Abstract

Objectives To evaluate the effect of incorporating zinc oxide (ZnO), copper (Cu), and bioactive glass (BG) nanoparticles into a universal adhesive on the resin-dentin bond stability under a cariogenic challenge. The influence of these nanoparticles on enzymatic activity, mineral deposition, nanoleakage (NL), and microtensile bond strength (& micro;TBS) was assessed. Methods Five experimental adhesives were formulated by adding nanoparticles to a commercial universal adhesive: Control (0%), ZnO/Cu (0.2 wt% Cu + 2.5 wt% ZnO), 5 wt% BG + ZnO/Cu, 10 wt% BG + ZnO/Cu, and 10 wt% BG. Human dentin specimens were bonded using etch-and-rinse (ER) or self-etch (SE) strategies and restored with resin composite. After 24 h, specimens were evaluated at baseline and following a 5-day Streptococcus mutans biofilm challenge (pH approximate to 4.0). & micro;TBS and NL were measured before and after challenge. Matrix metalloproteinase (MMP) activity was analyzed via in situ zymography, and mineral deposition was characterized by SEM-EDX after immersion in simulated body fluid. Data were analyzed using ANOVA and Tukey's post hoc test (alpha = 0.05). Results Nanoparticle incorporation enhanced the biofunctional performance of the adhesive. The 10 wt% BG + ZnO/Cu formulation preserved & micro;TBS and significantly reduced NL after the cariogenic challenge (p < 0.05), whereas the control lost than 40% of its initial bond strength. SEM-EDX revealed increased Ca and P deposition at the hybrid layer, approaching hydroxyapatite-like composition. Although MMP activity varied between bonding strategies, no consistent inhibitory effect was detected.