Brown stains from anti-plaque agents are typically caused by which component?

Brown stains resulting from anti-plaque agents are primarily associated with chlorhexidine. This compound is commonly used in various dental treatments due to its powerful antibacterial properties. However, one of its known side effects is the staining of teeth and oral tissues. This discoloration occurs because chlorhexidine can bind to the salivary proteins and dental plaque, leading to noticeable brownish stains on the surfaces of the teeth, especially with prolonged use.

The other options, while they may be linked to other oral health issues or side effects, are not primarily responsible for brown staining of teeth. For instance, hydrogen peroxide can cause bleaching and may lead to temporary enamel changes, but it doesn't lead to brown stains. Iron supplements can cause dark staining, but they are not classified as anti-plaque agents like chlorhexidine. Sodium fluoride is generally used for its protective effects on teeth and does not typically cause staining. Thus, chlorhexidine stands out as the main culprit when it comes to brown stains linked to the use of anti-plaque agents.