Comparison of Enamel Fluoride Uptake and Fluoride Release from Liquid and Paste Dentifrices

Patients with high risk caries are frequently prescribed prescription level fluoride products. Commonly used products are 5000 ppm toothpaste formulas. Objective: The fluoride activity from a liquid dentifrice and a traditional dental paste containing 5000 ppm fluoride was evaluated for fluoride uptake into enamel and fluoride release in water. Methods: Enamel fluoride uptake was evaluated using FDA Method #40. The fluoride release was performed by adding a pre-weighed amount of product into water and measuring the fluoride released during one minute of mixing using an ion specific fluoride and reference electrode. The method was similar to the ADA test requirement for fluoride release that simulates use within the mouth. The test products were an experimental liquid-type dentifrice containing 5000 ppm fluoride and a traditional dental paste containing 5000 ppm fluoride (PreviDent 5000 Plus). Results: The enamel fluoride uptake was 1087 ppm fluoride for the liquid formula and 754 for the traditional dental paste. The fluoride release into water was measured at 0, 5, 10, 20, 30, 45 and 60 seconds. The release for the liquid formula was 0, 1616, 2215, 3514, 4201, 4421 and 4546 ppm fluoride. The release for the traditional dental paste was 0, 257, 1508, 2601, 3321, 3958 and 4462 ppm fluoride. Statistical analysis showed the liquid formula exhibited greater enamel fluoride uptake and fluoride release at 5, 10, 20 and 30 seconds than the traditional dental paste (p<0.05). Conclusions: The greater enamel fluoride uptake may indicate enhanced fluoride bio-availability in the liquid dentifrice formula. Those people who brush for less than one minute may also benefit from the faster release of fluoride.