Fluoride Uptake from Refluoridated Glass-Ionomer-Cement in and on Enamel

Objective: Fluoride release from glass-ionomer-cement (GIC) is one reason to choose these materials for tooth restoration. The “rechargement” of GIC by topical fluoride applications is stated to enhance the GIC fluoride releasing effect. Aim of this study was to compare the fluoride uptake by deciduous and permanent enamel with or without fluoridation of adjacent GIC samples. Methods: From 20 exfoliated deciduous molars and 24 surgically removed third molars each two enamel samples were cut. One sample served as control to examine the fluoride uptake, the other one was fixed next to a standardized GIC sample (Ketac fil®, 3M Espe) into a vessel with 2.5 ml regularly changed artificial saliva. On each sample pellicle with human whole saliva was formed. Test specimens were divided into two groups. The specimens of group A were not fluoridated, while the GIC-samples of group B received a sodium fluoride solution twice daily for 3 min, with 100 ppm fluoride for deciduous and 200 ppm fluoride for permanent enamel. After 28 days, loosely bound and structurally incorporated fluoride were determined and statistically compared between control and test enamel samples (Wilcoxon-Test). Results: In deciduous teeth, loosely bound fluoride was increased from 0.29 ± 0.09 to 0.42 ± 0.17 µg/cm² in group A, and from 0.21 ± 0.08 to 0.44 ± 0.27 µg/cm² in group B, the latter uptake being significant. The gain of structurally bound fluoride was from 1145 ± 450 to 1629 ± 382 ppm (group A) and from 869 ± 291 to 1444 ± 616 ppm (group B), p<0.05 for both groups. In permanent teeth, only the increase of structurally bound fluoride in group B was significant. Conclusion: The study shows that regular refluoridation of GIC may contribute to an accumulation of fluoride in and on enamel which is particularly meaningful in deciduous enamel.