Tin(II) fluoride
Tin(II) fluoride, also known as stannous fluoride, is an inorganic chemical compound with the formula SnF2. It is a white solid used in toothpaste to prevent dental caries (cavities).
Properties
Stannous fluoride is a white, crystalline solid. It is soluble in water, forming acidic solutions due to hydrolysis. In solution, it exists as various hydrated species. It is also soluble in many organic solvents. The compound is a reducing agent and reacts with oxidizing agents.
Preparation
Tin(II) fluoride can be prepared by reacting tin metal with anhydrous hydrogen fluoride gas or aqueous hydrofluoric acid:
Sn + 2HF → SnF2
Uses
The primary use of tin(II) fluoride is in dental care products, particularly toothpaste and mouthwash. It is an effective anticariogenic agent, working by several mechanisms:
- Fluoride Incorporation: It delivers fluoride ions to the tooth enamel, which are incorporated into the hydroxyapatite structure, forming fluorapatite. Fluorapatite is more resistant to acid attack from bacteria in the mouth.
- Antibacterial Action: Stannous fluoride exhibits some antibacterial properties, inhibiting the growth and metabolism of bacteria involved in plaque formation.
- Dentin Tubule Occlusion: Stannous fluoride can help to occlude dentin tubules, reducing sensitivity.
Stannous fluoride is sometimes used in other industrial applications, such as in the preparation of other tin compounds.
Safety
While effective in preventing cavities, tin(II) fluoride can cause staining of teeth, particularly with prolonged use at higher concentrations. This staining is generally superficial and can be removed by a dentist or dental hygienist. Excessive ingestion of fluoride can lead to fluorosis, a condition that affects tooth enamel development, especially in children. Therefore, it is important to use fluoride-containing dental products as directed.