In the Nooks and Crannies – Biofilm Treatment for the Hard to Reach Areas of a Denture: an In Vitro Study

Objectives: The aim of this study was to investigate the anti-biofilm and anti-microbial activity of a newly developed denture cleanser (DC) tablet in hard to reach places between the interdental spaces of dentures in vitro. Methods: An 11-species biofilm model was grown in a sequential manner for 8-days on full palate-less dentures or denture sections. Following maturation, biofilms were treated on a daily basis for 7 days, with DC tablets dissolved in ddH2O, for 3 or 15 mins, with or without physical debridement using a toothbrush. Untreated controls were used as appropriate controls. Post-treatment, biofilms were imaged at a macroscopic or microscopic level, using crystal violet (CV) or fluorescent dyes (SYTO-9 and propidium iodide; PI). Additional dentures were sonicated for microbiological outputs using the Miles and Misra cell counting methodology and live/dead quantitative PCR technique to determine total and viable counts. Results: All DC treatments were effective in reducing biofilm biomass and/or viable cells present on the denture, when compared to untreated controls. Fluorescence microscopy and macroscopic assessment with CV revealed treatment was effective in removing biofilm on the tooth surface as well as within the interdental spaces (Nooks and Crannies) of the dentures. In unbrushed controls, remaining biomass was more apparent than combinational therapy of DC with brushing, whilst fluorescent staining showed the bioburden was largely non-viable, as evidenced by excessive staining with PI. Microbiological outputs highlighted a time-dependent killing effect of DC treatment, with 15 min treatment more effective (>2- log reduction) than the 3 min regime (~1-log reduction). Conclusions: This in vitro study highlights the efficacy of DC treatment in reducing biofilm bioburden and overall viability. It ultimately emphasizes the need for appropriate denture sterilisation methods to be implemented by edentulous patients to ensure the maintenance of good oral health.