Antibacterial, physical and mechanical properties of flowable resin composites containing zinc oxide nanoparticles

ObjectivesThe aim of this study is evaluating the antibacterial activity of resin composites containing ZnO nanoparticles against Streptococcus mutans and examining their physical and mechanical properties.MethodsThe properties of flowable resin composites containing 0–5 wt.% nano-ZnO are investigated using different tests:A.Antibacterial activity (including agar diffusion test on the cured resins, direct contact test using bacteria in a liquid medium, evaluating the effect of aging while the samples are adjacent to a liquid medium, and scanning electron microscopy (SEM)).B.Mechanical behavior (including flexural and compressive strength and modulus).C.Curing aspects (including depth of cure and degree of conversion).D.Adhesion properties (including micro-shear bond strength).ResultsAlthough the agar diffusion test reveals no significant difference between the groups, the direct contact test demonstrates that by increasing the nanoparticle content, the bacterial growth is significantly diminished (p < 0.05). In the aging test, however, the antibacterial properties reduce significantly (p < 0.05). The flexural strength and compressive modulus remains unchanged by incorporation of nanoparticles (p > 0.05) while the compressive strength and flexural modulus significantly increase (p < 0.05). The ZnO containing resins show significantly lower depth of cure (p < 0.05), and higher bond strength (p < 0.05). There is no significant difference between the degrees of conversion, measured by FTIR technique, of the groups (p > 0.05).SignificanceProduction of a dental resin composite with antibacterial activity without significant sacrificing effect on the mechanical properties is desirable in dental material science.