Micro-rotary Fatigue Resistance of a HEMA-free One-step Adhesive

HEMA-free all-in-one adhesives exhibit phase separations if not applied using thorough air-blowing (Van Landuyt et al., J Dent Res, 2005). This might compromise the bonding effectiveness, especially on the long-term. Objectives: to determine the effect of thorough air-blowing on the static and dynamic bonding effectiveness of a HEMA-free all-in-one adhesive bonded to class-I cavity-bottom dentin. Methods: G-Bond (GC, Japan) was applied to standardized occlusal class-I cavities, using either mild or strong air-blowing of the primer. After restoring the cavity using a composite resin (Gradia Anterior, GC) micro-specimens with a rounded composite/dentin interface were prepared. These were inserted in a micro-rotary fatigue testing device (De Munck et al., Biomaterials, 2004), or loaded statically until failure in a similar way as the fatigue set-up (control). Fatigue specimens were tested at 4 Hz until failure or until 10⁵ cycles were reached. The mean load at which 50% of the samples failed (median micro-rotary fatigue resistance, µRFR) was determined (in MPa) using logistic regression and the 2 groups were compared using multiple logistic regression. Control results were analyzed using a paired t test.

*Means with the same superscript are not significantly different

Conclusion: The kind of air blowing had no effect on the static or dynamic bonding effectiveness. even despte the very strong (5 bar) and long air-blowing procedure. SEM analysis revealed that in both groups phase-separations occurred. Ineffective air-blowing and pooling of the adhesive in a narrow cavity diminished the effect of strong air-blowing of the all-in-one adhesive.