title: Cyclic fatigue resistance of four nickel-titanium rotary instruments: a comparative study.
abstract: OBJECTIVE
  The aim of this study is to investigate cyclic fatigue resistance of four nickel - titanium rotary (NTR) instruments produced by a new method or traditional grinding processes.
  
  
  METHODS
  FOUR NTR INSTRUMENTS FROM DIFFERENT BRANDS WERE SELECTED: group 1. Twisted File produced by a new thermal treatment of nickel - titanium alloy; group 2. Revo S SU; group 3. Mtwo and group 4. BioRaCe BR3 produced by traditional grinding processes. A total of 80 instruments (20 for each group) were tested for cyclic fatigue resistance inside a curved artificial canal with a 60 degree angle of curvature and 5 mm radius of curvature. Time to fracture (TtF) from the start of the test until the moment of file breakage and the length of the fractured tip was recorded for each instrument. Means and standard deviations (SD) of TtF and fragment length were calculated. Data were subjected to one-way analysis of variance (ANOVA).
  
  
  RESULTS
  Group 1 (Twisted File) showed the highest value of TtF means. Cyclic fatigue resistance of Twisted File and Mtwo was significantly higher than group 2 (Revo S SU) and 4 (BioRace BR3), while no significant differences were found between group 1 (Twisted File) and 3 (Mtwo) or group 2 (Revo S SU) and 4 (BioRaCe BR3).
  
  
  CONCLUSIONS
  The cyclic fatigue resistance of Twisted File was significantly frigher than instruments produced with traditional grinding process except of Mtwo files.
authors.affiliation: Department of Surgery, University of Catania, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Pedullà
authors.forename: Gianluca
authors.initials: G
authors.lastname: Plotino
authors.forename: Nicola Maria
authors.initials: NM
authors.lastname: Grande
authors.forename: Alfio
authors.initials: A
authors.lastname: Pappalardo
authors.forename: Ernesto
authors.initials: E
authors.lastname: Rapisarda
keywords: cyclic fatigue; grinding process; nickel-titanium; rotary instruments; twisted file