Made available in DSpace on 2014-10-09T12:42:58Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:29Z (GMT). No. of bitstreams: 1 06218.pdf: 6174037 bytes, checksum: 8832d40832348b30017cfa64b7199926 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:32:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:15Z (GMT). No. of bitstreams: 1 03369.pdf: 1560275 bytes, checksum: 905c046cbaa9aa4972b03e4674cdde9a (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2015. / Dental alloys are widely used in direct contact with oral tissue. In recent years after the price of gold significantly increased, cheaper dental materials were generally considered in the market particularly dental alloys such as cobalt-chromium (Co–Cr), nickel-chromium (Ni–Cr) and titanium alloys. Cobalt– chromium alloys for example, are used in prosthetic for the fabrication of removable partial dentures and also for the fabrication of some fixed prosthetic appliances, due to its excellent properties such as biocompatibility, good mechanical behavior and corrosion resistant. In this work, the corrosion behavior of three different dental alloys, namely PD CASTA H, CERACAST NB Beryllium Free and PD 2000 alloys were studied and tested in Ringers solution (artificial saliva) at different pH values and temperature. The dental alloys were immersed in the Ringers solution for 14 days. The microstructure characterization and composition of selected alloys were done before and after 14 days of corrosion test on artificial saliva, using scanning electron microscopy (SEM). The surface roughness of the alloys was investigated by atomic force microscopy (AFM). The EDS, XRD, and TOF–SIMS were also used in the study. Electrochemical measurement on dental alloys was performed using cyclic voltammetry (CV). A saturated calomel electrode (SCE) was used as reference electrode, platinum was used as counter-electrode and Ni–Cr and Co–Cr alloys were used as working electrode. The polarization curves were plotted in the potential range of -1000 mV/SCE to +1000 mV/SCE at scanning rate of 0.2 mVss-1. It has been shown in the present study that the corrosion behavior of PD CASTA H and PD 2000 alloys, containing Co and a high Cr content, displays the best corrosion resistance compared to CERACAST NB alloy. The influence in the temperature and pH of the solution had effects on the properties of dental alloys. The electrochemical behavior of dental alloys were studied to provide a comprehensive examination of various biomedical materials used in dental application. However, the surface roughness and the surface morphology of the alloys are very important in dental study and application.

Made available in DSpace on 2014-10-09T12:36:51Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:04Z (GMT). No. of bitstreams: 1 04375.pdf: 2570523 bytes, checksum: 66673910e669a76a08e5020adcac30c0 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:36:58Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:24Z (GMT). No. of bitstreams: 1 04492.pdf: 7071793 bytes, checksum: d4d17862f6e76da4daea9d8b7345891e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:30Z (GMT). No. of bitstreams: 1 05065.pdf: 3573902 bytes, checksum: fa9368ab741a4e14bd802e16f0bbd409 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:36:46Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:33Z (GMT). No. of bitstreams: 1 04247.pdf: 1350775 bytes, checksum: 0913235ef02d78d0cfecf1e68d0c6900 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:14Z (GMT). No. of bitstreams: 1 06441.pdf: 2524983 bytes, checksum: 8c518f35a229f2345835f93c97fd57f5 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:51:35Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:05Z (GMT). No. of bitstreams: 0 / A inoculação de sementes de leguminosas de grãos tais como soja [Glycine max. (L.)], feijão (Phaseolus vulgaris L.) e pastagens tem sido uma estratégia efetiva e conveniente para introduzir estirpes eficientes de Bradyrhizobium/Rhizobium em solos agrícolas sem histórico de cultivo anterior dessa cultura ou quando as estirpes ivas são ineficientes no processo biológico de aquisição de nitrogênio. Através do uso de substrato turfoso previamente esterilizado como veículo da bactéria, os efeitos ambientais adversos podem ser amenizados, pois este substrato atua diretamente, na sobrevivência da bactéria através do fornecimento de nutrientes. O Brasil requer que os substratos turfosos sejam pré-esterilizados através de radiação gama de cobalto-60 (60Co), sendo recomendada a dose de 50 kGy para uma efetiva eliminação de patógenos e saprófitas, que podem competir com a bactéria introduzida. Recentemente, a utilização de aceleradores de elétrons foi considerada uma nova alternativa de radiação para pré-esterilização da turfa, pois, por se constituir de processo oxidativo avançado, gera radicais altamente reativos, eficientes na eliminação de agentes contaminantes. Esta técnica é considerada ecologicamente mais segura que a radiação gama, além de ser um processo mais rápido. Há, porém, a característica de ter menor profundidade de penetração da radiação em relação ao 60Co. O presente estudo comparou o método usando doses crescentes de radiação gama por 60Co e por feixe de elétrons (0, 10, 20, 30, 40 e 50 kGy). Os dados experimentais (7, 14, 21 e 28 dias para a fase curta e 150, 180 e 210 dias para a fase longa de incubação) mostraram um elevado número de células da bactéria Rhizobium tropici CM-01 gusA+ inoculada em substratos turfosos submetidos aos dois processos de esterilização, sendo que ambos processos atenderam aos padrões mínimos requeridos pelas normas brasileiras (validade de 180 dias e presença acima de 1 x 108 células/g de substrato). Sob doses mais elevadas, acima de 40 kGy, o método por feixe de elétrons foi mais eficiente em eliminar actinobactérias, consideradas sérias antagonistas de bactérias inoculantes em turfas e que surgiram após 150 dias. Em um segundo estudo, usando o isolado CM-01 celB+ por um período de 30 dias, os resultados confirmaram a eficiência do método por feixe de elétrons na fase de crescimento bacteriano, mesmo para dose baixa de 10 kGy. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:51:36Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:26Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP