Since the early 1970's there have been a number of investigations into the preparation of dense sintered hydroxyapatite for medical applications. However, there have been few studies reporting the production of sintered carbonate apatite, which resembles more closely the composition of human bone mineral. This work has studied the precipitation, processing and sintering of carbonate apatites. Crystallisation variables such as temperature and bicarbonate ion concentration have been investigated in order to determine some effects on the size, morphology and composition of carbonate apatite precipitates. By employing the correct conditions, nanoscale precipitates have been produced that have enabled the use of a colloidal filtration route in processing. The effect of sintering atmosphere, green density, and carbonate content were investigated isochronally over a range of temperatures. Isothermal experiments demonstrated the evolution of microstructure and changes in density with time. Results from this study indicated that translucent 99.9% relative density carbonated hydroxyapatite could be produced by sintering in an atmosphere of carbon dioxide and water. Water was found to enhance densification in carbon dioxide furnace atmospheres. The temperature at which maximum densification occurred decreased with carbonate content. Bloating was found to be related to carbonate content as larger expansions were observed in higher carbonate content materials. The partial pressure of water did not effect the composition of the carbonate apatite, whereas the green composition did, contrary to the findings of other workers.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Orientador: Joni Augusto Cirelli / Banca: Raquel Scarel Caminaga / Banca: Willian Fernando Zambuzzi / Resumo: Com a evolução no desenvolvimento de biomateriais, a utilização de matrizes tridimensionais (scaffolds), construídas a partir de impressão tridimensional (3DP), via SLS (selective laser sinterization) e por Extrusão de Filamentos, vêm ganhando bastante destaque no ramo da engenharia tecidual óssea. A possibilidade de impressão de modelos 3D, baseado em modelo virtual prévio, com forma, tamanho, e porosidade altamente controlados, assemelha o material ao osso perdido, favorecendo a reconstrução de defeitos ósseos em substituição aos autoenxentos, considerados "padrão ouro". O objetivo deste trabalho foi caracterizar físico-química e biologicamente scaffolds à base de Poli(3-hidroxibutirato) (PHB), confeccionados por impressão 3D via SLS, revestidos com celulose bacteriana (CB), funcionalizados ou não com apatitas (HA) e/ou peptídeo de crescimento osteogênico (osteogenic growth peptide - OGP) (Estudo 1), assim como matrizes de Poli(hidroxibutirato-co-valerato) (PHBV) e PHBV-apatita radiopaca dopada com Lantânio (PHBV-La20OAP) confeccionadas por Extrusão de Filamentos (Estudo 2), com finalidade de regeneração óssea. Os resultados de caracterização físico-química por meio da MEV/EDS demonstraram que os scaffolds produzidos apresentaram composição química e arquitetura (forma e porosidade) adequadas. A resistência mecânica nos scaffolds de PHB não sofreu alteração significativa após o revestimento com CB; porém, teve redução com a adição de apatita. O lantânio promoveu um aumento ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: With the evolution in the development of biomaterials, the use of three-dimensional matrices (scaffolds), constructed from three-dimensional printing (3DP) via SLS (selective laser sinterization) and Filament Extrusion are gaining a lot of attention in the field of bone tissue engineering. The possibility to print 3D models based on previous virtual models with highly controlled shape, size and porosity, makes the material similar to the lost bone and favours the reconstruction of bone defects in the replacement of autografts considered "gold standard". The aim of this study was to physicochemically and biologically characterize Poly (3-hydroxybutyrate) (PHB) scaffolds, made by 3D printing via SLS coated with bacterial cellulose, functionalized or not with apatite (HA) and / or osteogenic growth peptide- (OGP) (Study 1) and matrices of Poly (hydroxybutyrate-co-valerate) (PHBV) and PHBV-La containing radiopaque apatite (PHBV-La20OAP) made by filament extrusion (Study 2) for bone regeneration. Results from physicochemical characterization by SEM/EDS demonstrated that the all produced scaffolds presented appropriate chemical composition and architecture (shape and porosity). The mechanical strength of the PHB scaffolds was not significantly affected my CB coating but was reduced after apatite addition. The La allowed an increase in the elasticity modulus of PHBV matrices. Experiments for analysis of the biological behaviour of the scaffolds showed that they allowed the maintenan... (Complete abstract click electronic access below) / Mestre

