O NbAl3 e algumas ligas intermetálicas do sistema Nb-Ni-AI foram sintetizadas por combustão a partir dos pós de seus elementos constituintes. O efeito de variáveis de processo, como o tamanho de partícula dos pós, a composição química, a pressão de compactação, o tratamento de desgaseificação e a taxa de aquecimento, foram investigados na síntese do NbAl3 na forma de pastilhas cilíndricas. A síntese de ligas do sistema Nb-Ni-AI foi realizada a partir de misturas com as composições Nb10Ni70AI, Nb20Ni65AI e Nb30Ni60AI. A microestrutura das amostras reagidas foi caracterizada por microscopia óptica, microscopia eletrônica de varredura, EDS e difração de raios-X (método de Rietveld). Foram obtidas pastilhas de NbAl3 com 98,5 % da densidade teórica, superior ao valor encontrado na literatura (95%), mediante o controle de variáveis de processo. Nas pastilhas contendo níquel, a combustão ocorreu nas pastilhas de todas as composições. Fases metaestáveis, presentes na microestrutura das pastilhas baitas de reação, foram transformadas após tratamento térmico, originando ligas trifásicas com diferentes concentrações de fases (NbAl3, NiAI e NbNiAI), conforme a composição inicial do compactado. Algumas propriedades mecânicas de amostras brutas de reação e tratadas termicamente foram determinadas pela técnica da impressão (microdureza e tenacidade). Os resultados obtidos são comparáveis aos da literatura, salvo algumas discrepâncias atribuídas a processos de fabricação distintos. As etapas de reação da síntese do NbAl3 e de ligas Nb-Ni-AI foram posteriormente investigadas mediante interrupção da reação durante sua propagação ao longo de barras paralelepipédicas compactadas. Verificou-se que a síntese do NbAl3 ocorre pela dissolução de nióbio no alumínio fundido, seguida da precipitação do NbAl3. Nas amostras contendo níquel, a síntese ocorre em dois estágios: no primeiro estágio formam-se o Ni2Al3 ou o NiAl3, em quantidades relativas dependentes da composição geral. As reações deste primeiro estágio podem disparar as reações do segundo estágio, referentes à síntese do NbAl3. / NbAl3 and Nb-Ni-AI intermetallic alloys have been obtained by pressureless combustion synthesis from elemental powders. The effects of process variables as powder particle size, composition, compaction pressure (green density), degassing treatment and heating rate on the combustion (thermal explosion mode) of NbAl3 cylindrical pellets were studied. Combustion synthesis of Nb-Ni-AI alloys was performed on powder mixtures with nominal compositions Nb10Ni70AI, Nb20Ni65AI and Nb30NI60AI. The microstructure of reacted samples was characterized by optical microscopy, scanning electron microscopy, EDS and X-ray diffraction (Rietveld method). It was shown that careful control of the processing conditions allowed near full (98,5%) dense pellets of NbAl3. In the nickel containing pellets, reaction occurred for all the compositions investigated. Metastable phases were seen to be present in the as reacted pellets, which were transformed after a heat treatment, producing a three phase alloy (NbAl3, NiAI and NbNiAI) with different phase concentrations, depending on the initial compact composition. Some mechanical properties, like microhardness and tenacity were measured by microidentation technique on the as reacted and heat-treated samples. The results are comparable with the literature, excepted for some discrepancies caused by different fabrication processes. The reaction sequence for both cases (NbAl3 and Nb-Ni-AI alloys) was further investigated by DSC analysis and also by interrupting the reaction during its propagation along compacted parallelopipedal bars. It was found that the NbAl3 synthesis occurs through niobium dissolution in molten aluminum and precipitation of NbAl3. In the nickel containing samples, synthesis occurs as two-stage reaction: Ni2Al3 or NiAl3 are formed in the first stage, with relative amounts depending on the general composition. This first stage reaction can trigger the second one, related to the formation of NbAl3.

Foram ensaiadas quatro cerâmicas VMK 95, Omega 900, IPS d. Sign e Cergogold. Os ensaios realizados foram: 1) resistência de união, por ensaio de tração, à dentina humana, de cones (6 x 3 x 5mm) de cerâmica, unidos por meio de cimentos fosfato de zinco, resinosos Rely X e Panávia F (n=10); 2) rugosidade pelos parâmetros Ra, Rt, Ry, Rz e Rp, de superfícies tratadas com ácido fluorídrico a 10% e polidas (n=10); 3) durezas Knoop e Vickers (n=4); 4) análise por microscopia de força atômica de superfícies polidas apenas (n=5). Os dados foram analisados pela análise de variância e testes de Tukey foram feitos quando necessário. A resistência de união com o fosfato de zinco e o parâmetro de rugosidade Ra foram analisados em separado, por apresentarem variâncias bem menores que as correspondentes aos demais agentes cimentantes e parâmetros. Os resultados mostraram que a resistência de união com o fosfato de zinco foi muito baixa (1,61 a 2,91MPa), nas condições dos ensaios. Com cimentos resinosos a resistência média variou de 16,61 a 18,47MPa. O cimento Rely X apresentou menor resistência em média, mas isto também depende da cerâmica.As rugosidades das superfícies tratadas com ácido fluorídrico a 10% foram bem maiores do que nas polidas. Nessas o parâmetro Ra variou de 2,15 a 4,26µm e os demais parâmetros de 10,99 a 21,93µm. Nas superfícies polidas o Ra variou de 0,53 a 0,84µm. Os demais parâmetros apresentaram médias de 2,01 a 5,23µm. A dureza Knoop variou de 418,9 a 493,8 kgf/mm2 e a Vickers de 492,5 a 572,2 kgf/mm2. Esta última apresentou valores maiores. A microscopia de força atômica permitiu visualizar irregularidades de superfícies. As principais conclusões foram: o cimento de fosfato de zinco, na condição do ensaio (por tração) apresentou resistência de união muito baixa; com os cimentos resinosos a resistência de união foi bem alta; as rugosidades foram muito altas após o tratamento superficial com ácido fluorídrico a 10%, mas, as polidas apresentaram valores bem baixos; as durezas Vickers fornecem valores maiores que a Knoop. / Four ceramics (VMK 95, Omega 900, IPS d.Sign and Cergogold) were tested regarding: 1) tensile bond strength to human dentin of ceramic cones (6 x 3 x 5mm), cemented with zinc phosphate, and resin cements, Rely X and Panávia F (n=10); 2) roughness by means of parameters Ra, Rt, Ry, Rz and Rp, of HF (10%) surface treated and polished surfaces (n=10); 3) Knoop and Vickers hardness (n=4); 4) atomic force microscopy; only of polished surfaces (n=5). Data were analyzed by ANOVA and when necessary were used Tukey’s tests. Tensile bond strength with zinc phosphate cement and Ra roughness parameter were analyzed separately because of their low variances when compared with those of resin cements and the other roughness parameter. Results showed that tensile bond strength of zinc phosphate was very low (1.61 to 2.91MPa) in this test condition (tensile test). Resin cements presented tensile bond strength at range 16.61 to 18.47MPa. Cement Rely X presented lower strength, but it depends also of ceramic. HF (10%) treated surfaces presented much higher roughness than polished ones. In HF (10%) treated surfaces parameter Ra ranged from 2.15 to 4.26µm and the other parameter ranged from 10.99 to 21.93µm. Roughness of polished surfaces Ra ranged from 0.53 to 0.84µm. Range of the other parameter was from 2.01 to 5.23µm. Knoop hardness ranged from 418.9 to 493.8 kgf/mm2 and Vicker’s from 492.5 to 572.2 kgf/mm2. This type presented higher values. Atomic force microscopy permited good vision of surface irregularities. Main conclusions were: zinc phosphate cement at test conditions (tensile) presented low bond strength; resin cements presented high tensile bond strength; surface treatment with HF (10%) led to high roughness but in polished one it was low; Vicker’s hardness presented higher values than Knoop one.

