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Objective: The aim of this study was to evaluate and compare the effects of the superficial application of two different modeling resins on the surface microhardness and discoloration of composite resins. Material and Methods: The present study used two different composites and modeling resins. The composites were placed in plastic molds. Subsequently, the modeling resins were applied on the surface of the two composite groups. The microhardness and color pertaining to all the groups were evaluated. The current study used the One-Way ANOVA and Kruskal Wallis tests, in order to perform the statistical evaluation (p<0.05). Results: The present study compared the microhardness pertaining to the groups and the highest microhardness values were observed in the Estelite Asteria group (none), whereas the lowest values were observed in the GC Essentia group (Ultradent). Moreover, the current study evaluated the color stability and the greatest discoloration was observed in the control group of the GC Essentia group, whereas the least discoloration was observed in the Estelite Asteria group that included the samples prepared using Ultradent Wetting Resin. Conclusions: The results of the present study demonstrated that the use of modeling resins, which facilitate the placement of composite resins, reduced the microhardness and discoloration of composite resins. The aforementioned effect can be attributed to the variations in the structure of the filling. However, further studies are warranted to support and verify the results of the current study. Objetivo: El objetivo del presente estudio fue evaluar y comparar los efectos de la aplicación superficial de dos resinas humectantes sobre la microdureza superficial y la decoloración de las resinas compuestas. Material y métodos: El presente estudio utilizó dos resinas humectantes y resinas de modelado diferentes. Las resinas compuestas se colocaron en moldes de plástico. Posteriormente, se aplicaron las resinas humectantes sobre la superficie de los dos grupos. Se evaluó la microdureza y el color de todos los grupos. El presente estudio utilizó las pruebas One-Way ANOVA y Kruskal Wallis, para realizar la evaluación estadística (p<0.05). Resultados: Los valores más altos de microdureza se observaron en el grupo Estelite Asteria, mientras que los menores valores se observaron en el grupo GC Essentia (Ultradent). La mayor decoloración se observó en el grupo control o el grupo GC Essentia, mientras que la menor decoloración se observó en el grupo Estelite Asteria con Ultradent Wetting Resin. Conclusiones: Los resultados del presente estudio demostraron que el uso de resinas humectantes, que facilitan la colocación de resinas compuestas, redujo la microdureza y decoloración de las resinas compuestas. El efecto mencionado anteriormente se puede atribuir a las variaciones en la estructura del relleno. Sin embargo, se necesitan más estudios para respaldar y verificar los resultados del presente estudio.

To determine the surface microhardness of white portland cement associated with niobium nanoparticles, white portland cement associated with zirconium nanoparticles, and mineral trioxide aggregate. The present study is an experimental in-vitro study. The sample consisted of 03 study groups. These were divided into 09 subgroups of 04 hours, 14 days and 28 days. The instrument used to record the surface mechanical microhardness was the Vickers microdurometer. The Shapiro-Wilk statistical analysis was then performed to identify the normality of the data. The Anova test was applied to compare between the three groups and then the Tukey test for multiple comparisons with a 95% confidence level. White Portland cement associated with zirconium nanoparticles had the highest hardness value (p<0.05), followed by white Portland cement associated with niobium nanoparticles and aggregate control cement of mineral trioxide. The lowest value of surface microhardness was obtained by the addition of mineral trioxide (p<0.05). Surface microhardness values were significantly higher at 28 days than at 04 hours for all groups evaluated. White Portland cement with/without nanoparticulate additives generated higher surface microhardness than the control group added mineral trioxide in the evaluation periods. Determinar la microdureza superficial de cemento portland blanco asociado a nanopartículas de niobio, cemento portland blanco asociado a nanopartículas de circonio y agregado de trióxido mineral. El presente estudio es un estudio experimental in vitro. La muestra estuvo compuesta por 03 grupos de estudio. Estos se dividieron en 09 subgrupos de 04 horas, 14 días y 28 días. El instrumento utilizado para registrar la microdureza mecánica de la superficie fue el microdurómetro Vickers. Luego se realizó el análisis estadístico Shapiro-Wilk para identificar la normalidad de los datos. Se aplicó la prueba de Anova para comparar entre los tres grupos y luego la prueba de Tukey para comparaciones múltiples con un nivel de confianza del 95%. El cemento Portland blanco asociado a nanopartículas de circonio tuvo el mayor valor de dureza (p<0.05), seguido del cemento Portland blanco asociado a nanopartículas de niobio y el cemento de control de agregados de trióxido mineral. El valor más bajo de microdureza superficial se obtuvo mediante la adición de trióxido mineral (p<0,05). Los valores de microdureza superficial fueron significativamente mayores a los 28 días que a las 04 horas para todos los grupos evaluados. El cemento Portland blanco con/sin aditivos nanoparticulados generó mayor microdureza superficial que el grupo control al que se le añadió trióxido mineral en los periodos de evaluación.

