Methods: Three types of GICs namely; a conventional GIC (Fuji II), a resin-modified GIC (Fuji II LC) and a highly viscous GIC (Fuji IX) were used. From each material, 3 groups e.g., using manufacturer recommendation powder/liquid ratio, 20% less powder than recommended and 20% more powder were made. In general, 45 disc-shaped samples (4x2 mm) comprises 5 samples in each group were produced. The samples were immersed in 5 mL double distilled water during test period. Fluoride released was measured by selective electrode ion method on day 1 to 7, 13, 14, 15, 28, 29, 30, 58, 59, 60, 88, 89, 90. After each measurement the distilled water was renewed. Mean and standard deviation were calculated and the data were analyzed by 3-way analysis of variance and Tukey test. A level of p <0.05 was regarded as statistically significant.
Results: The cumulative fluoride release from Fuji IX was higher than Fuji II, however, this difference was not statistically significant (p= 0.589). Tukey test revealed that the lowest amount of fluoride release was from Fuji II LC (p <0.05). Twenty percent variations in powder/liquid ratio did not change the fluoride release significantly for all three glass-ionomers.
Conclusions: Fluoride release from GICs is time-dependent and decreases with time. Resin-modified GIC released less fluoride than conventional and highly viscous GICs. In addition, 20% changes in powder/liquid ratio had no significant effect on fluoride release for all types of GICs.