Effect of Cleaning After Silica-Coating on the Resin Bond Strength to Zirconia

This study assessed whether the cleaning protocol of the bonding surface of translucent zirconia, after silica-coating by air-abrasive particles, affects its resin bond strength before and after long-term aging. Zirconia slices (15×15×2 mm) (IPS e.max ZirCAD MT, Ivoclar) were air-abraded with silica-coated alumina particles, and then assigned to four cleaning protocol groups: air-jet only (AJ), air/water spray (AWS), ultrasonic bath with alcohol (UB-A), or ultrasonic bath with distilled water (UB-W). All surfaces received a primer (Monobond Plus, Ivoclar) followed by bonding the resin cement cylinders (Variolink Esthetic DC, Ivoclar; n=15), to be tested in microshear bond strength (µSBS) after 24 h of water storage (baseline) or after aging (90 days of water storage + 20,000 thermocycles, 5- 55 °C). Surface topography, elemental composition, and failure modes were also performed. Two-way ANOVA showed no significant effects of cleaning protocol (F=0.383, p=0.765), aging (F=3.196, p=0.077), or their interaction (F=0.443, p=0.723) on bond strength, although aged groups exhibited a higher incidence of pre-test failures. SEM revealed similar surface morphology among all groups, characteristic of silica-coated air abrasion. EDS detected residual silica in the AJ (0.8%) and AWS (0.13%) groups, whereas UB-A showed lower silica content (0.07%), and no silica was detected in UB-W. Despite these chemical differences, all cleaning protocols resulted in comparable bonding performance, with adhesive and cohesive failures observed across all groups. These findings indicate that cleaning protocol does not significantly affect zirconia-resin bond strength, and simpler approaches, such as air or air/water jets, are effective for maintaining bond strength after aging.