title: Kinematic Effects of Nickel-Titanium Instruments with Reciprocating or Continuous Rotation Motion: A Systematic Review of In Vitro Studies.
abstract: BACKGROUND
  This review aimed to compare the kinematic effect of nickel-titanium instruments with reciprocating and continuous rotation motion for cyclic fatigue resistance, shaping ability, apical debris extrusion, and dentinal defects or cracks.
  
  
  METHODS
  Articles were selected for inclusion in this review if they fulfilled all of the following criteria: described in vitro studies performed on either extracted human teeth or an artificial canal model, assessed both reciprocating and rotary instruments, compared reciprocating files and rotary files for the kinematics of files, and evaluated reciprocating and rotary files regarding the aim of this study. The electronic search was undertaken in MEDLINE, Cochrane database, and manual searches, including journals, reference lists, and other reviews.
  
  
  RESULTS
  Twelve studies were chosen for cyclic fatigue, 19 studies for shaping ability, 14 studies for apical debris extrusion, and 13 studies for dentinal defects or cracks. Most of the studies showed that reciprocating motion had a higher resistance to cyclic fatigue. Nine studies from the shaping studies reported less canal transportation by using the reciprocating motion than the continuous rotation. The reciprocating instruments tended to extrude more dentin debris than the continuous rotating instruments, but many of the studies showed conflicting results. In addition, 2 studies from the defects or cracks studies claimed the reciprocating motion produced more dentinal defects than the continuous rotating motion.
  
  
  CONCLUSIONS
  Instruments with reciprocating motion seemed to have better resistance to cyclic fatigue with less canal transportation tendency than the instruments with continuous rotating motion.
authors.affiliation: Microscope Center, Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Ahn
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea.
authors.forename: Hyeon-Cheol
authors.initials: HC
authors.lastname: Kim
authors.affiliation: Microscope Center, Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Korea. Electronic address: andyendo@yuhs.ac.
authors.forename: Euiseong
authors.initials: E
authors.lastname: Kim
mesh_terms: D001696:Biomechanical Phenomena; D003762:Dental Instruments; D004867:Equipment Design; D066298:In Vitro Techniques; D008422:Materials Testing; D009038:Motion; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D019415:Torque
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Apical debris extrusion; cyclic fatigue; dentinal defects; reciprocating; rotating; shaping ability