title: Bending Resistance and Cyclic Fatigue Life of Reciproc, Unicone, and WaveOne Reciprocating Instruments.
abstract: BACKGROUND
  This study evaluated the bending resistance and cyclic fatigue life of a new single-file reciprocating instrument (Unicone; Medin, Nové Město na Moravě, Czech Republic). Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer) instruments were used as references for comparison.
  
  
  METHODS
  Flexibility was determined by 45° bending tests using a universal testing machine. The cyclic fatigue test was performed using a custom-made device. For this test, an artificial canal with a 60° angle and a 5-mm radius of curvature was used. Scanning electron microscopic analysis was performed to determine the mode of fracture and possible deformations at the helical shaft. Statistical analysis for the bending resistance test was performed using parametric methods (ie, 1-way analysis of variance). Post hoc pair-wise comparisons were performed using the Tukey test for multiple comparisons (P < .05). Weibull analysis was used to calculate the mean life, beta, and eta parameters.
  
  
  RESULTS
  Reciproc presented significantly lower bending resistance than the other tested systems (P < .05), whereas no differences were observed between WaveOne and Unicone (P > .05). When mean life was compared among the brands, Reciproc lasted longer than WaveOne with a probability of 99.9%, longer than Unicone in the "RECIPROC ALL" mode with a probability of 99.9%, and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.9% (all statistically significant). Moreover, WaveOne lasted longer than Unicone in the "RECIPROC ALL" mode with a probability of 98.5% and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.8% (all statistically significant). Finally, Unicone in the "RECIPROC ALL" mode lasted longer than Unicone in the "WAVEONE ALL" mode with a probability of 95.3% (statistically significant).
  
  
  CONCLUSIONS
  The new reciprocating instrument Unicone showed lower cyclic fatigue resistance compared with Reciproc R25 and WaveOne Primary files.
authors: Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro, RJ, Brazil. Electronic address: nogueiraemmanuel@hotmail.com.
authors: Emmanuel João Nogueira Leal
authors: EJ
authors: Silva
authors: Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro, RJ, Brazil.
authors: Laise Silva
authors: LS
authors: Villarino
authors: Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro, RJ, Brazil.
authors: Victor Talarico Leal
authors: VT
authors: Vieira
authors: Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro, RJ, Brazil.
authors: Thais
authors: T
authors: Accorsi-Mendonça
authors: Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro, RJ, Brazil.
authors: Henrique Dos Santos
authors: HD
authors: Antunes
authors: Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro, RJ, Brazil.
authors: Gustavo
authors: G
authors: De-Deus
authors: Department of Endodontics, School of Dentistry, Estácio de Sá University (UNESA), Rio de Janeiro, RJ, Brazil.
authors: Hélio Pereira
authors: HP
authors: Lopes
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003762:Dental Instruments; D003799:Dental Stress Analysis / Q000295:instrumentation; D004867:Equipment Design; D004868:Equipment Failure; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D011897:Random Allocation; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium
keywords: Bending resistance; cyclic fatigue; reciprocating movement