Development of a fluoride varnish formulation containing sodium trimetaphosphate: effect on dental caries and erosion in in vitro, in situ and in vivo protocols

The present study assessed the effect of fluoridated varnishes containing sodium trimetaphosphate (TMP) on the demineralization, remineralization and erosive wear of dental enamel, using in vitro and in situ protocols, as well as on the development of caries lesions in children and adolescents, in a randomized and controlled clinical protocol. The study was conducted in 6 different phases. Phases 1 to 5 were performed using bovine dental enamel specimens, over which the varnishes were applied only once, remaining in contact for 6 hours. In the first phase, varnishes containing 5% NaF (positive control), 2.5% NaF supplemented with O, 3.5, 5.0 and 10.0% TMP, and also a formulation without F or TMP (PLA, placebo) were tested in an in vitro protocol. The specimens were submitted to erosive challenges (ERO -Sprite Zero®, 5 min, 4x/ day, 5 days), followed or not by brushing (ERO+ABR). In the second phase, the effect of PLA, 5% NaF and 2.5% NaF varnishes (supplemented or not with 5% TMP) on ERO and ERO+ABR were analyzed in situ. Volunteers (n=10) used acrylic palatal devices containing 4 blocks of enamel. ERO was performed ex vivo (immersion in citric acid, 5 min, 4x/day, 5 days), while ERO+ABR was produced by brushing 2 of the blocks (15 s, F-free dentifrice). In both phases, the varnishes containing TMP promoted significantly lower wear and integrated hardness loss in depth (∆KHN) when compared to the other varnishes, both for ERO and ERO+ABR. In the 3rd and 4th phases, varnishes containing 2.5% NaF and 5% NaF, supplemented or not with 5% TMP, PLA, a commercial formulation (Duraphat®, 5% NaF) and a varnish containing 5% TMP were assessed regarding their remineralizing (artificial caries lesions) and protective (sound enamel) effects, using pH cycling models (7 days). A synergistic effect between F and TMP was observed on the percentage of surface hardness recovery (3rd phase), on the percentage of surface hardness loss (4th stage), as well as on ΔKHN (3rd and 4th stages). In the 5th stage, the remineralizing effect of PLA, 5% NaF and 5% NaF + 5% TMP varnishes was evaluated using a short-term (3 days) in situ protocol, confirming the findings of the 3rd phase, in individuals using fluoridated dentifrice. Finally, in the 6 th phase, PLA, 5% NaF and 5% NaF + 5% TMP varnishes were evaluated in a randomized controlled trial conducted in children (n = 390, 3-4 years of age) and adolescents (n = 570, 11-15 years of age) living in Boa Vista (northern region of Brazil), who received quarterly applications of the varnishes and were examined along a 12-month period. The lowest dmfs and DMFS increments were observed for the groups treated with 5% NaF + 5% TMP varnish, followed by 5% NaF and PLA. It was concluded that the addition of TMP to fluoride varnishes is a promising alternative in the prevention and treatment of caries lesions, with potential application in the reduction of erosive dental wear