title: The effect of cervical preflaring using different rotary nickel-titanium systems on the accuracy of apical file size determination.
abstract: BACKGROUND
  An exact determination of the apical root canal diameter is crucial for correct cleaning and shaping of a root canal. The aim of this study was to investigate the discrepancies of the initial apical root canal diameter and the diameter that is measured by the initial apical file (IAF) after cervical flaring using current rotary nickel-titanium systems.
  
  
  METHODS
  Mesiobuccal canals of 40 extracted mandibular molars were randomly assigned to four groups. In the first group, root canals were not flared. Root canals of the other groups were preflared using FlexMaster (VDW, Munich, Germany), ProTaper (Dentsply, Konstanz, Germany), or RaCe (FKG Dentaire, Genf, Switzerland) instruments. The tooth length was determined by inserting an ISO 06 K-file to the apical foramen. The working length (WL) was set 1 mm short of the apical foramen. File sizes were increased after binding sensation was felt at the WL. Transversal sections of the WL regions were examined under stereomicroscope, and the diameter of the root canal and the IAF at WL were assessed.
  
  
  RESULTS
  Canals preflared with RaCe instruments had the lowest discrepancy between the apical root canal diameter and the IAF diameter (15.7 ± 9.7 μm) followed by ProTaper (22.2 ± 11.0 μm) and FlexMaster (35.0 ± 17.2 μm).
  
  
  CONCLUSIONS
  Preflaring of root canals prevents underestimation of the actual apical root canal diameter. The type of instruments used for preflaring show differences on the accuracy of IAF determination. Preflaring with larger tapered instruments leads to a more accurate apical sizing, and this information is crucial concerning the appropriate final diameter for complete apical shaping.
authors.affiliation: Department of Operative Dentistry and Periodontology, University School and Dental Hospital, Albert-Ludwigs-University Freiburg, Freiburg i. Br, Germany. christian.tennert@uniklinik-freiburg.de
authors.forename: Christian
authors.initials: C
authors.lastname: Tennert
authors.forename: Josef
authors.initials: J
authors.lastname: Herbert
authors.forename: Markus Jörg
authors.initials: MJ
authors.lastname: Altenburger
authors.forename: Karl-Thomas
authors.initials: KT
authors.lastname: Wrbas
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D006801:Humans; D008334:Mandible; D008963:Molar; D009532:Nickel; D009811:Odontometry; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D018709:Statistics, Nonparametric; D014025:Titanium; D019227:Tooth Apex / Q000033:anatomy & histology*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium