title: Efficacy of D-RaCe and ProTaper Universal Retreatment NiTi instruments and hand files in removing gutta-percha from curved root canals - a micro-computed tomography study.
abstract: OBJECTIVE
  To compare the efficacy of two rotary NiTi retreatment systems and Hedström files in removing filling material from curved root canals.
  
  
  METHODS
  Curved root canals of 57 extracted teeth were prepared using FlexMaster instruments and filled with gutta-percha and AH Plus. After determination of root canal curvatures and radii in two directions, the teeth were assigned to three identical groups (n = 19). The root fillings were removed with D-RaCe instruments, ProTaper Universal Retreatment instruments or Hedström files. Pre- and postoperative micro-CT imaging was used to assess the percentage of residual filling material as well as the amount of dentine removal. Working time and procedural errors were recorded. Data were analysed using analysis of covariance and analysis of variance procedures.
  
  
  RESULTS
  D-RaCe instruments were significantly more effective than ProTaper Universal Retreatment instruments and Hedström files (P < 0.05). Hedström files removed significantly less dentine than the rotary NiTi systems (P < 0.0001). D-RaCe instruments were significantly faster compared to both other groups (P < 0.05). No procedural errors such as instrument fracture, blockage, ledging or perforation were detected in the Hedström group. In the ProTaper group, four instrument fractures and one lateral perforation were observed. Five instrument fractures were recorded for D-RaCe.
  
  
  CONCLUSIONS
  D-RaCe instruments were associated with significantly less residual filling material than ProTaper Universal Retreatment instruments and hand files. Hedström files removed significantly less dentine than both rotary NiTi systems. Retreatment with rotary NiTi systems resulted in a high incidence of procedural errors.
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cariology, University of Göttingen, Göttingen Centre for Statistics, University of Göttingen, Germany. troedig@med.uni-goettingen.de
authors.forename: T
authors.initials: T
authors.lastname: Rödig
authors.forename: T
authors.initials: T
authors.lastname: Hausdörfer
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: D003722:Dental Alloys / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000293:injuries / Q000648:ultrastructure*; D003804:Dentin / Q000648:ultrastructure; D004853:Epoxy Resins / Q000737:chemistry; D004867:Equipment Design; D004868:Equipment Failure; D006171:Gutta-Percha / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry; D019233:Retreatment; D012387:Root Canal Filling Materials / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D055114:X-Ray Microtomography
chemical_list: D003722:Dental Alloys; D004853:Epoxy Resins; D012387:Root Canal Filling Materials; C534916:epoxy resin-based root canal sealer; C040654:titanium nickelide; D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium