Analysis of the effect of design parameters and their interactions on the strength of dental restorations with endodontic posts, using finite element models and statistical analysis

Many previous studies, both in vitro and with model simulations, have been conducted in an attempt to reach a full understanding of how the different design parameters of an endodontically restored tooth affect its mechanical strength. However, differences in the experimental set-up or modelling conditions and the limited number of parameters studied in each case prevent us from obtaining clear conclusions about the real significance of each parameter. In this work, a new approach is proposed for this purpose based on the combination of a validated three-dimensional parametric biomechanical model of the restored tooth and statistical analysis using full factorial analysis of variance. A two-step approach with two virtual tests (with, respectively, 128 and 81 finite element models) was used in the present work to study the effect of several design parameters on the strength of a restored incisor, using full factorial designs. Within the limitations of this study, and for cases where the parameters are within the ranges that were tested, the conclusions indicate that the material of the post is the most significant factor as far as its strength is concerned, the use of a low Young's modulus being preferable for this component. Once the post material has been chosen, the geometry of the post is of less importance than the Young's modulus selected for the core or, especially, for the crown.This research is supported by Universitat Jaume I through Project P1·1B2012-10

Interpreting finite element results for brittle materials in endodontic restorations

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

CAD 3D con SolidWorks® Tomo I: Diseño básico (2a ed.) Volumen 4. Anotaciones

Departament d'Enginyeria Mecànica i Construcció. Codis assignatura: ET1009, EM1009, EQ1009, EE1009, ET1028, EM1025, DI2028, SDI12

On the Internationalization of CAD Learning Through an English Glossary

Comunicació presentada al XXIX Congreso International INGEGRAF 2019 "La transformación Digital en la Ingeniería Gráfica” (20-21 Junio 2019, Logroño - La Rioja)The internationalization of higher education is an essential factor to improve the quality and efficiency of Spanish universities, providing students with the main skills, and knowledge to interact effectively in an international and multicultural work context as professionals. The internationalization of universities must be a transversal process, not exclusive of its territorial dimension, aimed at advancing towards a society and a knowledge economy that propitiate a solid and stable model of development and growth. To this end, professors in the area of Graphic Expression for Engineering at the Universitat Jaume I (UJI) have developed an online glossary of specific terms in English related to the 3D modelling CAD tools used in Graphic Engineering subjects. This new online tool seeks to train students to increase their technical vocabulary in English and improve their learning and communication skills to face possible collaborations in future European projects. The glossary is introduced weekly to the students during the course. Subsequently, a survey is conducted to the students to verify the effectiveness of the training. This work collects the results and conclusions of this analysis

Training Engineers in the Use of Constraints to Create Quality 2D Pro les for 3D Models

Historically, different strategies utilized in engineering and technical graphics reflect growing concern about improvement in CAD instruction and the introduction of product quality data in curricular activities. Our vision was that early introduction of quality criteria through "good practices" is feasible and increases the quality, robustness, and reliability of CAD models. This paper describes a strategy applied to improve the knowledge of novice CAD users on the use of geometric constraints in 2D parametric profiles. This approach consists of supplementing student training with activities in order to provide rapid and effective feedback. A Chi-Squared Test was performed to assess the effectiveness of this strategy, indicating that trainees need continuous and additional autonomous learning to create quality 2D parametric pro les. Future work will include developments to promote student awareness of the need for quality in 3D models using an online checker that acts as a filter of semantic quality errors while providing feedback

Mechanical performance of endodontic restorations with prefabricated posts: sensitivity analysis of parameters with a 3D finite element model

