Objective: To develop nano-SiO_2 coated orthodontic stainless steel wires and to study the surface characters and the basic physical properties of the coating. Methods: Nano silicon dioxide film was deposited on the surface of stainless steel orthodontic wire by using unbalanced magnetron sputtering method. The surface and cross section properties of the coatings were observed with scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). We also compared the changes of friction property be...