A universal adhesive containing copper nanoparticles improves the bonding and mechanical properties of resin cement–root dentin interface: an in vitro study

The aim of this study was to evaluate the anti-MMP activity of two concentrations of copper nanoparticles (CuNp) and the effect of their addition to a universal adhesive system on resin cement-radicular dentin in situ degree of conversion (DC), elastic modulus (EM), nanoleakage (NL), and push-out bond strength (PBS). Anti-MMP activity was evaluated for several MMPs. Seventy-two roots of endodontically prepared human lower premolars were randomly divided into six groups according to CuNp concentration (0% [control], 0.1%, 0.2%) and adhesive strategy (etch-and-rinse [ER] and self-etch [SE]). Fiber posts were cemented, DC was measured using micro-Raman spectroscopy, the EM of the hybrid layer and adhesive layer was measured using a nano-indenter, the NL was evaluated by scanning electron microscopy, and PBS was tested at 0.5 mm/min. Data were analyzed by two-way ANOVA and Tukey’s test (α = 0.05). CuNp demonstrated anti-MMP activity (p < 0.01). CuNp containing-adhesives showed significant increased DC (p = 0.01), increased EM in the hybrid layer and adhesive layer (p = 0.001), decreased NL values (p = 0.001), and increased PBS (p = 0.0001). Adhesive strategy was not statistically significant (p > 0.47). Usually, a significant difference among root thirds was observed, except for DC and NL when CuNp 0.2% was evaluated. This is the first in vitro study showing that the incorporation of CuNp in an adhesive is an achievable alternative that can provide anti-MMP activity and improve the mechanical and bonding properties to root canal dentin.