Shear Bond Strength of Airborne-Particle-Abraded Base Metal Alloys to Self-Adhesive Resin Cement: Effects of Delay Time and Storage

This study evaluated the effect of delay time and storage conditions after airborne-particle abrasion on the shear bond strength between base metal alloys (BMA) and self-adhesive resin cement. It also assessed whether vacuum sealing or re-airborne-particle abrasion could counteract the time-related degradation of bond strength. Sixty BMA specimens were airborne-particle-abraded and divided into six groups (n = 10): immediate bonding; 1-day, 7-day, and 14-day delays; 14-day vacuum-sealed; and 14-day delay with re-airborne-particle abrasion. Resin cement was applied to standardized bond areas, and composite rods were bonded. All specimens were stored in water at 37 °C for 24 h before shear bond strength testing. Failure modes were examined under a stereomicroscope. One-way ANOVA revealed significant differences among groups (p < 0.05). Immediate bonding yielded the highest strength (26.50 ± 2.74 MPa). Bond strength declined with delays, namely, 1-day (21.19 ± 4.94 MPa), 7-day (15.20 ± 4.52 MPa), and 14-day (16.01 ± 4.69 MPa), with no significant difference between the 7- and 14-day groups. Vacuum sealing for 14 days preserved bond strength (25.92 ± 3.94 MPa) comparable to immediate bonding. Re-airborne-particle abrasion restored bond strength (20.66 ± 3.70 MPa). Prolonged delays resulted in 100% adhesive failures, whereas immediate bonding and intervention groups showed 80% adhesive and 20% mixed failures. Delayed bonding after airborne-particle abrasion significantly reduces bond strength due to oxide layer formation on the BMA surface. However, surface sealing might prevent surface oxidation and maintain bonding potential, while re-airborne-particle abrasion can restore bond strength when delays are unavoidable. Clinically, bonding should be performed immediately after airborne-particle abrasion, or appropriate surface management protocols should be implemented to maintain optimal adhesion.