The purpose of this study was to evaluate and compare the effect of carbonated beverage on the surface microhardness of two acrylic materials used to fabricate temporary restorations. The study was experimental in vitro. Forty blocks of acrylic resins used in provisional restorations were made, 20 from Alike® (GC AMERICA INC., Lot 1712161) and 20 from Acryptemp® (Zhermack S.P.A., Lot 302334). After that, the blocks were immersed in distilled water for 24 hours. After this time, the initial surface microhardness was measured. Then the 20 samples of the experimental group were immersed in a carbonated drink (coca cola - soda) for 12 minutes per day, for 5 days. Finally, the final surface microhardness was measured using the Vickers microdurometer. Measures of central tendency and dispersion were used, and the Student's t test and ANOVA were performed. A mean surface microhardness of 8.8 and 7.2HV was found for the PMMA resin group (Initial and final respectively), and 9.5 and 8HV for the bisacrylate group. Statistically significant differences were found when comparing the beginning and end of each group and when comparing the two materials. The acrylic resin of polymethylmethacrylate (Alike® GC AMERICA INC.) Presented higher surface microhardness compared to the bis acrylic resin (Acrytemp® Zhermack S.P.A), after being exposed to a carbonated drink. El propósito de este estudio fue evaluar y comparar el efecto de la bebida carbonatada en la microdureza superficial de dos materiales acrílicos utilizados para confeccionar restauraciones provisionales. El estudio fue experimental in vitro. Se confeccionaron 40 bloques de resinas acrílicas utilizadas en provisorios, 20 de Alike® (GC AMERICA INC., Lote 1712161) y 20 de Acryptemp® (Zhermack S.P.A., Lote 302334). Posterior a ello, se sumergió los bloques en agua destilada por 24 horas. Pasado este tiempo se procedió a medir la microdureza superficial inicial. Luego las 20 muestras del grupo experimental se sumergieron en una bebida carbonatada (coca cola-gaseosa) durante 12 minutos por día, durante 5 días. Por último se midió la microdureza superficial final mediante el microdurómetro de Vickers. Se utilizaron medidas de tendencia central, dispersión y se realizaron la prueba t de Student y ANOVA. Se encontró una microdureza superficial media de 8,8 y 7,2HV para el grupo de resina PMMA (Inicial y final respectivamente), y  9,5 y 8HV para el grupo de bisacrilato. Se halló diferencias estadísticamente significativas al comparar el inicio y final de cada grupo y al comparar los dos materiales. La resina acrílica de polimetilmetacrilato (Alike® GC AMERICA INC.) presentó mayor microdureza superficial en comparación con la resina bis acrílica (Acrytemp® Zhermack S.P.A), después de ser expuestas a una bebida carbonatada.

Evaluate the influence of different cavity depth and consequent light-tip/material distance, on the degree of conversion, biaxial flexural strength and microhardness of a nanohybrid resin-composite (top/bottom), employing the incremental technique. Quadrangular samples (4x4mm) with thickness variations (cavity-depth simulation: 2, 4, and 6 mm; n=10) were made using a nanohybrid resin-composite (Forma, A3, Ultradent) employing the incremental technique. Vickers Microhardness and degree of conversion were assessed on top/bottom surfaces. Biaxial flexural strength was tested on resin-composite discs (8.5mm diameter, 2mm thick) using 3D-printed molds (vertically stacked). Microhardness and Degree of conversion data were analyzed employing 2-way/ANOVA, Biaxial flexural strength with 1-way/ANOVA.For microhardness, “distance” factor plus “surface/distance” interaction resulted statistically significant (p<0.05). The 2 mm group, followed by the 4 mm group, showed the highest results (99.41±52.23 and 84.1±15.74 VHN), while the 6 mm group had the lowest (68.60±18.69 VHN), with lower values observed on the bottom surfaces for the latter group only. Biaxial flexural strength data showed no significant differences among groups. Degree of conversion was significantly higher at the top surfaces compared to the bottom surfaces (top: 47.74±9.67%; bottom: 21.93±8.57%). At 2 and 4 mm distance, polymerization quality remained adequate (top/bottom surfaces). A 6 mm distance produced lower quality polymerization, mainly on the bottom surfaces. In such scenario, an additional photopolymerization cycle may be desirable. The current outcomes may be related only to the conditions (RBC, distances and LCU) employed in this study. Evaluar la influencia de la profundidad cavitaria/distancia de la luz fotopolimerizante y el material sobre el grado de conversión, resistencia a flexión biaxial y microdureza de una resina nanohíbrida (superficies superior/inferior), mediante técnica incremental. Se fabricaron muestras cuadrangulares (4x4 mm) con variaciones de espesores de 2, 4 y 6 mm (n=10 por medida), simulando la profundidad de una preparación cavitaria, utilizando una resina nanohíbrida (Forma, A3, Ultradent) empleando la técnica incremental. Se evaluó microdureza Vickers y grado de conversión en superficies superior/inferior. La resistencia a la flexión biaxial se probó en discos de resina (8,5 mm diámetro, 2 mm espesor) utilizando moldes impresos 3D (apilados verticalmente). Microdureza y grado de conversión se analizaron empleando ANOVA de 2 vías y resistencia a la flexión biaxial con ANOVA de 1 vía. Para microdureza, el factor “espesor” más la interacción “superficie/espesor” resultaron estadísticamente significativos (p<0,05). El grupo de 2 mm mostró resultados más altos (99,41±52,23), seguido por 4 mm (84,1±15,74 VHN), mientras que 6 mm tuvo los más bajos (68,60±18,69 VHN), observándose valores más bajos en las superficies inferiores para este último grupo. Resistencia a la flexión biaxial no mostró diferencias significativas entre grupos. El grado de conversión fue significativamente mayor en superficies superiores en comparación con las superficies inferiores (superior: 47,74±9,67 %; inferior: 21,93±8,57 %). Para los grupos de 2 mm/4 mm, la polimerización siguió siendo adecuada (superficies superior/inferior). 6 mm produjo una polimerización de menor calidad, especialmente en superficies inferiores. El grado de conversión fue mayor en superficies superiores para todos los grupos. No se observó impacto significativo en el grado de conversión o resistencia a flexión según la distancia desde la luz fotopolimerizante. Las propiedades físicas y el grado de conversión no fueron proporcionales.

This study aimed to investigate the impact of the combination of Benzalkonium chloride (BAC) and sodium hypochloride (NaOCl) and its application after ethylenediaminetetraacetic acid (EDTA) in root canal irrigation procedures on the microhardness and mineral content of dentin. Distal roots of mandibular third molars were embedded in auto-polymerizing acrylic resin, sectioned coronally to apically resulting in fifty-four root sections. Thirty sections underwent microhardness evaluation, and twenty-four sections were randomly chosen for mineral analysis. The microhardness assessment comprised three groups: Group 1 (2.5% NaOCl), Group 2 (2.5% NaOCl with 0.084% BAC), and Group 3 (2.5% NaOCl with 0.084 BAC post-17% EDTA). Initial and post-irrigation microhardness values were measured for each group. For mineral analysis, samples were categorized into four groups: distilled water, 2.5% NaOCl, 2.5% NaOCl with 0.084% BAC, and 17% EDTA+2.5% NaOCl with 0.084% BAC. X-ray photoelectron spectroscopy immediately measured magnesium, phosphorus, and calcium mineral contents on dentin surfaces post-irrigation. Results indicated a significant reduction in root dentin microhardness for all solutions (p<0.05). However, no statistically significant difference in the percentage of reduction was observed among the groups (p>0.05). XPS analysis revealed no significant disparity in dentin surface mineral content among the groups (p>0.05). In conclusion, the addition of Benzalkonium chloride to sodium hypochloride, either alone or after EDTA, did not induce a significant alteration in dentin microhardness or mineral content. These findings contribute to a nuanced understanding of dental irrigation protocols and their effects on dentin properties during endodontic procedures.

