfaces for 30 s and left undisturbed for additional 30 s. Excess solvent was evaporated for 20 s and a layer of bonding agent was then applied. Resin composite buildups were constructed incrementally. After storage in water for 24 h at 37 °C, the specimens were prepared for microtensile bond strength (μTBS) testing. Data were analyzed statistically by three-way ANOVA and Holm–Sidak method for multiple comparisons α = 0.05%.

Results . The highest immediate and long-term μTBS values were observed when both primers, HEMA/EtOH and Bis-GMA/EtOH, were applied to ethanol-wet dentin. These values were significantly higher than those observed applied to water-wet dentin ( p < 0.05). HEMA/EtOH exhibited higher immediate μTBS than Bis-GMA/EtOH when applied to water-wet dentin ( p < 0.05). Significant reduction in μTBS using HEMA/EtOH was observed after 6 months of water storage.

Conclusions . The ethanol wet-bonding promoted more reliable immediate and long-term bond strengths for the Bis-GMA/EtOH. Water storage resulted in reduced bond strength for HEMA/EtOH, regardless of the bonding technique employed.