title: Comparison of debris extruded apically and working time used by ProTaper Universal rotary and ProTaper retreatment system during gutta-percha removal.
abstract: OBJECTIVE
  The aim of this study was to evaluate the in vitro action of ProTaper retreatment files and ProTaper Universal in the retreatment of mandibular premolars.
  
  
  METHODS
  The amount of debris extruded apically was measured and the time to reach the working length and to complete the removal of gutta-percha was observed. Thirty teeth had their canals prepared using ProTaper Universal files and were obturated by the single cone technique. The teeth were then stored at 37ºC in a humid environment for 7 days. During the use of the rotary instruments for root canal filling removal, the apical portions of the teeth were attached to the open end of a resin tube to collect the apically extruded debris.
  
  
  RESULTS
  ProTaper Universal files were significantly faster (p=0.0011) than the ProTaper retreatment files to perform gutta-percha removal, but no significant difference was found between the files regarding the time to reach the working length or the amount of apical extrusion.
  
  
  CONCLUSIONS
  ProTaper Universal rotary had better results for endodontic retreatment, and both techniques promote similar apical extrusion of debris.
authors.affiliation: University Cruzeiro do Sul, São Paulo, SP, Brazil.
authors.forename: Mary Kinue Nakamune
authors.initials: MK
authors.lastname: Uezu
authors.forename: Maria Leticia Borges
authors.initials: ML
authors.lastname: Britto
authors.forename: Cleber K
authors.initials: CK
authors.lastname: Nabeshima
authors.forename: Raul Capp
authors.initials: RC
authors.lastname: Pallotta
mesh_terms: D003762:Dental Instruments; D006171:Gutta-Percha; D006801:Humans; D066298:In Vitro Techniques; D009532:Nickel; D019233:Retreatment / Q000295:instrumentation; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D018709:Statistics, Nonparametric; D013997:Time Factors; D014025:Titanium
chemical_list: D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium