title: Resistance to torsional failure and cyclic fatigue resistance of ProTaper Next, WaveOne, and Mtwo files in continuous and reciprocating motion: An in vitro study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the resistance to torsional failure and cyclic fatigue resistance of ProTaper Next (PTN), WaveOne, and Mtwo files in continuous and reciprocating motion.
  
  
  METHODS
  Randomized control trial in a tertiary care setting.
  
  
  METHODS
  A total of 10 new size 25.06 taper PTN X2, 25.06 taper Mtwo files, and 25.08 taper WaveOne primary files each was selected. A custom fabricated cyclic fatigue testing device with a 70° angle of curvature and 3 mm width; curvature starting at 6 mm from the tip was used. All instruments were rotated and reciprocated till fracture occurred and time till fracture of each instrument was recorded in seconds. For torsional failure testing 5 mm tip of each file was embedded in composite resin block and uniform torsional stresses (300 rpm, 2.0 Ncm) were applied repetitively by an endodontic motor with auto stop mode until file succumbed to torsional failure. Number of load applications leading to failure was recorded.
  
  
  METHODS
  Data were analyzed using t-test for equality of means, Pearson correlation, and ANOVA test.
  
  
  RESULTS
  All the files showed superior resistance to cyclic fatigue in reciprocating motion when compared with continuous rotation mode. WaveOne primary files displayed maximum resistance to cyclic fatigue both in continuous and reciprocating motion. WaveOne primary files also demonstrated maximum resistance to torsional failure followed by PTN with Mtwo files exhibiting least resistance.
  
  
  CONCLUSIONS
  Operating files in reciprocating motion enhances their cyclic fatigue resistance. WaveOne files showed maximum resistance to cyclic fatigue and torsional failure due to their cross-sectional diameter coupled M-Wire technology.
authors.affiliation: Department of Conservative Dentistry and Endodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India.
authors.forename: N O
authors.initials: NO
authors.lastname: Varghese
authors.affiliation: Department of Conservative Dentistry and Endodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Pillai
authors.affiliation: Department of Conservative Dentistry and Endodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India.
authors.forename: U-Nu
authors.initials: UN
authors.lastname: Sujathen
authors.affiliation: Department of Conservative Dentistry and Endodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India.
authors.forename: Shan
authors.initials: S
authors.lastname: Sainudeen
authors.affiliation: Department of Conservative Dentistry and Endodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India.
authors.forename: Abe
authors.initials: A
authors.lastname: Antony
authors.affiliation: Department of Conservative Dentistry and Endodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India.
authors.forename: Sinju
authors.initials: S
authors.lastname: Paul
keywords: Cyclic fatigue; ProTaper Next; reciprocation; torsional failure