Influence of ZnO Nanoparticles on the Color and Surface Roughness of Composite and Glass-Ionomer Materials

Objective: The effect of incorporating various concentrations of 210 nm ZnO nanoparticles (ZnO-NPs) into resin-based composites (RBCs) and glass-ionomer cement (GIC) on their color and surface roughness after immersion in red wine is evaluated. Materials and Methods: 12 experimental groups (n = 12) were tested, including three commercial restorative materials: a microhybrid RBC (Gradia Direct®), a nanohybrid RBC (Evetric®) and a GIC (Fuji IX®). These were modified with ZnO-NPs at weight concentrations of 1%, 2%, and 3%. Color coordinates (L*,a*,b*) were measured using a spectrophotometer (CIEDE2000 formula) before and after 24 h immersion in red wine (37 °C). Surface roughness (Ra) was analyzed using contact profilometry. Results: The addition of ZnO-NPs increased the lightness (L*) and decreased the a* values in all materials. In resin-based composites, even a 1% concentration of ZnO-NPs caused a color change above the clinical acceptability threshold (ΔE00 > 1.8; observed values ranged from 3.2 to 8.0). After immersion in wine, all materials exhibited further discoloration (ΔE00 up to 12.5 for composites). Surface roughness values increased from 0.42 μm (control composite) to 1.95 μm (3% ZnO-NP-modified GIC). Conclusions: Addition of ZnO-NPs influences the aesthetics and topography of restorative materials. Their concentration must be balanced to maintain visual and surface integrity.