Evaluation of Coating Stability, Surface Characteristics and Biocompatibility of Nano Particle Coated Stainless Steel, Nickel-Titanium and Beta-Titanium Orthodontic Arch Wires in Comparison with Uncoated Wires: An In-Vitro Study

Friction plays a major role during tooth movement as it takes up to 60% of the applied force, hence reducing the force available for tooth movement. Coating the surface of orthodontic wires by various techniques is being developed to improve their mechanical and biological properties. To evaluate the characteristics of nano particle coated and uncoated stainless steel, nickel-titanium, and beta-titanium wires for (1) coating stability, (2) surface characteristics and (3) biocompatibility after 21 days of exposure to artificial saliva. Six types of wires were tested for coating stability, surface characteristics before and after exposure to artificial saliva using scanning electron microscope and the artificial saliva was tested for leaching of ions by inductively coupled plasma optical emission spectrometer. Coating thickness was reduced in each group after exposure to artificial saliva which was statistically significant. Significant changes in surface morphology such as delamination and irregularity of the coating was noted. Coated NiTi wires showed lesser leaching of ions when compared with uncoated NiTi wires but the difference was not statistically significant. Coating delamination and irregularities were seen in many areas. The highest concentration of ions leached among all the groups were of iron, followed by silica.