Surface Protective Mechanism of SnF2 Against Irreversible Acid Damage

Deposition of an invisible barrier layer onto the enamel surface has been proposed as a potentially superior means for protecting enamel against an ever increasing level of acid based challenges from both dietary and food sources. Objectives: The purpose of this study was to demonstrate the barrier layer deposited onto pellicle coated enamel surfaces from stannous fluoride (SnF2) containing toothpaste using laser ablation ICP-MS. Methods: Squares of bovine enamel (5x5x1mm) were exposed overnight to pooled human saliva, resulting in the deposition of a reasonably mature pellicle layer on the enamel specimens. Specimens were treated with the supernatant of a 1:3 slurry of toothpaste:water for 2 minutes (SnF2, NaF, or Water control), then rinsed with deionized, distilled water. Surface analysis of specimens was done using laser ablation ICP-MS, with a field of view for all images being 790mm x 590mm. The intensity of all isotopes was corrected pixel by pixel using 13C as the internal standard. Results: Deposition of a relatively continuous stannous layer onto the pellicle coated enamel surface was clearly demonstrated, with significant deposition of stannous (using isotopes 117Sn + 120Sn) measured incorporated into or onto the pellicle coated enamel surface. Conclusions: This study confirms the deposition of an invisible stannous containing layer into/onto the pellicle coated enamel surface as a result of treatment with a stannous fluoride containing dentifrice. These results, coupled with in vitro and in situ demonstrations of effective protection against dietary acid challenges, support the superiority of stannous fluoride for its potential to protect enamel against the emerging trend of irreversible tooth surface loss.