title: Master file size and apical transportation in severely curved root canals.
abstract: OBJECTIVE
  A curvature leads to asymmetrical removal of root dentine, which results in an increase in the incidence of canal transportation. The aim of this study was to evaluate the effect of master apical file (MAF) size on the apical transportation (AT) of teeth with severe canal curvatures.
  
  
  METHODS
  Thirty-six mesial roots of human mandibular first molars were included. Inclusion criteria consisted of mature roots with closed apices, absence of carious lesions and resorptions, and root canal curvatures (CC) of 45 degrees < CC < 60 degrees. The root canals were prepared using a crown-down pressureless technique. The samples were equally divided into groups A, B, and C based on MAF size: group A: MAF size equivalent to #20; group B: MAF size equivalent to #25, and group C: MAF size equivalent to #30. Cone beam computed tomography was used to evaluate the AT.
  
  
  RESULTS
  There were no statistically significant differences in the AT between the canals with different curvature angles up to MAF size #30 (P = 0.55).
  
  
  CONCLUSIONS
  Using flexible hand files for canal preparation, an increase in MAF size up to #30 does not significantly influence AT in severely curved canals.
authors.affiliation: Department of Endodontics, Mashhad University of Medical Sciences, Iran.
authors.forename: S
authors.initials: S
authors.lastname: Moradi
authors.forename: R
authors.initials: R
authors.lastname: Disfani
authors.forename: H
authors.initials: H
authors.lastname: Baziar
authors.forename: F
authors.initials: F
authors.lastname: Daneshvar
authors.forename: H
authors.initials: H
authors.lastname: Jafarzadeh
mesh_terms: D019412:Anatomy, Cross-Sectional / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D003786:Dental Pulp Cavity / Q000473:pathology*; D003804:Dentin / Q000473:pathology*; D004492:Edetic Acid / Q000627:therapeutic use; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008963:Molar / Q000473:pathology; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation*; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D019227:Tooth Apex / Q000473:pathology
chemical_list: D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite