Evaluation of total, soluble and ionic fluoride concentration in whitening and desensitizing toothpastes.

Purposes: Due to the popularity and increasing launch of toothpastes with whitening and sensitivity properties on the market, this study aimed to evaluate the fluoride concentrations in these products, since the concentrations of fluoride directly interfere with the anti-caries potential.

Methods: This is an experimental, in vitro study, where 37 samples from different batches (n = 3) purchased in different countries, were analysed in duplicate, via the ion-selective electrode technique to verify the concentration (μg/g or ppm F^-) of total fluoride (TF), total soluble fluoride (TSF) and ionic fluoride (IF). For a comparative data analysis, ANOVA was applied followed by a Tukey's test for multiple comparisons. The level of confidence adopted was 95%.

Results: In the 37 assessed toothpastes, 45.9% contained NaF and 54.1% sodium monofluorophosphate (MFP). The TF found in the formulations ranged from 902.8 to 1539.4 ppm of F (mean: 1165.2 ± 179.3); fluoride concentration in the TSF fraction ranged from 708.8 to 1306.7 ppm of F (mean: 959.5 ± 162.4); IF results ranged from 101.9 to 1162.3 ppm of F (642.2 ± 294.1). Significant differences (p < 0.05) were found in the concentrations of the 59.5% assessed toothpastes in comparisons between declared and measured total fluoride (TF) concentrations, as well as in 62.2% when total fluoride (TF) and total soluble fluoride (TSF) were compared.

Conclusions: In this study, most of the samples evaluated showed discrepancies when compared to the information declared by the manufacturers. In addition, the soluble concentrations found in half of the samples were lower than total concentrations and this may affect anti-caries effectiveness.