title: Synchrotron-based Phase Contrast-enhanced Micro-Computed Tomography Reveals Delaminations and Material Tearing in Water-expandable Root Fillings Ex Vivo.
abstract: BACKGROUND
  This study evaluated the integrity of calcium silicate sealer-based fillings made with hygro-expandable cones (HEC) that are commercially known as CPoint or Smartpoint.
  
  
  METHODS
  Fourteen human canines were prepared according to a standardized, conventional endodontic treatment protocol and filled with the HEC/calcium silicate sealer. Three-dimensional imaging was performed with laboratory micro-computed tomography (μCT) at its highest resolution and was compared with synchrotron phase contrast-enhanced μCT (PCE-CT) scans of the treatment extending 1-7 mm from the apex. Conventional destructive optical microscopy validated observations by comparison with virtual slices in the tomographic data.
  
  
  RESULTS
  Conventional laboratory μCT at 10-μm resolution did not reveal the existing voids and defects within the root canal fillings. PCE-CT revealed elongated interfacial delamination localized mainly at the HEC-sealer interface forming extended through-and-through gaps along the root canal filling.
  
  
  CONCLUSIONS
  Endodontic studies that use conventional laboratory μCT may underestimate thin defects and delamination within root canal fillings made with HEC because of limited resolution and contrast of laboratory-based broad-spectrum low intensity x-ray sources. These limitations favor use of high-brilliance, monochromatic synchrotron-based PCE-CT to reveal the important micrometer details within large (millimeter sized) samples. PCE-CT revealed the existence of a range of significant structural defects in recently placed HEC fillings, confirmed by optical microscopy after physical sectioning. Substantial delamination spanning 20%-40% of the circumferential interface as well as other structural defects were identified within root canal fillings made of HEC and calcium silicate sealer.
authors.affiliation: Department of Endodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands. Electronic address: a.moinzadeh@acta.nl.
authors.forename: Amir T
authors.initials: AT
authors.lastname: Moinzadeh
authors.affiliation: Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Lydia
authors.initials: L
authors.lastname: Farack
authors.affiliation: Helmholtz-Zentrum Geesthacht (HZG), Geesthacht, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Wilde
authors.affiliation: Department of Endodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors.forename: Hagay
authors.initials: H
authors.lastname: Shemesh
authors.affiliation: Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Zaslansky
mesh_terms: D019412:Anatomy, Cross-Sectional; D017610:Calcium Compounds; D003481:Cuspid / Q000000981:diagnostic imaging; D003804:Dentin / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012388:Root Canal Irrigants; D012389:Root Canal Obturation / Q000379:methods; D018915:Root Canal Preparation / Q000295:instrumentation; D017640:Silicates / Q000737:chemistry; D017356:Synchrotrons / Q000295:instrumentation*; D019227:Tooth Apex / Q000000981:diagnostic imaging / Q000648:ultrastructure; D014867:Water / Q000737:chemistry*; D055114:X-Ray Microtomography / Q000295:instrumentation* / Q000379:methods*
chemical_list: D017610:Calcium Compounds; D012387:Root Canal Filling Materials; D012388:Root Canal Irrigants; D017640:Silicates; D014867:Water; C031293:calcium silicate
keywords: Calcium silicate sealer; hydro-expandable cone; root canal fillings; water sorption; μCT