title: An in vitro CT Comparison of Gutta-Percha Removal with Two Rotary Systems and Hedstrom Files.
abstract: BACKGROUND
  To evaluate the efficacy of NiTi mechanical rotary instrumentation and Hedstrom file for gutta-percha/sealer removal computed tomography (CT) was utilized in vitro.
  
  
  METHODS
  Thirty extracted human single rooted teeth, each with a single canal were selected. The samples were decoronated with a double faced diamond disk to have 17-mm root; teeth roots were instrumented with K-files up to master apical file #30 using step back technique. Samples were obturated using cold lateral condensation of gutta-percha and AH Plus root canal sealer. The teeth were then randomly divided into three groups of 10 specimens each. After 2 weeks 3-dimensional images of the roots were obtained by CT and the volume of root filling mass was measured. All the canals were then retreated by either the ProTaper retreatment files, Mtwo retreatment files or Hedstrom files. The canals were irrigated with 2 mL of 2.5% sodium hypochlorite irrigating solution during each change of instrument. The volume of remaining filling materials after the retreatment procedures was assessed by CT. Statistical analysis was performed with one-way ANOVA and Tukey's post hoc test.
  
  
  RESULTS
  Neither of studied systems completely removed the root filling material. No significant difference was observed between the rotary systems. The volume of remaining filling materials was significantly less in rotary instrumentation than hand files. There was no significant difference for debris extruded from the apical foramen between the groups.
  
  
  CONCLUSIONS
  Under the experimental conditions, Mtwo and ProTaper retreatment files left less gutta-percha and sealer than H files; however, complete removal of filling materials was not achieved by the three systems investigated.
authors.affiliation: Department of Conservative Dentistry and Endodontics, Maulana Azad Institute of Dental Sciences, New Delhi, India.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Yadav
authors.forename: Makonahalli Jaganath
authors.initials: MJ
authors.lastname: Bharath
authors.forename: Chickmagravalli Krishnegowda
authors.initials: CK
authors.lastname: Sahadev
authors.forename: Praveen Kumar
authors.initials: PK
authors.lastname: Makonahalli Ramachandra
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Rao
authors.forename: Ambereen
authors.initials: A
authors.lastname: Ali
authors.forename: Shahnawaz
authors.initials: S
authors.lastname: Mohamed
keywords: Computed Tomography; Instrumentation; NiTi Files; Root Canal Retreatment