BackgroundFinite 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.MethodsDifferent 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.ResultsResults 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.ConclusionsFrom 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 test.

Numerous research works have studied the effect of post-design parameters on the mechanical behaviour of restored teeth without reaching any clear conclusions. Previous works by the authors ascertained the effect of material and post-dimensions for non-crowned restored teeth. The aim of this work was to study the effect of post-material and diameter for crowned teeth. First, an experimental fracture strength test was performed on eighteen extracted human maxillary central incisors. Teeth were decoronated, treated endodontically and restored (nine with glass fibre posts and nine with stainless steel posts). Several post-diameters were used. The final crown restoration was carried out using a reinforced glass-ceramic material. Failure loads were recorded and results were compared using the one-way anova. Secondly, the finite element technique was used to model the restored teeth and to compare the estimated stress distributions. The addition of the crown did not affect the strength of the restoration to any significant extent and post-diameter did not influence the biomechanical performance of either of the post-systems. The crown acts as a protector, thus eliminating the influence of the post-diameter that was found previously when using stainless steel posts, but it does not completely rule out the possibility of a root fracture. Significantly, lower failure loads were found experimentally for teeth restored with stainless steel posts. The stress distributions predicted by the model corroborated these findings and allowed the authors to propose the use of glass fibre posts as a more robust restorative technique.

No abstract

Versión / Versió: Preprint Cita bibliográfica / Cita bibliogràfica (ISO 690):GONZÁLEZ-LLUCH, Carmen, et al. Mechanical performance of endodontic restorations with prefabricated posts: sensitivity analysis of parameters with a 3D finite element model. Computer methods in biomechanics and biomedical engineering, 2014, vol. 17, no 10, p. 1108-1118.

Previous works studied the effect of the material and the dimensions of the post on the biomechanical performance (fracture strength and stress distribution) of restored teeth, under static loads. The aim of this work was to study the effect of the post material (glass fibre and stainless steel) on restored teeth, which have the final crown, under dynamic conditions. The use of a biomechanical model, including a fatigue analysis from FEA, is presented as a powerful method to study the effect of the material of the intraradicular post. The inclusion of the fatigue analysis allows for a more realistic study that takes into account the dynamic nature of masticatory forces. At the same time, the results obtained are easier to interpret by both dentists and mechanical engineers. No differences were found, with the load and number of cycles considered, between glass fibre and stainless steel as material for the intraradicular post used in premolars restorations.