Influence of dentifrice pH on plaque and nails fluoride concentrations

Objective: This study evaluated the influence of dentifrice pH and fluoride concentration ([F]) on fluoride (F) uptake in dental plaque and nails. Methods: Eighty-four 4-6-year-old children were divided into four groups which differed according to the type of dentifrice they had been using for one year: A, experimental liquid dentifrice, 1,100 ppm F (NaF), pH 7,0; B, experimental liquid dentifrice, 1,100 ppm F (NaF), pH 4,5; C, experimental liquid dentifrice, 550 ppm F (NaF), pH 4,5; D, commercial toothpaste, 1,100 ppm F (NaF), pH 7,0. The experimental dentifrices and toothpaste were loaded onto the toothbrush using the “drop” and “transverse” techniques, respectively. Fingernails and toenails were clipped in two separate occasions, after being allowed to grow for 14 days. Plaque samples were collected 1hr after the last use of the respective dentifrices. Plaque and nails [F]s were analyzed with the electrode, after HMDS-facilitated diffusion. Plaque data were tested by ANOVA and Tukey's test, while nails data were analyzed by two-way repeated-measures ANOVA and Bonferroni's test (p<0.05). Results: Mean (±se, unit mmol/Kg dry weight) plaque [F]s were 1.667±0.410a, 3.091±0.984a, 1.448±0.303a and 0.455±0.103b for A, B, C and D, respectively. Fingernails [F]s were significantly higher when compared to toenails. The highest [F]s were found for D that significantly differed from the experimental liquid dentifrices, except for A (toenails only). The lowest [F]s were found for C, which significantly differed from all the other dentifrices. The experimental 1,100 ppm F dentifrices led to intermediary [F]s in nails and did not significantly differ from each other. Conclusions: The reduction of the dentifrice pH increases the F uptake in dental plaque and does not affect nails [F]s. Thus, the use of low-fluoride acidic dentifrices seems to be a good alternative to reduce the F intake from dentifrice in small children. Support: FAPESP-05/03975-6.