ENAMEL FLUORIDE UPTAKE FROM FLUORIDE PRODUCTS. AN IN VITRO, STUDY

Aim: Fluoride products plays a major role in caries prevention reducing caries development in several ways: reducing bacterial acid production and acidurance; the equilibrium solubility of apatite; and by means the fluoridation of apatite crystal surfaces, reducing the dissolution rate. Fluoride has been introduced in toothpastes through different compounds: fluoride of sodium, tin or zinc; sodium monofluorophosphate and amine fluoride. This study evaluated the enamel fluoride uptake produced by the use of fluoride products and its available after the cessation of use. Materials and methods: Sixteen enamel slabs were treated for 15 days as following: - Group A with an amine fluoride-based toothpaste and mouthrinse (1250 and 250 mg/L-1); Group B with an amine fluoride toothpaste (1250 mg/L-1); Group C with a sodium fluoride toothpaste (1250 mg/L1) and mouthrinse -(250 mg/L-1). Chemical biopsies were performed: at baseline after wash-out period (t0), at the end of the 15 days treatment phase (t1) and 48 hours after the cessation of fluoride use (t2). Results: The main results of this study are that fluoride reservoir levels are still relatively high after 48 hours after the use of fluoride compounds with an increase of the fluoride content in the superficial layer of the enamel. After 15 days of treatment, Group A showed higher fluoride uptake (0.19 g mm2) than the other two groups (0.16 g mm2) p<0.05. Six days after not using fluoridated fluoride, concentration higher than at baseline was found only in Group A. Fluoride uptake was higher with amine fluoride than with other fluoride products. Conclusions: It is well known that the formation of intra-oral fluoride reservoirs is a crucial factor in topical treatment and the combination of amine fluoride toothpaste and mouthrinse seems to achieve this purpose. In this study, amine fluoride seems to have a better preventive action than sodium fluoride. Amine fluoride significantly reduced bacterial adhesion to salivary pellicles and Streptococcus mutans growth. The electrostatic interaction between cationic amine fluoride and negatively charged bacterial cell surfaces is pivotal in establishing reduced biofilm formation by amine fluoride. From a clinical standpoint, clinical and experimental several data suggest that fluoride incorporated into the enamel mineral during tooth development has little effect on the caries process. The presence of fluoride post-eruptively in the aqueous phase during the caries challenge is of fundamental importance. The most effective caries preventive fluoride regimen is the frequent (daily) application of low concentration of fluoride through toothpastes and/or mouthrinses All fluoride products tested produced an enamel uptake, and the amine fluoride toothpaste and mouthrinse were the most effective in promoting a long-term uptake