Does extended air-drying time improve bond strength of universal adhesives to enamel?

ObjectiveTo investigate the effect of extended air-drying time on the microshear bond strength (MSBS) of universal adhesives to enamel.Materials and MethodsThe distal and mesial specimens from third molars were wet-ground and randomly assigned to three groups according to adhesives tested (n = 60): Clearfil Bond Universal, Gluma Bond Universal, and G-Premio Bond. The adhesives were applied in etch-and-rinse or self-etch modes, followed by air-drying for 5, 15, or 25 s. Composite buildups were constructed and subjected to the MSBS test after 24-h or thermocycling. MSBS results were evaluated using a four-way ANOVA. The thickness of the adhesive layer and the degree of solvent evaporation were further evaluated.ResultsAt 24-h, MSBS of G-Premio Bond significantly improved with the 25 s air-drying in both of the etching modes when compared to the 5 s air-drying. After thermocycling, the extended air-drying did not produce a significant difference on the MSBS, regardless of the application strategy. Extended air-drying (25 s) evaporated almost all of the volatile part of Gluma Bond Universal and G-Premio Bond.ConclusionsExtended air-drying times increased solvent evaporation but did not contribute to the bonding effectiveness of the adhesives, regardless of the etching mode.Clinical SignificanceAir-drying applications for more than 5 s had no significant effect on enamel bonding performance of universal adhesives.