Which ingredient found in some mouthwashes and oral care products is most associated with extrinsic tooth staining?

Stannous fluoride (SnF2) is associated with extrinsic brown tooth staining due to the tin (stannous) ion, which reacts with dietary chromogens and bacterial pigments to form tin sulfide deposits on the tooth surface. This staining is particularly notable with older, unstabilized stannous fluoride formulations. Modern stabilized stannous fluoride products have reduced but not eliminated this side effect. Cetylpyridinium chloride (CPC) can also cause staining, but less commonly than stannous fluoride. Chlorhexidine causes the most significant staining of all mouthwash ingredients. Sodium fluoride and sodium lauryl sulfate do not cause significant staining. Note: This question is from Section 9 and may test stannous fluoride specifically as the answer.