title: Effect of modified nonequilibrium plasma with chlorhexidine digluconate against endodontic biofilms in vitro.
abstract: BACKGROUND
  Nonequilibrium plasma has been reported to effectively kill Enterococcus faecalis in endodontic biofilm compared with chlorhexidine digluconate (CHX). The purpose of this study was to evaluate the antimicrobial in vitro activity of modified nonequilibrium plasma with CHX against E. faecalis and multispecies biofilms on bovine dentin discs.
  
  
  METHODS
  Sterile bovine dentin discs were incubated with E. faecalis or a mixture of bacteria from human dental root canal infections to form 1- and 3-week-old biofilms. The specimens were subjected to nonequilibrium plasma, modified nonequilibrium plasma with CHX, and 2% CHX for 2- and 5-minute exposure. After treatment, the biofilms were stained with viability dyes and examined by confocal laser scanning microscopy and 3-dimensional reconstruction analysis. The proportions of bacterial cells killed by the treatments were calculated.
  
  
  RESULTS
  The 3-dimensional reconstruction images showed that 1- and 3-week-old biofilms adhered to bovine dentin discs. The proportions of dead cells increased significantly with the longer exposure in each treatment group (P < .05). Modified nonequilibrium plasma was the most effective in killing bacteria in E. faecalis and multispecies biofilms at both 2 and 5 minutes (P < .05). No significant difference was detected between nonequilibrium plasma and CHX groups (P > .05). Significantly more cells were killed in 1-week-old biofilms than in 3-week-old biofilms in all groups (P < .05).
  
  
  CONCLUSIONS
  The modified nonequilibrium plasma killed more bacteria than conventional nonequilibrium plasma and 2% CHX in E. faecalis and multispecies endodontic biofilms in vitro and thus shows promise as an additional tool in infection control during endodontic treatment.
authors.affiliation: Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Tianfeng
authors.initials: T
authors.lastname: Du
authors.forename: Qi
authors.initials: Q
authors.lastname: Shi
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.forename: Yingguang
authors.initials: Y
authors.lastname: Cao
authors.forename: Jingzhi
authors.initials: J
authors.lastname: Ma
authors.forename: Xinpei
authors.initials: X
authors.lastname: Lu
authors.forename: Zilan
authors.initials: Z
authors.lastname: Xiong
authors.forename: Markus
authors.initials: M
authors.lastname: Haapasalo
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects*; D002417:Cattle; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004396:Coloring Agents; D003786:Dental Pulp Cavity / Q000382:microbiology*; D003788:Dental Pulp Diseases / Q000382:microbiology; D003804:Dentin / Q000382:microbiology; D013293:Enterococcus faecalis / Q000187:drug effects*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D050296:Microbial Viability / Q000187:drug effects; D018613:Microscopy, Confocal / Q000379:methods; D058626:Plasma Gases / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000891:Anti-Infective Agents, Local; D004396:Coloring Agents; D058626:Plasma Gases; C010882:chlorhexidine gluconate; D002710:Chlorhexidine
keywords: Bacterial biofilm; Enterococcus faecalis; chlorhexidine digluconate; endodontic treatment; nonequilibrium plasma