Papers by Author: Marcelo Henrique Prado da Silva

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Authors: C. Marques, Luis Henrique Leme Louro, Marcelo Henrique Prado da Silva
Abstract: Bioactive ceramics have the ability to chemically bond to bone. This class of biomaterials can be used as coatings on metallic implants, alloplastic bone defect fillers and as scaffold for tissue engineering. The most widely used bioactive ceramics are hydroxyapatite, Ca10(PO4)6(OH)2 and tricalcium phosphate, Ca3(PO4)2. This study presents new bioactive ceramics based on Nb2O5 and Ta2O5. These materials were produced from bioinert ceramics chemically activated by an alkali hydrothermal treatment. Scanning electron microscopy, energy dispersion X-ray spectroscopy and X-ray diffraction analyses on samples incubated in simulated body fluid showed the presence of bone-like apatite, confirming that the modified ceramics surface became bioactive.
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Authors: Marcelo Henrique Prado da Silva, Gloria Dulce de Almeida Soares, Carlos Nelson Elias, Iain R. Gibson, Serena Best
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Authors: Daniel Navarro da Rocha, Leila Rosa de Oliveira Cruz, Luciano de Andrade Gobbo, Marcelo Henrique Prado da Silva
Abstract: Hydroxyapatite is a bioceramic material of great interest for use as bone substitute because of its similarity with the composition of biological apatite. Cationic and anionic substitutions in the apatite structure have been made in order to optimize the synthesis and accelerate the process of bone repair. In the present study, niobate apatite was synthesized by a patented aqueous precipitation method. The bioactivity of the samples was assessed by X-ray diffraction analyses (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy with field emission gun (FEG-SEM; FEI Quanta FEG 250) in the samples before and after an incubation period in simulated body fluid. The results showed that after 3 days a bone-like apatite coating was formed onto the niobate apatite surface. A peculiar morphology comprised by nanosized wires was also observed on the niobate apatite surface.
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Authors: Willian Trindade, Marcelo Henrique Prado da Silva, Alaelson Vieira Gomes, Carlos Frederico de Matos Chagas, Luis Henrique Leme Louro, José Brant de Campos
Abstract: This work investigated the sintering behavior of alumina doped with 4wt% niobia. Three sintering temperatures were investigated: 1400°C, 1450°C and 1500°C. The first temperature leads to solid-phase assisted sintering (SSS) while the other ones develop liquid-phase assisted sintering (LPS). The presence of liquid phase in the second case is due to an eutectic reaction occurring at 1440°C ± 20°C in the alumina-niobia system. The sintering behavior was assessed by measuring the final densities. The results indicated that the 1400°C solid-state sintering, comparatively, was better. This paper proposes that defects associated to the substitution of Al+3 by Nb+5 in the alumina cation sub-lattice, fostered diffusion and SSS. Sintering at 1500°C presented the lowest density, apparently due to niobate (liquid phase) loss, at this temperature as observed by XRD results.
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Authors: Vera Lúcia Praxedes de Oliveira, Marcelo Henrique Prado da Silva, Eduardo de Sousa Lima, Claudinei dos Santos, Luis Henrique Leme Louro
Abstract: Glasses with two different compositions were added to yttria-stabilized zirconia TZP powder: a CAS glass and a bioactive glass. These additions allowed liquid phase sintering to occur at temperature as low as 1300 °C. The concentrations of each glass additions were of 1, 3, and 5 wt%. The prepared compositions were uniaxially pressed at 50 MPa and sintered at 1300oC for 2 hours. The sintered samples were characterized for their mechanical properties, by measuring four-point bending mechanical strength, Vickers microhardnesses, and fracture toughness ( KIc ). Vickers microhardness measured values ranged from 10 to 12 GPa, while fracture toughness, from 3.8 to 4.4 MPa.m1/2. The flexural mechanical strength was situated between 302 and 408 MPa. The achieved mechanical properties, from sintered samples were possible due to glassy phase additions. These properties, associated to biocompatibility, enable such materials to be used in different applications, including bioceramics.
