Antimicrobial effect of different physical and chemical compounds of zinc oxide and graphene oxide added to composite resins

Graphene oxide (GO), a product of graphite, is a candidate for nano‑reinforcing cement‑based materials due to its good water dispersibility and excellent mechanical properties. On the other hand, zinc oxide (ZnO) is well‑known for its antibacterial characteristics as well. Therefore, we aimed to evaluate the impacts of adding ZnO and GO nanoparticles on the antibacterial properties of flowable composites.

In this, in vitro experimental study was designated into five groups containing:(1) no nanoparticles as control group,(2) 1 wt.% ZnO nanoparticle,(3) 1 wt.% GO,(4) 1 wt.% physical compound of ZnO and GO, and (5) 1 wt.% chemical compound of ZnO and GO. The antibacterial properties of composite resin discs were evaluated by direct contact test. Data were analyzed using a one‑way analysis of variance, followed by Tukey’s post hoc tests (P = 0.05).

Streptococcus mutans colony counting in the first 24 h showed the least growth rate in the chemical compound group (2.2 × 105 ). However, in 7 days, the least colony number was observed in the GO group (2 × 103 ). Moreover, the physical compound showed the least bacterial adhesion.

Adding GO alone to composites, compared to adding ZnO or physical and chemical compounds of GO‑ZnO, was more helpful to increase the antimicrobial characteristics.