title: Comparison of autoclaving effects on torsional deformation and fracture resistance of three innovative endodontic file systems.
abstract: BACKGROUND
  Recent innovative manufacturing techniques have produced nickel-titanium (NiTi) rotary instruments with reports of superior properties compared with standard NiTi files. These include Profile Vortex made from M-Wire (PV), Twisted Files (TF), and 10 Series files made from CM Wire (CM). Sterilization is recommended before use and is repeated if files are reused and/or carried forward between cases. The purpose for this study was to compare the effects of multiple autoclaving cycles on the torsional load resistance of these 3 new rotary endodontic files.
  
  
  METHODS
  PV, TF, and CM files (n = 100; size 25/.04) were divided into 5 groups (n = 20). Files were steam autoclaved for 1, 2, 3, and 7 sterilization cycles. A control group was not subjected to autoclaving. Files were tested in a torsiometer in general accordance with ISO 3630-1 standards. Torsional load and degrees of rotation to failure were recorded. Mean data were analyzed by using Kruskal-Wallace/Dunn post hoc tests (P < .05).
  
  
  RESULTS
  Autoclave cycles had no significant overall effect on file performance for any of the instrument systems tested. PV and CM displayed significantly greater resistance to torsional load than TF (P < .001) but were not different from each other (P > .05). Angular deflection values for TF and CM were significantly higher than for PV (P < .001), with TF demonstrating greater rotational distortion than CM (P < .05).
  
  
  CONCLUSIONS
  Under the conditions of this study, repeated steam autoclaving did not affect torsional resistance for unused files of the systems evaluated. In addition, CM Wire files might have a combined advantage of greater torsional strength and high deformation before failure.
authors: Department of Endodontics, Keesler Medical Center, Keesler Air Force Base, Mississippi, USA.
authors: Rhett B
authors: RB
authors: Casper
authors: Howard W
authors: HW
authors: Roberts
authors: Mark D
authors: MD
authors: Roberts
authors: Van T
authors: VT
authors: Himel
authors: Brian E
authors: BE
authors: Bergeron
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D003799:Dental Stress Analysis; D004548:Elasticity; D017743:Equipment Reuse; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D013227:Steam; D013242:Sterilization / Q000379:methods; D014025:Titanium; D054159:Torsion, Mechanical
chemical_list: D003722:Dental Alloys; D013227:Steam; C040654:titanium nickelide; C093824:Martensite; D009532:Nickel; D014025:Titanium