Many studies have investigated the effect of different parameters of the endodontically restored tooth on its final strength, using in vitro tests and model simulations. However, the differences in the experimental set-up or modelling conditions and the limited number of parameters studied in each case prevent us from obtaining clear conclusions about the relative importance of each parameter. In this study, a validated 3D biomechanical model of the restored tooth was used for an exhaustive sensitivity analysis. The individual influence of 20 different parameters on the mechanical performance of an endodontic restoration with prefabricated posts was studied. The results bring up the remarkable importance of the loading angle on the final restoration strength. Flexural loads are more critical than compressive or tensile loads. Young’s modulus of the post and its length and diameter are the most influential parameters for strength, whereas other parameters such as ferrule geometry or core and crown characteristics are less significant

Effect of post design on endodontically restored teeth

En aquest article es fa una revisió de l'efecte del disseny del pern en les prestacions de les dents endodonciades a partir de l'anàlisi de la bibliografia i dels treballs dels autors. De l'estudi es conclou que existeixen proves suficients de l'efecte d'alguns paràmetres en determinades característiques de la dent restaurada: la longitud del pern facilita la retenció de la restauració, que és major en el cas dels perns actius, seguits dels cilíndrics, mentre que els cònics presenten menor retenció. El diàmetre del pern ha de mantenir-se inferior a la meitat de l'amplària de l'arrel. Amb els perns de fibra s'obtenen distribucions de tensions menys sensibles al diàmetre o a la longitud del pern que amb els metàl·lics. No existeixen conclusions clares sobre altres aspectes de la restauració, com ara l'efecte de la forma del pern en la seva resistència, l'efecte del diàmetre en la retenció o el comportament dels diferents sistemes davant de càrregues de fatiga. Els treballs previs dels autors han permès desenvolupar un model biomecànic per a elements finits, validat amb dades experimentals, que pot servir d'ajuda per a clarificar l'efecte de cada paràmetre en les prestacions finals de la restauració.In this article a review is carried out on the effect that post design has on the performance of endodontically treated teeth by analysing the bibliography and the works by the authors themselves. We can conclude from this study that sufficient evidence exists of the effect that some parameters have on specific characteristics of the restored tooth. Post length facilitates retention, which is greater for active posts, followed by cylindrical posts, and tapered posts. The diameter of the post must be less than half the root width. Stress distributions that are less susceptible to post diameter or post length are better obtained with fibre posts than with metallic ones. However, no clear conclusions exist for other aspects of restoration, such as how the shape of the post affects its resistance, how the diameter affects retention or how different systems perform under cyclic loading. The previous works by the authors have made it possible to obtain a finite element biomechanical model, validated with experimental data, which could help to clarify the effect of each parameter on the final properties of tooth restoration

An in vitro study and 3D finite element analysis

Endodontically treated teeth are known to have reduced structural strength. Periodontal ligament (PDL) may influence fracture resistance. The purpose of this study was to assess the influence of including the PDL in biomechanical studies about endodontically treated and restored teeth. Forty human maxillary central incisors were treated endodontically and randomly divided into four groups: non-­crowned (with and without an artificial ligament) and crowned (with and without an artificial ligament) with glass-­ceramic crowns. All groups received prefabricated glass fiber posts and a composite resin core. Specimens were tested, under a flexural-­compressive load, until failure occurred. The failure mode was registered for all specimens. The failure loads were recorded and analyzed using an ANOVA test (P␣<0␣.05). These results were compared with those predicted by a finite element model. The ANOVA did not show significant differences between the use of crown on the failure load (P=0␣. ) and the use of PDL (P=0.185). A cohesive mode in crown appeared in crowned teeth and in core in non-­crowned group. For non-­crowned teeth, and adhesive failure occurred along the cement-­enamel junction with a slight tendency in specimens without PDL. Furthermore, an unfavorable failure mode affecting partially the root with no differences regarding to non-­ crown specimens. In crowned teeth, the tendency was an adhesive failure along the cement-­ enamel junction. The model predicted a distribution of the safety factor consistent with these results. The present study showed that inclusion of PDL is not particularly important on biomechanical behaviour of post-­retained restorations. However, we recommend its inclusion in fatigue studies.The authors thank the University Jaume I for its financial support throughout the project P1·1B2012-­1