The Effects of Oral Hygiene Products on Candida Biofilm Disinfection

Objectives: Elderly denture wearers are susceptible to colonisation by various Candida species on the surfaces of their artificial dentures, which results in the disease called denture stomatitis. During the treatment of these patients, it is important to disinfect the dentures contaminated with the causative microorganism (usually Candida species). These are present as biofilms, which are notoriously difficult to treat effectively. The aim of this study was to examine different Candida species biofilms, and to assess the efficacy of commercially available oral hygiene products on killing of biofilms. Methods: A range of different Candida species that were previously isolated from the oral cavity of denture stomatitis patients were used in this study. Single species and mixed species biofilms were formed, and measured semi-quantitatively for biofilm biomass using a crystal violet assay. Those combinations that formed biofilms were subsequently treated with a range of oral hygiene products, including, Boots Smile, Dentural, Steradent, Listerine, Corsodyl, Difflam™, Oraldene, Peroxyl. Biofilms were exposed to these products, and then subsequently assessed using a metabolic assay. Biofilms were then washed, new media added and viability reassessed after 24 h. Results: Biofilms containing C. albicans and C. parapsilosis formed biofilms effectively, whereas the other species exhibited scant biofilms. Biofilms initially exposed to the range of oral hygiene products exhibited a greater than 90% reduction of metabolic activity for all products, as compared to controls. However, biofilm viability was re-established following washing and addition of new media. Conclusion: Filamentous forms of Candida were able to form dense biofilms in association with all other species examined, i.e. C. albicans and C. parapsilosis. Initial indications suggested than commercially available cleaners were effective in their killing action. However, reintroduction of media induced re-growth; thus indicating an ineffective killing action. Therefore, products which promote biofilm removal, rather than killing, are preferential denture cleansers.