Fluoride release and uptake in vitro from a composite resin and two orthodontic adhesives

The aim of this study was to investigate the fluoride release and uptake characteristics of a composite resin (Tetric) and two orthodontic adhesives (VP 862 and Saga Bond), with a type-II glass ionomer cement (Ketac Fil) as a control. Test specimens in 2 ml deionized water released fluoride over a period of 33 days. Ketac Fil released 54 and 15 times more fluoride than Tetric after 24 h and 1 month, respectively, whereas the two adhesives released amounts between these values. Specimen exposure to 1000-ppm NaF solution increased the 24-h fluoride release from all materials, with near pre-exposure levels reached after 2-3 days. Ketac Fil had a tendency to recharge not seen with the other materials. The ytterbium trifluoride filler in Tetric has a very low water solubility, and it is therefore suggested that the increases in fluoride release from Tetric after exposure to fluoride were most probably due to release of surface-retained fluoride.