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Authors: Vera Lúcia Praxedes de Oliveira, Marcelo Henrique Prado da Silva, Eduardo de Sousa Lima, Claudinei dos Santos, Luis Henrique Leme Louro
Abstract: TZP yttria-stabilized zirconia powder was mixed with two types of glasses as sintering additives: CAS glass and a bioactive glass. These additions were designed toward the material applications as bioceramics. The glassy phase was chosen to promote liquid phase sintering at lower temperature, when compared to pure material. This procedure contributed to reduce the fabrication costs while keeping the material biocompatibility. Each type of glass was added in concentrations of 1, 3, and 5 wt%. The prepared powders were uniaxially pressed at 50 MPa, and then sintered at 1300°C for two hours. The sintering behavior was evaluated by measuring the final sintered densities. It was found that the samples with bioactive glass additions were denser than those with CAS glass. Zirconia TZP powders without glassy additions would not sinter in this temperature. The microstructure of the sintered samples was characterized by SEM and XRD. The sintered ceramics exhibited both submicrometric and uniform grains. The analyzed grain sizes were slightly lower for the samples with CAS additions than for those with bioactive glass additions.
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Authors: Tatiana Borges Skaf, Luis Henrique Leme Louro, André Luís de Vasconcelos Cardoso, Alaelson Vieira Gomes, Marcelo Henrique Prado da Silva
Abstract: Lithium fluoride as well as calcium oxide were used as sintering additives to magnesium aluminate ceramics in order to provide both transparency and better densification. This work assessed the dynamic behavior of MgAl2O4 by performing split Hopkinson bar dynamic tests. The total amount of additives was 1.5 wt% in which the percentage of LiF and CaO varied from 0 to 100 wt% with an increment of 25 wt%. The obtained results indicated that CaO low concentrations induced low strength values to the ceramics of different compositions. By increasing the amount of CaO, the MgAl2O4 dynamic strengths were higher. The strain rate was reduced as the amount of CaO increased, indicating a higher trend of energy absorption corroborated by KIc measured values. On the other hand, the ceramic strain increased with the increment CaO additions.
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Authors: Willian Trindade, Marcelo Henrique Prado da Silva, Alaelson Vieira Gomes, Carlos Frederico Matos Chagas, Luis Henrique Leme Louro
Abstract: Niobia has been successfully used as sintering additive to alumina in order to lower its sintering temperature. This effect can also be obtained by reducing the ceramic particle size. This work investigated the effect of the particle size on the ceramic final density of alumina with 4 wt% niobia. For that two milling media were used. The as-received powders were submitted to ball and planetary milling and then sintered at 1450°C. The planetary milling medium was more efficient in reducing particle size when compared to ball milling. However, planetary milling caused significant contamination in the niobia powder, from the alumina balls used as milling agents. It forced composition balance in order to keep the original proposed formulation. The planetary milled sintered samples showed better densification and lower grain size in comparison with ball milled ones. It could be concluded that the milling medium choice directly affected both microstructure and properties of the sintered alumina with 4wt% of niobia. .
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Authors: J.F. Oliveira, Lídia Ágata de Sena, Marcelo Henrique Prado da Silva, Gloria Dulce de Almeida Soares, Antonella M. Rossi
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Authors: G.V.O. Fernandes, Gutemberg Alves, A.B.R. Linhares, Marcelo Henrique Prado da Silva, J.M. Granjeiro
Abstract: The pursuit for an ideal bone substitute remains the main focus of many tissue engineering researchers. Among the myriad types of grafts available, synthetic bone grafts are of special importance, because it is available in large amounts, reduce the surgical trauma and eliminate the risk of diseases’ transmission. In this context, bioactive glasses have received attention mostly due to its described biocompatibility and rapid rate of surface reactivity when compared with other materials, allowing for faster interactions with the local tissue. The addition of niobium to this material has been shown as increasing the chemical resistance of the compound and providing greater stability. However, alterations on the chemical composition of biomaterials may impact on its biocompatibility. Therefore, the aim of this study was to evaluate the in vitro biocompatibility of bioglass-Niobium (BgNb) granules, in comparison with standard commercial bioglass (Biogran®) throughout an interesting multiparametrical approach, employing Phenol 2% and dense polystyrene beads as positive and negative controls, respectively. Extracts from each material were prepared by 24 hours incubation in culture medium (DMEM). Human primary osteoblasts were then exposed for 24 hours to each extract and cell viability was evaluated by three parameters: mitochondrial activity (XTT method), membrane integrity (neutral red dye uptake) and cell density (crystal violet dye exclusion test). BgNb extracts were highly compatible, since the levels of viable cells were similar to the control group (unexposed cells), on all parameters studied. The mean cell density on the Biogran® group was slightly lower than BgNb, even though this material was also non-cytotoxic. The excellent in vitro response for BgNb granules indicates the suitability of this material to future studies on its biological and physical properties when applied in vivo.
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