title: Effects of self-adjusting file, Mtwo, and ProTaper on the root canal wall.
abstract: BACKGROUND
  The purpose of this ex vivo study was to observe the incidence of cracks in root dentin after root canal preparation with hand files, self-adjusting file (SAF), ProTaper, and Mtwo.
  
  
  METHODS
  One hundred extracted mandibular premolars with single canals were randomly selected. Two angulated radiographs were taken for each tooth, and the width of the canal was measured at 9 mm from the apex. Five groups of 20 teeth each were comparable in canal width. The control group was left unprepared. Four experimental groups were instrumented with hand files, ProTaper, Mtwo, and SAF. Roots were then sectioned horizontally and observed under a microscope. The presence of dentinal cracks and their location were noted. The difference between the experimental groups was analyzed with a χ(2) test.
  
  
  RESULTS
  No cracks were observed in the control group. In the experimental groups, ProTaper, Mtwo, and SAF caused cracks in 35%, 25%, and 10% of teeth, respectively. The hand-file group did not show any dentinal cracks (P < .0001). ProTaper and Mtwo caused more cracks than hand files (P < .05), but SAF did not (P > .05).
  
  
  CONCLUSIONS
  Instrumentation of root canals with SAF, Mtwo, and ProTaper could cause damage to root canal dentin. SAF has a tendency to cause less dentinal cracks as compared with ProTaper or Mtwo.
authors: Department of Endodontology, Academic Centre of Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors: Ellemieke S
authors: ES
authors: Hin
authors: Min-Kai
authors: MK
authors: Wu
authors: Paul R
authors: PR
authors: Wesselink
authors: Hagay
authors: H
authors: Shemesh
mesh_terms: D001641:Bicuspid / Q000473:pathology; D003786:Dental Pulp Cavity / Q000473:pathology*; D003804:Dentin / Q000473:pathology*; D004867:Equipment Design; D006801:Humans; D012388:Root Canal Irrigants / Q000008:administration & dosage; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D012973:Sodium Hypochlorite / Q000008:administration & dosage; D013499:Surface Properties; D007507:Therapeutic Irrigation / Q000379:methods; D019227:Tooth Apex / Q000473:pathology
chemical_list: D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite