title: Photodynamic Inactivation of Root Canal Bacteria by Light Activation through Human Dental Hard and Simulated Surrounding Tissue.
abstract: BACKGROUND
  Photodynamic inactivation of bacteria (PIB) may be a supportive antimicrobial approach for use in endodontics, but sufficient activation of photosensitizers (PS) in root canals is a critical point. Therefore, aim of this study was to evaluate the ability of PS absorbing blue (TMPyP) or red light (Methylene Blue; MB) for light activation through human dental hard and simulated surrounding tissue to inactivate root canal bacteria.
  
  
  METHODS
  A tooth model was fabricated with a human premolar and two molars in an acrylic resin bloc simulating the optical properties of a porcine jaw. The distal root canal of the first molar was enlarged to insert a glass tube (external diameter 2 mm) containing PS and stationary-phase Enterococcus faecalis. Both PS (10 μM) were irradiated for 120 s with BlueV (20 mW/cm(2); λem = 400-460 nm) or PDT 1200L (37.8 mW/cm(2); λem = 570-680 nm; both: Waldmann Medizintechnik), respectively. Irradiation parameters ensured identical numbers of photons absorbed by each PS. Three setups were chosen: irradiating the glass pipette only (G), the glass pipette inside the single tooth without (GT) and with (GTM) simulated surrounding tissues. Colony forming units (CFU) were evaluated. Transmission measurements of the buccal halves of hemisected mandibular first molars were performed by means of a photospectrometer.
  
  
  RESULTS
  PIB with both PS led to reduction by ≥ 5 log10 of E. faecalis CFU for each setup. From transmission measurements, a threshold wavelength λth for allowing an amount of light transmission for sufficient activation of PS was determined to be 430 nm.
  
  
  CONCLUSIONS
  This study can be seen as proof of principle that light activation of given intra-canal PS from outside a tooth may be possible at wavelengths ≥ 430 nm, facilitating clinical application of PIB in endodontics.
authors.affiliation: Department of Conservative Dentistry and Periodontology, University Medical Center Regensburg Regensburg, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Cieplik
authors.affiliation: Department of Conservative Dentistry and Periodontology, University Medical Center Regensburg Regensburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Pummer
authors.affiliation: Department of Conservative Dentistry and Periodontology, University Medical Center RegensburgRegensburg, Germany; Private PracticeGeiselhöring, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Leibl
authors.affiliation: Department of Dermatology, University Medical Center Regensburg Regensburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Regensburger
authors.affiliation: Department of Conservative Dentistry and Periodontology, University Medical Center RegensburgRegensburg, Germany; Department of Preventive, Restorative and Pediatric Dentistry, School of Dental Medicine, University of BernBern, Switzerland.
authors.forename: Gottfried
authors.initials: G
authors.lastname: Schmalz
authors.affiliation: Department of Conservative Dentistry and Periodontology, University Medical Center Regensburg Regensburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Buchalla
authors.affiliation: Department of Conservative Dentistry and Periodontology, University Medical Center Regensburg Regensburg, Germany.
authors.forename: Karl-Anton
authors.initials: KA
authors.lastname: Hiller
authors.affiliation: Department of Dermatology, University Medical Center Regensburg Regensburg, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Maisch
keywords: Enterococcus faecalis; endodontics; optical fiber; photodynamic; transmission