Stannous fluoride is used in toothpastes and dental rinses
to protect tooth enamel from attack by bacteria (cavities,
also known as caries). It was the first fluoride
used for that purpose, in the toothpaste Crest.
The active part of the molecule is the fluoride ion, which
is why two other fluorine containing compounds,
sodium fluoride, and
are also used.
Stannous fluoride can be used with abrasives
that contain calcium, which prevents sodium fluoride from
being effective. Sodium monofluorophosphate was developed
to avoid infinging on the Crest patent.
Fluorides work in two ways. They reduce the ability of
bacteria to make acids, and they remineralize the areas of
the tooth that have been attacked by acids from bacteria.