Readily soluble in water, SnF2 is hydrolysed. At low concentration, it forms species such as SnOH+, Sn(OH)2 and Sn(OH)3−. At higher concentrations, predominantly polynuclear species are formed, including Sn2(OH)22+ and Sn3(OH)42+. Aqueous solutions readily oxidise to form insoluble precipitates of SnIV, which are ineffective as a dental prophylactic. Tin(II) fluoride, commonly referred to commercially (with tin(II) in Latin) as stannous fluoride, is a chemical compound with the formula SnF2. It is a colorless solid used as an ingredient in toothpastes that are typically more expensive than those that use sodium fluoride. Stannous fluoride has both bactericidal and bacteriostatic properties, which fight plaque and treat/prevent gingivitis. The stannous fluoride also deposits a protective mineral barrier over exposed dentinal tubules to help prevent sensitivity pain from triggers such as hot or cold liquids and foods. Stannous fluoride is used under the trade name "Fluoristan" in the original formulation of the toothpaste Crest, though it was later replaced with sodium monofluorophosphate, or "Fluoristat". It is the active ingredient in Crest Pro Health brand toothpaste. Crest Pro Health issues a warning on the tube that stannous fluoride may cause staining, which can be avoided by proper brushing, and that its particular formulation is resistant to staining. Any stannous fluoride staining that occurs due to improper brushing is not permanent. Stannous fluoride is also used in Oral-B Pro-Expert. Stannous fluoride is also readily available in over-the-counter rinses.