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Orientador: Antonio Carlos Guastaldi / Banca: José Augusto Marcondes Agnelli / Banca: José Carlos Bressiani / Banca: Cecília Amélia de Carvalho Zavaglia / Banca: Eliana Cristina da Silva Rigo / Resumo: Neste trabalho, estruturas porosas de Polietileno de Ultra Alto Peso Molecular (PEUAPM) recobertas com diferentes fases de apatita de importância biológica foram desenvolvidas com o objetivo de se obter um biomaterial adequado para a substituição e regeneração óssea, com a combinação das propriedades mecânicas do polímero, da bioatividade das biocerâmicas de apatita e do comportamento favorável dos materiais porosos. Devido às dificuldades de obtenção de recobrimentos de apatita sobre o PEUAPM relatadas na literatura, realizou-se inicialmente um Estudo Preliminar para avaliar a utilização de solução de peróxido de hidrogênio (H2O2) 30% para a modificação química da superfície do polímero, analisando a influência dos períodos de modificação de 24 e 48 horas na variação das propriedades mecânicas do PEUAPM e na obtenção das diferentes fases de apatita de importância biológica empregando-se o método biomimético. Os resultados obtidos, analisados por Microscopia Eletrônica de Varredura - MEV, Microanálise Semi-quantitativa por Energia Dispersiva de Raios X - EDX, Difratometria de Raios X - DRX, Espectroscopia no Infravermelho com Transformada de Fourier - FTIR, medidas de ângulo de contato e ensaio mecânico de resistência à tração, indicaram que a utilização de solução de H2O2 30% pelo período de 48 horas mostrou-se adequada como método de modificação da superfície do PEUAPM, pois possibilitou a formação de grupos funcionais hidrofílicos na superfície do polímero e resultou em menores alterações das propriedades mecânicas e elásticas do polímero. Constatou-se também que o emprego do método biomimético para o recobrimento da superfície do PEUAPM somente foi adequado com a utilização de soluções SBF com composições modificadas. Para o desenvolvimento das estruturas porosas de PEUAPM recobertas com ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, porous samples of Ultra High Molecular Weight Polyethylene (UHMWPE) coated with different apatite phases of biological importance were developed, aiming to obtain a suitable biomaterial for bone replacement and regeneration, balancing the mechanical properties of the polymer, the bioactivity of apatite bioceramics and the favorable behavior of the porous materials. Due to the difficulties in obtaining apatite coatings on UHMWPE in the literature, a Preliminary Study was conducted to evaluate the use of a 30% solution of hydrogen peroxide (H2O2) for the chemical modification of the polymer surface, analyzing the influence of the modification periods of 24 and 48 hours on the variation of the mechanical properties of UHMWPE and in obtaining the different apatite phases of biological importance using the biomimetic method. The results obtained, analyzed by Scanning Electron Microscopy - SEM, Semi-quantitative microanalysis by Energy Dispersive X-ray - EDX, X-Ray Diffractometry - XRD, Fourier Transform Infrared Spectroscopy - FTIR, contact angle measurements and tensile strength mechanical tests, indicated that the use of a 30% solution of H2O2 for a period of 48 hours proved adequate as a surface modification method of UHMWPE, since it allowed the formation of hydrophilic functional groups on the surface of the polymer, resulting in lower changes of the mechanical and elastic properties of the polymer. It was also found that the use of the biomimetic method for the surface coating of UHMWPE was only appropriate with the use of SBF solutions with modified compositions. For the development of porous samples of UHMWPE coated with apatites, UHMWPE porous supports were obtained using NaCl as a pore-forming agent in proportions of 50, 60 and 70% (m/m) with particle size in the range of 175-350µm, 350-500µm and 175- 500µm. The apatite coatings were ... (Complete abstract click electronic access below) / Doutor

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