Effect of Fluoride Concentration in Citrate Solution During Enamel Erosion

Objectives: The presence of fluoride ion in an acidic solution stabilizes enamel surfaces against erosion. Hypothesis: there is a dose response of fluoride concentration for different concentrations of citric acid (CA) to protect the enamel. To determine the relationship between CA concentration and the amount of fluoride required to stabilize the enamel surface during an erosive attack.
Methods: Polished sound human enamel slabs (4x4x1.3)mm were coated with fingernail varnish leaving 1mm stripes of unprotected surfaces. The samples were exposed for 4h to experimental CA-fluoride solutions at various CA and fluoride concentrations at stirred at 200rpm. The slabs were sliced into ~1 mm cross-sectional specimens. Digital microphotographs were taken and enamel loss determined by use of Image-J software. The erosive challenges were CA at (0.25 and 1.0)% at pH 3.6 to 3.7 with (0, 25, 50, and 100)ppm F (n=3 for each solution) for 4h at room temperature with stirring.
Results: Two-way ANOVA found the strength of the CA and the dose of fluoride to be significant (p≤0.05) factors on the amount of erosive loss. The interaction between the acid strength and fluoride dose was not significant (p≥0.05).
Conclusions: The hypothesis is supported as there is a dose response of fluoride concentration for stabilizing the surface of enamel against CA induced erosion. More fluoride concentration is needed to stop the erosive effect of the more concentrated CA solution.