Pre-Heating effect on the microhardness and depth of cure of Bulk-Fill composite resins / Efecto del precalentamiento de las resinas compuestas Bulk-Fill en la microdureza y la profundidad de curado

Abstract 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. 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). 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. 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.

Resumen El objetivo fue investigar el efecto del precalentamiento de tres resinas Bulk-fill, una resina compuesta convencional sobre la microdureza Vickers y la profundidad de curado de estas resinas. Se utilizaron tres composites Bulk-Fill-SDR Plus (SDR), Estelite BULK FILL Flow (EST), Admira® Fusion x-tra (AFX), y una resina compuesta convencional G-ænial POSTERIOR (GP) como grupo de control. Las muestras se obtuvieron a temperatura ambiente (24°C) y a 55°C en modo T2 después de haber sido colocadas en un dispositivo de calentamiento durante 10 minutos. Se dividieron en ocho grupos (n=10) según el tipo de material y el proceso de calentamiento que se utilizó (precalentado y no calentado). Se probaron con un medidor de microdureza Vickers (VHN) en las superficies inferior y superior. Las primeras mediciones se obtuvieron en la línea de base; la segunda se realizó después de que las muestras se almacenaran en agua destilada a 37°C durante 24 horas. La profundidad de curado se calculó utilizando una relación de dureza inferior/ superior de las mediciones. El análisis estadístico se realizó utilizando el SPSS V23 y las pruebas de Shapiro-Wilk. Por último, se utilizó la prueba de Duncan para las comparaciones múltiples (p<0,05). VHN aumentó tras el procedimiento de precalentamiento en las resina Bulk-Fill, disminuyó en los GP. No hubo diferencias entre los valores de VHN de referencia y de 24 horas en SDR y GP. Después de 24 horas, mientras que el VHN de EST aumentó, el VHN de AFX disminuyó. No hubo diferencias entre los ratios de dureza de las muestras de AFX y EST (p<0,001) y los ratios de dureza fueron mayores que los de GP y SDR. Al comparar los valores de referencia y los de 24 horas, el VHN dependió del tipo de materiales. Se obtuvo una profundidad de curado suficiente en todos los grupos con un grosor de 2mm.

Effects of Polishing Systems on Surface Roughness and Colour Stability of Microhybrid Composite Resin

@#Introduction: Discolouration of microhybrid composite resin is a common problem faced by both dental practitioners and patients. The accumulation of plaque, penetration of colourant particles from foods and beverages, dietary habits and the smoothness of restorations have been known to influence the quality of the aesthetic restoration. The purpose of this study was to determine the effects of polishing systems on surface roughness that led to discolouration of the microhybrid composite resin. Methods: Forty five samples of microhybrid composite resin (Filtex Z100) restorations were polished with two different polishing systems; one-step polishing (OP) system on the distal surface and multiple-step polishing (MP) system on the mesial surface. All samples were then immersed in two common beverages: black coffee and cocoa, for 20 minutes daily throughout 28 days of the experimental period. Results: Data on visual colour measurement and spectrometer colour spectrum was subjected to one-way ANOVA test at a significance level of 0.05. Both solutions were found to cause a significant colour change (p=0.0195) on the microhybrid composite resin. Black coffee solution obtained the highest score (71.6) of visual colour change and the lowest reflectance value (62.818) on the distal surface. Surface roughness evaluation using a scanning electron microscope (SEM) had presented that both polishing systems used produced low level of surface roughness. Conclusion: Although MP system produced a smoother surface compared to OP system, a prolonged exposure to colourant particle found to cause an unacceptable discolouration of microhybrid composite resin