Background: Finite element simulation has been used in last years for analysing the
biomechanical performance of post-core restorations in endodontics, but results of
these simulations have been interpreted in most of the works using von Mises stress
criterion. However, the validity of this failure criterion for brittle materials, which are
present in these restorations, is questionable. The objective of the paper is to analyse
how finite element results for brittle materials of endodontic restorations should be
interpreted to obtain correct conclusions about the possible failure in the restoration.
Methods: Different failure criteria (Von Mises, Rankine, Coulomb-Mohr, Modified
Mohr and Christensen) and material strength data (diametral tensile strength and
flexural strength) were considered in the study. Three finite element models (FEM)
were developed to simulate an endodontic restoration and two typical material tests:
diametral tensile test and flexural test.
Results: Results showed that the Christensen criterion predicts similar results as the
Von Mises criterion for ductile components, while it predicts similar results to all
other criteria for brittle components. The different criteria predict different failure
points for the diametral tensile test, all of them under multi-axial stress states. All
criteria except Von Mises predict failure for flexural test at the same point of the
specimen, with this point under uniaxial tensile stress.
Conclusions: From the results it is concluded that the Christensen criterion is
recommended for FEM result interpretation in endodontic restorations and that the
flexural test is recommended to estimate tensile strength instead of the diametral
tensile tes