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.