In vitro Evaluation of Dentifrice with Low Fluoride Content Supplemented with Trimetaphosphate

Abstract

One way to reduce dental fluorosis is by reducing the fluoride (F) concentration in dentifrice, but low-F dentifrice should be as effective as a standard dentifrice. This study evaluated in vitro whether the supplementation with sodium trimetaphosphate (TMP) of a dentifrice with low F content (500 μg/g) would provide a similar effect to that of a standard dentifrice. Bovine enamel blocks were submitted to a pH cycling regime incorporating daily exposures to a slurry of dentifrice: a low-F dentifrice with or without 0.1–3.0% TMP; an F-free, phosphate-free dentifrice (negative control), or a dentifrice with 1,100 μg/g F (positive control). The addition of TMP to dentifrice with or without F was associated with higher surface hardness and decreased loss of integrated subsurface hardness after pH cycling. The combination of 1% TMP and 500 μg F/g had a greater effect than the positive control dentifrice. It is concluded that the addition of TMP to the 500-μg F/g dentifrice allowed a similar or larger effect as compared with a standard dentifrice in this in vitro model.

Effect of Sodium Trimetaphosphate on Hydroxyapatite Solubility: An In Vitro Study

“…This statement is supported by data from this study that observed reduction in F concentration in the hydroxyapatite with the addition of TMP, while in the study by Favretto et al (8) there was an increase of F in the enamel with 0.4% TMP. The adsorption of TMP on enamel surface can modify the selective permeability of the enamel by facilitating the diffusion of ions (12,14,20). In the present study, there was not an organized solid enamel surface and the hydroxyapatite crystals were free to react promptly with the TMP and F.…”

“…Several studies have suggested that TMP reduces the demineralization process, and that an ideal TMP/F ratio allows an enhancement of the effects of F-containing products (7,8,(10)(11)(12)(13). When TMP and F are co-administered, the adsorption of TMP on the enamel surface can change the selective permeability and facilitate the diffusion of ions such as Ca and F (12) into the enamel (20,21).…”

“…In the presence of 100 ppm F, the Ca/P ratio showed a peak at 0.4% TMP and a subsequent gradual reduction until it intersects at a concentration of 2% TMP, with the curve for HA treated with TMP only. Despite the suggestions that TMP and F have different mechanisms of action or different sites of action (14), the TMP/NaF ratio is important for optimizing the anti-caries effect (7,12). According to the TMP/F ratio, this association influences the loss of Ca from HA (Fig.…”

“…On the other hand, Favretto et al (8) reported that the addition of 0.4% TMP increased F concentration in enamel. In this case, the adsorption of TMP occurs on the enamel surface and it acts facilitating the diffusion of Ca and F (12,14,20). Yet, even though the deposition of the two F forms on HA is reduced, the presence of a relatively low amount of TMP (between 0.2% and 0.6%) improved the Ca/P ratio.…”

“…It has also been observed a higher F content in the enamel after use of this mouthrinse, although the type of F deposits on the enamel has not been identified: loosely bound F (calcium fluoride -CaF 2 ) or firmly bound F (fluorapatite -FA) (11). Other studies demonstrated that an adequate TMP/F ratio can improve the effectiveness of F-based products even at low F concentrations (12)(13)(14). Nevertheless, the mechanism of TMP action is not yet completely clear.…”