Fluoride release and uptake by various dental materials after fluoride application

To measure the amounts of fluoride released from fluoride-containing materials before and after daily topical fluoride applications.

A conventional glass-ionomer: Fuji Ionomer Type II (F2); a resin-modified glass-ionomer: Fuji Ionomer Type II LC (LC); two "giomer" materials: Reactmer Paste (RP), and Beautifil (BT); a fluoride-containing resin composite: Unifil F (UF); and a non-fluoride resin composite: AP-X (AP) were used in this study. Each material was filled into a plastic mold, with inner diameter of 9 mm wide x 3 mm high. The specimens were stored in vials filled with 8 ml distilled deionized water for 24 hours at 37 degrees C. The specimens were then removed from the vials and the amount of fluoride released into the water, over the 24-hour period, was measured. The amount of fluoride released was measured by using specific fluoride electrode and an ion-analyzer. These procedures were repeated at Days 2, 3, 7, 14, and 21. After 21 days, all specimens were exposed to 1000 ppm F NaF solution for 5 minutes once a day. This procedure and measurement of fluoride release were continued for 14 days. After 14 days, the specimens were placed in water for 7 days and fluoride release was measured. The results were statistically analyzed using Kruskal-Wallis and Mann-Whitney U-test (P< 0.05).

At the 22nd day (1 day after starting fluoride exposure), there was no difference between the F2 and RP, though there were significant differences between the two GICs and the groups BT and UF. After that day, there were significant differences between GIC and the group RP, BT and UF. All materials showed a decrease in fluoride release 7 days after end of the fluoride immersion period. F2, LC, and UF showed no significant difference of fluoride release between Day 21 and 1 day after the end of the fluoride immersion period (P= 0.310: F2 and UF, 0.548: LC). On the other hand, RP and BT revealed lower fluoride release 1 day after the end of the fluoride immersion period as compared to Day 21 (P= 0.075: RP, 1.000: BT). For AP, fluoride release was not detected after the fluoride immersion period.