title: Efficacy of reciprocating and rotary NiTi instruments for retreatment of curved root canals assessed by micro-CT.
abstract: OBJECTIVE
  To compare the efficacy of reciprocating and rotary NiTi-instruments in removing filling material from curved root canals using micro-computed tomography.
  
  
  METHODS
  Sixty curved root canals were prepared and filled with gutta-percha and sealer. After determination of root canal curvatures and radii in two directions as well as volumes of filling material, the teeth were assigned to three comparable groups (n = 20). Retreatment was performed using Reciproc, ProTaper Universal Retreatment or Hedström files. Percentages of residual filling material and dentine removal were assessed using micro-CT imaging. Working time and procedural errors were recorded. Statistical analysis was performed by variance procedures.
  
  
  RESULTS
  No significant differences amongst the three retreatment techniques concerning residual filling material were detected (P > 0.05). Hedström files removed significantly more dentine than ProTaper Universal Retreatment (P < 0.05), but the difference concerning dentine removal between both NiTi systems was not significant (P > 0.05). Reciproc and ProTaper Universal Retreatment were significantly faster than Hedström files (P = 0.0001). No procedural errors such as instrument fracture, blockage, ledging or perforation were detected for Hedström files. Three perforations were recorded for ProTaper Universal Retreatment, and in both NiTi groups, one instrument fracture occured.
  
  
  CONCLUSIONS
  Remnants of filling material were observed in all samples with no significant differences between the three techniques. Hedström files removed significantly more dentine than ProTaper Universal Retreatment, but no significant differences between both NiTi systems were detected. Procedural errors were observed with ProTaper Universal Retreatment and Reciproc.
authors.affiliation: Department of Preventive Dentistry Periodontology and Cariology, University Medical Center, Göttingen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Rödig
authors.forename: P
authors.initials: P
authors.lastname: Reicherts
authors.forename: F
authors.initials: F
authors.lastname: Konietschke
authors.forename: C
authors.initials: C
authors.lastname: Dullin
authors.forename: W
authors.initials: W
authors.lastname: Hahn
authors.forename: M
authors.initials: M
authors.lastname: Hülsmann
mesh_terms: D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging*; D004708:Endodontics / Q000295:instrumentation*; D009532:Nickel; D014025:Titanium; D055114:X-Ray Microtomography
chemical_list: D009532:Nickel; D014025:Titanium
keywords: ProTaper Universal Retreatment; Reciproc; curved root canals; gutta-percha; micro-CT; retreatment