Fluoride Uptake by Enamel from Calcium-containing Glass-ionomer Sealants

Glass-ionomer sealant has anti-caries effect by fluoride uptake of enamel. Objectives: The purpose of this study was to compare fluoride uptake by human enamel from 12.6% (Fuji Ionomer Type‡V: T‡V) and 0.1% (Fuji‡V: F‡V) Ca-containing glass-ionomer sealant, of which F content in powder were 10.8 and 10.4%, respectively. Methods: Sealant was applied on the labial surface of extracted noncarious canines, and then the tooth was stored in water (n=8). After 1 day or 1 month, the sealant was removed, and the enamel was sampled by successively dissolving with HClO4. The fluoride and calcium content in the samples were determined by GC and AAS, respectively. The mean fluoride concentrations for standardized 4µm enamel layers were calculated. Moreover, fluoride release from sealants to water was determined using F-ion selective electrode method up to 4 weeks. The results were analyzed using ANOVA and t-test (p<0.05). Results: The fluoride uptake at the outermost layer was highest for both sealants and the acquired fluoride decreased with deepening layers. For T‡V, total fluoride uptake (ng/ mm2) by enamel to a 24µm depth for 1 day and 1 month were 28.0 (SD: 11.6) and 33.9 (17.2); for F‡V, 23.6 (13.1) and 24.5 (10.9), respectively. There were no significant differences between sealants or between duration. In comparison of each layer between 1 day and 1 month, though there was no significant difference in all layers for F‡V, the uptake at subsurface layers for T‡V significantly increased over time. Total fluoride (µg/mm2) released for 4 weeks from T‡V (4.41 (0.62)) was significantly lower than from F‡V (6.27 (0.70)). Conclusion: Fluoride uptake of high Ca-containing sealant might be different, due to diffusion into enamel and uptake/release ratio , compared to less Ca- containing sealant.