OBJECTIVE: The aim of this study was to investigate the effect of preheating three bulk-fill and one conventional composite resin on the Vickers microhardness and depth of cure of these composites. METHODS: In this study, three bulk-fill composites-SDR Plus (SDR), Estelite BULK FILL Flow (EST), Admira® Fusion x-tra (AFX), and one conventional composite resin G-ænial POSTERIOR (GP) were used as the control group. The samples were obtained at room temperature (24°C) and at 55°C in T2 mode after being placed in a heating device for 10 minutes. The samples were divided into eight groups (n=10) according to the type of material and heating process that was utilized (preheated and nonheated). All samples were tested with a Vickers microhardness (VHN) tester on the bottom and top surfaces. The first measurements were obtained at baseline; the second set of measurements was performed after the samples were stored in distilled water at 37°C for 24 hours. The depth of cure was calculated using a bottom/top hardness ratio of measurements. Statistical analysis was performed utilizing the SPSS V23 and Shapiro-Wilk tests. Lastly, the Duncan test was used for multiple comparisons (p<0.05). RESULTS: While the VHN increased after the preheating procedure in bulk-fill composites, it decreased in GP. There was no difference between the baseline and the 24-hour VHN values in SDR and GP. After 24 hours, while the VHN of EST increased, the VHN of AFX decreased. There was no difference between the hardness ratios of the AFX and EST samples (p<0.001) and hardness ratios were greater than GP and SDR. CONCLUSION: When comparing the baseline and the 24-hour values, the VHN depended on the type of materials. Sufficient curing depth was obtained in all groups with a thickness of 2mm.

This text describes the plasma nitriding of a ductile iron, to increase the surface hardness and improve its wear behavior. A ferritic ductile iron was used and processed with gases (N2 + H2) for 5 hours in a treatment chamber built at the UNAM Physics Institute. The treated samples were characterized using scanning electron microscopy, atomic force microscopy, microhardness and X-ray diffraction. The presence of Fe-N compounds was corroborated on the surface of the material. Modifications in surface morphology and a 30% increase in microhardness were also obtained.

In this work, the effect of the torsion process angle of twist and distance from the center of cylindrical bars on the microhardness profile of annealed AISI 1045 steel was studied. The results showed that the microhardness increase with the evaluated parameters and the hardening is related to the plastic deformation caused by the process rather than by microstructural transformations. Based on the experimental results, ANOVA-Pareto analysis was conducted proving that the angle of twist is the most influential control factor (59.35%) among the parameters investigated. Finally, a model to predict the microhardness profile from the torsion process is presented.

Surface changes of restorative materials after bleaching have clinical importance in terms of the durability and survival of restorations. This study aimed to evaluate the effect of home bleaching on the surface roughness, microhardness, and surface analysis of four different types of chairside computer-aided design and computer-aided manufacturing (CAD/CAM) materials. Specimens were prepared from composite resin (Brilliant Crios: BC), resin nanoceramic (Lava Ultimate: LU), polymer-infiltrated ceramic-network (Vita Enamic: VE), and zirconia-reinforced lithium silicate glass-ceramic (Vita Suprinity: VS) CAD/CAM materials. Specimens were polished using 800, 1000, 1200, and 2000 grit SiC papers. Each restorative material was randomly divided into two groups; control and bleaching (n=10). The 16% carbamide peroxide bleaching agent (Whiteness Perfect 16%, FGM) was applied to the specimens for 4 h/day for 14 days. Surface roughness values (Ra) were obtained using a profilometer, and microhardness values (VHN) were obtained using a Vickers microhardness test. Surface analysis of specimens was evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Data were analyzed Two-way ANOVA and Fisher’s Least Significant Difference (LSD) test (p<0.05). After bleaching, the surface roughness of BC (p<0.001) and VE (p<0.032) significantly increased. Bleaching did not significantly affect the microhardness of CAD/CAM materials. SEM evaluation showed material-dependent surface damages after bleaching procedures. The effect of 16% carbamide peroxide home bleaching agent on surface roughness and microhardness of chairside CAD/CAM materials is material-dependent. Before bleaching, restorative materials should be protected by applying a protective barrier and contact with the bleaching agent should be minimized. Also, after bleaching, the restoration surface should be carefully inspected, and re-polishing might be beneficial.

En este trabajo se estudió el efecto del ángulo de giro del proceso de torsión y la distancia desde el centro en barras cilíndricas en el perfil de microdureza del acero AISI 1045 recocido. Los resultados mostraron que la microdureza aumenta con los parámetros evaluados y el endurecimiento se relaciona con la deformación plástica causada por el proceso más que por transformaciones microestructurales. Con base en los resultados experimentales, se realizó un análisis ANOVA-Pareto que demostró que el ángulo de giro es el factor de control más influyente (59,35%) entre los parámetros investigados. Finalmente, se presenta un modelo para predecir el perfil de microdureza del proceso de torsión.