Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion

Objectives: Sn2+ has promising erosion-inhibiting properties in solutions, but little is known about respective effects in toothpastes. In addition, biopolymers might have protecting potential. Aim of this study was to investigate the effects of Sn2+ in toothpastes and of a biopolymer (chitosan) added to a Sn2+ formulation on erosion/abrasion. Methods: Enamel samples were subjected to cyclic erosion procedures (10 days; 0.50% citric acid, pH 2.5; 6 x 2 min/day), and brushing (2 x 15 s/day, load 200 g) during immersion in slurries (2 min). The toothpastes were NaF formulations (NaF/1, NaF/2, NaF/3) and Sn2+ formulations (NaF/SnCl2, AmF/SnF2, AmF/NaF/SnCl2) and AmF/NaF/SnCl2 + 0.5% chitosan. Declared concentrations of active ingredients in toothpastes were 1400-1450 mu g/g F- and 3280-3500 mu g/g Sn2+. Negative controls were erosion only and placebo, positive control was a SnF2 gel. Tissue loss was quantified profilometrically, Sn on enamel surfaces was measured by energy dispersive X-ray spectroscopy. Results: Loss values (mu m) for erosion only and placebo were 14.4 +/- 4.5 and 20.2 +/- 3.8, respectively, and 4.6 +/- 1.9 for the positive control (p <= 0.001 each compared to erosion only). The other loss values were: NaF/1 16.5 +/- 3.0, NaF/2 14.0 +/- 2.7, NaF/3 12.6 +/- 3.9, NaF/SnCl2 14.7 +/- 5.1, AmF/SnF2 13.5 +/- 4.8, AmF/NaF/SnCl2 12.4 +/- 4.2, AmF/NaF/SnCl2 + chitosan 6.6 +/- 3.5 (except NaF/1 all p <= 0.01 compared to placebo). AmF/NaF/SnCl2/chitosan was more effective than all other toothpastes (p <= 0.01 each). Sn on the enamel surface ranged between 1.3 +/- 0.3 and 2.8 +/- 0.04 wt.% with no obvious relationship with efficacy. Conclusions: The NaF and Sn2+ toothpastes without chitosan exhibited similar anti-erosion and abrasion-prevention effects. The experimental Sn2+ formulation with chitosan revealed promising results similar to those of the positive control. Clinical significance: NaF toothpastes offer a degree of protection against erosion/abrasion, which is likely sufficient for most subjects with average acid exposures. For patients with initial erosive lesions, however, more effective toothpaste is desirable. The combination of Sn2+ and a biopolymer appears promising in this context. (C) 2012 Elsevier Ltd. All rights reserved.