title: Identification of root filling interfaces by microscopy and tomography methods.
abstract: OBJECTIVE
  To assess differences in observed cross-sectional areas of root canals and filling materials, as imaged by three microscopy and two tomography methods.
  
  
  METHODS
  Six roots filled with laterally compacted Gutta-percha and AH26 were scanned with phase-contrast enhanced microtomography in a synchrotron facility. Reconstructed virtual slices were compared with sections of both wet and acrylic-embedded roots, evaluated also by light and electron microscopy (EM) and laboratory-based microtomography (μCT). The different contrasts of Gutta-percha, voids, sealer and root dentine were identified and correlated. Inner canal border, outer Gutta-percha rim and the external margin of a void were manually delineated, and the enclosed areas were repeatedly measured by three observers. Interobserver and interimaging method differences were tested by 2-way anova with Bonferroni adjustments (P < 0.05). Percentages of Gutta-percha-filled canal areas (PGP) were determined.
  
  
  RESULTS
  Phase-contrast enhanced microtomography revealed internal interfaces and detailed 3D volumes of accentuated voids as well as micrometre-sized particles and gaps within the treated roots. Overestimates in the cross-sectional areas were obtained by light microscopy, whereas underestimates were obtained by μCT and EM. Differences exceeded 40%; however, PGP values by all methods were within 5% for the same slice. Differences between observers were sometimes significant, but they were not method related (<3%).
  
  
  CONCLUSIONS
  Phase-contrast enhanced microtomography is a powerful non-destructive ex vivo investigation method for studying the interfaces within root canals and filling materials at a micrometre resolution. The method does not require damage-prone sectioning/polishing during sample preparation procedures. Caution should be used when quantifying the extent of Gutta-percha in root fillings by measurements using μCT, light and EM.
authors.affiliation: Department of Biomaterials, Max-Planck Institute of Colloids and Interfaces, Potsdam, Germany. paul.zaslansky@mpikg.mpg.de
authors.forename: P
authors.initials: P
authors.lastname: Zaslansky
authors.forename: P
authors.initials: P
authors.lastname: Fratzl
authors.forename: A
authors.initials: A
authors.lastname: Rack
authors.forename: M-K
authors.initials: MK
authors.lastname: Wu
authors.forename: P R
authors.initials: PR
authors.lastname: Wesselink
authors.forename: H
authors.initials: H
authors.lastname: Shemesh
mesh_terms: D000704:Analysis of Variance; D019412:Anatomy, Cross-Sectional; D018772:Dental Marginal Adaptation / Q000592:standards*; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging* / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D008858:Microscopy, Phase-Contrast; D012387:Root Canal Filling Materials / Q000592:standards*; D012389:Root Canal Obturation / Q000592:standards*; D018709:Statistics, Nonparametric; D055114:X-Ray Microtomography / Q000295:instrumentation / Q000379:methods*
chemical_list: D012387:Root Canal Filling Materials