title: Mechanical behavior of ProTaper universal F2 finishing file under various curvature conditions: a finite element analysis study.
abstract: BACKGROUND
  The purpose of this study was to visualize the stresses and strain distribution patterns in ProTaper Universal F2 files (Dentsply Maillefer, Ballaigues, Switzerland) and to establish the stress- and strain-curvature relationship for this instrument under various conditions by using a dynamic, three-dimensional finite-element model.
  
  
  METHODS
  An accurate geometric model of a ProTaper Universal F2 instrument was created. Two short, straight tubes were also modeled to represent the parts of root canal apical and coronal to the curvature. Then, the file was constrained to a curve of varying degree, curve length, and position. The maximum von Mises stress and strain on the tension side of the instrument was measured at 5-degree intervals in a numerical simulation package (LS-DYNA; Livermore Software Technology, Livermore, CA).
  
  
  RESULTS
  The mechanical performance of the ProTaper F2 file under various conditions was simulated. A long curvature length produced lower values of stress and strain under the same angle of curvature. An increase in the curvature angle generally induces higher stress and strain. For the same degree and curve length, the stress and strain increased if the curved portion was situated further up the shaft of the instrument (ie, with a larger diameter).
  
  
  CONCLUSIONS
  The dynamic, numerical model may be used to evaluate and compare the effect of various root canal curvatures on the behavior of different designs of root canal instrument. The magnitude of stress and strain imposed on the instrument is influenced by the abruptness and degree of curvature as well as the location of the curved portion.
authors.affiliation: State Key Laboratory of Oral Diseases, West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Gary S P
authors.initials: GS
authors.lastname: Cheung
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D003799:Dental Stress Analysis / Q000379:methods; D004548:Elasticity; D004867:Equipment Design; D020342:Finite Element Analysis; D019563:Mechanics; D009532:Nickel; D009716:Numerical Analysis, Computer-Assisted; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D014025:Titanium
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium