Effect of ammonia-free silver fluoride application on the resin–dentin interface subjected to an in situ cariogenic challenge

This study aimed to evaluate whether an ammonia-free silver diamine fluoride solution can prevent adhesive interface degradation when subjected to an in situ cariogenic challenge (CC). Fifty-six sound human molars were sectioned to obtain flat mid-coronal dentin surfaces, and half of the specimens received ammonia-free silver diamine fluoride pretreatment. Specimens were then restored using two universal adhesives (Single Bond Universal, SBU; and Zipbond, ZIP) applied with either the etch-and-rinse (ER) or self-etch (SE) strategy. Composite buildups were constructed, sectioned into resin–dentin bonded sticks, and allocated for immediate testing or after an in situ cariogenic challenge. Twenty volunteers wore (14 days) palatal devices containing eight resin–dentin sticks from different groups. CC were induced (20% sucrose solution; 4×/day). Microtensile bond strength (µTBS) was assessed, and failure modes were classified. Adhesive interfaces were analyzed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDX-SEM). Data were analyzed using four-way repeated measures ANOVA and Tukey’s post hoc test (α = 0.05). At immediate evaluation, no significant differences were observed between groups, while after the CC, µTBS values significantly decreased in groups without Riva Star Aqua. Ammonia-free silver diamine fluoride solution treatment maintained µTBS, showing higher µTBS compared to untreated groups (p < 0.05). EDX-SEM confirmed silver and calcium deposition within the hybrid layer and dentinal tubules after ammonia-free silver diamine fluoride treatment. Pretreatment with ammonia-free silver diamine fluoride solution preserved resin–dentin bond strength under cariogenic conditions. ammonia-free silver diamine fluoride solution pretreatment may protect adhesive interfaces in high-caries-risk patients by enhancing hybrid layer stability and reducing biofilm-related degradation.