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

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

Scalability of the Muscular Action in a Parametric 3D Model of the Index Finger

A method for scaling the muscle action is proposed and used to achieve a 3D inverse dynamic model of the human finger with all its components scalable. This method is based on scaling the PCSA (physiological cross-sectional area) in a Hill muscle model. Different anthropometric parameters and maximal grip force data have been measured and their correlations have been analysed and used for scaling the PCSA of each muscle. A linear relationship between the normalised PCSA and the product of the length and breadth of the hand has been finally used for scaling, with a slope of 0.01315 cm-2, with the length and breadth of the hand expressed in centimetres. The parametric muscle model has been included in a parametric finger model previously developed by the authors, and it has been validated reproducing the results of an experiment in which subjects from different population groups exerted maximal voluntary forces with their index finger in a controlled postur

Experimental strength of restorations with fibre posts at different stages, with and without using a simulated ligament

The aim of this study was to analyse the strength and failure mode of teeth restored with fibre posts under retention and flexural-compressive loads at different stages of the restoration and to analyse whether including a simulated ligament in the experimental setup has any effect on the strength or the failure mode. Thirty human maxillary central incisors were distributed in three different groups to be restored with simulation of different restoration stages (1: only post, 2: post and core, 3: post-core and crown), using Rebilda fibre posts. The specimens were inserted in resin blocks and loaded by means of a universal testing machine until failure under tension (stage 1) and 50º flexion (stages 2–3). Half the specimens in each group were restored using a simulated ligament between root dentine and resin block and the other half did not use this element. Failure in stage 1 always occurred at the post-dentine interface, with a mean failure load of 191·2 N. Failure in stage 2 was located mainly in the core or coronal dentine (mean failure load of 505·9 N). Failure in stage 3 was observed in the coronal dentine (mean failure load 397·4 N). Failure loads registered were greater than expected masticatory loads. Fracture modes were mostly reparable, thus indicating that this post is clinically valid at the different stages of restoration studied. The inclusion of the simulated ligament in the experimental system did not show a statistically significant effect on the failure load or the failure mode

Premolars restored with posts of different materials: fatigue analysis

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

Independent Validation of the SEND-PD and Correlation with the MDS-UPDRS Part IA

Introduction. Neuropsychiatric symptoms in Parkinson's disease can be assessed by the MDS-UPDRS part IA. The Scale for Evaluation of Neuropsychiatric Disorders in Parkinson's disease (SEND-PD) has been recently developed to assess the severity of some neuropsychiatric symptoms. The objective of this study is to compare the performance of the SEND-PD with the corresponding items of the MDS-UPDRS part IA. Methods. Patients with Parkinson's disease were evaluated using the MDS-UPDRS and the SEND-PD by independent raters. Partial SEND-PD and neuropsychiatric MDS-UPDRS part IA were constructed with equivalent items for comparison. Results. A total of 260 consecutive patients were included. Overall, 61.2% of the patients did not report any psychotic symptom and 83.5% did not report any ICD symptom. On the other hand, 78.5% of the patients did report at least one symptom related to apathy, depression, or anxiety. The partial SEND-PD score was 2.9 ± 3.1 (range from 0 to 16). The neuropsychiatric MDS-UPDRS part IA score was 2.9 ± 3 (range from 0 to 14). The correlation coefficient between corresponding items ranged from 0.67 to 0.98 and between both summary indexes was r s = 0.93 (all, P < 0.001). Conclusion. A high association between equivalent items of the SEND-PD and the MDS-UPDRS was found.S

Componentes principales aplicados al estudio de la dinámica del pie supinado y normal durante la marcha

Comunicación presentada en el XXI Congreso Nacional de Ingeniería Mecánica, celebrado en Elche en Noviembre de 2016.Las variaciones en el índice postural del pie (pronados, supinados) suelen asociarse con una incorrecta función del miembro inferior que lo predispone a lesiones. El análisis riguroso de la dinámica del pie es complejo, pues han de manejarse simultáneamente las evoluciones temporales de ángulos y momentos durante la marcha en sus diferentes articulaciones, y en los tres planos de movimiento. Por ello, los análisis comparativos que pueden encontrarse en la literatura se han acometido sobre determinados parámetros específicos de la marcha, y no de forma sistemática. Aunque la marcha es una actividad compleja, diferentes trabajos han puesto de manifiesto la coordinación cinemática existente entre cadera, rodilla y tobillo mediante el uso del análisis de componentes principales (ACP). Sin embargo, la coordinación de ángulos y momentos en las articulaciones del pie durante la marcha ha sido poco explorada hasta ahora. En este trabajo se propone el análisis sistemático de las diferencias en la dinámica de pies supinados frente a pies normales, por aplicación de la reducción dimensional mediante el uso del ACP. Para ello se registró la dinámica del tobillo y de las articulaciones mediotarsiana y metatarsofalángica de 30 sujetos con pies normales y de 20 con pies supinados, mientras caminaban descalzos a lo largo de un pasillo de 7 m. La aplicación de ACPs (valores propios> 1, rotación varimax) sobre los sujetos con pies normales permitió identificar 3 componentes principales (CPs) explicando el 68% de la varianza de los ángulos articulares, y 3 CPs explicando el 87% de la varianza de los momentos, reduciendo las 18 variables temporales originales (9 ángulos y 9 momentos) a 6 factores. Las evoluciones temporales de estos factores permitieron identificar un conjunto de parámetros que se proponen para el análisis sistemático de la dinámica del pie durante la marcha. En el trabajo se presenta cuáles de esos parámetros se ven afectados por el índice postural del pie (mediante ANOVAs), así como las diferencias en la coordinación entre pies normales y supinados (comparando componentes principales de ambos grupos de sujetos), y se discuten sus posibles repercusiones clínicas

Educational robotics from research as a pedagogical strategy supported by tic in school

La robótica educativa es un medio de aprendizaje basado en el diseño y construcción de objetos controlados a través de sistemas computacionales, convirtiéndose en un escenario donde los estudiantes estimulan la capacidad de creación. El propósito del estudio fue implementar la robótica educativa desde la investigación como estrategia pedagógica apoyada en TIC en la escuela. Este estuvo guiado bajo los lineamientos metodológicos de la IEP con un diseño basado en las trayectorias de indagación. La población estuvo conformada por cuarenta (40) estudiantes de la IED Gabriel García Márquez del Municipio de Aracataca, Como técnicas de recolección de datos se utilizaron el diario de campo y la observación. Se evidencio que los estudiantes apropian el conocimiento a partir de actividades prácticas donde la integración la investigación permite realizar el proceso de asociación entre la teoría y la aplicación de la misma en el contexto social donde se desenvuelve el estudiante.Educational robotics is a learning medium based on the design and construction of controlled objects through computer systems, becoming a scenario where students stimulate the ability to create. The purpose of the study was to implement educational robotics from research as a pedagogical strategy supported by ICT in the school. This was guided under the methodological guidelines of the IEP with a design based on the trajectories of inquiry. The population consisted of forty (40) IED students Gabriel Garcia Marquez from the Municipality of Aracataca, chosen through stratified random sampling taking as criteria of inclusion the grade level and the working day. Data logging and observation were used as data collection techniques. It was evidenced that the students appropriate the knowledge from practical activities where the integration of the research allows to realize the process of association between the theory and the application of the same in the social context where the student develops, generating in this way a significant learning