Efficacy of Stannous Ions on Enamel Demineralization under Normal and Hyposalivatory Conditions: A Controlled Randomized in situ Pilot Trial

The study aim was to investigate the effect of antierosive agents on enamel under normal and hyposalivatory conditions. This double-blind crossover in situ pilot study evaluated 4 toothpastes: placebo (0 ppm F), sodium fluoride (NaF, 1,450 ppm), stannous/sodium fluoride (SnF/NaF, 1,450 ppm F - , 1,090 ppm Sn 2+ ), and sodium fluoride, stannous chloride and chitosan (NaF/Sn/Ch, 1,450 ppm F - , 3,500 ppm Sn 2+ , 0.5% Ch). Twenty participants were assigned to 2 groups (n = 10 each): normal and low salivary flow. Participants wore palatal appliances holding 4 bovine enamel specimens previously eroded in vitro (D1) for 20 min prior to an in situ phase after which they were eroded again (D2). Surface microhardness was determined at baseline (BL), after D1, in situ phase and D2 to assess hardness loss (%SMH), residual hardness loss (%RHL) and erosion resistance (%RER). Additional specimens were evaluated by scanning electron microscopy after the in situ phase. ANOVA and a factorial analysis for between-subject effects were performed. Sn-based toothpastes showed the best effects (p < 0.05). Under normal flow, SnF/NaF showed higher efficacy, with a significant difference compared to NaF/Sn/Ch, NaF, and placebo (p < 0.05). Under low flow, SnF/NaF and NaF/Sn/Ch were comparable (p > 0.05); NaF and placebo were statistically similar. Comparing salivary conditions, there were significant differences for SnF/NaF for %SMH after the in situ phase (%SMH total) ), %RHL and for all toothpastes in case of %RER. Factorial analysis revealed interactions between toothpaste and saliva flow for %SMH total and %RHL. Salivary flow can influence the efficacy of the antierosive toothpastes; however, Sn 2+ preparations show even under low salivary flow conditions the highest efficacy in the prevention of enamel erosion.