The Effect of ZnO Nanoparticles on Resistance to Sliding of Nickel Titanium Orthodontic Wires

NiTi wires which are considered the ideal alloys used during the alignment and leveling stage of comprehensive orthodontic treatment exhibit very high frictional resistance. Therefore, overcoming such resistance to sliding results in a rapid tooth movement and proper anchorage control. Recently, coating the wires with nanoparticles has been introduced to decrease resistance to sliding. The aim of this invitro study was to evaluate effect of ZnO nanoparticles on resistance to sliding of nickel titanium orthodontic wires. 40 straight pieces of 0.016-inch NiTi wires were evaluated in two groups with and without spherical ZnO nanoparticle coating, along with 40 standard system 0.018 stainless steel brackets. ZnO nanoparticles were deposited on NiTi wires and analyzed by SEM. A universal testing machine was used to determine friction between the wires and brackets at an angle of 5°. Student’s t-test were used for data analysis. The SEM results confirmed the homogeneous deposition of ZnO nanoparticles on NiTi wires. At 5º angle between the wires and brackets the means of frictional forces were 1.2475±0.13 and 1.5075±0.12 N with and without ZnO nanoparticle deposits on the wires, respectively, revealing a significant decrease of 17.24% in frictional forces in coated wires (P<0.001). Based on the results of this study, ZnO nanoparticle coating reduces the resistance to sliding of nickel titanium orthodontic wires.