Methods: The material used in the study was the conventional glass ionomer cement, Ketac-Cem Maxicap (capsuled) (3M). Group 1 (G1) specimens were prepared by mechanically mixing the cement, while Group 2 (G2) specimens were prepared by removing the powder and liquid from the capsules and hand mixing. Five cylinders (4mm diameter, 6mm height) specimens of each group were prepared. The porosity of specimens was evaluated by non-destructively using X- ray microfocus computerized tomography (micro- CT). Five discs (15mm diameter, 1mm thickness) of each group were prepared and stored in 100% humidity for 24h before being lapped. Specimens were then stored in deionised water at 37oC and fluoride release was measured at 1, 2, 3, 5, 7, 14, 28 days respectively using the ion selective electrode (ISE). Another two groups of specimens of each material was prepared as above and stored at 37oC for 90 days. Then each group was either recharged at 37oC or 55oC in 250ppm sodium fluoride solution for 15mins. The results were analysed using ANOVA.
Results: The porosity of G1 was significantly higher than that of G2 (p<0.05). The cumulative fluoride release of G1 (µg/cm2) at 37oC was 134.24 ± 1.24 which was significantly higher than that of G2 which was 105.03 ± 0.48(p<0.05). The re-release of fluoride after recharge was measured 24 hours later. The fluoride re-release of G1 (µg/cm2) at 37oC was 5.94 ± 0.09 which was significantly higher than that of G2 which was 5.07 ± 0.18 (p<0.05).
Conclusion: A high porosity introduces more water reservoirs into the matrix of GICs. The presence of these reservoirs increases the fluoride release and fluoride re-charge levels.