Fluoride release from light-cured orthodontic bonding materials

Abstract

The purpose of this study was to compare the rate of fluoride release with time of one non-fluoridated and three fluoride-containing orthodontic bonding materials in distilled water and artificial saliva. Materials tested were: Assure (Reliance, Itasca, IL), Fuji Ortho LC (GC America Inc., Alsip, IL), Python (TP Orthodontics Inc., LaPorte, IN), and Transbond XT (3M, St Paul, MN). Twenty specimens of each material were polymerized and placed in polyethylene tubes. Half the specimens were stored in 1 mL of distilled water and half in 1 mL of unstimulated artificial saliva, at 37C and 100% relative humidity. Fluoride release was measured with an ion-specific electrode. Readings were taken-at 1, 2, 3, 5, 7 and 9 days from time of immersion, then weekly for three weeks and monthly for 5 months. To prevent cumulative measurements, storage solutions were changed 24 h prior to the weekly and monthly readings. Results showed Assure to release the most fluoride, followed by Fuji Ortho LC, Python, and Transbond. The fluoride release rates were greatest during the first days of testing, declining to low but stable levels. The type of storage medium did not dramatically affect fluoride release. Throughout the study, daily fluoride release rates of all three fluoride-containing materials were within the therapeutic range for the reduction of enamel demineralization. The second part of the study tested the twenty samples of Assure for a further two-week period, after exposure to running and still distilled water. Although fluoride release rates declined with time, they were again within the therapeutic range. Release rates were similar in running and still water at all time points.