Abstract
The ability of mouth rinses, available in the international market, to form reaction products on demineralized enamel (bioavailability test) was evaluated in vitro. Nine mouth rinses purchased in Chile were evaluated; eight formulated with NaF (one containing 100 µg F/mL and seven containing 226) and one with Na2FPO3 (226 µg F/mL as ion F). Demineralized enamel slabs (n=15 per mouth rinse) were sectioned; one half was subjected to the assigned mouth rinse treatment for 10 min and the other half was used to obtain baseline data. Loosely bound and firmly bound fluoride formed on enamel were determined with an ion-specific electrode and the values were expressed in µg F/cm2. The concentration of fluoride and the pH of the mouth rinses were previously determined. Concentrations of loosely bound and firmly bound fluoride formed on enamel were independently analyzed by ANOVA and Tukey's test (α=5%). The loosely bound and firmly bound fluoride concentrations (µg F/cm2) formed ranged from 3.2 to 36.2 and 0.4 to 1.7, respectively. Loosely bound fluoride formed on enamel was significantly more effective in discriminating the effect of different commercial mouth rinses than firmly bound fluoride. Mouth rinses with 226 ppm F as NaF and low pH presented significantly greater bioavailability of fluoride on enamel than those with higher pH or lower NaF concentration. The mouth rinse with Na2FPO3 showed low reactivity. Although further studies are necessary, the findings showed that commercial fluoride-containing mouth rinses have important variations in enamel fluoride bioavailability, which may result in differences on anticaries efficacy.
Highlights
According to the best available scientific evidence, mouth rinses with sodium fluoride (NaF) 0.05% (226 ppm F) for daily use or with 0.2% (900 ppm F) for weekly use are effective for caries control [1]
Our results reject the null hypothesis formulated because they clearly showed that the commercial mouth rinses evaluated were different regarding fluoride bioavailability on enamel, providing new knowledge about these products
This discussion will be focused on loosely bound fluoride formed on enamel rather than firmly bound fluoride because the former: i) is considered more important for the anticaries effect of topical fluorides than the firmly bound fluoride formed [12]; ii) is able to differentiate the effect of fluoride salts from control solutions; and iii) is able to separate the mouth rinses into four groups (E,G>B,C,D>A,F>H) compared with only two groups (E>A,C,D,G,I) if data of firmly bound fluoride were considered (Table 2)
Summary
According to the best available scientific evidence, mouth rinses with sodium fluoride (NaF) 0.05% (226 ppm F) for daily use or with 0.2% (900 ppm F) for weekly use are effective for caries control [1]. Commercial fluoride mouth rinses are products with a cosmetic rather than a therapeutic use. These products contain complex formulations with several ingredients to make the product attractive to the consumer. Some of these substances can positively or negatively interfere with the anticaries mechanism of action of fluoride [3]. Fluoride retention occurs by the enrichment of dental biofilms and the formation of reaction products with enamel [5,6,7]. While the diffusion of fluoride throughout the biofilm is a simple phenomenon that depends only on fluoride solubility in the mouth rinse [6], other ingredients of the formulation, such as detergents, preservatives, and some additives [8,9,10,11], might influence the formation of reaction products on clean dental surfaces
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