Effect of low-fluoride toothpastes combined with hexametaphosphate on in vitro enamel demineralization

The aim of this study was to evaluate the anticaries effect of low-fluoride toothpastes combined with hexametaphosphate (HMP) on enamel demineralization.

Bovine enamel blocks were subjected to pH cycling and treatment with toothpaste's slurries (15 groups; 2×/day). Toothpaste mixtures contained the following: no fluoride (F) plus HMP (from 0 to 3.0%); 250ppm F plus HMP (from 0 to 3.0%); 500ppm F; 1100ppm F; and a commercial toothpaste (1100ppm F). After pH cycling, surface and cross-sectional hardness, as well as F present in the enamel were determined. The demineralization depth was analyzed using polarized light microscopy. The variables were subjected to 1-way ANOVA, followed by Student-Newman-Keuls' test (p<0.05).

In the absence of fluoride, 0.5% HMP promoted the lowest mineral loss and its effect was similar to that of a 250ppm F toothpaste (p>0.05). The combination of 0.5% HMP and 250ppm F resulted in lower mineral loss (p<0.05) and similar lesion depth when compared to the 1100ppm F toothpaste (p>0.05).

To conclude, the combination of 0.5% HMP and 250ppm fluoride in a toothpaste has a similar inhibitory effect on enamel demineralization in vitro when compared to a toothpaste containing 1100ppm F.

The anticaries effect of toothpaste containing 250ppm F combined with 0.5% HMP was similar to that of a 1100ppm F toothpaste, despite the 4-fold difference in F concentration. Although such effects still need to be demonstrated in clinical studies, it may be a viable alternative for preschool children.