FLUORIDE RELEASE AND EFFECT ON ENAMEL SOFTENING BY FLUORIDE-TREATED AND FLUORIDE-UNTREATED GLASS-IONOMER SPECIMENS

The effect of fluoride application on fluoride release and enamel prot ection was studied using conventional and light-activated glass ionome rs and composite. The specimens prepared from the materials were teste d as (1) freshly mixed, (2) aged (29 days), (3) aged and fluoride trea ted, and (4) aged, fluoride treated, and aged (29 days). For fluoride application, the specimens were immersed in 1.2% NaF solution for 10 m in and washed. After handling, the specimens were glued on polished bo vine enamel slabs and immersed in lactic acid (pH 5.0) for 3 h. The mi crohardness of the enamel was measured before and after the acid immer sion. Freshly mixed glass ionomers significantly prevented enamel soft ening. The effect disappeared (conventional glass ionomer) or decrease d (light-activated glass ionomer) during aging, but was reestablished by fluoride application. After the subsequent 4 weeks of aging, no sig nificant protective effect could be seen for either of the glass ionom ers. The fluoride release, which was greatly increased by fluoride app lication, was still elevated after 4 weeks of aging for both materials .