Purpose: To determine the effect of thorough air drying on the static and dynamic bonding effectiveness of a HEMAfree all-in-one adhesive bonded to Class-I cavity-bottom dentin. Materials and Methods: G-Bond (GC, Japan) was applied to standard occlusal Class I cavities following either a gentle (1 bar) or strong (4 bar) air-drying technique. After restoring the cavity using a composite resin (Gradia Anterior, GC), microspecimens were prepared that were loaded until failure or inserted in a microrotary fatigue testing device. Results: Strong air drying had no effect on the static (39.1 vs 38.4 MPa) or the dynamic (19.0 vs 18.6 MPa) strength of the interface complex. Conclusion: Strong air drying did not improve the static or the dynamic bonding effectiveness, although a very thorough (4 bar) and long air-drying procedure was employed. SEM analysis revealed that even when the adhesive was strongly air dried, droplets originating from phase separations could still be observed, albeit to a reduced extent. Ineffective drying and pooling of the adhesive in a narrow cavity diminished the effect of strong air drying of the all-in-one adhesive.

Keywords: adhesion, dental adhesive, fatigue, enamel, dentin