Bactericidal Efficacy of Cold Plasma at Different Depths of Infected Root Canals In Vitro

Sascha R. Herbst1, #, Moritz Hertel2, #, Husam Ballout1, Philipp Pierdzioch1, Klaus-Dieter Weltmann3, Henrik C. Wirtz1, Shady Abu-Sirhan1, Eckehard Kostka1, Sebastian Paris1, Saskia Preissner1, *
1 Charité - Universitätsmedizin Berlin, Department of Operative and Preventive Dentistry, Germany;
2 Charité - Universitätsmedizin Berlin, Department of Oral Medicine, Dental Radiology and Oral Surgery, Germany;
3 INP Greifswald, Leibniz Institute for Plasma Science and Technology, Greifswald, Germany

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© Herbst et al. ; Licensee Bentham Open.

open-access license: This is an open access articles licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (, which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided that the work is properly cited.

* Address correspondence to this author at the Charité - Universitätsmedizin Berlin, Department of Operative and Preventive Dentistry, Assmannshauser Str. 4-6, 14197 Berlin, Germany; Tel: +49 30 450 562675; Fax: +49 30 450 562932; E-mail:
# These authors contributed equally to this work.


Objectives: Cold plasma (CP) has been shown to be effective even against multiresistant microorganisms. As previous investigations on the effect of CP in root canals showed promising results, the aim of the present study was to analyze the bactericidal efficacy of CP in different depths of infected dentin. Methods: 32 standardized root canals of human mandibular premolars were infected with Enterococcus faecalis and incubated for one week. Specimens were randomly selected for one of four disinfection methods: control (5mL NaCl), 5mL chlorhexidine (CHX), CP alone (CP), and a combination of 5mL CHX and cold plasma (CHX+CP). CHX was ultrasonically activated for 30s, while cold plasma was used for 60s in the root canals. Dentin samples at depths of 300, 500 and 800 µm were obtained and diluted serially. Colony forming units (CFUs) were counted on agar plates after 24h of incubation. Results: The highest overall logarithmic reduction factors (RF) were obtained from CHX+CP (log RF 3.56 p<0.01; Mann-Whitney U test), followed by CP (log RF 3.27 p<0.01) and CHX alone (log RF 2.65 p<0.01) related to the control. All disinfection methods showed significantly lower CFU counts compared to the control group in 300 µm and 800 µm (both p<0.01, Kruskal-Wallis test). Discussion: The adjuvant use of CP might be beneficial in highly infected root canals to improved disinfection. However, the disinfection effect against Enterococcus faecalis of CP is comparable to ultrasonically activated CHX.

Keywords: Cold plasma, dentinal tubules, disinfection, Enterococcus faecalis, penetration depth, tissue tolerable plasma.