Abstract : Esthetic coated NiTi arch wires are the desired to match esthetic brackets in the clinical orthodontics; but the presence of coating layer is greatly affected friction during sliding mechanics. The aims of this study were to evaluate the influence of total wire dimension with the coating material types (coating and ion implanted) and thickness of coating layers on frictional force of coated nickel titanium wires. The sample of this study consisted of 140 segments of coated Nickle titanium arch wires involving two wire dimensions (0.016 × 0.022 inch and 0.019 × 0.025 inch). The samples were supplied from four companies (IOS, Orthotechnology, DANY and Hubit) and the uncoated control samples were supplied from IOS Company. Wire dimensions and thickness of coating layer were measured by the metallurgical light incident microscope and the static frictional force was measured through pulling the wires through a set of ceramic brackets by the universal testing machine. The data were then statistically analyzed using ANOVA tests. Generally, the stated dimensions of the wires by the manufacturer do not match the measured wire dimensions. The frictional forces of coated wires differ from uncoated control being higher in the control and polymer coated wires and lesser in the rhodium, gold implanted and labial Teflon coated wires owing to differences in the wire dimension, thickness of coating layer, and physical properties of coating materials. When tested in vitro, rhodium implanted wires produce the least amount of friction