Glass Ionomer Cement (GIC) and Resin Modified Glass Ionomer Cement (RMGIC) are two restorative materials in dentistry that have the capacity of releasing fluoride to saliva, dentino-enamel substance, and the ability to form fluoroapatite crystal. This study aims to compare the amount of fluoride release in saliva and dentino-enamel substance. A total of 48 caries free premolar teeth were prepared to form a cavity with the dimension of 4 x 4 x 2 mm on the buccal surfaces. These teeth were then divided into 3 groups (control, GIC, RMGIC groups). These teeth were then soaked in artificial saliva without fluoride content and were incubated at room temperature (37 C). Each group was divided again into 4 sub groups, with different periods of soaking (1, 3, 10, and 20 days). The fluoride content of saliva was analyzed using ion chromatography. The fluoroapatite on dentino-enamel substance was analyzed using x-ray diffraction or XRD. While there was a significant difference in fluoride release in saliva and no significant difference in fluoroapatite formation on dentino-enamel substance within 3 groups. Fluoride content in saliva showed a significant difference within the 3 groups. No significant difference was found in the fluoroapatite content on dentino-enamel substance.