Comparación in vitro del espesor y homogeneidad de la capa de cementación en carillas indirectas, realizado con resina fluida vs cemento de resina fotodependiente / Comparison of thickness and homogeneity of thecementationlayer in indirectveneers, madewith fluidresin vs. light-cure resincement: in vitro study

Resumen Objetivo: Comparar el grosor y homogeneidad de la capa de cementación entre un cemento de resina fotodependiente y una resina fluida. Materiales y métodos: Para la obtención de la muestra se talló la preparación en un diente de marfilina, el cual fue escaneado y luego replicado 92 veces en un polímero ABS. La muestra se dividió en 2 grupos con 46 muestras cada uno. Se realizó la cementación de las carillas con resina fluida Tetric N-Flow en el grupo G1, y con cemento de resina fotodependiente VariolinkEsthetic en el grupo G2. Cada muestra fue previamente lavada con alcohol de 70°, luego secada y se aplicó una capa de adhesivo TetricN-Bond. Se utilizó presión digital para lograr el asentamiento final de las carillas. Finalmente se realizó un corte medial y uno paramedial para obtener muestras de 2 mm aproximadamente, las cuales se observaron y midieron en un microscopio óptico. Resultados: El promedio de grosor para Tetric N-Flow fue de 119μm en incisal, 113μm en medio y 107μm en cervical. Para VariolinkEsthetic el promedio fue de 117μm, 112μm y 110μm en incisal, medio y cervical respectivamente. La homogeneidad fue de un 93,3% para G1 y 91,3% para G2. Conclusión: No existe diferencia significativa en el grosor y homogeneidad de la capa de cementación realizado con resina fluida y con cemento de resina fotodependiente.

Abstract Objective: Compare the thickness and homogeneity of the cementing layer between a light-cure resin cementand a flowable resin. Materials and methods: To obtain the sample, the preparation was carved in a replica of tooth 1.1 (EWL modelteeth, Kavo), which was scanned and then replicated 92 times in an ABS polymerby 3D printing. The simple was divided into 2 groupswith 46 sample seach. The cementation of the veneres was performed with Tetric N-Flow flowable resin in the G1 group, and with Variolink Esthetic light-cure resin cement in the G2 group. Each simple was previously washed with 70° alcohol, then dried and a layer of Tetric N-Bond was applied. Digital pressure was used to achieve the final settlement of the veneers. Finally, a medial and a paramedial section were made to obtain approximately 2 mm thick samples. The cementation layer was observed with an optical microscope. Results: The average thickness for Tetric N-Flowwas 119μm in incisal, 113μm in medium and 107μm in cervical. For Variolink Esthetic the average was 117μm, 112μm and 110μm in incisal, middle and cervical respectively. The homogeneity was 93.3% for G1 and 91.3% for G2. Conclusion: There is no significant difference in the thickness and homogeneity of the cementing layer made with flowable resin and with light-cure resincement.

Influence of incorporation of fluoroalkyl methacrylates on roughness and flexural strength of a denture base acrylic resin

Fluorinated denture base acrylic resins can present more stable physical properties when compared with conventional polymers. This study evaluated the incorporation of a fluoroalkyl methacrylate (FMA) mixture in a denture base material and its effect on roughness and flexural strength. A swelling behavior assessment of acrylic resin specimens (n=3, per substance) after 12 h of FMA or methyl methacrylate (MMA) immersion was conducted to determine the solvent properties. Rectangular specimens (n=30) were allocated to three groups, according to the concentration of FMA substituted into the monomer component of a heat-polymerized acrylic resin (Lucitone 550), as follows: 0 percent (control), 10 percent and 20 percent (v/v). Acrylic resin mixed with concentrations of 25 percent or more did not reach the dough stage and was not viable. The surface roughness and flexural strength of the specimens were tested. Variables were analyzed by ANOVA and Tukey's test (a=0.05). Immersion in FMA produced negligible swelling, and MMA produced obvious swelling and dissolution of the specimens. Surface roughness at concentrations of 0 percent, 10 percent and 20 percent were: 0.25 ± 0.04, 0.24 ± 0.04, 0.22 ± 0.03 mm (F=1.78; p=0.189, not significant). Significant differences were found for flexural strength (F=15.92; p<0.001) and modulus of elasticity (F=7.67; p=0.002), with the following results: 96 ± 6, 82 ± 5, 84 ± 6 MPa, and 2,717 ± 79, 2,558 ± 128, 2574 ± 87 MPa, respectively. The solvent properties of FMA against acrylic resin are weak, which would explain why concentrations over 20 percent were not viable. Surface changes were not detected after the incorporation of FMA in the denture base acrylic resin tested. The addition of FMA into denture base resin may lower the flexural strength and modulus of elasticity, regardless of the tested concentration.

Nano-composition of riboflavin-nafion functional film and its application in biosensing.

