Concentration and Stability of Fluoride Chemically Available in Charcoal-Containing Toothpastes

Among the wide variety of commercially oral hygiene products, activated charcoal-based toothpastes have irrupted the market, claiming multiple benefits. Although most are fluoride free, others incorporate fluoride into their formulations, yet the chemical availability and stability of fluoride in these products remain unclear. Our study aimed to assess the chemical availability and stability of fluoride in commercially fluoridated toothpastes formulated with activated charcoal.

We purchased duplicate samples with different lot numbers of different brands containing fluoride (F) and activated charcoal (n = 20) in the USA and Chile. Three toothpastes, one non-fluoridated, one containing sodium fluoride (NaF), and another with sodium monofluorophosphate (Na2FPO3), were used as controls. All toothpastes were evaluated at the time of purchase (fresh) and after their expiration date (aged). We determined total F and available total soluble F (TSF), using a F-specific ion electrode. Values were expressed in mg F/kg (ppm F, w/w).

Most evaluated toothpaste contained NaF (70%) or Na2FPO3 (30%) as the F salt, and all declared to contain silica. The TSF concentration ranged from 952.6 to 1,438.1 and from 925.7 to 1,493.7 ppm F for fresh and aged toothpaste, respectively. TSF remained close to total F and in agreement with the F concentration reported by the manufacturer. After expiring, the commercial toothpastes did not form insoluble F, except the Na2FPO3-/CaCO3-based control.

The silica-based toothpastes formulated with activated charcoal present fluoride potentially bioavailable and chemically stable to control caries. However, concerns regarding abrasiveness, as raised by other researchers, cast doubt on the suitability of these toothpastes for widespread use.