title: Electrochemical dissolution of nickel-titanium endodontic files induces periodontal ligament cell death.
abstract: BACKGROUND
  Fractured endodontic files present a major problem. A novel method has been proposed to retrieve fractured nickel-titanium (NiTi) endodontic files by using electrochemical dissolution. However, the effect of file dissolution on adjacent soft tissues such as the periodontal ligament (PDL) has not been investigated. The aim of this study was to determine the effects of the dissolution products on PDL fibroblasts.
  
  
  METHODS
  Endodontic files were dissolved in sodium fluoride (NaF) by passing a 50-mA current through the NiTi files while immersed in the NaF solution. NaF/NiTi solutions were diluted with minimal essential medium-α media containing 10% serum. PDL cells were treated for up to 24 hours, and cell viability was quantified by using calcein AM to label live cells and ethidium homodimer to label dead cells. This was repeated by using artificial saliva (AS) as an alternative to NaF.
  
  
  RESULTS
  NaF solution reduced PDL cell survival, and the NaF/NiTi solution further reduced PDL cell survival. AS alone did not reduce cell survival, whereas AS/NiTi solution reduced PDL cell survival. Particles that resulted from the electrochemical dissolution of NiTi files were highly cytotoxic.
  
  
  CONCLUSIONS
  Electrochemically dissolving NiTi files in NaF results in solutions that are cytotoxic to PDL fibroblasts. AS may be a less toxic alternative for dissolving NiTi files.
authors.affiliation: Department of Endodontics, Center of Excellence in Oral and Craniofacial Biology, Louisiana State University Health Science Center, School of Dentistry, New Orleans, Louisiana 70119, USA.
authors.forename: Quinn
authors.initials: Q
authors.lastname: Mitchell
authors.forename: Billie Gail
authors.initials: BG
authors.lastname: Jeansonne
authors.forename: Diana
authors.initials: D
authors.lastname: Stoute
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Lallier
mesh_terms: D018929:Cell Culture Techniques; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D011232:Chemical Precipitation; D003470:Culture Media; D003722:Dental Alloys / Q000737:chemistry / Q000633:toxicity*; D055664:Electrochemical Techniques; D004572:Electrolysis; D004868:Equipment Failure; D004996:Ethidium / Q000031:analogs & derivatives; D005347:Fibroblasts / Q000187:drug effects; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry / Q000633:toxicity*; D010513:Periodontal Ligament / Q000166:cytology / Q000187:drug effects*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012464:Saliva, Artificial / Q000737:chemistry; D012969:Sodium Fluoride / Q000737:chemistry; D012995:Solubility; D013997:Time Factors; D014025:Titanium / Q000737:chemistry / Q000633:toxicity*
chemical_list: D003470:Culture Media; D003722:Dental Alloys; D005452:Fluoresceins; D005456:Fluorescent Dyes; D012464:Saliva, Artificial; C040654:titanium nickelide; C085925:calcein AM; C018533:ethidium homodimer; D009532:Nickel; D012969:Sodium Fluoride; D014025:Titanium; D004996:Ethidium