Synergistic Effects of Polyphenols and Stannous Ions on Pellicle Modification and Erosion Protection In Situ

Background: Stannous ions and polyphenols are effective substances in preventive dentistry. The present study's aim was to investigate whether a combination of these substance groups can achieve increased efficacy. Methods: Initial biofilm formation was performed on bovine enamel slabs, carried by 10 subjects intraorally. The subjects rinsed with tannic acid, SnCl₂, SnF₂, a combination (50:50) of tannic acid and SnCl₂, or a combination of tannic acid and SnF₂, with no rinsing in the negative control. Bacterial adherence, glucan formation (8 h, 48 h oral exposition,) and calcium release kinetics were measured (pH 2; 2.3; 3). Statistics were performed with the Kruskal-Wallis test (p < 0.05), Mann-Whitney U test (p < 0.05), and Bonferroni-Holm correction. Results: All rinsing solutions reduced bacterial adherence by more than 50%. Initial bacterial colonization and glucan formation was significantly reduced by SnF₂ and SnCl₂ as well as their combinations with tannic acid. The most significant reductions in calcium release at pH 2; 2.3; and 3 were obtained by SnF₂ and the combination of SnF₂ and tannic acid. At the acidic pH 2.0, SnF₂, SnCl₂, and tannic acid and SnF₂ showed significant protection compared to the control (p ≤ 0.01). TEM micrographs indicated that rinsing with SnF₂ and tannic acid leads to pronounced electron dense, thick pellicle layers. Conclusions: SnCl₂ and SnF₂, as well as their combinations with tannic acid, led to a reduction in initial bacterial colonization and glucan formation, showing an erosion-protective effect. These findings confirm the clinical applicability hitherto suspected by in vitro findings.