Antimicrobial Properties and Shear Bond Strength of Composite Used in Orthodontics Following the Addition of Curcumin-Reduced Nanographene Oxide

Background: Composites used in the direct bonding of brackets in fixed orthodontics are considered a suitable environment for the multiplication of cariogenic bacteria and the establishment of microbial plaques by creating a distance between the bracket, tooth surface, and surface properties such as porosity. In the present study, we decided to combine curcumin-reduced nano-graphene oxide (rGO-NCUR) with a composite resin used in orthodontics to achieve a composite with optimal shear bond strength (SBS) and antimicrobial properties against Streptococcus mutans as a main cariogenic bacterium. Methods: In the present study, nanoparticle of graphene oxide (NGO) was synthesized by the modified Hummers’ method using graphite powder and reacted by NCUR to regenerate reduced-NGO (rGO-NCUR). Scanning electron microscopy (SEM) was used to confirm the synthesis of NGO, NCUR, and rGO-NCUR. SBS and antimicrobial activity of Transbond XT composite containing 5% rGO-NCUR were performed against S. mutans biofilms. SPSS software, one-way ANOVA test, and Tukey post hoc test with a significance level equal to or less than 0.05 were used to analyze the data. Results: The synthesis of NGO, NCUR, and rGO-NCUR in nanoscale was confirmed by SEM. The amount of SBS in the composite sample with 5% w/w rGO-NCUR was 12.30 ± 0.65 MPa. The optical density of S. mutans in the biofilm structure formed on composite containing 5% w/w rGO-NCUR was significantly reduced (62.10%) compared with the control group, namely, original composites used in orthodontics (P < 0.05). Conclusions: Based on the data of the present study, it can be concluded that composite containing 5% w/w rGO-CUR, without adverse effect on the physical-mechanical properties of composites, can be used as an antimicrobial additive of composites used in orthodontics to control biofilm formation and caries around orthodontic brackets