Metabolic activity of Streptococcus mutans biofilms after treatment with different mouthwash formulations

Aim: The aim of this study was to investigate the metabolic activity of Streptococcus mutans biofilms after treatment with mouthwashes with different compositions.
Methods: S. mutans biofilms were growth on polystyrene plates during 18 h, washed with sterile saline and treated with the following mouthwashes during 1 min: Listerine®, Oral B®, Parodontax® and Periogard® with and without alcohol. After the treatment, the biofilms were incubated with complete medium containing sucrose during 60, 120 or 180 min, and then samples were collected for pH measurements. In addition, biofilms were grown in microscope coverslips treated as described above, followed by staining with Propidium Iodide and Fluoresceine for visualization with a confocal laser scanning microscopy.
Results: For all mouthwashes evaluated, treatment was deleterious to cell metabolism, since little or no acidification was observed at least 60 min after treatment. Mouthwashes containing 0.2% chlorhexidine (Parodontax®) or essential oils (Listerine®) induced a significant reduction in the metabolic activity of biofilms during the tested time points (120 and 180 min after treatment), being thus more effective than the mouthwashes containing 0.12% chlorhexidine (Periogard®) or cetylpyridinium plus fluoride (Oral B®). The confocal analysis overall confirmed the results observed in the analysis of metabolic activity.
Conclusions: The treatment of biofilms with mouthwashes containing 0.2% chlorhexidine or essential oils induced significant reduction in S. mutans metabolism.