title: Dentinal microcrack formation during root canal preparations by different NiTi rotary instruments and the self-adjusting file.
abstract: BACKGROUND
  The purpose of this study was to compare dentinal microcrack formation while using hand files (HFs), 4 brands of nickel-titanium (NiTi) rotary files and the self-adjusting file.
  
  
  METHODS
  One hundred forty mandibular first molars were selected: 20 teeth were left unprepared and served as control, and the remaining 120 teeth were divided into 6 groups. HFs, HERO Shaper (HS; Micro-Mega, Besancon, France), Revo-S (RS, Micro-Mega), Twisted File (TF; SybronEndo, Orange, CA), ProTaper (PT, Dentsply Maillefer), and SAFs were used to prepare the 2 mesial canals. Roots were then sectioned 3, 6, and 9 mm from the apex, and the cut surface was observed under a microscope and checked for the presence of dentinal microcracks.
  
  
  RESULTS
  The control, HF, and SAF groups did not show any microcracks. In roots prepared with the HS, RS, TF, and PT, dentinal microcracks were observed in 60%, 25%, 44%, and 30% of teeth, respectively. There was a significant difference between the control/HF/SAF group and the 4 NiTi rotary instrument groups (P < .0001). However, no significant difference was found among the 4 NiTi rotary instruments (P > .005).
  
  
  CONCLUSIONS
  All rotary files created microcracks in the root dentin, whereas the SAF file and hand instrumentation presented with satisfactory results with no dentinal microcracks.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, University of Cukurova, Adana, Turkey.
authors.forename: Oguz
authors.initials: O
authors.lastname: Yoldas
authors.forename: Sehnaz
authors.initials: S
authors.lastname: Yilmaz
authors.forename: Gokhan
authors.initials: G
authors.lastname: Atakan
authors.forename: Cihan
authors.initials: C
authors.lastname: Kuden
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Kasan
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000293:injuries*; D003804:Dentin / Q000293:injuries*; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D008963:Molar; D009532:Nickel / Q000737:chemistry*; D012388:Root Canal Irrigants / Q000008:administration & dosage; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*; D012399:Rotation; D012973:Sodium Hypochlorite / Q000008:administration & dosage; D013499:Surface Properties; D007507:Therapeutic Irrigation / Q000295:instrumentation; D014025:Titanium / Q000737:chemistry*; D019415:Torque; D014732:Vibration
chemical_list: D003722:Dental Alloys; D012388:Root Canal Irrigants; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite