Synthesis of ZnO Nanorod-Decorated Graphene Oxide for Application in Dental Resin Composites

Biofilm formation on resin composite surfaces is associated with the occurrence of secondary caries around restorations. As a promising antibacterial nanomaterial, graphene oxide is effective to suppress the viability of the cariogenic bacteria Streptococcus mutans (S. mutans). However, GO naturally expresses brown, which limits its potential application in dentistry. In this work, ZnO nanorod-decorated graphene oxide (GOn@ZnO) particles were synthesized via a facile hydrothermal method, and their optical property was regulated by changing the amount of seeded GO (n value) in the microemulsion. Among all hybrid particles, GO3@ZnO exhibited a bright gray color and lowest UV absorbance and therefore was selected as an optimal functional filler to produce dental composites with different loadings (0.1, 0.5, 1, and 3 wt %). The effects of GO3@ZnO loading on light transmittance, polymerization conversion, mechanical property, in vitro cell viability, and antibacterial effect of dental composites were systematically explored. The results exhibited that the 0.5 wt % GO3@ZnO-filled composite demonstrated comparable degree of conversion (60 s), higher flexural strength and modulus, and similar cell viability to the control. This composite also effectively inhibited the growth of S. mutans, giving a significantly lower bacterial concentration (3.9 x 107 CFU/mL) than the unfilled resin (8.5 x 107 CFU/mL) and the 0.5 wt % GO-filled composite (6.6 x 107 CFU/mL), respectively. The introduction of GO3@ZnO in dental composites could be a promising strategy to prevent secondary caries and extend service life.