Light-Curing Units, Photoinitiators System, and Monomers on Physico-Mechanical Properties of Experimental Composite Resins

This study evaluated the physico-mechanical properties of experimental composite resins made with different resin matrix and light-curing units. Experimental composite groups were divided according to monomers (BisGMA + TEGDMA-BT and BisGMA + BisEMA + UDMA + TEGDMA-BBUT) and photoinitiator system (camphorquinone-CQ and 1-phenyl-1,2-propanedione-PPD). A quartz tungsten halogen (QTH) or light-emitting diode (LED) were used to light cure all materials. Knoop microhardness (n = 10) was determined using Knoop microhardness test. Compressive strength, diametral tensile strength, and Young modulus (n = 7) were obtained using a universal testing machine at crosshead speed of 1.0 mm/min. The data were submitted to a three-way ANOVA and the Tukey post-hoc test (α = 0.05). QTH presented the highest total irradiance values and similar total radiant exposure to LED. For the compressive strength test, BT-PPD light-cured with LED group showed the lowest mean value. BT-CQ light-cured with LED group exhibited the lowest diametral tensile strength results. The BBUT-composite resins presented lowest Young modulus values, with no statistical difference between light-curing units (QTH and LED) and photoinitiators system (CQ and PPD). Application of QTH or LED in BT-based composite resins with PPD photoinitiator generated suitable results regarding the physico-mechanical properties.Keywords: Biomaterials; blends; dental composites; polymerization; shrinkag

Influence of Pre-Heating Regular Resin Composites and Flowable Composites on Luting Ceramic Veneers with Different Thicknesses

The aim of this study was to evaluate of pre-heating, filler contents and ceramic thickness on film thickness, microshear bond strength, degree of conversion and color change on ceramic veneers. Two experimental composites were prepared (Bis-GMA/UDMA/BisEMA/ TEGDMA), with different amounts of filler (65% or 50%wt) simulating a conventional and a flowable composite. The flowable (F) was used at room temperature and, the conventional either at room temperature (C) or pre-heated (CPH). Disk-shaped ceramics with different thickness (0.4 mm, 0.8 mm, 1.5 mm) were prepared. The film thickness was evaluated according to the ISO 4049 (n=10). The microshear bond strength (n=10) was evaluated in enamel using tubing specimens light-cured through the ceramic veneer. The degree of conversion was evaluated using Raman spectroscopy. The color change of the ceramic restorations (n=10) was evaluated by spectrophotometry. The results were submitted to 2-way ANOVA and Tukey’s post hoc test (a=5%). For the film thickness 1-way ANOVA was used (a=5%). The C presented the thicker film thickness; the CPH produced a similar film thickness in comparison to the F. All composites showed similar microshear bond strength. The degree of conversion of the F was higher than the C and CPH. The degree of conversion of the composites photo-activated through a 0.4 mm was higher than the composites photo-activated through thicker ceramics. The C showed the highest color change, while the CPH showed similar color change to the F. In conclusion, pre-heated conventional composites seem to be a potential alternative to lute ceramic veneers such as the flowable composites

Biometric characterization, water absorption curve and vigor on araçá-boi seeds

Araçà-boi is a fruit, which awakes great interest for presenting pulp of quality. Their seeds are recalcitrant and present a relatively short period of viability. The water absorption by seeds is a mechanism of growth resuming of the embryo with a subsequent of the tegument breakage by the radical. The seed electric conductivity is a vigor testing is directly related to the membrane permeability. Study of the curve of water absorption by the araçá-boi seeds will contribute to characterize their germination process. In this context, studies concerned with seeds were conducted, which characterized the mass, biometrics, water content, electric conductivity and water imbibition by seeds. It was found that the population of plants established in Manaus-AM produces small, medium and large seeds and which present 70.2, 68.2 and 47.5% of moisture. The greatest water increase takes place in the first hour of absorption, regardless of the size of seeds and water absorption velocity is not influenced by their size. The imbibition curves characterized in the 144-hour period, independent of the size of seeds, show changes of two physiological phases. Both the large and medium seeds present smaller conductivity values, obtaining smaller percentages of germination for possessing increased vigor indices

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Different Wavelengths of LEDs on Cutaneous Wound Healing in Wistar Rats

This study evaluates different wavelengths of LED therapy in Wistar rats skin injuries. LEDs (Light Emitting Diodes) are phototherapeutic resource nowadays, since it is considered a good alternative to Low Level Laser Therapy in injury healing because of the lower cost. Twenty-five male Wistar rats were divided in five groups: Control, Red LED (630-780 nm), Green LED (490-565 nm), Blue LED (440-490 nm) and Yellow LED (590-630 nm). It´s a experimental research that it was performed during 4 weeks. Twenty-four hours after surgical injury (1cm²) was applied LED therapy for 6 minutes during five days. Red LED presented best anti-edematous effects in comparison to the other wavebands. The perimeters were reduced in all groups, but in Green and Red LED groups were significantly diminished (

Different Wavelengths of LEDs on Cutaneous Wound Healing in Wistar Rats

This study evaluates different wavelengths of LED therapy in Wistar rats skin injuries. LEDs (Light Emitting Diodes) are phototherapeutic resource nowadays, since it is considered a good alternative to Low Level Laser Therapy in injury healing because of the lower cost. Twenty-five male Wistar rats were divided in five groups: Control, Red LED (630-780 nm), Green LED (490-565 nm), Blue LED (440-490 nm) and Yellow LED (590-630 nm). It´s a experimental research that it was performed during 4 weeks. Twenty-four hours after surgical injury (1cm²) was applied LED therapy for 6 minutes during five days. Red LED presented best anti-edematous effects in comparison to the other wavebands. The perimeters were reduced in all groups, but in Green and Red LED groups were significantly diminished (

Resumos concluídos - Engenharia de Materiais

Resumos concluídos - Engenharia de Materiai