Dual cure activator improves bond performance of etch-and-rinse mode universal adhesives to bleached enamel

To evaluate the effect of dual cure activator (DCA) on the bond strength of universal adhesives to bleached enamel and to analyze changes in surface morphology and elemental composition.

Bovine enamel specimens (n = 198) were divided into bleached and unbleached groups. DCA (Clearfil DC Activator) was applied to etched enamel surfaces before application of three universal adhesives: Clearfil Universal Bond Quick (UBQ), Optibond Universal (OBU), and Palfique Universal Bond (PUB). Shear bond strength (SBS) was measured after 24-hour water storage. Surface morphology and elemental composition were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). Statistical analysis was performed using one-way ANOVA with Dunnett's T3 post hoc test (α=0.05).

PUB demonstrated the lowest bond strength to unbleached enamel but showed significant improvement with DCA application (p < 0.001). Bleaching significantly reduced SBS across all adhesive groups (p < 0.001), with UBQ showing the least reduction. DCA application significantly increased SBS to bleached enamel for OBU (p < 0.001) and PUB (p < 0.001) but had no significant effect on UBQ (p = 0.72). SEM/EDS analysis revealed morphological alterations after bleaching and confirmed successful DCA incorporation through sulfur detection.

Bleaching significantly compromised the bond strength of universal adhesives to enamel in etch-and-rinse mode. The application of DCA can enhance the bonding performance of bleached enamel, particularly with specific adhesives. These findings underscore DCA as a viable clinical strategy for immediate post-bleaching restorative procedures in certain scenarios.