Durability of resin dentin interfaces: effects of surface moisture and adhesive solvent component

Objectives. To analyze the effects of different surface moisture on bond strength (BS) durability of an ethanol/water based, Single Bond (SB); an acetone-based, One-Step (OS); and a water-based, Syntac Single Component (SC) adhesive system to dentin. Methods. Forty-five human third molars had their superficial dentin surface exposed flat by abrasion. The adhesives were applied to a delimited area of 52 mm2 on either air-dried (30 s) or rewetted surfaces (2.5 or 4.0 μl) followed by resin composite build-ups. After storage in water at 37 °C (24 h), the teeth were sectioned to obtain bonded sticks with a cross-sectional area of 0.8 mm2. The sticks, from each tooth, were divided, stored in water at 37 °C and tested either immediately or after 6 months (6 M) at 0.5 mm/min. BS was expressed as an index that considers cohesive failures and estimated values of premature debonded specimens. Results. Three-way ANOVA showed statistically significant effects for moisture degree, storage time and double interactions (p<0.05). While SB and SC achieved higher BS at 0 and 2.5 μl of water, for OS the BS was higher at 4.0 μl of water. Regardless of the moisture degrees, reductions in BS were observed after 6 M storage for SB and OS (p<0.05), but not for SC (p>0.05). No difference in BS between the 24 h and 6 M storage was found when the moisture was set at the extreme conditions. Significant reduction in BS was observed when the moisture was set at 2.5 μl. Significance. The bond strength of different solvent-based adhesive systems gradually decreases over time, regardless of the variable moisture pattern used for the bonding procedure.