Determination of Free Fluoride in 20 International Toothpastes

Optimum levels of fluoride ion plays an important role in caries prevention. Manufacturers have been developed many anti-caries toothpastes, and labeled them as having fluoride to attract consumers. However, only Free Fluoride can act as an anti-caries agent. Free fluoride can easily become bound to compounds in the toothpaste and become unavailable in the mouth. Objective: To determine the Free and Total Fluoride in Toothpastes from Foreign countries utilizing Fluoride electrode. Methods: 20 commercially available toothpastes from different countries: China(6), Korea(1), Brazil(3), Spain(1), Philippines(2), Egypt (1), Poland(1), India(2), USA(3) were collected. 2g of each toothpaste was dissolved in 10ml of distilled water. Samples were vortexed, centrifuged for 5 minutes and free Fluoride ion was determined using 100 µl of supernatant added to 4.9 ml of distilled water, and 5ml of TISABII (Total Ionic Strength Adjustment Buffer). A Fluoride electrode made in France by Radiometer Analytical S.A. was utilized to measure the free Fluoride. Total Fluoride was determined by hydrolyzing 1ml of the above supernatant with 1ml of 2N perchloric acid in a plastic vial for overnight. 100 µl of the hydrolyzed sample were diluted with 4.9ml of distilled water and 5.0ml of TISAB II to constitute 10ml volume. Solid sodium acetate was added to bring the pH of the solution to be 5.5. The fluoride electrode was utilized to measure the total fluoride in solution. Results: 14 of the 20 toothpastes had Free Fluoride levels well below therapeutic levels (even when labeled as anti-caries). Only 2 of the 20 toothpastes are at therapeutic level. Conclusion: Absence of monitoring the fluoride available in toothpastes results in toothpastes that do not meet routine anti-caries level. Free ionizable fluoride concentrations of toothpastes were different than what was declared on the toothpaste.