Comparative assessment of the orthodontic wire’s friction coated with zinc oxide nanoparticles by two methods of chemical precipitation and hydrothermal process

Introduction: In orthodontic treatment with sliding technique, reduction of frictional forces could result in a more effective treatment. Recently, wire coating with nanoparticles were proposed to reduce frictional forces.Aim: The aim of this study was to evaluate the effect of coating wires with zinc oxide nanoparticle by two methods of chemical precipitation and direct hydrothermal process on the wire-bracket frictional force.Materials and methods: In this study, 30 pieces of stainless-steel arch wire with and without zinc oxide nanoparticles and 30 metal brackets with a 0.022-inch slot were divided into three groups: group 1 – control (uncoated wires); group 2 – wires coated with zinc oxide nanoparticles, and group 3 – wires with a thin layer of nanostructured zinc oxide. In the first method, the nanoparticles were made by chemical precipitation method, and in the second method, nanostructure was directly formed on wires. Additionally, SEM observations were used to confirm the presence of nanoparticles on the wires. Friction between wires and brackets was measured using Universal Testing Machine. SPSS v. 20 and ANOVA test was used in order to analyze the data. The significance level was considered as p<0.05.Results: The mean value of frictional forces were 1.73 N, 1.52 N, and 1.56 N in the control group, chemical precipitation method group and thin layer of nanostructured zinc oxide group, respectively. There was no significant difference in friction rate between brackets and stainless-steel wire coated by any of these two methods (p=0.555).Conclusion: Coating of orthodontic wires with zinc oxide nanoparticles can reduce friction with brackets during sliding. There was no difference in the established value of friction between coating of orthodontic wires with chemical precipitation method and thin layer coating method.