In Vitro Dissolution of Sodium Fluoride Tablets and Fluoride Bioavailability

Aim: Dietary fluoride (F) supplements in the form of tablets, lozenges, liquids were introduced to provide systemic F in areas where water fluoridation is not available. Since 1990, the use pf F supplements in caries prevention has been evaluated in several countries. Objectives: 1. To examine the mode sodium fluoride (NaF) tablets administration, dissolution rate. 2. Interaction with dietary and beverage’s components, 3. The amount and the rate of F released from the tablet. 4. Explore whether the in-vitro availability of F from tablets corresponds to its bioavailability in humans. Materials and methods: Tablets containing 0.55 mg NaF (0.25 mg F each) were added to deionized water, orange juice, Coca-Cola, tea, milk + water, milk + tea (1:1 by volume), and milk. The solutions were stirred at room temperature and samples taken at intervals for F analysis. To simulate the gastric juices, F tablets were mixed with milk acidified at 37 oC. The F concentration was determined using a F- ion electrode. Results: The amount of F released from F tablets in water, Coca-Cola, and orange juice was 97.4 ± 2.1 (SD)% of the F content in the tablets within 5 minutes. During 10 to 15 minutes, tablets released 82% in tea, 74% in milk + water, and milk 65% of their F content. Fluoride released from tablets in milk acidified to pH 2.3 (simulated gastric juice) was 77.4 ± 1.8% at 30 minutes and 74.2 ± 2.3% at 180 minutes. Conclusion: The amount and rate of F released from NaF tablets in different solutions vary greatly, with significantly lower in milk. Factors that affect F release include temperature, pH, and composition of the solution. Fluoride availability in acidified milk is close to the bioavailability in humans. The therapeutic effect and the safety of F can only be determined by understanding the kinetics of F metabolism, bioavailability, and potential toxicity.