This study was conducted to compare the amount of fluoride release from two commercially available glass ionomer based restorations: C-GIC (Fuji IX) and RMGIC (Fuji II LC) under different pH conditions (pH 4 – pH 6.7) measured at different time intervals (Day 1 – Day 14 – Day 28.)Samples were divided into four groups. A total of 52 specimens were tested (13 in each of the 4 groups). The sample size was calculated according to previous study (Apostolovic et al. 2013.)The acidic pH 4 was chosen to resemble a cariogenic environment, while neutral pH 6.7 was to chosen to resemble normal physiologic saliva in the oral cavity.The results of the study showed higher fluoride release from Fuji II LC compared to Fuji IX at both pH conditions that was insignificant in the first day, but showed a significant difference when measured on Day 14 and Day 28.Fluoride release from Fuji II LC were significantly higher at pH 4 than pH 6.7 at Day 14 and Day 28, While Fuji IX showed a significant difference under pH 4 only at Day 28. Therefore, low pH stimulates higher fluoride release from glass ionomer cements, which is considered a smart behavior, as fluoride is much needed in acidic media to help in re-mineralization process.