title: Efficacy of ProTaper and Mtwo Retreatment Files in Removal of Gutta-percha and GuttaFlow from Root Canals.
abstract: BACKGROUND
  The aim of this in vitro study was to compare the efficacy of ProTaper retreatment (ProTaper R) and Mtwo retreatment (Mtwo R) files in removing gutta-percha and GuttaFlow from endodontically treated straight root canals.
  
  
  METHODS
  The root canals of 60 human mandibular single-rooted premolars were prepared and randomly divided into two groups (n=30). In groups A and B the root canals were obturated using lateral condensation of gutta-percha plus AH 26 and GuttaFlow, respectively. The canal orifices were temporarily sealed and the roots were incubated for 3 months at 37(º)C and 100% humidity. Primary cone-beam computed tomography (CBCT) images were taken after incubation period. The specimens in each group were randomly divided into two subgroups (n=15). ProTaper R files (D1, D2, and D3) were used in groups A1 and B1 while Mtwo R files (25/0.05 and 15/0.05) were used in groups A2 and B2. The time required to extirpate the root filling was also recorded. After retreatment, another CBCT scan was taken at the same position. The volume of remaining filling materials inside the canals was calculated before and after retreatment. The data was analyzed using the two-way ANOVA and independent t-test.
  
  
  RESULTS
  The remaining filling materials in the canals treated with ProTaper were less than Mtwo. The remaining volume of GuttaFlow was less than gutta-percha regardless of the system applied. Mtwo R files removed root fillings faster than ProTaper R.
  
  
  CONCLUSIONS
  ProTaper R removed filling material more efficiently compared to Mtwo R which required less time to remove root filling material.
authors.affiliation: Dental Research Center, Department of Endodontics, Dental School, Tehran University of Medical Sciences and Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran;
authors.forename: Sedigheh
authors.initials: S
authors.lastname: Khedmat
authors.affiliation: Department of Prosthodontics, Dental School, Tehran University of Medical Sciences, Tehran, Iran;
authors.forename: Abbas
authors.initials: A
authors.lastname: Azari
authors.affiliation: Research Center for Caries Prevention, Dentistry Research Institute, Department of Community Oral Health, Dental School, Tehran University of Medical Sciences, Tehran, Iran;
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Shamshiri
authors.affiliation: Dental School, Tehran University of Medical Sciences, Tehran, Iran;
authors.forename: Mehdi
authors.initials: M
authors.lastname: Fadae
authors.affiliation: Department of Dental Radiology, Dental school, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hoorieh
authors.initials: H
authors.lastname: Bashizadeh Fakhar
keywords: Gutta-Percha; Mtwo Retreatment Files; ProTaper Retreatment Files; Root Canal Retreatment