Thesis (M.S.) --University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

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Synthesis of chemically modified or ion-substituted hydroxyapatite (HA) as a bioactive bone replacement material is of great interest since the main component of hard tissues in vertebrates is a substituted apatite. The most abundant species in natural bone mineral other than calcium and phosphate ions is carbonate ions. Carbonate ions can be substituted at 2 distinct sites in the HA lattice; the hydroxide (OH) site and the phosphate (PO4) site. Synthetic silicate substituted HA (SiHA) and carbonate-substituted HA (CHA) have each previously been shown to enhance new bone formation when compared to HA in vivo. The positive bioactive properties that result, individually, from carbonate or silicate substitution led to the hypothesis that simultaneous co-substitution of these two ions in to the HA lattice would lead to further improved bioactivity. A range of novel silicate and carbonate co-substituted HA (SiCHA) materials were prepared with silicate substitution of up to 12.5 wt% (3.8 wt% Si) and carbonate substitution up to 8.2 wt%. These compositions were characterised extensively, examining both their chemical and physical attributes. These compositions were single phase after sintering in a wet CO2 atmosphere to near-theoretical density, and contained carbonate ions on both hydroxide and phosphate sites. The grain sizes of these ceramic specimens of these compositions were intermediate between those of CHA and SiHA controls. Further controlled synthesis demonstrated that carbonate and silicate ions could be substituted in non-equimolar quantities, and increased amounts of carbonate could be substituted independently on to the hydroxide site of the SiCHA samples. The biological response to these materials was assessed by completing direct and indirect cell culture experiments using both the MG-63 osteoblast-like cell line and primary human osteoblast (pHOB) cells. The silicate and carbonate co-substituted materials and their dissolution products were not toxic to either of the cell lines, and cell proliferation was observed with all materials studied. The effect of the synthesis route on the purity of silicate-substituted hydroxyapatite (SiHA) was also assessed, with a particular focus on the role of tetraethyl orthosilicate (TEOS) as the source of silicate. The outcomes of this study showed that the final composition of SiHA was strongly dependent on how and when the tetraethyl orthosilicate (TEOS) solution was incorporated during the precipitation reaction.

Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--University of Michigan, 1979.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / O objetivo deste trabalho foi a síntese e a caracterização físico-química e microestrutural de matrizes cerâmicas porosas à base de hidroxiapatita de cálcio, bem como a avaliação de um pó de hidroxiapatita comercial, com potencialidade para atuarem como matrizes para incorporação de radionuclídeos de fontes radioativas para uso em braquiterapia. Pós de hidroxiapatita de cálcio foram sintetizados por via co-precipitativa de soluções precursoras de cálcio e fosfato em meio básico. As matrizes correspondentes foram obtidas a partir da compactação axial dos pós à baixa pressão e sinterizadas ao ar. Difração de raios X, fluorescência de raios X, espectrofotometria de infravermelho, análise BET, análise térmica TG-DTA e microscópia eletrônica de varredura foram realizadas para caracterização dos pós e matrizes. O iodo foi incorporado nas matrizes através de um inpregnação de solução aquosa de iodeto de sódio. Foi realizada a quantificação de iodo (simulador de radionuclídeo) nas matrizes através da técnica de análise por ativação neutrônica. Verificou-se que as hidroxiapatitas sintetizada e comercial têm características de hidroxiapatitas bioabsorvíveis. As matrizes de hidroxiapatita apresentaram uma baixa densificação. A porosidade total é da ordem de 55%, e a porosidade aberta de 54%. Comparações feitas entre os resultados de incorporação de iodo e as atividades das fontes de braquiterapia comerciais mostram que a matrizes bioabsorvíveis à base de hidroxiapatita têm grande potencial, porque elas podem ser carregadas com uma ampla faixa de atividade. / The aim of this work was the synthesis and physico-chemical and microstructural characterization of pores ceramic matrices of calcium hydroxyapatites, and also the evaluation of a commercial hydroxyapatite powder, and both with the potency do in view of their possible use act as matrices for radionuclide incorporation of bioresorbable radioactive sources for the use of brachytherapy. Calcium hydroxyapatite powders were synthesized by co-precipitation of precursor solutions of calcium and phosphate in basic environment. The corresponding matrices were obtained for uniaxial compaction of powders at low pressure and sinterized in air. X-rays diffraction and fluorescence, infrared spectrphotometry, surface area (BET), thermal analysis (TG-DTA), and scanning electron microscopy were carried out to characterize the powders and the matrices. Iodine was incorporated in the matrices through impregnation of sodium iodine aqueous solution. The amount of incorporated iodine (radionuclide simulator) was done by neutron activation. Both hydroxyapatites have characteristics for bioabsorption. The matrices showed a low densification with total porosity of about 55%, and open porosity of about 54%. Through comparisons done between the results of incorporated iodine and the activities of the commercial brachytherapy sources show that the bioresorbable matrices of hydroxyapatites have great potential.

Made available in DSpace on 2014-06-11T19:25:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-25Bitstream added on 2014-06-13T19:53:29Z : No. of bitstreams: 1 almeidafilho_e_me_araiq.pdf: 3265142 bytes, checksum: 2bf9ca6d5fd6073e7eed8a3b69720493 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As pesquisas em biomateriais caminham na busca de dispositivos nos quais, além da resistência mecânica, oferece adequada relação entre bioatividade/biocompatibilidade quando em contato com tecidos biológicos. Atualmente os biomateriais para serem utilizados como implantes são classificados como bioinertes, biotoleráveis e bioativos. No presente trabalho estudou-se as fases de apatitas presentes nos recobrimentos obtidos pelo método biomimético em substratos de titânio pré-modificados superficialmente empregando-se ablação por feixe de laser, objetivando a interação entre o substrato e o recobrimento, visando à aplicação clínica em implantes dentários e ortopédicos. Após estudos piloto, definiu-se condições pré-estabelecidas e as amostras tiveram suas superfícies irradiadas pelo laser Nd:YAG, em atmosfera normal. As amostras foram irradiadas pelo Laser pulsado Nd:YAG, e foram estabelecidas quatro condições de estudo para o trabalho, onde as irradiações foram realizados em ar e pressão atmosférica. Os recobrimentos, sobre as superfícies irradiadas, foram realizados pelo método biomimético, onde as amostras modificadas foram imersas na solução SBF (Simulated Body Fluid) e permaneceram por 4 dias, para a formação da camada de apatitas, este grupo ganhou destaque por possuírem composição semelhante ao tecido ósseo humano. As caracterizações das amostras foram realizadas pelas técnicas de microscopia eletrônica de varredura, espectroscopia de energia dispersiva, difração de raios-X e espectroscopia no infravermelho com transformada de Fourier. Resultados da modificação por feixe de Laser mostraram que as quatro condições estabelecidas sugeriram ter energia suficiente para promover a ablação na superfície irradiada. Verificou-se que na irradiação por feixe de laser ocorre o processos de fusão e solidificação rápida proveniente... / The researches biomaterials in walk in the search of devices us which, besides the mechanical resistance, offer appropriate relationship among bioativity/biocompatibility when in contact with woven biological. Nowadays the biomaterials to be used as implants are classified as bioinert, biotolerability and bioactives. In the work present was study the apatites phases current in the coating obtained by the biomimetic method in substratum of titanium pré-modify superficially being used ablation by laser bunch, aiming at the interaction between the substratum and the coating, seeking to the clinical application in dental and orthopedical implants. After pilot study, it was defined pré-established conditions and the samples had their surfaces irradiated by the laser Nd:YAG, in normal atmosphere. The samples were irradiated by the pulsed Laser Nd:YAG, and they were established four study conditions for the work, where the irradiations were accomplished in air and atmospheric pressure. The coatings, on the irradiated surfaces, were accomplished by the biomimetic method, where the modified samples were immersed in the solution SBF (Simulated Body Fluid) and they stayed for 4 days, for the formation of the apatites layer, this group won prominence for they possess composition similar to the human bone fabric. The characterizations of the samples were accomplished by the techniques o SEM, EDS, XRD and FTIR. Results of the modification for beam of Laser showed that the four established conditions suggested to have enough energy to promote the ablation in the irradiated surface. It was verified that in the irradiation for laser beam happens the processes melt and originating from fast solidification the irradiation for laser, in normal atmosphere, they induce the oxides formation of titanium stoichiometric and non-stoichiometric with different oxidation degrees as Ti3O and Ti6O and with different... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:33:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-20Bitstream added on 2014-06-13T21:05:39Z : No. of bitstreams: 1 silva_kg_dr_araca.pdf: 1119234 bytes, checksum: 5618d5d8828102cf1192a2ce0a173ef5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo desse estudo foi avaliar in situ o potencial remineralizador de selantes que contenham fosfato de cálcio amorfo e/ou fluoreto com lesão artificial de cárie em esmalte de superfície lisa. Dez voluntários participaram desse estudo triplo cego com duração de 5 dias para cada grupo (esmalte desmineralizado + Fluroshield, esmalte desmineralizado + Aegis (ACP), esmalte desmineralizado + Fluoreto (experimental), esmalte desmineralizado + ACP + Fluoreto (experimental) e esmalte desmineralizado – Controle) e intervalo de 7 dias entre eles. Dez dias antes do início e durante todo o experimento os voluntários utilizaram dentifrício não fluoretado. Após o período experimental, foram avaliadas a porcentagem de recuperação de microdureza de superfície (%MDS), recuperação da área mineral integrada (_Z) e determinada a concentração de fluoreto (μg F/mm3), cálcio (μg Ca/mm3) e fósforo (μg P/mm3) presentes no esmalte. Os dados obtidos da %MDS e _Z foram submetidos à Análise de Variância seguida do teste de Tukey, e os do fluoreto, cálcio e fósforo foram submetidos ao teste de Kruskal-Wallis (p<0,05). Todas as variáveis foram submetidas à análise de regressão e ajustadas de acordo com a tendência. Os grupos de materiais com fluoreto e/ou ACP apresentaram maior capacidade remineralizadora (%MDS e _Z) quando comparado com o grupo Controle. O grupo com apenas ACP apresentou resultado melhor ou semelhante quando comparado com os outros grupos e a associação do ACP e fluoreto não mostrou ser mais eficiente. A lesão de cárie mostrou-se mais remineralizada na distância de 150 ìm quando comparada com a de 600 ìm para os valores de %MDS. As concentrações de fluoreto, cálcio e fósforo presentes no esmalte variaram de acordo com o grupo analisado. Entre as variáveis avaliadas, somente foi verificada correlação entre %MDS e _Z. / The purpose of this study was to evaluate in situ the remineralizing potential of sealants containing amorphous calcium phosphate and/or fluoride in artificially induced carious lesions on smooth enamel surfaces. Ten volunteers took part in this triple-blind study, which had the duration of 5 days for each group: demineralized enamel + Fluroshield; demineralized enamel + Aegis (ACP); demineralized enamel + Fluoride (experimental); demineralized enamel + ACP + Fluoride (experimental) and demineralized enamel (Control). A wash-out period of 7 days was allowed between the treatments. Ten days before and during the whole experiment the volunteers used a non-fluoridated dentifrice. After the experimental period, the percentage recovery of surface microhardness (%RSM) and the recovery of integrated mineral area (HZ) were evaluated. The concentration of fluoride (Jg F/mm3), calcium (Jg Ca/mm3) and phosphorous (Jg P/mm3) present in enamel was also determined. Data obtained from %RSM and HZ were submitted to Analysis of Variance and Tukey’s test. Data from fluoride, calcium and phosphorous concentration were submitted to Kruskal-Wallis test. Significance level was set at 5%. All variables were also evaluated by regression analysis and adjusted according to the tendency. The groups with materials containing fluoride and/or ACP presented a higher remineralizing capacity (%RSM and HZ) than the Control group. The group with material containing only ACP showed a better or similar result compared to the other groups. The association between ACP and fluoride did not show a greater efficacy. For %RSM, the 150-Jm distance showed a higher remineralization of the artificially induced carious lesions compared to the 600-Jm distance. The concentrations of fluoride, calcium and phosphorous present in enamel varied according to the group.

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Orientadores: Celso Aparecido Bertran, Jose de Alencar Simoni / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-05T14:47:19Z (GMT). No. of bitstreams: 1 Simoni_DeborahdeAlencar_M.pdf: 1537289 bytes, checksum: aea471071313cd94cc22964fb9d8062b (MD5) Previous issue date: 2005 / Mestrado / Físico-Química / Mestre em Química