A comparative study of physical properties of TiO2 thin films according to a coating method on orthodontic wires and brackets

Koh, Eun Hee; Cho, Jin Hyoung

Abstract

The purpose of this study was to search for an appropriate method of coating TiO2 on orthodontic appliances. TiO2 thin films were deposited on orthodontic wires and brackets using sol-gel, CVD (Chemical Vapor Deposition) and PE-CVD (Plasma Enhanced-CVD) methods. The roughness of TiO2-coated surfaces was investigated via scanning electron microscope (SEM) and adhesive strength of TiO2 thin films was measured by adhesive tape pull test. Methylene blue degradation test was carried out to evaluate the photocatalytic activity of TiO2 and the corrosion resistance of TiO2 thin films against fluoride solution was also analyzed by observing the surfaces of TiO2-coated wires and brackets via SEM after immersion in sodium fluoride solution. Through the comparison of properties and photocatalytic activity of TiO2 thin films according to the coating methods, the following results were obtained. Smoother surfaces of TiO2 thin films were generated by CVD or PE-CVD methods than through the sol-gel method or the control. Adhesive strength of the TiO2 thin films was highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Photocatalytic activity of TiO2 thin films on methylene blue was the highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Corrosion resistance of TiO2 thin films against fluoride solution was stronger in CVD and PE-CVD methods than in the sol-gel method. The results of this study suggest that the CVD or PE-CVD methods is more appropriate than the sol-gel method for TiO2 coating on orthodontic wires and brackets.