Antibacterial Efficacy and Mechanical Strength of Direct Dental Composite Resins with Integrated Metal and Metal Oxide Nanoparticles: A Systematic Review of In-Vitro Studies

The present systematic review aimed to evaluate the antibacterial efficacy and mechanical strength of direct dental composite resins with integrated metal/metal oxide nanoparticles (NPs). A review was performed using different electronic databases employing MeSH terms for identifying relevant published literature, without any restrictions on language and date of publication. The antibacterial activity of metal/metal oxide NPs-incorporated composites for the prevention of secondary caries was the primary outcome, whereas the mechanical strength was designated as the secondary outcome. 6 studies used varying amounts of silver (AgNPs); 5 studies used zinc oxide (ZnO-NPs); 1 study used Ag-doped ZnO-NPs. Four studies found a statistically significant (p < 0.05) antibacterial activity of varying amounts of ZnO-NPs, five studies found a statistically significant (p < 0.05) antibacterial activity of AgNPs, two studies reported a statistically non-significant (p > 0.05), however greater antibacterial activity, by the incorporation of AgNPs. All included studies reported that the mechanical strength of the composites was not compromised by the addition of either ZnO-NPs or AgNPs. Metal/metal oxide-modified direct dental composite resins resulted in improved antibacterial efficacy without compromising their mechanical strength as compared to non-modified composite resins. However, it is imperative to determine an equilibrium between the mechanical features and antibacterial activity of these materials, and more in vivo investigations are recommended in this aspect.