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.