Enamel fluoride uptake from mouthrinses with up to 0.10% NaF

Methods: Sound human enamel specimens were selected and a 3mm diameter enamel core was prepared from each tooth. The resulting specimen was a 3mm enamel disk with all but the exposed surface covered with acrylic. Eighteen specimens per test group were prepared. 4 test treatments were included: Water; Listerine® Tooth and Gum Defence with 0.02% NaF (LGUM); Listerine® Total Care Enamel Guard (LGUARD) with 0.05% NaF; Sensodyne Pronamel® (SPRON) with 0.10% NaF.

Each enamel specimen was etched by immersion into 0.5ml of 1M HClO₄ for 15 seconds. A sample of each solution was buffered with TISAB and analyzed for fluoride and calcium. An incipient lesion was formed by immersion into a 0.1M lactic acid/ 0.2% Carbopol 907 solution for 24 hours at room temperature. The specimens were immersed into 25 ml of their assigned mouthrinse for 30 minutes. An enamel layer was removed from each specimen and analyzed for fluoride and calcium. The pretreatment fluoride level of each specimen was subtracted from the post-treatment value to determine the change in enamel fluoride. Comparisons of fluoride uptake were made using the Student t-test.

Results: Fluoride uptake (in ppm): Water = 10 ± 3; LGUARD = 3,669 ± 151; LGUM = 1,985 ± 57; SPRON = 1,168 ± 42. All mouthrinses promoted significantly higher uptake as compared to the water control (p<0.001). LGUARD achieved significantly higher uptake than LGUM and LGUM significantly higher than SPRON (p<0.001).

Conclusion: Sodium Fluoride mouthrinses were all effective in promoting fluoride uptake into incipient enamel lesions, with LGUARD promoting the highest level of fluoride uptake and SPRON the lowest.