An annoyed consumer, who happened to be lawyer Mark Rossman, filed a class-action suit in US District Court (So. Michigan) against P&G for brown stains that persisted on his teeth he alleges were due to the use of Crest Pro-Health mouthwash. He alleges breach of warranty and failure to warn. He may have a point...
In the spring of 2009 a series of unsolicited reports by users appeared on Drugstore.co
m; for example this quote published on 6/25/09: "I did notice a LOT of dark brown/black stains at my gumline and in between my teeth. However, I attributed it to my drinking of tea and coffee. When I had my dental check up, the dentist said I had horrrible coffee/tea stains." It is highly likely that P&G consumer affairs also would have received similar reports by phone or e-mails long before this August legal filing.
Crest Pro-Health mouthwash is an aqueous solution of the active ingredient 0.07% cetylpyridinium chloride (CPC) in glycerin, flavor, poloxamer 407, sodium saccharin, and blue #1 dye. CPC is a commonly used antimicrobial and is likely to be related to tooth staining.
But is there a connection between these unsolicited adverse events and the use of the product. The simple answer is yes. Although the poster child for teeth staining in oral care products is chlorhexidine (Peridex), charged antimicrobials like CPC have a propensity to stain as well. Predicting the risk of staining covaries with both the overall formula, the concentration of CPC, and cumulative exposure to food and drink such as coffee, tea, wine, etc. For example, a lab study done by Addy et al (J. Dentistry 23:95) in the UK in 1995 documents the effect of CPC on Perspex blocks pre-stained with tea then exposed to various CPC formulae. They observed staining that varied with formula. A warning statement would have been prudent.
Mouthwashes containing CPC as an active ingredient include: Crest Pro-Health (PG) , Breath-Rx (Discus), and Viadent (CL). 
Mouthwashes containing CPC as an inactive ingredient include: ACT (Chattem, #2), Scope (PG, #8), and Aim (Dr. Fresh, #11). The number is parentheses is the rank order of the presence of the inactive ingredient as listed on the label. 
Brands free of CPC include: Listerine, Plax, Rembrandt, Biotene, & Targon.
