Addition of silver nanoparticles to universal adhesive: In vitro effect on biofilm and shear bond strength

Silver nanoparticles (AgNPs) have been incorporated into dental materials at low concentrations to provide antibacterial action without compromising mechanical properties. This in vitro study evaluated the antibiofilm effect and bond strength of an experimental universal adhesive with AgNPs (EAg). Streptococcus mutans biofilm was induced by incubating samples with 0.01% and 0.02% AgNPs, based on a pilot study, compared to a control (experimental without AgNPs, ES) in a 20% sucrose medium. This was followed by sonication and counting of viable cells after 1 and 7 days (n = 9). Enamel and dentine bovine micro shear bond strength test (μ-SBS) was performed (n=10) with EAg0.01% and controls (ES and the commercial OPT (Optbond Universal; Kerr). μ-SBS data of enamel and dentin were evaluated for normality and homogeneity by Shapiro-Wilk and Levene, respectively, resulting in normality. Therefore, they were subjected to ANOVA. The failure type was evaluated using a stereoscopic magnifying glass at '40 and categorized as adhesive, cohesive, and mixed failure. The 0.01% concentration demonstrated the antibiofilm effect at the lowest AgNP concentration and was selected for the μ-SBS test. For μ-SBS ANOVA, there were no statistically significant differences between experimental and commercial adhesives (p<0.05). Evaluation of failure mode showed a predominance of adhesive failure on both substrates for all adhesives. The EAg exhibited antibiofilm activity with adhesive performance statistically similar to that of the commercial adhesive. Experimental universal adhesive containing silver nanoparticles showed antibacterial activity without compromising μ-SBS to enamel and dentin.