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

Role of Electrospinning Parameters on Poly(Lactic-co-Glycolic Acid) and Poly(Caprolactone-co-Glycolic acid) Membranes

[EN] Poly(lactic-co-glycolic acid) (PLGA) and poly(caprolactone-co-glycolic acid) (PCLGA) solutions were electrospun into membranes with tailored fiber diameter of 1.8 mu m. This particular fiber diameter was tuned depending on the used co-polymer by adjusting the electrospinning parameters that mainly influence the fiber diameter. The greatest setting of the fiber diameter was achieved by varying the polymer solution parameters (polymer concentration, solvents and solvents ratio). PLGA was adequately electrospun with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), whereas PCLGA required a polar solvent (such as chloroform) with a lower dielectric constant. Moreover, due to the amorphous morphology of PCLGA, pyridine as salt had to be added to the starting solution to increase its conductivity and make it electrospinnable. Indeed, the electrospinning of this co-polymer presents notable difficulties due to its amorphous structure. Interestingly, PCLGA, having a higher glycolic acid molar fraction than commonly electrospun co-polymers (caprolactone:glycolic acid ratio of 45:55 instead of 90:10), could be successfully electrospun, which has not been reported to date. To an accurate setting of fiber diameter, the voltage and the distance from needle to collector were varied. Finally, the study of the surface tension, conductivity and viscosity of the polymer solutions allowed to correlate these particular characteristics of the solutions with the electrospinning variables so that prior knowledge of them enables predicting the required processing conditions.M. Herrero acknowledges the Spanish Ministerio de Economia y Competitividad for the BES-2016-078024 grant. A.Valles acknowledges the support of the Generalitat Valenciana, Conselleria de Educacion, Investigacion, Cultura y Deporte through project AEST/2020/052. CIBER-BBN is an initiative funded by the VI National R&D & I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Herrero-Herrero, M.; Gómez-Tejedor, J.; Vallés Lluch, A. (2021). Role of Electrospinning Parameters on Poly(Lactic-co-Glycolic Acid) and Poly(Caprolactone-co-Glycolic acid) Membranes. Polymers. 13(5):1-11. https://doi.org/10.3390/polym13050695S11113

Microwaves as a Remedial Treatment of Wood

A pilot experiment of microwave treatment was carried out on an Art Nouveau residential building erected at the beginning of the 20th century in Valencia, Spain. The timber structure was affected by a combined damage caused by Anobium punctatum (common furniture beetle or common house borer) and Kalotermes flavicollis (yellownecked dry-wood termite). After performing an exhaustive preliminary study on the building and analyzing the different alternatives of wood treatment, it was decided to use a microwave machine especially designed to eliminate this type of wood boring insects. This machine generates microwaves, a type of electromagnetic radiation, with a frequency of 2.45 GHz. This circumstance makes it possible to produce a high-frequency alternating electric field that causes the rotation of the molecular dipoles of water. Because of this continuous rotation the temperature of the water rises considerably. By heating up the humidity inside a living being, as in the case of xylophagous insects, an artificial fever in the body is generated, and since the animal is not capable of tolerating this temperature, it dies. In order to eliminate xylophagous insects, the wood moisture content (usually between 10% and 12%) and the presence of water in wood boring insects (around 90%) must be taken into account. Due to the greater content of humidity the increase of the temperature is higher and quicker in insects than wood. Prior to this pilot intervention, several research works were carried out with the same microwave machine, especially on wooden works of art. In all these studies it was observed that no damage was caused either to the wood or to the finish of the works of art including pigments, polishes, stains etc. On the other hand, 100% efficacy was achieved in the elimination of xylophagous insects. This article describes the design, experimentation and perfecting process of this microwave machine and its pilot application on structural timber in an Art Nouveau residential building. Bringing the knowledge of the laboratory on-site and assessing the differences in the procedures.Martínez Lluch, A.; Vegas López-Manzanares, F.; Mileto, C.; Diodato, M. (2013). Microwaves as a Remedial Treatment of Wood. Advanced Materials Research. 778:620-627. doi:10.4028/www.scientific.net/AMR.778.620S620627778T. Strang, Principles of Heat Disinfestation, Integrated Pest Management for Collections. Proceedings of: A Pest Odyssey a joint conference of English Heritage, the Science Museum and the National Preservation Office (2001).M. Bini, D. Andreuccetti, A. Ignesti, R. Olmi, S. Priori, R. Vanni, A portable microwave system for woodworm disinfestation of artistic painted boards, J. Microwave Power and Electromagnetic Energy, Vol. 32(3), (1997) 180-187.G. Torgovnikov, P. Vinde, Microwave Modification of Wood Properties: Improvements in Wood Permeability, 31st Annual Meeting of The international Research Group on Wood Preservation, Section 4. Processes and Properties (2000).E. Pérez Marín, Mª V. Vivancos Ramón, Aspectos técnicos y conservativos del retablo barroco valenciano, Universitat Politècnica de València, Valencia, (2004).Mª V. Vivancos Ramón, E. Pérez Marín, Revisión crítica de los diferentes sistemas de desinfección aplicados a la retablística barroca, XIV Congreso de Conservación y Restauración de Bienes Culturales, Valladolid, (2002).Mª V. Vivancos Ramón, E. Pérez Marín, N. Valentin Rodrigo, La desinsectación de la madera, revisión de los últimos sistemas, Universitat Politècnica de València , Valencia, (2008).D. Benito Goerlich, La arquitectura del eclecticismo en Valencia. Vertientes de la arquitectura valenciana entre 1875 y 1925, Ayuntamiento deValencia, Valencia, (1983).M. Sanchis Guarner, La ciutat de València. Síntesi d'Història i de Geografia urbana, 6th edition, Generalitat Valenciana, Valencia (1997).F. Vegas López-Manzanares, C. Mileto, New old restoration techniques for modernista buildings. Refurbishment of la Casa de la Madrina, in: AA. VV., International Seminar on the management of the Shared Mediterranean Heritage, Institute de Recherche pour le Developpment, Alexandria, (2005).F. Vegas López-Manzanares, C. Mileto, Aprendiendo a Restaurar, Generalitat Valenciana, Valencia, (2011)

Growth factors reléase on P-PRP activeted with trombin assessment assay

The development of platelet concentrates has generated great expectations in bone surgery. These compounds provides autologous growth factors for tissue healing and regeneration, but disparity of methods hinders the patterns of use. The objective of our study is proposing a standard model for Platelet Rich Plasma preparation, involving growth factors release. Sheep peripheral blood were obtained with anticoagulant citrate dextrose 50 N (Citra), three different speed centrifugation methods and plasma activation (1000 units of thrombin and 10% CaCl2 per ml were performed. The release of growth factors were determined by ELISA (R & D systems). The higher platelets concentration was obtained with two centrifugations, first 500 g 10 min, followed by 1900g for 8 min. After activation clotting immediate release of growth factors by platelet degranulation were achieved. The PDGF increased more than 1.9 fold till 537.9 pg/ml and TGF-β1 increases almost 8 times till 7150 pgr/ml in 180 min. Our standard method proposed, triggers the release of growth factors, immediately after activation with a dose-response relationship between platelets and growth factors. This means that the PRP prepared in our experimental conditions is really a plasma rich in growth factors ready for clinical use

Comparison of Different Parameters to Evaluate Delamination in Edge Trimming of Basalt Fiber Reinforced Plastics (BFRP)

[EN] Delamination is one of the main problems that occur when machining fiber-reinforced composite materials. In this work, Types I and II of delamination are studied separately in edge trimming of basalt fiber reinforced plastic (BFRP). For this purpose, one-dimensional and area delamination parameters are defined. One-dimensional parameters (Wa and Wb) allow to know average fibers length while the analysis of area delamination parameters (Sd) allow to evaluate delamination density. To study delamination, different tests are carried out modifying cutting parameters (cutting speed, feed per tooth and depth of cut) and material characteristics (fiber volume fraction and fiber orientation). Laminates with a lower fiber volume fraction do not present delamination. Attending to one-dimensional parameters it can be concluded that Type II delamination is more important than Type I and that a high depth of cut generates higher values of delamination parameters. An analysis of variance (ANOVA) is performed to study area parameters. Although delamination has a random nature, for each depth of cut, more influence variables in area delamination are firstly, feed per tooth and secondly, cutting speed.This research was funded by Government of Spain, grant number PID2019-108807RB-I00.Navarro-Mas, M.; Meseguer, M.; Lluch-Cerezo, J.; García Manrique, JA. (2020). Comparison of Different Parameters to Evaluate Delamination in Edge Trimming of Basalt Fiber Reinforced Plastics (BFRP). Materials. 13(23):1-17. https://doi.org/10.3390/ma13235326S1171323Lopresto, V., Caggiano, A., & Teti, R. (2016). High Performance Cutting of Fibre Reinforced Plastic Composite Materials. Procedia CIRP, 46, 71-82. doi:10.1016/j.procir.2016.05.079Ozkan, D., Panjan, P., Gok, M. S., & Karaoglanli, A. C. (2020). Experimental Study on Tool Wear and Delamination in Milling CFRPs with TiAlN- and TiN-Coated Tools. Coatings, 10(7), 623. doi:10.3390/coatings10070623Nguyen-Dinh, N., Bouvet, C., & Zitoune, R. (2019). Influence of machining damage generated during trimming of CFRP composite on the compressive strength. Journal of Composite Materials, 54(11), 1413-1430. doi:10.1177/0021998319883335Razfar, M. R., & Zadeh, M. R. Z. (2009). Optimum damage and surface roughness prediction in end milling glass fibre-reinforced plastics, using neural network and genetic algorithm. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 223(6), 653-664. doi:10.1243/09544054jem1409Neeli, N., Jenarthanan, M. P., & Dileep Kumar, G. (2018). Multi-response optimization for machining GFRP composites using GRA and DFA. Multidiscipline Modeling in Materials and Structures, 14(3), 482-496. doi:10.1108/mmms-08-2017-0092Azmi, A. I., Lin, R. J. T., & Bhattacharyya, D. (2012). Machinability study of glass fibre-reinforced polymer composites during end milling. The International Journal of Advanced Manufacturing Technology, 64(1-4), 247-261. doi:10.1007/s00170-012-4006-6Jenarthanan, M. P., & Jeyapaul, R. (2018). Optimisation of machining parameters on milling of GFRP composites by desirability function analysis using Taguchi method. International Journal of Engineering, Science and Technology, 5(4), 22-36. doi:10.4314/ijest.v5i4.3Sreenivasulu, R. (2013). Optimization of Surface Roughness and Delamination Damage of GFRP Composite Material in End Milling Using Taguchi Design Method and Artificial Neural Network. Procedia Engineering, 64, 785-794. doi:10.1016/j.proeng.2013.09.154He, Y., Qing, H., Zhang, S., Wang, D., & Zhu, S. (2017). The cutting force and defect analysis in milling of carbon fiber-reinforced polymer (CFRP) composite. The International Journal of Advanced Manufacturing Technology, 93(5-8), 1829-1842. doi:10.1007/s00170-017-0613-6Raj, P. P., & Perumal, A. E. (2010). Taguchi Analysis of surface roughness and delamination associated with various cemented carbide K10 end mills in milling of GFRP. Journal of Engineering Science and Technology Review, 3(1), 58-64. doi:10.25103/jestr.031.11Hintze, W., Hartmann, D., & Schütte, C. (2011). Occurrence and propagation of delamination during the machining of carbon fibre reinforced plastics (CFRPs) – An experimental study. Composites Science and Technology, 71(15), 1719-1726. doi:10.1016/j.compscitech.2011.08.002Wang, F., Yin, J., Ma, J., Jia, Z., Yang, F., & Niu, B. (2017). Effects of cutting edge radius and fiber cutting angle on the cutting-induced surface damage in machining of unidirectional CFRP composite laminates. The International Journal of Advanced Manufacturing Technology, 91(9-12), 3107-3120. doi:10.1007/s00170-017-0023-9Li, M., Huang, M., Jiang, X., Kuo, C., & Yang, X. (2018). Study on burr occurrence and surface integrity during slot milling of multidirectional and plain woven CFRPs. The International Journal of Advanced Manufacturing Technology, 97(1-4), 163-173. doi:10.1007/s00170-018-1937-6Sheikh-Ahmad, J. Y., Dhuttargaon, M., & Cheraghi, H. (2017). New tool life criterion for delamination free milling of CFRP. The International Journal of Advanced Manufacturing Technology, 92(5-8), 2131-2143. doi:10.1007/s00170-017-0240-2Szwajka, K., & Trzepieciński, T. (2016). Effect of tool material on tool wear and delamination during machining of particleboard. Journal of Wood Science, 62(4), 305-315. doi:10.1007/s10086-016-1555-6Wang, F., Zhang, B., Jia, Z., Zhao, X., & Wang, Q. (2019). Structural optimization method of multitooth cutter for surface damages suppression in edge trimming of Carbon Fiber Reinforced Plastics. Journal of Manufacturing Processes, 46, 204-213. doi:10.1016/j.jmapro.2019.09.013Masek, P., Zeman, P., Kolar, P., & Holesovsky, F. (2018). Edge trimming of C/PPS plates. The International Journal of Advanced Manufacturing Technology, 101(1-4), 157-170. doi:10.1007/s00170-018-2857-1Dhand, V., Mittal, G., Rhee, K. Y., Park, S.-J., & Hui, D. (2015). A short review on basalt fiber reinforced polymer composites. Composites Part B: Engineering, 73, 166-180. doi:10.1016/j.compositesb.2014.12.011Navarro-Mas, M., García-Manrique, J., Meseguer, M., Ordeig, I., & Sánchez, A. (2018). Delamination Study in Edge Trimming of Basalt Fiber Reinforced Plastics (BFRP). Materials, 11(8), 1418. doi:10.3390/ma1108141

Effect of a Powder Mould in the Post-Process Thermal Treatment of ABS Parts Manufactured with FDM Technology

[EN] The post-process thermal treatment of thermoplastics improves their mechanical properties, but causes deformations in parts, making them unusable. This work proposes a powder mould to prevent dimensional part deformation and studies the influence of line building direction in part deformations in a post-process thermal treatment of 3D printed polymers. Two sets of ABS (acrylonitrile butadiene styrene) test samples manufactured by fused deposition modelling (FDM) in six different raster directions have been treated and evaluated. One set has been packed with a ceramic powder mould during thermal treatment to evaluate deformations and mould effectiveness. Thermogravimetric tests have been carried out on ABS samples, concluding that the thermal treatment of the samples does not cause degradations in the polymeric material. An analysis of variance (ANOVA) was performed to study internal building geometry and mould influence on part deformation after the thermal treatment. It can be concluded that powder mould considerably reduces dimensional deformations during the thermal treatment process, with length being the most affected dimension for deformation. Attending to the length, mould effectiveness is greater than 80% in comparison to non-usage of moulding, reaching 90% when the building lines are in the same direction as the main part.This research received partial funding from the Government of Spain under the project PID2019-108807RB-I00.Lluch-Cerezo, J.; Benavente Martínez, R.; Meseguer, M.; García Manrique, JA. (2021). Effect of a Powder Mould in the Post-Process Thermal Treatment of ABS Parts Manufactured with FDM Technology. Polymers. 13(15):1-16. https://doi.org/10.3390/polym13152422S116131

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

Historia de la danza contemporánea en España

Compilación histórica de la danza hasta llegar a España y su desarrollo desde las danzas primitivas hasta la danza contemporánea