title: Effect of Instrument Design and Access Outlines on the Removal of Root Canal Obturation Materials in Oval-shaped Canals.
abstract: BACKGROUND
  The aim of this study was to compare the effectiveness of TRUShape (TS) instruments with ProFile Vortex Blue (VB) instruments for the removal of obturation materials during retreatment of single-canal mandibular premolars performed through 2 access outlines.
  
  
  METHODS
  Initial root canal treatment was completed through a contracted endodontic cavity (CEC) design. Canals were instrumented to an F2 ProTaper instrument, obturated with warm lateral condensation of gutta-percha with AH Plus sealer, and allowed to set for 30 days at 37°C and 100% humidity. For retreatment, specimens were divided into 2 groups (n = 24) on the basis of access outline, CEC or traditional endodontic cavity (TEC). Retreatment was initiated by using ProTaper Retreatment instruments (D1-D3). Specimens were then stratified, further divided (n = 12), and reinstrumented up to TS 40 .06v or 40 .06 VB. Irrigation was performed by using 8.25% NaOCl and QMix 2in1. Retreatment time was recorded. Teeth were sectioned and photographed, and the percentage of remaining obturation materials was measured. Data were analyzed with Kruskal-Wallis analysis of variance for two-factor tests (α < 0.05).
  
  
  RESULTS
  The interaction between access design and instrument type showed that the combination of CEC-VB presented significantly higher amounts of remaining obturation materials on the canal surface when compared with TEC-VB, CEC-TS, and TEC-TS (P ≤ .05). None of these other combinations were different from each other (P > .05). Significantly more time was required for retreatment with CEC-TS (27.68 ± 1.4 minutes) than the other groups (P < .05).
  
  
  CONCLUSIONS
  Neither retreatment protocol was able to completely eliminate all obturation materials from the root canal surface of mandibular premolars. However, in the presence of a CEC access design, using TS instruments removed more obturating material in single-rooted, oval-shaped canals.
authors.affiliation: University of Tennessee Health Science Center College of Dentistry, Memphis, Tennessee.
authors.forename: Tuomas K
authors.initials: TK
authors.lastname: Niemi
authors.affiliation: University of Tennessee Health Science Center College of Dentistry, Memphis, Tennessee.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Marchesan
authors.affiliation: University of Tennessee Health Science Center College of Dentistry, Memphis, Tennessee. Electronic address: alloyd@uthsc.edu.
authors.forename: Adam
authors.initials: A
authors.lastname: Lloyd
authors.affiliation: Nova Southeastern University College of Dental Medicine, Davie, Florida.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Seltzer
mesh_terms: D001641:Bicuspid; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology; D004867:Equipment Design; D006801:Humans; D008334:Mandible; D008422:Materials Testing; D009532:Nickel; D019233:Retreatment / Q000379:methods; D012387:Root Canal Filling Materials; D012389:Root Canal Obturation / Q000295:instrumentation / Q000379:methods*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D014025:Titanium
chemical_list: D012387:Root Canal Filling Materials; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Endodontic cavity; ProFile Vortex Blue; TRUShape; instrumentation efficacy; nickel-titanium instrument; retreatment