Design improvement and failure reduction of endodontic files through finite element analysis: application to V-Taper file designs.

INTRODUCTION: Torsional stiffness and bending flexibility are essential characteristics as far as the performance and safety of the endodontic files are concerned. Inadequacy in addressing these requirements in file design leads to increased risk of file failure. The stiffness and flexibility of the endodontic file are greatly dependent on its geometric design. The aim of this study was to evaluate the influence of geometric features on the mechanical performance of endodontic files through numerical simulations.
METHODS: Finite element models of V-Taper file were developed, and the mechanical behavior of the file under bending and torsional loads was simulated. The influence of helix angle, taper, and flute length was evaluated through parametric studies.
RESULTS: In the helix angle range between 5 and 40 degrees, the bending flexibility and torsional stiffness both improve with increasing helix angle. The torsional stiffness increases with increasing taper or decreasing flute length, accompanied by a decrease in bending flexibility. Changing the flute length alone does not result in a change in the stress profile in the tip section. The elastic limit of V-Taper file tip section was estimated in the form of transverse deflection and angular deformation in bending and in torsion, respectively.
CONCLUSIONS: The influence of helix angle, taper, and flute length on the bending flexibility and torsional stiffness of V-Taper files was quantitatively assessed through parametric studies with finite element method. The elastic limit of the V-Taper file tip section was estimated. A design methodology for achieving improved mechanical performances was proposed. Copyright 2010 American Association of Endodontists. All rights reserved.