Antibacterial properties and shear bond strength of an orthodontic composite following addition of copper oxide/chitosan nanoparticles

Introduction: This study assessed the antibacterial properties and shear bond strength (SBS) of an orthodontic composite following addition of copper oxide (CuO)/chitosan nanoparticles (NPs).Materials and Methods: Forty-eight bovine teeth were randomized into 4 groups (n=12) for stainless steel bracket bonding with 0% (control), 1%, 0.5%, and 0.1% CuO/chitosan NPs added to Transbond XT composite. The bracket-tooth SBS was measured, and the adhesive remnant index (ARI) score was determined under a stereomicroscope. Transbond XT composite discs with 5 mm diameter were fabricated with 0%, 1%, 0.5%, and 0.1% CuO/chitosan NPs. The antibacterial properties of the discs were assessed against Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), and Lactobacillus acidophilus (L. acidophilus) using the disc agar diffusion (DAD), eluted component, and biofilm inhibition tests. Results: The maximum and minimum SBS values were recorded in the control, and 1% NP group, respectively. The 1% NP group had significantly lower SBS than other groups (P<0.05). The control group had significant differences with the three NP groups regarding the ARI score. The biofilm inhibition test showed significant differences among the groups in all three tested bacteria (P<0.05). The DAD test revealed no growth inhibition zone. The eluted component test indicated significant results for all groups and all bacteria (P<0.001). Conclusion: CuO/chitosan NPs in 0.1% and 0.5% concentrations significantly inhibited the biofilm formation by all three bacteria while preserved the SBS within the clinically acceptable range. However, the NPs did not show optimal solubility and dispersion at the tested concentrations.