title: Effect of Different Torque Settings on Crack Formation in Root Dentin.
abstract: BACKGROUND
  The aim of the present study was to observe the incidence of cracks in root canal dentin using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland) at low- and high-torque settings.
  
  
  METHODS
  Sixty-nine mandibular premolar teeth that had been extracted for different reasons were selected. The teeth were divided into 3 groups: an unprepared control group, a low-torque settings group (SX = 3, S1 = 2, S2 = 1, F1 = 1.5, F2 = 2, F3 = 2, F4 = 2 N/cm), and a high-torque settings group (SX = 4, S1 = 4, S2 = 1.5, F1 = 2, F2 = 3, F3 = 3, F4 = 3 N/cm). After a root canal procedure, all the teeth were horizontally sectioned at 2, 4, 6, and 8 mm from the apex. Then, under a stereomicroscope, all the slices were examined to determine the presence of cracks. A chi-square test was used for data analysis. The significance level was set at P = .05.
  
  
  RESULTS
  There were no cracks in the unprepared control group. Vertical root fractures were not observed in any of the groups. There were significantly fewer cracks (17.4% of the sections) in the low-torque group than in the high-torque group (29.4% of the sections) (P < .05).
  
  
  CONCLUSIONS
  In this in vitro study, the instrumentation of root canals with the ProTaper Universal instrument caused more crack formation in root canal dentin at high-torque than at low-torque settings.
authors.affiliation: Department of Pedodontics, Faculty of Dentistry, İzmir Katip Çelebi University, İzmir, Turkey. Electronic address: asimdane@hotmail.com.
authors.forename: Asım
authors.initials: A
authors.lastname: Dane
authors.affiliation: Department of Endodontics, Faculty of Dentistry, İzmir Katip Çelebi University, İzmir, Turkey.
authors.forename: Ismail Davut
authors.initials: ID
authors.lastname: Capar
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Atatürk University, Erzurum, Turkey.
authors.forename: Hakan
authors.initials: H
authors.lastname: Arslan
authors.affiliation: Department of Pedodontics, Faculty of Dentistry, İzmir Katip Çelebi University, İzmir, Turkey.
authors.forename: Merve
authors.initials: M
authors.lastname: Akçay
authors.affiliation: Department of Endodontics, Faculty of Dentistry, İzmir Katip Çelebi University, İzmir, Turkey.
authors.forename: Banu
authors.initials: B
authors.lastname: Uysal
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000293:injuries*; D003804:Dentin / Q000737:chemistry* / Q000293:injuries; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D012390:Root Canal Therapy / Q000295:instrumentation* / Q000379:methods; D012399:Rotation; D014025:Titanium / Q000737:chemistry; D014082:Tooth Fractures; D014092:Tooth Root / Q000737:chemistry* / Q000293:injuries; D019415:Torque
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Cracks; ProTaper Universal; controlled memory; dentinal damage; root canal instrumentation; root fracture; rotary nickel-titanium instruments