Preparation and antimicrobial assay of ceramic brackets coated with TiO₂ thin films

<b>Objective: </b>Different methods have been utilized to prevent enamel deminerali-zation and other complications during orthodontic treatment. However, none of these methods can offer long-lasting and effective prevention of orthodontic complications or interventions after complications occur. Considering the photocatalytic effect of TiO₂ on organic compounds, we hoped to synthesize a novel bracket with a TiO₂ thin film to develop a photocatalytic antimicrobial effect. <b>Methods: </b>The sol-gel dip coating method was used to prepare TiO₂ thin films on ceramic bracket surfaces. Twenty groups of samples were composed according to the experimental parameters. Crystalline structure and surface morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively; film thickness was examined with a surface ellipsometer. The photocatalytic properties under ultraviolet (UV) light irradiation were analyzed by evaluating the degradation ratio of methylene blue (MB) at a certain time. Antibacterial activities of selected thin films were also tested against <i>Lactobacillus acidophilus</i> and <i>Candida albicans</i>. <b>Results:</b> Films with 5 coating layers annealed at 700°C showed the greatest photocatalytic activity in terms of MB decomposition under UV light irradiation. TiO₂ thin films with 5 coating layers annealed at 700^oCexhibited the greatest antimicrobial activity under UV-A light irradiation. Conclusions: These results provide promising guidance in prevention of demineralization by increasing antimicrobial activities of film coated brackets.[Korean J Orthod 2016;46(3):146-154]