Stannous ions

Recent studies have shown that stannous ions play a substantial role in inhibiting erosive dental hard tissue loss (Hooper et al. 2007, Hove et al. 2007). Apart from stannous other polyvalent metal cations, like titanium, may also have erosion protective effects (Büyükilmaz et al. 1997, Hove et al. 2008).

It is well known that the application of tin-containing fluoride solutions leads to deposits on the tooth surface (Cooley 1961, Ellingsen 1986) that are relatively resistant to acids (Wiegand & Attin 2003, Ganss et al. 2008). The stannous ion reacts with pure hydroxyapatite (Babcock et al. 1978, Jordan et al. 1971) and with the surface of the dental hard tissue (Cooley 1961, Krutchkoff et al. 1972), resulting in reduced hydroxyapatite or enamel solubility (Ganss et al. 2008, Barbakow et al. 1985).

The effect of stannous ions in mild to moderate conditions:
  • Stannous fluoride toothpaste has been shown to provide significant protection against calcium loss in vivo compared to sodium fluoride toothpaste (Young et al. 2006).
  • They can reduce dissolution of enamel in vivo and, therefore, appear to be effective in the prevention of erosion (Willumsen et al. 2004).
  • One study showed in vitro (Ganss et al. 2008) that erosive mineral loss can almost be stopped under erosive conditions that are not too harsh (10 days: 6 x 2 min in 0.05 M citric acid (pH 2.3), 6 x 2 min treatment) by solutions containing SnF2 or AmF/SnF2.
  • Pure SnCl2 solutions without fluoride showed a moderate erosion protective effect in the range of NaF-solutions, indicating that the combined use of both stannous and fluoride is relevant for the anti-erosive effect. To achieve the optimal ratio between available stannous- and fluoride-ions, it is advantageous to use independent sources for each ion (e.g. SnCl2, AmF, NaF).
  • Furthermore, amine fluorides have the advantage of showing a stabilising effect on stannous salts.

The effect of stannous ions in harsh conditions:

  • Under a much harsher erosive regime (10 days: 6 x 5 min in 0.05 M citric acid (pH 2.3), 2 x 2 min treatment) systematic in vitro studies showed a positive effect of amine fluoride-containing SnCl2 solutions, even with short time applications (Schlueter et al. 2009).

The effect of stannous ions on eroded enamel:
  • A recent study has shown that stannous is not only retained on the tooth surface, but can also be incorporated into eroded enamel, forming structural modifications and less acid soluble surface zones (Schlueter et al. 2009).
  • The quantity of incorporation is concentration dependent, thus, a higher tin concentration in the solution leads to higher tin uptake and to better efficacy (Schlueter et al. 2009).
  • The newest in situ results demonstrate the superiority of stannous chloride, amine fluoride and sodium fluoride combinations over pure fluoride solutions (Ganss et al. 2009).

How stannous ion solutions work:

  • The efficacy of such solutions is based on the deposition of a stannous rich layer on the tooth surface and subsequent incorporation of stannous into the outermost tooth surface layers in the course of subsequent acid attacks (Schlueter et al. 2009).
  • The initially formed amorphous stannous and fluoride containing layer is at least partially dissolved and complex demineralisation and remineralisation processes take place, leading to the incorporation of low-solubility compounds into the eroded enamel. It is assumed that these compounds consist of different stannous and fluoride salts (Ganss & Schlueter 2009).