Effect of Regular and Low-Fluoride Dentifrices on Plaque Fluoride

It was recently hypothesized that fluoride (F) in low concentrations penetrates deeper into plaque when compared to high F sources, due to a higher formation of salivary CaF⁺/CaF₂ compounds after using concentrated products, which would retain predominantly onto plaque surface (J Dent Res 2008, 87:461-5). Objective: To evaluate if the use of a low-F dentifrice (LF) could lead to a proportionally higher F uptake by plaque when compared to a conventional dentifrice (C). Methods: Fifty-six 8-10-year-old Brazilian children from cities with different water F concentrations ([F]), Pirajuí (0.05ppm, n=19), Bauru (0.72ppm, n=20) and Brejo das Freiras (3.36ppm, n=17), participated. Children were randomly assigned to brush with C (Crest, 1,072 mgF/kg), LF (Crest, 513 mgF/Kg) or a F-free placebo (P) for 1 min, twice daily, and rinsed with 10 mL of water (double-blind, crossover protocol). After 1 week, plaque was collected 1 and approximately 12h after the last use of the dentifrices (split mouth). F was determined after HClO₄ extraction. Results were analyzed by 3-way ANOVA and Tukey's test (p<0.05). Results: Mean plaque [F] were directly related to water [F] regardless the dentifrice used. For Pirajuí and Bauru, the use of C and LF significantly increased plaque [F] 1h after brushing when compared to the P. In addition, such increases were virtually identical in these communities for both LF (ca. 1.9 mmolF/kg) and C (ca. 2.4 mmolF/kg). These effects were less pronounced in the high-F community. Conclusion: Considering the 2-fold difference between [F] in both toothpastes, a 100% increment of that obtained for LF would be expected after using C (ca. 3.8 mmolF/kg), but this was only around 63% higher (ca. 2.4 mmolF/kg), supporting the hypothesis that the use of LF promotes a proportionally higher F uptake by plaque when compared to C. Supported by FAPESP (2005/03426-2; 2006/07258-0) and CNPq (471395/2006-4).10-3-2008-->