Tin(II) fluoride

Stannous fluoride, also known as tin II fluoride, is the chemical compound with the formula SnF₂. This colourless solid is a common ingredient in toothpaste. In the enamel, it converts apatite into fluoroapatite, which is more resistant to attack by acids generated by bacteria. Sodium fluoride and sodium fluorophosphate perform similarly.

Stannous fluoride was used (under the trade name Fluoristan) in the original formulation of the toothpaste Crest, though it was later replaced with sodium monofluorophosphate.

Used in combination with abrasives that contain calcium, sodium fluoride is ineffective; stannous fluoride remains effective when used with such abrasives.