Determination of Available Fluoride and Antimicrobial Activity of Charcoal-Containing Dentifrices
Objectives: In recent years, charcoal-containing products have been introduced to the market, generating a lot of questions regarding their safety and efficacy, specifically on whether the charcoal might affect the availability of fluoride and whether antimicrobial claims are valid. The objectives of this study were to determine if charcoal-containing fluoride dentifrices have at least 90% of the labeled amount of fluoride available and to determine if charcoal-containing dentifrices showed antimicrobial activity against Streptococcus mutans.
Methods: Three different tubes each of 6 different charcoal-containing fluoride dentifrices with labeled fluoride ranging from 950-1400ppm were purchased. For fluoride availability measurements, 1g of dentifrice was homogenized in deionized water, diluted to 100mL with deionized water, mixed thoroughly, and filtered. Three prepared samples from each tube were analyzed in duplicate using ion chromatography. In vitro antimicrobial efficacy of 1 tube each of 8 charcoal-containing dentifrices was evaluated by agar diffusion test on S.mutans.
Results: All 6 fluoride dentifrices tested contained at least 90% of the labeled amount of fluoride as available fluoride. The average percent available fluoride found per dentifrice was 99.5±2.8%, 102.5±2.7%, 98.5±1.7%, 99.0±1.3%, 96.2±0.6%, and 101.1±2.4%. Out of the 8 dentifrices tested against S.mutans, only 4 showed a zone of inhibition indicating antimicrobial activity.
Conclusions: While all 6 charcoal-containing fluoride dentifrices tested contained at least 90% available fluoride, there are many criteria that have not yet been tested for these dentifrices from ANSI/ADA Standard No. 130. As the charcoal concentrations in these dentifrices are unknown, it is difficult to determine the charcoal concentration effect, if any, on fluoride availability. Only 4 out of the 8 charcoal-containing dentifrices tested showed antimicrobial activity against S.mutans. Further testing of charcoal-containing dentifrices is needed, including testing for fluoride uptake in enamel, relative dentin abrasivity, and heavy metals, in order to continue to evaluate the safety and efficacy of these products.