The Efficacy of Atmospheric Pressure Cold Plasma Jet Against Enterococcus faecalis Biofilms at Variable Time Interval
Objective: To study the time duration in which atmospheric pressure cold plasma is efficient in the elimination of Enterococcus faecalis biofilms on dentin slices.
Materials and methods: 90 slices of 5x5x1 mm human molar’s dentin were prepared and sterilized. The slices were incubated with E. faecalis to form 7-day-old biofilms. Specimens were divided into controls and five experimental groups. Groups 1-4 were subjected to atmospheric pressure cold plasma jet with 98% helium gas and 2% oxygen gas for 30 seconds, 1 minute, 2 minutes, and 5 minutes respectively. Group 5 was subjected to 5% sodium hypochlorite. The elimination of E. faecalis biofilm was determined by LIVE/DEAD®BacLight™ cell staining under Confocal Laser Scanning Microscope (CLSM). The proportion of viable bacterial cells were calculated. Changes in biofilm structure were studied under Scanning Electron Microscope (SEM). Results were statistically analyzed using One-way ANOVA and Tukey’s multiple comparison test at a confidence level of 95%.
Results: Dead cell proportion in experimental group 1-4 were 0.65, 0.61, 0.63 and 0.78 respectively. Group 4 showed significantly more elimination of biofilm than group 1-3 (p < 0.05). However, group 4 still demonstrated significantly less biofilm elimination than group 5 (p < 0.05). Image from SEM showed the disruption of E. faecalis biofilm and deformation of some bacteria.
Conclusions: Atmospheric pressure cold plasma jet was able to eliminate E. faecalis biofilms on dentin slices. The most effective time duration was 5 minutes. However, none of the experimental groups showed complete biofilm removal.
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