- Participants using the following mouth rinses, or taking the medications listed below: a) Regular use of mouthwashes containing ingredients that are known to impart staining. For example, chlorhexidine, essential oils or cetylpyridinium chloride (CPC). b) Use of a chlorhexidine, essential oil or CPC containing mouthwash within 14 days of Visit 2 or throughout the study. c) Current use of Listerine, or any antimicrobial mouth rinse. d) Use of minocycline, tetracycline or doxycycline within 30 days prior to screening. e) Use of minocycline, tetracycline or doxycycline between the screening and baseline visits. f) Daily doses of a medication and/or traditional/herbal ingredients which, in the opinion of the investigator, may affect study outcomes. For example, drugs or supplements containing metal ions known to impart staining to the enamel.