Papers by Ana Helena Bressiani
Materials Science and Engineering: C, 2016
Titanium alloys are widely used in biomedical applications due to their excellent properties such... more Titanium alloys are widely used in biomedical applications due to their excellent properties such as high strength, good corrosion resistance and biocompatibility. Titanium alloys with alloying elements such as Nb and Zr are biocompatible and have Young's modulus close to that of human bone. To increase the bioactivity of titanium alloy surfaces is used chemical treatment with NaOH followed by immersion in simulated body fluid (SBF). The purpose of this study was to produce the alloy Ti-27Nb-13Zr with low Young's modulus by powder metallurgy using powders produced by the HDH process. The formation of biomimetic coatings on samples immersed in SBF for 3, 7, 11 and 15 days was evaluated. Characterization of the coating was performed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and scanning electron microscope. The microstructure and composition of the alloy were determined using SEM and XRD, while the mechanical properties were evaluated by determining the elastic modulus and the Vickers microhardness. The sintered alloys were composed of α and β phases, equiaxed grains and with density around 97.8% of its theoretical density. The Vickers microhardness and elasticity modulus of the alloy were
European cells & materials
INTRODUCTION: Biomaterials based on titanium and its alloys are widely used in dentistry and orth... more INTRODUCTION: Biomaterials based on titanium and its alloys are widely used in dentistry and orthopaedics surgery due to their excellent mechanical properties and biological interaction. However, there are problems associated with the use of titanium as implant material. The high Young's modulus value when compared to the surrounding bone can cause problems of stress and subsequent dislocation of the implant 1 . To solve this problem have been developed osteoconductive porous materials for bone regeneration. One advantage in using materials with porous structure is the ability to allow a biological anchorage of surrounding tissues via bone ingrowth through the pores. Furthermore, the elastic modulus value can be adjusted between implant and trabecular bone values to match each other, thereby preventing bone resorption in the implant interface 2 . The Ti-13Nb-13Zr alloy studies has been developed due to its low elastic modulus combined with high values of mechanical strength and ...
Brazilian journal of medical and biological research = Revista brasileira de pesquisas médicas e biológicas / Sociedade Brasileira de Biofísica ... [et al.], 1994
The use of alumina (alpha-Al2O3) as a material for cardiovascular applications was investigated o... more The use of alumina (alpha-Al2O3) as a material for cardiovascular applications was investigated on the basis of protein adsorption and thrombus formation on the material. The adsorption of 125I-labelled albumin and fibrinogen from phosphate buffered saline (pH 7.35, 0.100 M NaCl, 8.66 mM KH2PO4 and 41 mM Na2HPO4) solution on ceramic discs of alumina was studied. Both albumin and fibrinogen presented affinity for ceramic surfaces, with adsorptions of 1.47 +/- 0.06 ng/cm2 and 0.198 +/- 0.01 ng/cm2, respectively. Scanning electron micrographs of the alpha-Al2O3 surfaces after contact of the discs with whole human blood showed a thrombogenic behavior of alumina alpha. These results indicate a hemoincompatible property. Although critical surface tension (gamma C: 21.8 dynes/cm) of the disc surfaces determined by contact angle technique of sessile drops indicates that alumina alpha is a biocompatible material, by this criterion, the data reported here indicate that alpha-Al2O3 cannot be u...
Manufacturing of novel reaction bonded Niobium Carbide (NbC) containing ceramic composites derive... more Manufacturing of novel reaction bonded Niobium Carbide (NbC) containing ceramic composites derived from polymer/filler mixtures was investigated. Poly(methylsiloxane) filled with 40 vol.% of a mixture of metallic Niobium (Nb) (reactive filler) and alumina powder (inert filler) was pyrolysed in inert atmosphere up to 1450°C. During pyrolysis metallic niobium reacted with carbon from the decomposition products of the preceramic polymer binder
Materials Science Forum, 2005
Silicon nitride was the first nitride developed for engineering applications. The excellent combi... more Silicon nitride was the first nitride developed for engineering applications. The excellent combination of thermomechanical properties makes silicon nitride a good candidate for applications where high hardness and mechanical properties are fundamental. However, the low fracture toughness of this material limits its use as structural material. The improve of mechanical properties of silicon nitride comes from many factors, like refined microstructure by restraining grain growth, localized stress, crack tip bridging, etc. Within these factors, microstructure formation of the silicon nitride is critically important for the final properties. The design of silicon nitride based composite materials is of particular interest because of their improved high temperature strength and fracture toughness. In this work, Si3N4-TaC particulate composite was investigated. For this study was prepared a basis composition (CB) with 90%wt a-Si3N4, 6%wt and 4%wt Y2O3 and Al2O3, respectively. TaC (20%vol...
Key Engineering Materials, 2001
ABSTRACT
Materials Science Forum, 2003
The chemistry of glass-ceramic interface was studied in two different diffusion couples, YSiAlO/S... more The chemistry of glass-ceramic interface was studied in two different diffusion couples, YSiAlO/Si 3 N 4 and SiO 2 Si 3 N 4 . Experiments were performed at 1500°C for 2 hours in argon atmosphere. The couples were analyzed through SEM and EDS to draw the concentration profiles across the interface. It was observed that aluminosilicate glass infiltrates within the ceramic secondary phase and detaches the silicon nitride grains. The free grains move toward the glass surface either by solution-reprecipitation or floating. The glass also dissolves silicon nitride grains and the nitrogen is absorbed, forming a broad zone of YSiAlON glass. In the SiO 2 /Si 3 N 4 couple there was extensive cation diffusion from the silicon nitride grain boundary to the silica glass, forming an aluminosilicate intermediary phase. It was observed crystallization of some yttrium-rich phase at the interface.
Key Engineering Materials, 2007
Materials Science Forum, 2006
In the last years, the porosity in ceramic materials for implants production has motivated the de... more In the last years, the porosity in ceramic materials for implants production has motivated the development of various technologies. Calcium phosphate ceramics, in special the tricalcium phosphate - TCP, are very promising as bone substitutes and scaffolds for tissue engineering. The macroporosity incorporation in TCP ceramics by porogenic, foaming and consolidator agent, as globular protein (ovalbumin) was the focus of this work. Preliminary studies of zeta potential were made to have a suitable suspension. Ovalbumin amounts (5-7 wt%) were added to the ceramic slurries and suspensions with a solid percentage higher than 60 wt% were obtained. The interaction albumin/surfactant with detergency properties was evaluated by pH and viscosity measurements. The foam was produced by mechanical stirring. The results suggested that the presence of the surfactant increase the volume and stability of foam. After drying, burnout and sintering (1200oC/30 min.) the phase composition of the foams wa...
Cerâmica, 2000
In view of considerable interest in the development of liquid phase sintered structural and high-... more In view of considerable interest in the development of liquid phase sintered structural and high-temperature ceramics on the base of silicon carbide, a comprehensive review of the data on structure, properties and the known methods of processing of silicon carbide seems timely. The most striking feature of silicon carbide is its polytypism, i.e. formation of a great number of different structural modifications without any change in composition. Although this feature of silicon carbide was extensively studied, no systematic up to date analysis was done. However, polytypism and the tendency of the polytypes to undergo structural transformations at working temperatures may lead to uncontrollable modification of the materials properties, and therefore needs to be fully understood. Furthermore, the recently developed liquid phase sintering technique for silicon carbide densification is of an undoubtful interest and the overview of the results achieved until present time may provide some ...
Materials Science Forum, 2014
The effects of adding polysiloxane (polymethylsilsesquioxane) on the sintering behavior, microstr... more The effects of adding polysiloxane (polymethylsilsesquioxane) on the sintering behavior, microstructure and hardness of alumina ceramics have been studied. The sintering kinetics of cold-pressed specimens was studied by dilatometry. Polymer sintering aid was used for alumina based ceramics sintered at 1650o C. The sintered materials were characterized using helium picnometry, x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectrometry and Vickers indentation. The addition of polymethylsilsesquioxane yielded alumina/Si2Al4O4N4 composites. The sintering studies in nitrogen atmosphere (1650 °C/1h) revealed that the highest densities were obtained for specimens with 1wt% PMS. The materials prepared with ceramic polymer precursors had higher hardness than the standard specimen. The preparation of ceramic composites using small amounts of polymer precursors is suited for alumina based ceramics. The processing route being...
Key Engineering Materials, 2009
<jats:p>In recent years, the processing of porous ceramic materials for implant application... more <jats:p>In recent years, the processing of porous ceramic materials for implant applications has motivated the development and optimization of new technologies. To this purpose, a globular protein based (i.e. ovalbumin) consolidation approach has been proposed. In the present study, a porous hydroxyapatite:b-tricalcium phosphate - biphasic ceramics (BCP), was processed by consolidation using the protein-action technique. The processed ceramic materials exhibited appropriate pore configuration in terms of size, morphology and distribution. The in vitro reactivity and dissolution behavior of the ceramics was evaluated in SBF and biocompatibility in an osteoblasts culture, respectively. Overall, the materials tested showed biocompatibility and suitable properties for osteoconduction. A rough surface pattern displayed by the ceramics seemed to have improved both; cell adhesion and proliferation processes. In conclusion, this study revealed that the porous matrices obtained, promoted suitable development of cell metabolism without cellular death.</jats:p>
Key Engineering Materials, 2007
Nanocrystalline hydroxyapatite was prepared by a precipitation method with add of ultrasonic irra... more Nanocrystalline hydroxyapatite was prepared by a precipitation method with add of ultrasonic irradiation. In this work the effect of H3PO4 addition rate during synthesis and the influence of the magnesium incorporation into apatite were studded. The results revealed that the morphology and cristalinity of synthesized nanopowders are significantly affected by ultrasonic irradiation. Monophase hydroxyapatite was obtained when magnesium was added into HA lattice during the synthesis with ultrasonic irradiation.
Cerâmica, 2011
A presença de aglomerados em pós cerâmicos é fonte conhecida de heterogeneidade e defeitos nos pr... more A presença de aglomerados em pós cerâmicos é fonte conhecida de heterogeneidade e defeitos nos produtos finais, uma vez que na etapa de sinterização ocorre densificação diferencial dos aglomerados. Assim, o controle de todas as etapas do processamento para obtenção de corpos cerâmicos livres de aglomerados e com microestrutura homogênea é de fundamental importância. Neste trabalho foram avaliadas as condições mais adequadas para reduzir a presença de agregados proveniente da etapa de moagem de alta energia, bem como o controle da etapa de secagem para a obtenção de uma microestrutura com tamanho de grãos pequenos e distribuição homogênea das partículas de inclusões no interior da matriz.
Materials Science Forum, 2012
Ceramic materials based on alumina are considered excellent for produce cutting tools used to mac... more Ceramic materials based on alumina are considered excellent for produce cutting tools used to machining hard metals. However, low mechanical strength and toughness presented by these materials limit their application. Traditionally particles, such as TiC, TiN and ZrO2, are added to the alumina matrix to improve their mechanical properties, increasing the range of applications. Recent studies have shown that the addition of particles of different sizes in alumina matrix can promote simultaneous increase in mechanical strength and tenacity. In this work sintering behavior of Al2O3 micro-nanocomposite containing nanometric particles of NbC and micrometric particles of WC, was studied by dilatometry using heating rate of 20°C/min up to 1800°C. The addition of carbides in alumina matrix is prejudicial to sintering causing an increase in temperature of shrinkage.
Materials Science Forum, 2006
The shear bond strength between a ceramic material (Titankeramik®, Vita Zahnfabrik, Germany) and ... more The shear bond strength between a ceramic material (Titankeramik®, Vita Zahnfabrik, Germany) and two biocompatible titanium alloys was investigated. Ti-13%Nb-13%Zr (TNZ) and Ti-35%Nb-7%Zr-5%Ta (TNZT) alloys were obtained based on the blended elemental technique followed by a sequence of cold uniaxial and isostatic pressing and sintering. Characterization involved microstructural analysis (SEM) and crystalline phase identification (XRD). Subsequently, samples were machined to 4 x 4 mm with a base of 5 x 1 mm. The base metals were blasted with Al2O3 particles followed by the application of a coupling agent and opaque ceramic. After ceramic firing, the specimens were loaded in a universal testing machine (0,5mm/min). XRD revealed the presence of α and β-phases for TNZ, and peaks related to β phases and Nb and Ta for the TNZT alloy. SEM evaluation (TNZ) depicted remaining pores and biphasic microstructure formation. SEM micrographs of the TNZT alloy revealed good densification and a hom...
As características das matérias primas têm grande influência na produção de peças cerâmicas. Dife... more As características das matérias primas têm grande influência na produção de peças cerâmicas. Diferenças na distribuição do tamanho e no formato das partículas podem modificar a cinética de sinterização dos compósitos e consequentemente suas propriedades finais. Neste trabalho foram utilizadas duas aluminas comerciais como matriz para o compósito Al2O3:NbC. Foram estudadas as principais características dos materiais de partida e a influência destas na sinterização do compósito. As aluminas comerciais e o NbC foram caracterizados quanto a distribuição de tamanho das partículas, área de superfície específica e quantidade de impurezas. O estudo de sinterização foi realizado em dilatômetro, com taxa de aquecimento de 20°C/min até 1800°C e patamar de 1h. Os resultados indicaram que amostras obtidas a partir da alumina com distribuição mais estreita e menor tamanho médio de partículas tiveram menores temperaturas de início e de máxima taxa de retração.
Journal of Tissue Engineering and Regenerative Medicine, 2013
An electrospun nanocomposite fibrous material holds promise as a scaffold, as well as a drug-deli... more An electrospun nanocomposite fibrous material holds promise as a scaffold, as well as a drug-delivery device to aid in root maturogenesis and the regeneration of the pulp-dentine complex. A novel threedimensional (3D) nanocomposite scaffold composed of polydioxanone (PDS II W) and halloysite nanotubes (HNTs) was designed and fabricated by electrospinning. Morphology, structure, mechanical properties and cell compatibility studies were carried out to evaluate the effects of HNTs incorporation (0.5-10 wt% relative to PDS w/w). Overall, a 3D porous network was seen in the different fabricated electrospun scaffolds, regardless of the HNT content. The incorporation of HNTs at 10 wt% led to a significant (p < 0.0001) fibre diameter increase and a reduction in scaffold strength. Moreover, PDS-HNTs scaffolds supported the attachment and proliferation of human-derived pulp fibroblast cells. Quantitative proliferation assay performed with human dental pulp-derived cells as a function of nanotubes concentration indicated that the HNTs exhibit a high level of biocompatibility, rendering them good candidates for the potential encapsulation of distinct bioactive molecules. Collectively, the reported data support the conclusion that PDS-HNTs nanocomposite fibrous structures hold potential in the development of a bioactive scaffold for regenerative endodontics.
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Papers by Ana Helena Bressiani