Comprehensive evaluation of the antibacterial and antibiofilm activities of NiTi orthodontic wires coated with silver nanoparticles and nanocomposites: an in vitro study.

Background: Fixed orthodontic appliances act as a niche for microbial growth and colonization. Coating orthodontic wires with antimicrobial silver nanoparticles (AgNPs) and nanocomposite was adopted in this study to augment the biological activity of these wires by increasing their antibacterial and antibiofilm properties and inhibiting bacterial infections that cause white spot lesions and lead to periodontal disease.

Methods: Three concentrations of biologically synthesized AgNPs were used for coating NiTi wires. The shape, size, and charge of the AgNPs were determined. Six groups of 0.016 × 0.022-inch NiTi orthodontic wires, each with six wires, were used; and coated with AgNPs and nanocomposites. The antimicrobial and antibiofilm activities of these coated wires were tested against normal flora and multidrug-resistant bacteria (Gram-positive and Gram-negative bacterial isolates). The surface topography, roughness, elemental percentile, and ion release were characterized.

Results: AgNPs and nanocomposite coated NiTi wires showed significant antimicrobial and antibiofilm activities. The chitosan-silver nanocomposite (CS-Ag) coated wires had the greatest bacterial growth inhibition against both Gram-positive and Gram-negative bacteria. The surface roughness of the coated wires was significantly reduced, impacting the surface topography and with recorded low Ni and Ag ion release rates.

Conclusions: NiTi orthodontic wires coated with AgNPs, and nanocomposites have shown increased antimicrobial and antibiofilm activities, with decreased surface roughness, friction resistance and limited- metal ion release.