Objective: The aim of this study was to determine whether different antiseptic mouthrinses show different penetration kinetics into Streptococcus mutans biofilms.
Materials and methods: The biofilms, grown on glass-based dishes, were exposed to one of four mouthrinses containing chlorhexidine digluconate, essential oil, cetylpyridinium chloride, or isopropylmethylphenol. Then, penetration velocities were determined by monitoring fluorescence loss of calcein AM-stained biofilms with time-lapse confocal laser scanning microscopy. Bactericidal activity was assessed with fluorescent bacterial viable cell (Live/Dead) staining and viable cell counts. Bacterial detachment after the mouthrinse exposure was determined by measuring fluorescence reduction of SYTO9-stained biofilms.
Results: The essential oil-containing mouthrinse showed significantly faster penetration velocity than the other mouthrinses (ANCOVA and Bonferroni test, p < 0.05). However, even 5 min of exposure left the biofilm structure almost intact. After 30 s (consumer rinsing time) of exposure, the essential oil-containing mouthrinse showed the highest log reduction of viable cells (2.7 log CFU) measured by Live/Dead staining, and the mean reduction of total viable cells was 1.41 log CFU measured by viable cell count.
Conclusions: The essential oil-containing mouthrinse showed the best penetration. Within 30 s of exposure, however, no mouthrinses injured all the microorganisms and all mouthrinses left the biofilm structure nearly intact.
Clinical relevance: The mouthrinses tested showed different levels of biofilm penetration. The essential oil rinse was superior to other rinses by all three of the in vitro measurements performed.