A tablet or liquid which when applied to the tooth surface renders bacterial plaque more visible. An erythrosine dye stains plaque red but two tone solutions stain older plaque blue and more recent plaque red. Aniline dye is thought by some authorities to be carcinogenic and is not recommended, though the research data is inconclusive. Organic food colourants are also effective plaque disclosing agents.
Kieser J. B., Wade A. B. Use of food colourants as plaque disclosing agents. J Clin Periodontol 1976;3(4):200–07.