MTA HP Repair stimulates in vitro an homogeneous calcium phosphate phase coating deposition

To study the mineralization capacity in vitro of the bioceramic endodontic material MTA HP Repair. Bioactivity evaluation in vitro was carried out, by soaking processed cement disk in simulated body fluid (SBF) during 168 h. The cement surface was studied by Fourier transform infrared spectroscopy (FT-IR), field emission gun scanning electron microscopy (FEG-SEM) and energy dispersive X-ray analysis (EDX). Release to the SBF media of ionic degradation products was monitored using inductively coupled plasma atomic emission spectroscopy (ICP-AES). FT-IR showed increasing formation of phosphate phase bands at 1097, 960, 607 and 570 cm-1 with prolonged SBF soaking. FEG-SEM analysis reveals that HP produces a effectively surface covering consisting in homogeneous spherical phosphate phase aggregates with an average diameter of 0.5-1.0 µm. EDX analysis comparing un-treated (hydrated), 24 h and 72 h SBF treated surfaces of MTA HP Repair revealed phosphate deposition after 24 h, with high phosphorous/silicon element ratio signal measured after 24 h, indicating a very high phosphate phase deposition for this material. The study shows that MTA HP Repair produces a quick and effective bioactive response in vitro in terms of crystalline calcium phosphate surface coating formation. The high bioactive response of MTA HP Repair makes it an interesting candidate for endodontic use as repair cement

Physicochemical parameters - hydration performance relationship of the new endodontic cement MTA Repair HP

To characterize the chemical composition and textural parameters of the MTA Repair HP precursor powder and their influence to hydration performance. Un-hydrated precursor material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), laser diffraction (LD), N2 physisorption and field emission gun scanning electron microscopy (FEG-SEM). Setting time was assessed according to ASTM specification C 266. Hydrated material was analysed by XRD, FT-IR, energy dispersive X-ray (EDX) analysis and FEG-SEM. Ca3SiO5 and Ca2SiO4, in addition to CaWO4 as radiopacifier are the main compositional phases. Other measured parameter indicates high specific surface area of 4.8 m2 g-1, high aluminium content of 1.7 wt.% and low initial and final setting times of 12 and 199 min, respectively. Singular microstructural features consisting of high aspect ratio nanoparticles are main constituents of un-hydrated precursor. Besides, FEM-SEM observation shows notably growth of hexagonal shaped plate-like morphologies homogeneously distributed along the sample during hydration process. The short setting time measured for HP Repair, is correlated with high surface area of precursor powder, high Al content and the absence of compositional sulphate phases

Mecanizado por arranque de viruta asistido por electropulsos

Este artículo trata sobre una nueva técnica de mecanizado: el proceso de torneado asistido in situ con corriente eléctrica, a través de la influencia de electropulsos. Un generador ha sido fabricado para inducir intensidades de corriente de 90 A, duraciones de pulso entre los 50 y 200 μs y frecuencias de descarga de 100 a 300 Hz. Se ha estudiado para acero 1045, la influencia de las diferentes configuraciones eléctricas que asisten el proceso de mecanizado respecto a las propiedades superficiales y el consumo de potencia eléctrica. Los resultados muestran que el proceso asistido mejora la mecanibilidad reduciéndose el consumo de potencia en 104 W y la energía especifica corte en un 22%. También modifica las propiedades superficiales, reduciendo la rugosidad media en un rango del 7 al 22% comparado con el proceso de torneado convencional

Expression and immunohistochemical localization of leptin in human periapical granulomas

Background: Leptin, initially described as an adipocyte-derived hormone to regulate weight control, is expressed in normal and inflamed human dental pulp, being up-regulated during pulp experimental inflammation. Leptin receptor (LER) has been identified in human periapical granulomas. The aim of this study was to analyze and characterize the expression of leptin in human periapical granulomas. Material and Methods: Fifteen periapical inflammatory lesions were obtained from extracted human teeth and teeth which underwent periapical surgery. After their morphological categorization as periapical granulomas and gradation of the inflammatory infiltrate, they were examined by immunohistochemistry using human leptin policlonal antibodies. Leptin mRNA expression was also determined by quantitative real-time PCR (qRT-PCR) and the amount of leptin protein was analyzed by immunoblot. Results: All periapical lesions exhibited the characteristic of chronic granulomatous inflammatory process with inflammatory infiltrate grade III. Leptin+ cells were detected in 13 periapical granulomas (86.6%). The median number of Leptin+ cells in periapical granulomas was 1.70 (0.00-7.4). Amongst the inflammatory cells in the periapical granulomas, only macrophages were reactive to leptin antibodies. Western blot analysis revealed the presence in all samples of a protein with apparent molecular weight of approximately 16 kDa, corresponding to the estimated molecular weights of leptin. The expression of leptin mRNA was confirmed by qRT-PCR analysis and the size of the amplified fragment (296 bp for leptin and 194 bp for cyclophilin) was assessed by agarose gel electrophoresis. Conclusions: For the first time, it has been demonstrated that human periapical granuloma expresses the adipokine leptin

