What type of fluoride may cause brown stains?

Stannous fluoride is the correct choice because it has been associated with the occurrence of brown stains on teeth. This type of fluoride is known for its antibacterial properties and ability to reduce tooth sensitivity, but it can also react with compounds in the dental biofilm and plaque, leading to staining. The stannous ion in stannous fluoride can precipitate with other components, creating a noticeable discoloration in some cases, particularly if it is not effectively removed through regular oral hygiene.

In contrast, sodium fluoride, acidulated phosphate fluoride, and neutral sodium fluoride are less likely to cause staining. These forms of fluoride primarily work by promoting remineralization of enamel and do not have the same propensity to react with the oral environment to produce discoloration. Consequently, stannous fluoride stands out as the fluoride type that can lead to brown stains on teeth, making it crucial for dental professionals to counsel patients about proper use and maintenance of oral hygiene when using products containing it.