title: Comparison of hand and rotary instrumentation for removing gutta-percha from previously treated curved root canals: a microcomputed tomography study.
abstract: OBJECTIVE
  To compare the efficacy of hand and rotary nickel-titanium (NiTi) instruments in removing filling material from curved root canals of root filled teeth with unknown preparation parameters.
  
  
  METHODS
  Ninety mandibular molars with root fillings in curved root canals and homogenous root canal filling extending to 0-2 mm short of the radiographic apex were selected. Root canal curvatures and radii were measured in two directions and microcomputed tomography (micro-CT) scans were used to determine preoperative volumes of the filling material. Subsequently, the teeth were assigned to two identical groups (n = 14). The root fillings were removed with Hedström files or FlexMaster NiTi rotary instruments. 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 compared using analysis of covariance and analysis of variance procedures.
  
  
  RESULTS
  Root canals retreated with Hedström files were associated with less remaining filling material compared with FlexMaster instruments (P < 0.05). Both retreatment techniques removed similar amounts of dentine with no significant differences (P > 0.05). FlexMaster instruments were significantly faster than Hedström files (P < 0.05). No procedural errors were detected in the Hedström group, whilst three instruments fractured in the FlexMaster group.
  
  
  CONCLUSIONS
  Hand instrumentation resulted in significantly less residual filling material than retreatment with rotary NiTi instruments. Dentine removal was not significantly different for both techniques. FlexMaster NiTi rotary files were significantly faster than Hedström files, but were associated with a higher risk of instrument fracture.
authors.affiliation: Department for Preventive Dentistry, Periodontology and Cariology, University of Göttingen, Göttingen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Rödig
authors.forename: J
authors.initials: J
authors.lastname: Kupis
authors.forename: F
authors.initials: F
authors.lastname: Konietschke
authors.forename: C
authors.initials: C
authors.lastname: Dullin
authors.forename: S
authors.initials: S
authors.lastname: Drebenstedt
authors.forename: M
authors.initials: M
authors.lastname: Hülsmann
mesh_terms: D003762:Dental Instruments; D006171:Gutta-Percha / Q000302:isolation & purification*; D012387:Root Canal Filling Materials / Q000302:isolation & purification*; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D012387:Root Canal Filling Materials; D006171:Gutta-Percha
keywords: FlexMaster; Hedström files; curved root canals; gutta-percha; micro-CT; retreatment