Fluoride exchange from glass ionomer preventive resin restorations

The purposes of this in vivo study were to determine if placing a sealant over a glass ionomer restoration modifies its fluoride release, and to examine the effect on glass ionomer of a 4-min application of topical fluoride. Fluoride release from glass ionomer preventive resin restorations placed in 21 bovine teeth was measured before and after removing their sealants. Fuji II, Ketac Silver, and Fuji LC were evaluated, representing the three generations of glass ionomers. Fluoride was extracted from the restorations by incubating the specimens in 5 ml deionized water and was measured by specific ion electrodes at 1 and 2 days, then once weekly for 7 weeks. The results indicated that fluoride release was not significantly different in pattern or quantity in the three types of ionomer (P > 0.05). A significant reduction in fluoride release occurred when the restorations were covered with a sealant when compared with control restorations of the same materials (P < 0.001). After removing the sealant from the glass ionomer preventive resin restorations, a significant release of fluoride occurred when compared with sealed restorations (P < 0.001). After 63 days in water, the unsealed restorations were subjected to a 4-min topical APF treatment and reimmersed in water for an additional 27 days to examine the ability of the various materials to absorb fluoride. The fluoride-depleted restorations treated with fluoride released significantly more fluoride than fresh, untreated ionomer restorations (P < 0.001) or amalgam restorations. As a result of fluoride release, the glass ionomer preventive resin restoration may afford chemical protection to the tooth if sealant loss occurs.