Obtenção de cerâmicas à base de tricálcio fosfatos utilizando óxido de manganês como aditivo

The calcium phosphate ceramics have been very investigated as material for bone implants. The tricalcium phosphate (β-TCP) had a great potential for application in temporary implants like a resorbable bioceramic. This material presents a limitation in its sintering temperature due to occurrence of the allotropic transformation β → α at temperatures around 1200°C, not allowing the attainment of dense ceramic bodies. This transformation also causes cracks, what diminishes the mechanical strength, limiting its use to applications of low mechanical requests. This work studies the influence of the addition of manganese oxide in the sintering of β-TCP. Two processing routes were investigated. The first was the powder metallurgy conventional process. The test bodies (samples) were pressed and sintering at temperatures of 1200 and 1250°C. The second route was uniaxial hot pressing and its objective was to obtain samples with high relative density. The samples were physically characterized through density and porosity measurements. The thermal behavior was studied through dilatometric, thermal differential and thermogravimetric analysis. The mechanical properties were characterized by three point flexure test and Vickers microhardness measurements. The microstructure was analyzed by scanning electron microscopy. The addition of manganese oxide caused an improvement of the mechanical strength in relation to the material without additive and promoting the stabilization of β-TCP to greater temperatures

Aplicação de agentes remineralizantes sobre o esmalte clareado: eficácia contra o manchamento por café

The aim of this study was to evaluate the influence of remineralizing agents on the susceptibility of enamel cleared by the coffee pigmentation during office bleaching. Fifty bovine incisors were selected and randomly assigned into 5 groups (n = 10) on the basis of remineralizing agents: G1 gel hydrogen peroxide to 35% (control group); G2, hydrogen peroxide gel and a 35% gel 2% neutral fluorine; G3, hydrogen peroxide gel and a 35% nanostructured calcium phosphate gel, G4, hydrogen peroxide gel and a 35% casein fosfoptídia-phosphate and amorphous calcium folder; G5 hydrogen peroxide gel to 35% without mineralizing agent. All groups exception G1 (control group) were subjected to pigmentation soluble coffee according to the manufacturer's guidelines. The samples were immersed in coffee at temperature of 55° C, 1 time a day for 4 minutes. Color changes were performed by Easyshade spectrophotometer at CIE Lab method before and after 3 whitening sessions. Data were analyzed by analysis of variance ANOVA. The results showed statistically significant differences between the remineralizing substances for the parameters L *, a *, b * ΔE (p <0.0001). The L * values for the group G5, and the b * for G2 and G5 groups differed from the control group. After the 3rd whitening session, Fluor's group (G2) and that without mineralizing agent (G5) showed ΔE values less than the control group that did not undergo pigmentation. It was concluded that only the nanoclusters remineralizing agents Phosphopeptides Casein-Amorphous Calcium Phosphate and Calcium Amorphous phosphate were able to reduce the coffee interference whitening efficacy of hydrogen peroxide.