The efficacy of plasma-treated water as a root canal irrigant

Kaname Yamamoto, DMD (1), Tomoko Ohshima, DMD, PhD (2,3), Katsuhisa Kitano, PhD (2,3), Satoshi Ikawa, PhD (4), Hiromitsu Yamazaki, DMD, PhD (2), Nobuko Maeda, DMD, PhD (2), and Noriyasu Hosoya DMD, PhD (1)

(1) Department of Endodontology, (2) Department of Oral Microbiology, Tsurumi University School of Dental Medicine, Yokohama, (3) Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Osaka, and (4) Technology Research Institute of Osaka Prefecture, Osaka, Japan

Purpose: In recent years, attention has been drawn to disinfection techniques by plasma irradiation on human bodies, however, the efficacy is not sufficient in the root canal. Therefore, the authors generated plasma-treated water (PTW) to concentrate the active species, and investigated the efficacy of PTW as a root canal irrigant.
Materials and Methods: PTW was produced using plasma prepared from helium containing nitrogen. Three tested microorganisms, Enterococcus faecalis, Candida albicans, and Candida glabrata, were selected, and their growth with PTW was evaluated to determine minimum inhibitory concentration (MIC). Infected root canal models were created using 76 extracted human anterior teeth whose root canals were prepared and inoculated with one of the bacterial/fungal suspensions and cultured. A bacterial/fungal test of the root canals was performed following PTW treatment. The effect of PTW was evaluated in an in situ model of infected root canal with E. faecalis of 12 bilateral mandibular first molars of six 4-week-old male Wistar rats.
Results: PTW had a sterilizing effect against all tested microorganisms significantly. The MIC of PTW was a dilution ratio of 0.125 against E. faecalis and a dilution ratio of 0.25 against C. albicans and C. glabrata. No growth of microorganisms were observed in any of PTW experimental groups, that means the significant efficacy of PTW in all test-infected root canal models in vitro and in situ of the rat.
Conclusion: PTW showed a sterilizing effect against E. faecalis, C. albicans, and C. glabrata, even in root canals without obvious effect on oral mucosal tissue.
(Asian Pac J Dent 2017; 17: 23-30.)
Key Words: Candida, Enterococcus faecalis, plasma disinfection, root canal irrigation