Dentist´s knowledge, attitudes and determining factors of the conservative approach in teeth with reversible pulpitis and deep caries lesions

The aim of this study was to investigate dentists` knowledge, attitudes and factors regarding the conservative approach in the management of deep caries lesions (DCLs) in teeth with reversible pulpitis. 187 dentists were contacted directly or by mail, and 125 (67%) were finally included in the study. Dentists were requested to answer an open/discursive questionnaire about the routine approach to the diagnosis and treatment of DCLs, including knowledge-related attitudinal items. Total caries excavation was the preferred treatment option for more than 80% of dentists in case of DCL with reversible pulpitis. Only a small percentage (8%) chose partial caries removal, leaving some carious dentin close to the pulp to avoid pulp exposure. More than a half (51%) of respondents considered that cariogenic microorganisms must be removed or caries would progress. Dentists teaching at the University strongly disagreed with this statement (OR = 4.6; 95% C.I. = 1.3 ? 15.8; p = 0.017). Good clinical result was the most chosen reason (83%) to choose a specific treatment. Patient?s oral health (84%) and patient?s age (70%) were the two patient-related factors most taken into account for the choice of treatment. Total caries excavation is still the most frequently chosen treatment in teeth with DCL and reversible pulpitis. The joint assessment of the answers given by respondents allows to conclude that the new knowledge and concepts about caries lesions and the more conservative approach to DCLs have not still been incorporated by dentists into their usual clinical practice

Criteria and treatment decisions in the management of deep caries lesions : is there endodontic overtreatment?

The aim of this study was to investigate the diagnostic criteria and treatment decisions in the management of deep caries lesions (DCLs). The null hypothesis tested was that DCLs are managed according to the current scientific evidence. A total of 288 dentists were contacted directly or by mail, and 125 (43%) were included in the study. Dentists were requested to answer a questionnaire about the routine approach to the diagnosis and treatment of DCLs. Logistic regression analyses were carried out to calculate odds ratios (OR). Pulp sensitivity tests were used by 65% of dentists when assessing pulpal health in cases of DCLs, particularly those who had followed courses in cariology (OR = 3.8; p = 0.005). Dentine hardness was the most frequent criterion used during DCLs excavation (98%). Two thirds of the respondents (65%) removed carious tissue until they felt hard dentine, and feeling hard dentine correlated with caries removal even at the risk of pulpal exposure (OR = 15.8; p = 0.0000). Acute transient pain or sensitivity to cold or heat (reversible pulpitis) were considered by 58% of respondents as a reason to provide endodontic therapy. The null hypothesis tested is rejected. The evidence-based more conservative approach on the management of DCLs is not being translated to clinical dentistry. Root canal treatment is being indicated in cases of DCLs in which the diagnosis is reversible pulpitis. Likewise, it can be concluded that non-conservative management of DCLs, with endodontic overtreatment, could be occurring

Influence of the regime of electropulsing-assisted machining on the plastic deformation of the layer being cut

In this article, the influence of electropulsing on the machinability of steel S235 and aluminium 6060 has been studied during conventional and electropulsing-assisted turning processes. The machinability indices such as chip compression ratio ¿, shear plane angle f and specific cutting energy (SCE) are investigated by using different cutting parameters such as cutting speed, cutting feed and depth of cut during electrically-assisted turning process. The results and analysis of this work indicated that the electrically-assisted turning process improves the machinability of steel S235, whereas the machinability of aluminium 6060 gets worse. Finally, due to electropluses (EPs), the chip compression ratio ¿ increases with the increase in cutting speed during turning of aluminium 6060 and the SCE decreases during turning of steel S235.Peer ReviewedPostprint (published version

Electropulsing effects on mechanical and metallurgical behavior of AISI-SAE 4140 steel

The electroplasticity phenomenon (EP) produces changes in the mechanical properties of a metal, due to the simultaneous application of mechanical stresses of compression, bending, etc., and high instantaneous current pulses. The changes produced on the plastic deformation rate by the EP are due to thermal effects (such as Joule effect) and other effects associated to the electric and magnetic fields. There are only a few studies that consider, as this paper does, the effects of electropulsing effect on tensile test processes in which the electron flow is esteemed as the main reason. In this paper, the results of a research on tensile test on specimen of AISI-SAE 4140, assisted by high-current-density electric pulses are presented. The aim is to evaluate the effect of these pulses on the microstructure and mechanical properties of metallic materials. The phase transformations and microstructural changes in the metallic specimens exposed to EP were analysed using Scanning Electron Microscopy (SEM), Diffraction Ray X (DRX) and Differential Scanning Calorimetry (DSC). Preliminary results show there are some differences in the material behaviour, between the specimens tensile tested with and without EP, such as: decreases values of yield and ultimate strength and XRD analyses attests to a slight displacement and intensity reduction of diffraction. Moreover, the application of current density in the order of 2.18 A/mm² is enough to produce changes in mechanical and metallographic properties of AISI/SAE 4140.Peer ReviewedPostprint (published version

Predictive model for polishing times in mould finishing

El pulido, proceso final utilizado en la producción de piezas, es a menudo lento y se aplica manualmente. Normalmente define la rugosidad superficial y la precisión de la pieza. Se lleva a cabo utilizando partículas duras para producir la abrasión de la superficie de la pieza a pulir. En este documento se propone un modelo para predecir el progreso del frente de pulido. El modelo tiene en cuenta la topografía resultante antes de la mecanización a través de su curva de Abbott - Firestone, la velocidad relativa del material abrasivo, la fuerza aplicada, el material de la pieza y el tamaño de los granos abrasivos. Separa las aportaciones realizadas por el material de la pieza y el tipo abrasivo de la topografía previa. También muestra los valores recomendados para los diferentes parámetros de proceso a ser utilizados en la predicción de la evolución del frente de pulido en algunos materiales. Además se estima el tiempo de pulido necesario para eliminar completamente la topografía resultante del fresado utilizando una estrategia de perforación transversal. Por último, se muestra la predicción del modelo del frente de pulido, lo que confirma que el mecanismo de abrasión caracteriza dicho proceso.Polishing, the final process used in the production of parts, is often slow and often applied manually. It normally defines the surface roughness and part accuracy. It is performed using hard particles to produce abrasion of the workpiece surface to be polished. In this paper a model for predicting the progress of the polishing face is proposed. The model considers the topography resulting from prior mechanizing through its Abbott-Firestone curve, the relative speed of the abrasive material, the applied force, the workpiece material and the size of the abrasive grains. It separates the contributions made by the workpiece material and the abrasive type from the prior topography. It also shows recommended values for different process parameters to be used in predicting the evolution of the polishing front in some materials. Additionally, the polishing time required to completely remove the topography that results from ball milling using a cross drilling strategy is estimated. Finally, the model's correct prediction of the polished front is shown, confirming that the abrasion mechanism characterizes the sandpaper polishing process.Peer Reviewe

Analysis of the Part Distortions for Inconel 718 SLM: A Case Study on the NIST Test Artifact

The present paper evaluates the misalignment and geometry distortion of the standard National Institute of Standards and Technology (NIST) test artifact in Inconel 718 alloy, when several layers with and without supports are employed to manufacture it by the Selective Laser Melting (SLM) process. To this end, a coordinate-measuring machine (CMM) is used to measure the geometrical distortion in each manufacturing configuration, following the same measurement protocol. The results show that the laser path strategy favors a thermal gradient which, consequently, induces geometrical distortions in the part. To prove this hypothesis, a numerical simulation is performed to determine the thermal gradient and the pattern of the residual stresses. It was found that the geometrical distortion certainly depends on the position of the feature position and laser strategy, where thermal cycles and residual thermal stresses had an impact in the end-part geometry, especially if a high strength-to-weight ratio commonly used in aeronautics is present.This work is supported by the Serra Húnter program (Generalitat de Catalunya) reference number [UPC-LE-304 (2018)] and by the Aeronautics Advanced Manufacturing Center (CFAA) in the JANO—Joint action toward digital transformation project framework. Diego Celentano acknowledges Pontificia Universidad Católica de Chile (PUC), Wallonie-Bruxelles International (WBI) and National Council for Scientific and Technological Research CONICYT (FONDECYT Projects No. 3180006 and 1180591) for the financial supports provided for this work