Polymer-enhancement of Fluoride Uptake into Enamel Erosive Lesions

Objective: Dynamic Secondary Ion Mass Spectrometry (DSIMS) has been used to study the effect of a unique combination of polymers on fluoride penetration into human enamel containing artificial erosive lesions. Methods: Erosive lesions were prepared in human enamel specimens by immersing the enamel in 1.0% citric acid, pH3.8 for 5min. Specimens were subsequently incubated for 2min in agitated treatment solutions. The treatment solutions were a) deionised water, b) 300ppm fluoride in dH₂O (from sodium fluoride), c) the unique combination of polymers in dH₂O, and d) the unique combination of polymers in 300ppm fluoride. Treated specimens were initially depth profiled using DSIMS to determine the relative fluoride concentration in the first few microns of their surface. Following this, the specimens were vertically sectioned and DSIMS imaging employed to generate cross-sectional images of the fluoride depth distribution. Results: Depth profiles of the enamel surfaces showed that fluoride uptake was greater for the specimens treated with the solution containing the unique combination of polymers and fluoride, than for the specimens treated with the solution containing fluoride alone. Specimens treated with either of the two control solutions (a or c) contained minimal levels of fluoride at their surface. DSIMS cross-sectional imaging confirmed these observations and showed that in specimens treated with a combination of fluoride and the polymers, fluoride was incorporated into the enamel to a depth of approximately 50μm. Conclusion: This study has shown that fluoride uptake into human enamel from a sodium fluoride containing solution can be enhanced by the presence of a specific combination of polymers.