title: Investigation on the shaping ability of nickel-titanium files when used with a reciprocating motion.
abstract: BACKGROUND
  The introduction of nickel-titanium (NiTi) files into clinical practice has improved the quality of canal shaping, but increasing the curvature of the root canal (or the diameter of the master instrument that prepares the full working length) could result in more transportation, straightening, and aberration of the canal. Nickel-titanium instruments are significantly safer and have an extended cyclic fatigue life when used with a reciprocating movement. The purpose of this study was to compare the shaping ability of FlexMaster NiTi instruments when used in either continuous or reciprocating movements.
  
  
  METHODS
  Thirty-two Endo Training Blocks ISO 15, 2% taper, 10-mm radius of curvature, and 70° angle of curvature were prepared, according to the group, with FlexMaster NiTi instruments either in continuous rotation or in reciprocating (60° clockwise, 40° counterclockwise) movement. Preoperative and postoperative images of the simulated canals were taken under standardized conditions. The preoperative and postoperative images were combined exactly. The amount of resin removed was determined both for the inner (convex) and the outer (concave) sides of the curvature at 10 different points.
  
  
  RESULTS
  In the most apical third of the canal, the Continuous group produced the largest enlargement of the canal as compared with the Reciprocating group (P < .05). In the apical third, the Continuous group displayed significantly greater enlargement of the canal at the external side.
  
  
  CONCLUSIONS
  The shaping of simulated canals is more centered by using a reciprocating motion when compared with continuous rotation, but the reciprocating motion could be more time-consuming.
authors.affiliation: Department of Health Tecnologies, Istituto di Ricovero e Cura a Carattere Scientifico, Istituto Ortopedico Galeazzi, University of Milan, Milan, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Franco
authors.forename: Cristiano
authors.initials: C
authors.lastname: Fabiani
authors.forename: Silvio
authors.initials: S
authors.lastname: Taschieri
authors.forename: Augusto
authors.initials: A
authors.lastname: Malentacca
authors.forename: Monica
authors.initials: M
authors.lastname: Bortolin
authors.forename: Massimo
authors.initials: M
authors.lastname: Del Fabbro
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D003765:Models, Dental; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D012399:Rotation; D013997:Time Factors; D014025:Titanium
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium