Effects of pH and fluoride concentration of dentifrices on fluoride levels in saliva, biofilm, and biofilm fluid in vivo.

Introduction: Acidic dentifrices have been shown to be more effective than neutral ones against dental caries using in vitro, in situ, and clinical protocols.
Objectives: Given the scarcity of studies assessing intraoral fluoride (F) retention after using such formulations, the present study evaluated the influence of pH and F concentration of dentifrices on F uptake by saliva, biofilm, and biofilm fluid.
Methods: Volunteers (n = 22) were randomly assigned to dentifrices containing 0 (placebo), 550 (LFD, low-fluoride dentifrice), and 1100 ppm F (CD, conventional dentifrice) at pH 4.5 and 7.0 and brushed their teeth 3 times/day following a double-blind, crossover protocol. Saliva and biofilm samples were collected after 7 days of using the dentifrices, 1 and approximately 12 h after last brushing. F and calcium (Ca) analyses were performed with the inverted electrode after buffering with TISAB III and the Arsenazo III method, respectively. Data were analyzed by 3-way ANOVA, Tukey's HSD test, and Pearson's correlation coefficient (p < 0.05).
Results: F concentrations in biofilm fluid and whole biofilm 1 h after brushing with acidic F-toothpastes were higher than those related to neutral counterparts, although the differences were small and not significant; no increases were observed in salivary F concentrations influenced by dentifrice pH. Moreover, no definite trend was observed for Ca concentrations in these compartments.
Conclusion: Dentifrice pH had some influence on F uptake by the biofilm fluid, having lesser or no impact on F uptake by the biofilm and saliva, respectively.
Clinical Significance: Toothbrushing with acidic toothpastes leads to slight increases in F concentrations in the biofilm fluid when compared to neutral formulations, which may contribute to the higher anticaries effect of acidic formulations.