Fluoride coatings on orthodontic wire for controlled release of fluorine ion

Abstract

The purpose of this study was to develop a new method of releasing fluorine in a controlled manner for applications in the field of orthodontic Ti-based wire, namely the coating of fluorides on Ti. Thin films of two fluoride compounds, CaF 2 and MgF 2 , were coated on Ti via the electron-beam evaporation method. The fluorine was released rapidly from the as-deposited MgF 2 coating within a short period , and then the release rate slowed down. When the MgF 2 coating was heat treated, this initial burst effect was decreased, but a significant amount of cracks were generated. On the other hand, in the case of the as-deposited CaF 2 coating, fluorine was released linearly for the entire period, without an initial burst. In the heat-treated CaF 2 coatings the trend was similarly observed. The linear fluorine release from the CaF 2 coatings, even in the as-deposited state, was attributed to the high degree of crystallinity of the coatings. A preliminary cell test showed favorable cell viability on both the fluoride coatings. Given their sustained and controlled fluorine release, these fluoride coatings, particularly CaF 2 , are suggested to be potentially useful in the field of orthodontic Ti-based wire.