Background: Incidence of white spots due to demineralization of enamel and gingival problems is an unacceptable result of orthodontic treatment. Plaque accumulation and bacterial biofilm growth are responsible for these phenomena. The resin-based dental composites used as bonding agents in orthodontics play a major role in mentioned problems. As recent researches assert the antimicrobial effects of chitosan (CS) and zinc oxide (ZnO) nanoparticles (NPs), it seems that adding these nanoparticles to the composite can be beneficial in reducing the number and function of microorganisms. The aim of this study was to evaluate the antimicrobial effects of ZnO-NP and CS-NP-containing orthodontic composite.
Methods: Antibacterial effectiveness of ZnO-NPs and CS-NPs was assessed in four groups against Streptococcus mutans, Streptococcus sanguis and Lactobacillus acidophilus grown both planktonic and as a biofilm on composites. One group as the unmodified control group and three groups consisting of three different concentrations of ZnO-NPs and CS-NPs mixture: 1%, 5% and 10% (1:1 w/w). 108 CFU/ml microorganism suspensions were provided with spectrophotometer. Biofilm formation was quantified by viable counts. Disc agar diffusion (DAD) test was carri