title: Ultrasonic activation and chemical modification of photosensitizers enhances the effects of photodynamic therapy against Enterococcus faecalis root-canal isolates.
abstract: BACKGROUND
  The aim of this study was to evaluate the effect of photodynamic therapy (PDT) on Enterococcus faecalis biofilms in artificially infected root canals using modified photosensitizers and passive ultrasonic activation.
  
  
  METHODS
  Two hundred and seventy extracted human teeth with one root canal were instrumented utilizing ProTaper files, autoclaved, infected with E. faecalis T9 for 72 h and divided into different groups: irrigation with 3% sodium hypochlorite (NaOCl), 20% ethylenediaminetetraacetic acid (EDTA), or 20% citric acid, PDT without irrigation, PDT accompanied by irrigation with NaOCl, EDTA, or citric acid, PDT using an EDTA-based photosensitizer or a citric-acid-based photosensitizer and PDT with ultrasonic activation of the photosensitizer. A 15 mg/ml toluidine blue served as the photosensitizer, activated by a 100 mW LED light source. Sterile paper points were used for sampling the root canals and dentin chips were collected to assess the remaining contamination after treatment. Samples were cultured on blood agar plates and colony forming units were quantified.
  
  
  RESULTS
  PDT alone achieved a reduction in E. faecalis counts by 92.7%, NaOCl irrigation alone and combined with PDT by 99.9%. The antibacterial effects increased by the combination of irrigation using EDTA or citric acid and PDT compared to irrigation alone. More than 99% of E. faecalis were killed using PDT with the modified photosensitizers and ultrasonic activation.
  
  
  CONCLUSIONS
  NaOCl based disinfection achieved the highest antimicrobial effect. Using PDT with an EDTA-based or citric-acid-based phozosensitizer or activating the photosensitizer with ultrasound resulted in a significantly higher reduction in E. faecalis counts compared to conventional PDT.
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: Christian.tennert@uniklinik-freiburg.de.
authors.forename: C
authors.initials: C
authors.lastname: Tennert
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: annina83@gmx.net.
authors.forename: A M
authors.initials: AM
authors.lastname: Drews
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: vanessa_walther@gmx.net.
authors.forename: V
authors.initials: V
authors.lastname: Walther
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: Markus.altenburger@uniklinik-freiburg.de.
authors.forename: M J
authors.initials: MJ
authors.lastname: Altenburger
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: Lamprini.karygianni@uniklinik-freiburg.de.
authors.forename: L
authors.initials: L
authors.lastname: Karygianni
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: Thomas.wrbas@uniklinik-freiburg.de.
authors.forename: K T
authors.initials: KT
authors.lastname: Wrbas
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: Elmar.hellwig@uniklinik-freiburg.de.
authors.forename: E
authors.initials: E
authors.lastname: Hellwig
authors.affiliation: University of Freiburg-Medical Center, Department of Operative Dentistry and Periodontology, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address: Ali.al-ahmad@uniklinik-freiburg.de.
authors.forename: A
authors.initials: A
authors.lastname: Al-Ahmad
mesh_terms: D018441:Biofilms / Q000187:drug effects*; D019343:Citric Acid / Q000627:therapeutic use; D004492:Edetic Acid / Q000627:therapeutic use; D013293:Enterococcus faecalis / Q000187:drug effects*; D006801:Humans; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D018915:Root Canal Preparation / Q000379:methods; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D007507:Therapeutic Irrigation / Q000379:methods*; D014048:Tolonium Chloride / Q000627:therapeutic use; D014465:Ultrasonics / Q000379:methods*
chemical_list: D017319:Photosensitizing Agents; D014048:Tolonium Chloride; D019343:Citric Acid; D004492:Edetic Acid; D012973:Sodium Hypochlorite
keywords: Disinfection; Endodontic treatment; Enterococcus faecalis; Irrigation; Photodynamic therapy; Photosensitizer