2013 Volume 56 Issue 2 Pages 105-112
Purpose: Listerine mouthrinse has been reported to show a rapid membrane-damaging effect on biofilm bacteria. One drawback of Listerine, however, is that it may be irritative to oral mucosa due to the ethanol contained as a solvent. The aim of this study was to evaluate the penetration kinetics and antimicrobial effects of a new alcohol-free essential oil mouthwash (Listerine Zero), which has been developed to lower the irritative action of Listerine. Methods: Listerine Zero (Z), Listerine Fleshmint (F) and a chlorhexidine gluconate-containing mouthrinse (Peridex; P) were investigated as test mouthrinses, and a buffer was used as a negative control. Streptococcus mutans biofilms were grown on glass-based dishes for 24 h under anaerobic conditions. Penetration kinetics of the mouthrinses were analyzed with time-lapse confocal laser scanning microscopy where the fluorescence loss of calcein-AM-stained biofilms was monitored after exposure to mouthrinse. Antimicrobial effects of the mouthrinses were also compared using live/dead staining and plate counting. Results: The maximum biofilm thickness developed in this study was approximately 32 μm. The time required to reach 50 % of the initial fluorescence intensity (T50) and biofilm thickness exhibited a high correlation coefficient. P showed significantly smaller penetration velocity compared with the others, whereas there was no significant difference between Z and F. The live/dead staining analysis after 30 s exposure revealed that propidium iodide (a dead cell marker)-positive percentage was 99.8±0.1 % for Z and F and 41.4±5.9 % for P When viable cell counts after 30 s of mouthrinse exposure were determined by plate counting, all of the mouthrinses caused a significant reduction compared with the control. F and Z caused significantly smaller counts than P whereas there was no significant difference between Z and F Conclusion: Listerine Zero was as effective as Listerine Fleshmint in penetration property and antimicrobial effect against S. mutans biofilms of less than 32 μm thick. Both of these mouthrinses also showed significantly superior penetration property and antimicrobial effect than the chlorhexidine gluconate-containing mouthrinse.
