title: Torsional and Cyclic Fatigue Resistance of a New Nickel-Titanium Instrument Manufactured by Electrical Discharge Machining.
abstract: BACKGROUND
  The purpose of this study was to evaluate the torsional and cyclic fatigue resistance of the new Hyflex EDM OneFile (Coltene/Whaledent AG, Altstatten, Switzerland) manufactured by electrical discharge machining and compare the findings with the ones of Reciproc R25 (VDW, Munich, Germany) and WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland).
  
  
  METHODS
  One hundred-twenty new Hyflex EDM OneFile (#25/0.08), Reciproc R25, and WaveOne Primary files were used. Torque and angle of rotation at failure of new instruments (n = 20) were measured according to ISO 3630-1 for each brand. Cyclic fatigue resistance was tested measuring the number of cycles to failure in an artificial stainless steel canal with a 60° angle and a 3-mm radius of curvature. Data were analyzed using the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons. The fracture surface of each fragment was examined with a scanning electron microscope.
  
  
  RESULTS
  The cyclic fatigue of Hyflex EDM was significantly higher than the one of Reciproc R25 and WaveOne Primary (P < .05 and P < .001, respectively). Hyflex EDM showed a lower maximum torque load (P < .05) but a significantly higher angular rotation (P < .0001) to fracture than Reciproc R25 and WaveOne Primary. No significant difference was found comparing the maximum torque load, angular rotation, and cyclic fatigue of Reciproc R25 and WaveOne Primary (P > .05).
  
  
  CONCLUSIONS
  The new Hyflex EDM instruments (controlled memory wire) have higher cyclic fatigue resistance and angle of rotation to fracture but lower torque to failure than Reciproc R25 and WaveOne Primary files (M-wire for both files).
authors.affiliation: Department of General Surgery and Surgical-Medical Specialties, University of Catania, Catania, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Pedullà
authors.affiliation: Department of Industrial Engineering, University of Catania, Catania, Italy. Electronic address: flosavio@dii.unict.it.
authors.forename: Fabio
authors.initials: F
authors.lastname: Lo Savio
authors.affiliation: MATIS, Institute of Microelectronics and Microsystems, National Research Council, Catania, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Boninelli
authors.affiliation: Department of Endodontics, Sapienza University of Rome, Rome, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Plotino
authors.affiliation: Department of Endodontics, Sapienza University of Rome, Rome, Italy.
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Grande
authors.affiliation: Department of Industrial Engineering, University of Catania, Catania, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: La Rosa
authors.affiliation: Department of General Surgery and Surgical-Medical Specialties, University of Catania, Catania, Italy.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Rapisarda
mesh_terms: D003722:Dental Alloys; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D014025:Titanium; D019415:Torque
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Cyclic fatigue; Hyflex EDM; M-wire; electrical discharge machining; torsional resistance