Fluoride Uptake in Incipient Enamel Lesions After Fluoride-Containing Mouthrinse Treatment

Objectives: The objective of this in vitro study was to determine the effect of commercially available acidulated phosphate fluoride mouthrinses and neutral pH, fluoride-containing mouthrinses on promoting fluoride uptake into incipient enamel lesions.
Methods: This observer-blind, controlled study tested the following parallel groups (n=12/group): A-D: essential oil, acidulated phosphate fluoride mouthrinses (EO-APF) (0.02% sodium fluoride, NaF); E-G: cetylpyridinium chloride (CPC), pH-neutral fluoride mouthrinses (0.02-0.05% NaF); H: sterile water (negative control). Enamel fluoride uptake was tested similar to Procedure 40 in U.S. Food and Drug Administration’s monograph on anticaries drug products for over-the-counter human use. Human enamel specimens were ground and polished to create a flat surface. Specimens were etched using a standard 1M perchloric acid etch technique and solutions analyzed for fluoride (ion selective electrode) and calcium (atomic absorption spectroscopy) concentrations for calculation of the pre-treatment enamel fluoride concentration. Lesion formation occurred using 0.1M lactic acid and 0.2% Carbopol-907 and was 50% saturated with hydroxyapatite at pH 5.0 for 24hr at 37°C. Specimens were immersed into respective mouthrinse for 30min. A post-treatment etch was performed and solutions analyzed as detailed above. Experimentation was conducted by Therametric Technologies, Inc. Statistical comparisons were performed using an analysis of variance with treatment as a factor. Each fluoride-containing mouthrinse was compared pairwise vs. water using a two-sided test at the 5% significance level. Additionally, pairwise comparisons between fluoride products were conducted.
Results: A, the EO-APF kids mouthrinse (0.02% NaF) exhibited 3.45X higher fluoride uptake than E, the CPC, neutral pH mouthrinse (0.05% NaF) (p<0.001). B-D, EO-APF (0.02% NaF) mouthrinses, demonstrated 2.1-4.1X higher fluoride uptake compared to F-G, commercially similar neutral pH CPC mouthrinses (0.02-0.05% NaF) (p<0.001).
Conclusions: This study demonstrates that acidulated phosphate fluoride-containing (0.02% NaF) mouthrinses show significantly higher fluoride uptake in incipient enamel lesions compared to neutral pH fluoride-containing mouthrinses.