Effect of zinc oxide-doped hydroxyapatite nanoparticles on the friction reduction and antibacterial properties of orthodontic ceramic brackets and stainless-steel wires

The objective of this study was to assess the friction reduction and antibacterial properties of orthodontic brackets and wires coated with ZnO-doped HAP nanoparticles. ZnO-doped HAP nanoparticles were characterized with SEM, FTIR, and XRD analysis. After characterization, ZnO-doped HAP nanoparticles were coated onto orthodontic brackets and wires employing the dip coating method. The samples were then divided into four groups, control group Z0 (uncoated wires and brackets, and HAP only) and experimental group Z5(5%ZnO+HAP), Z10 (10% ZnO+HAP), Z15 (15% ZnO+HAP). The prepared samples were then subjected to mechanical and antibacterial testing. Mechanical properties such as friction resistance and microhardness improved with the coating of ZnO-HAP nanoparticles. The lowest friction was observed for the Z15 group (7.81 ± 1.10 N) while the highest was observed for the control group Z0 (21.25 ± 0.92 N). Friction force decreased with coating and with increasing concentration of ZnO nanoparticles in the composites in the order of Z0 > Z5 > Z10 > Z15. Microhardness of the brackets and wires improved with the coating, with the highest microhardness values observed for groups Z10 and Z15 of 2253 ± 93.7 and 2239 ± 123.1, respectively. The hardness of the wires also improved with the coating with the lowest value observed for the uncoated Z0 (351 ± 45.17). Agar well diffusion test showed an inhibition zone of 11.3 ± 0.57 mm, 15.3 ± 0.57 mm, 14.6 ± 1.15 mm, and 15.1 ± 1.14 mm for Z0, Z5, Z10 and Z15, respectively. The result of this study showed that zinc oxide-doped hydroxyapatite nanoparticle coating improved the mechanical and antibacterial properties of orthodontic brackets and wires.