title: Ex Vivo Comparison of Mtwo and RaCe Rotary File Systems in Root Canal Deviation: One File Only versus the Conventional Method.
abstract: OBJECTIVE
  Cleaning and shaping of the root canal system is an important step in endodontic therapy. New instruments incorporate new preparation techniques that can improve the efficacy of cleaning and shaping. The aim of this study was to compare the efficacy of Mtwo and RaCe rotary file systems in straightening the canal curvature using only one file or the conventional method.
  
  
  METHODS
  Sixty mesial roots of extracted human mandibular molars were prepared by RaCe and Mtwo nickel-titanium (NiTi) rotary files using the conventional and only one rotary file methods. The working length was 18 mm and the curvatures of the root canals were between 15-45°. By superimposing x-ray images before and after the instrumentation, deviation of the canals was assessed using Adobe Photoshop CS3 software. Preparation time was recorded. Data were analyzed using three-way ANOVA and Tukey's post hoc test.
  
  
  RESULTS
  There were no significant differences between RaCe and Mtwo or between the two root canal preparation methods in root canal deviation in buccolingual and mesiodistal radiographs (P>0.05). Changes of root canal curvature in >35° subgroups were significantly more than in other subgroups with smaller canal curvatures. Preparation time was shorter in one file only technique.
  
  
  CONCLUSIONS
  According to the results, the two rotary systems and the two root canal preparation methods had equal efficacy in straightening the canals; but the preparation time was shorter in one file only group.
authors.affiliation: Assistant Professor, School of Dentistry, AJA University of Medical Sciences, Tehran, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Aminsobhani
authors.affiliation: Associate Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Endodontics, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hasan
authors.initials: H
authors.lastname: Razmi
authors.affiliation: Assistant Professor, Department of Endodontics, School of Dentistry, Gilan University of Medical Sciences, Rasht, Iran.
authors.forename: Solmaz
authors.initials: S
authors.lastname: Nozari
keywords: Instrumentation; Root Canal Preparation; Transportation