Fluoride release/uptake of conventional and resin-modified glass ionomers, and compomers

Objectives: To assess the levels of fluoride ions released from a range of freshly-prepared aesthetic restorative materials, and then the effects of a topical acidulated phosphate fluoride (APF) gel. Methods: Five specimens each of four conventional GICs, two resin-modified GICs, two compomers, and a resin composite (control) were assessed for their fluoride ion release over 6 weeks, before being exposed to 1.23% APF gel for 4 min and then measuring their fluoride ion levels for another 6 weeks. Results: Following an initial brief, variable burst of fluoride ion release, the rates then fell quickly for most materials and, although high rates of fluoride ion release were measured immediately following the application of APF gel, these rates also fell quickly for most materials. After 12 weeks, the mean fluoride ion levels were much lower than immediately before gel application. The APF gel treatment caused surface damage to all materials, especially to the conventional GICs. Conclusion: The results of this study suggested that much of the increased fluoride ion release found following topical exposure of the fluoridated restorative materials to APF gel was caused by surface effects rather than by chemical recharging.