Fluoride Formed on Fluorotic-Enamel Subjected to a pH-Cycling-Regimen Under F-Dentifrice

Objectives:
Higher fluorosis severity makes enamel less resistant to developing caries but this deficiency could be compensated by fluoride dentifrice (FD) use. The aim of this pilot study was to evaluate loosely (“CaF₂”) and firmly-bound (FAp) fluoride formed on fluorotic enamel which had been subjected to a pH-cycling regimen and under FD treatment.
Methods: After Research Ethics Committee approval (No. 1.321.263), paired enamel slabs (n=4/group) from sound and fluorotic human teeth (Thylstrup & Fejerskov index: TF0 to TF4) were treated 2x/day with placebo dentifrice (PD) or FD (1,100 µg F/g as NaF). Half of the enamel surface area of each slab was covered with nail varnish and used as a control. The other half was submitted to a pH-cycling model simulating a high cariogenic challenge. The pH-cycling regimen consisted of 6 and 18 h, respectively, in demineralizing and remineralizing solutions, and the treatments with dentifrices were made before de- and re- phases. After 10 days, “CaF₂” formed was extracted with KOH followed by FAp extraction with HCl. Fluoride concentration in the extracts was determined with an ion-specific electrode. The net “CaF₂” and FAp concentration was expressed as µg F/cm² and µg F/g of enamel, respectively. The data for TF1 and TF2, and for TF3 and TF4 were pooled and analyzed by two-way ANOVA (Dentifrice and TF as factors) with repeated measures, followed by Tukey’s test (α = 5%).
Results: The dentifrice has a significant effect on both “CaF₂” and FAp formation, being the concentrations higher for FD(p<0.001). The TF has a significant effect only on FAp formation (p<0.05), with TF1-2 and TF3-4 groups presenting higher FAp formation than sound enamel (TF0).
Conclusions: The findings of this pilot study suggest that during caries process simulation, FD can increase FAp formation on fluorotic enamel.