A novel nafion-riboflavin membrane was constructed and characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy and cyclic voltammetric techniques. The estimated average diameter of the designed nanoparticles was about 60 nm. The functional membrane showed a quasi-reversible electrochemical behaviour with a formal potential of -562 +/- 5 mV (vs Ag/AgCl) on the gold electrode. Some electrochemical parameters were estimated, indicating that the system has good and stable electron transfer properties. Moreover, horseradish peroxidase (HRP) was immobilized on the riboflavin-nafion functional membrane. The electrochemical behaviour of HRP was quasi-reversible with a formal potential of 80 +/- 5 mV (vs Ag/AgCl). The HRP in the film exhibited good catalytic activity towards the reduction of H2O2. It shows a linear dependence of its cathodic peak current on the concentration of H2O2, ranging from 10 to 300 (micro)M.

Electrocatalytic oxidation of SMZ at multi-wall carbon nanotubes-Nafion modified glassy carbon electrode and its electrochemical determination application / 药学学报

Electrochemical behaviors, electrochemical kinetics and electrochemical determination of sulfamethoxazole (SMZ) at both glassy carbon electrode (GCE) and multi-wall carbon nanotubes-Nafion modified glassy carbon electrode (MWCNTs-Nafion/GCE) were investigated by cyclic voltammetry (CV), chronocoulometry (CC), chronoamperometry (CA), linear scan voltammetry (LSV) and amperometric i-t curve. The experimental results showed that the electrochemical oxidation of SMZ was sluggish on GCE, but the oxidation peak current of SMZ increased significantly at MWCNTs-Nafion/GCE in comparison with that at the bare GCE, which indicated that MWCNTs-Nafion/GCE could catalyze the electrochemical oxidation of SMZ very well. The plot of oxidation peak currents versus the square roots of the scanning rates for the redox in the potential range of 10-1,000 mV x s(-1) showed a straight line, as expected for a diffusion-limited electrochemical process for SMZ electrochemical oxidation. At the bare GCE and MWCNTs-Nafion/GCE the oxidation peak current was linearly proportional to the concentration of SMZ over the concentration range 5.0 x 10(-5)-2.5 x 10(-3) mol x L(-1) and 1.0 x 10(-5)-6.0 x 10(-3) mol x L(-1). The detection limits were 1.0 x 10(-5) and 5.0 x 10(-7) mol x L(-1). The relative standard deviation was between 0.85% -1.98% and the recovery was in the range of 98%-101.2%. This MWCNTs-Nafion/GCE could be applied in SMZ electrochemical determination with satisfied results. The proposed method can be applied to the determination of SMZ in tablet samples with satisfied results.

Comparação de tratamentos preventivos à calcificação em biomaterial (pericárdio bovino) empregado para a confecção de válvulas cardíacas protéticas / Comparison of preventive treatments to the calcification in biomaterial (bovine pericardio) applied on preparation of prosthetic heart valves

Biopróteses de válvulas cardíacas derivadas de tecidos animais que sofreram ligações cruzadas por ação do glutaraldeído, como o pericárdio bovino, têm uso terapêutico limitado devido ao fato de que tendem a sofrer processo de calcificação. Para prevenir a calcificação, diversas modificações podem ser feitas nos biomateriais; uma das estratégias empregadas é introduzir moléculas volumosas que podem ocupar os espaços entre as estruturas, e por efeito estérico, impedir o crescimento dos cristais de cálcio. Assim o objetivo deste trabalho foi depositar um filme de polímero fluorado (tipo Teflon®), e um filme de carbono amorfo tipo diamante por entre as fibras de colágeno que compõem o pericárdio bovino, e com isso promover um impedimento estérico nos locais onde os cristais de cálcio poderiam se desenvolver...

Avaliaçäo das alteraçöes oculares pelo uso prolongado de lentes de contato fluorcarbonadas / Valuation of ocular changes induced by extended wear fluoro-silicone/acrylate contact lenses

As alteraçöes oculares pelo uso prolongado das LC FLUORCARBONADAS (POLYSIL - FC) foram estudadas em 19 pacientes míopes de -1,00 a -4,25 D, com idade média de 23,9 anos, durante 12 semanas. Foram analisados os comportamentos da acuidade visual, do exame biomicroscópico do segmento anterior, da espessura corneana, da ceratometria, da estesiometria corneana, da topografia corneana pela fotoceratoscopia, da funçäo lacrimal pelo teste de Schirmer, e da pressäo intra-ocular pela tonometria de aplanaçäo. A espessura corneana apresentou aumento significativo apenas durante as duas primeiras semanas de uso das lentes de contato. A ceratometria evidenciou aplanamento corneano discreto, porém significativo, do meridiano vertical. Em relaçäo à acuidade visual, biomicroscopia do segmento anterior, estesiometria corneana, fotoceratoscopia, tonometria de aplanaçäo e teste de Schirmer, näo houve diferença significativa entre os valores obtidos antes e após a adaptaçäo das lentes de contato. Os resultados foram semelhantes em ambos os olhos. O uso prolongado destas lentes mostrou ser bastante seguro, näo ocorrendo nenhum caso de infecçäo ocular, alteraçäo da acuidade visual ou edema corneano significativo após o período estudado.