Influence of warm air-drying on enamel bond strength and surface free-energy of self-etch adhesives

We examined the effect of warm air‐drying on the enamel bond strengths and the surface free‐energy of three single‐step self‐etch adhesives. Bovine mandibular incisors were mounted in self‐curing resin and then wet ground with #600 silicon carbide (SiC) paper. The adhesives were applied according to the instructions of the respective manufacturers and then dried in a stream of normal (23°C) or warm (37°C) air for 5, 10, and 20 s. After visible‐light irradiation of the adhesives, resin composites were condensed into a mold and polymerized. Ten samples per test group were stored in distilled water at 37°C for 24 h and then the bond strengths were measured. The surface free‐energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths varied according to the air‐drying time and ranged from 15.8 to 19.1 MPa. The trends for the bond strengths were different among the materials. The value of the γS + component increased slightly when drying was performed with a stream of warm air, whereas that of the γS − component decreased significantly. These data suggest that warm air‐drying is essential to obtain adequate enamel bond strengths, although increasing the drying time did not significantly influence the bond strength.