title: Fracture resistance of retreated roots using different retreatment systems.
abstract: OBJECTIVE
  This study was designed to evaluate the fracture resistance of retreated roots using different rotary retreatment systems.
  
  
  METHODS
  Forty eight freshly extracted human canine teeth with single straight root canals were instrumented sequentially increasing from size 30 to a size 55 using K-files whit a stepback technique. The teeth were randomly divided into three experimental and one control groups of 12 specimens each. The root canals were filled using cold lateral compaction of gutta-percha and AH Plus (Dentsply Detrey, Konstanz, Germany) sealer in experimental groups. Removal of gutta-percha was performed with the following devices and techniques: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), R-Endo (Micro-Mega, Besançon, France), and Mtwo (Sweden & Martina, Padova, Italy) rotary retreatment systems. Control group specimens were only instrumented, not filled or retreated. The specimens were then mounted in copper rings, were filled with a self-curing polymethylmethacrylate resin, and the force required to cause vertical root fracture was measured using a universal testing device. The force of fracture of the roots was recorded and the results in the various groups were compared. Statistical analysis was accomplished by one-way ANOVA and a post hoc Tukey tests.
  
  
  RESULTS
  There were statistically significant differences between the control and experimental groups (P<.05). However, there were no significant differences among the experimental groups.
  
  
  CONCLUSIONS
  Based on the results, all rotary retreatment techniques used in this in vitro study produced similar root weakness.
authors.affiliation: Akdeniz University, Faculty of Dentistry, Department of Endodontics, Antalya, Turkey.
authors.forename: Kursat
authors.initials: K
authors.lastname: Er
authors.forename: Tamer
authors.initials: T
authors.lastname: Tasdemir
authors.forename: Seyda Herguner
authors.initials: SH
authors.lastname: Siso
authors.forename: Davut
authors.initials: D
authors.lastname: Celik
authors.forename: Sabri
authors.initials: S
authors.lastname: Cora