Este trabalho avaliou a influência da densidade de energia da pré-cura, e de diferentes tratamentos pós-cura na otimização das propriedades físicas (Resistência à Flexão e Dureza Knoop) de resinas compostas diretas, visando a possibilidade de indicação para restauraçoes indiretas. Foram usadas as resinas diretas Fillmagic, Concept, Glacier, Z100, Masterfill e W3D Master e as indiretas Solidex e Belleglass HP como controle. Para cada resina direta foram confeccionados 60 espécimes em barra (10x2x2mm), 30 irradiados em uma face e 30 nas duas faces (30 espécimes = 10 controle, 10 autoclave e 10 forno de luz). Para as resinas indiretas foram preparados 10 espécimes conforme processamento de seus fabricantes. 380 espécimes foram submetidos ao ensaio de resistência à flexão (Kratos). De cada condição experimental, 10 fragmentos foram usados para ensaio de microdureza Knoop (Shimadzu HMV-2). A análise de variância e o teste de Tukey demonstraram significância para resistência à flexão nos fatores Resina (p<0,001) e Tratamento (p=0,001) e na interação Resina x Tratamento (p=0,001). Para a microdureza Knoop os três fatores e as interações foram significantes: Resina (p=0,001); Face (p=0,001) Tratamento (p=0,017); Resina x Face (p=0,001); Resina x Tratamento (p=0,007); Face x Tratamento (p=0,001) e Resina x Face x Tratamento (p=0,024). A maior média de cada resina direta, independente da condição experimental, foi comparada às médias das resinas indiretas. Os resultados apontam que na resistência à flexão (Z100 = W3D = Fillmagic = Glacier) e (Z100 > Masterfill > Belleglass HP > Concept > Solidex). Na Dureza Knoop (Z100 > Belleglass HP, Fillmagic, W3D, Concept, Glacier, Masterfill e Solidex). Conclusão: as propriedades físicas (resistência à flexão e dureza Knoop) não são obstáculos na indicação de resinas compostas de uso direto para restaurações indiretas / This study evaluated the influence of pre-cure energy density, and additional post-cure treatments in optimizing the physical properties (Flexural strength and Knoop microhardness) of direct resin composites with the aim at allowing their use for indirect restorations. Direct resin composites evaluated were Fillmagic, Concept, Glacier, Z100, Masterfill and W3D Master; indirect composites were Solidex and Belleglass HP. Sixty bar-shaped specimens (10x2x2mm) were prepared for each material, so that 30 of them were light-cured by one surface and 30 on both surfaces. From the 30 specimens of each group, 10 were control, 10 were submitted to additional autoclave and 10 to light oven treatment. Ten specimens were prepared with each indirect composite following the manufactures’ recommendations. The 380 specimens were submitted to flexural strength test (Kratos universal testing machine), and values obtained at fracture were reported. After that, 10 fragments were chosen for each experimental condition and assessed for Knoop microhardness (Shimadzu HMV-2). Data were submitted to analysis of variance and Tukey’s test at p<0.05. Statistically significant differences were found among flexural strength results regarding composite materials (p<0.001), treatments (p<0.001) and interactions (composite x treatment, p<0.001). Regarding Knoop microhardness, both three factors and their interactions were also significant: composite (p<0.001), surface (p<0.001) and treatment (p<0.017), composite x surface (p<0.001), composite treatment (p<0.001), surface x treatment (p<0.001) and composite x surface x treatment (p<0.024). The highest mean value for each direct composite, regardless of the experimental condition, was compared to the mean values obtained for the indirect materials. With regard to flexural strength, comparisons point out that Z100 = W3D = Fillmagic = Glacier and Z100 > Masterfill > Belleglass HP > Concept > Solidex, whereas for Knoop microhardness Z100 > Belleglass HP, Fillmagic, W3D, Concept, Glacier, Masterfill and Solidex. Conclusion: considering the physical properties evaluated in this study, they are not an obstacle to the indication of direct composites for indirect restorations

O objetivo deste trabalho foi avaliar o efeito da ação do calor e do frio sobre a estabilidade de cor, rugosidade de superfície e microdureza de restaurações de resina composta (FiltekMR Z250 XT 3M ESPE®), cimento de ionômero de vidro (KetacTM Fil Plus 3M ESPE®) e amálgama de prata em cápsulas (gs-80 SDI®), na tentativa de simular o comportamento desses materiais, quando presentes nos elementos dentais de vítimas carbonizadas ou mortas por congelamento. Foram selecionados 180 dentes bovinos que foram preparados (6 X 6 mm com 2 mm de profundidade) e separados em grupos de 30 dentes, segundo o tipo de material restaurador utilizado. Em seguida, foram realizadas as leituras iniciais de cor (Espectrofotômetro VITA® Easyshade), rugosidade de superfície (Rugosímetro Mitutoyo® Surftest SJ-201P) e microdureza Knoop (Microdurômetro Shimadzu® Micro Hardness Tester HMV-2), que foram consideradas os padrões iniciais. Subsequentemente, os dentes foram separados aleatoriamente em grupos (n=10) segundo a temperatura utilizada para simulação de congelamento (-80°C), (-20°C) e 2,5°C; e carbonização (100°C, 200°C e 300°C). A submissão a altas temperaturas foi realizada pela colocação dos dentes restaurados em forno (ALUMINI Sinter-Press EDG®), pelo período de 15 minutos, e as baixas temperaturas foram realizadas em refrigerador (RFGE 700 GE®) a 2,5°C; congelador (CVU18 Consul®) a (-20°C) e freezer (Ultra Freezer AL 374 - 80V American Lab®) a (-80°C). Após 7 e 30 dias de ação do frio e da submissão ao calor, os dentes foram submetidos às leituras finais de cor, rugosidade e microdureza. No calor, os valores de alteração de cor (&Delta;E*, &Delta;L*, &Delta;a* e &Delta;b*), dos dois materiais estéticos, rugosidade superficial e microdureza dos três materiais restauradores, foram submetidos à análise estatística One-way ANOVA, Tukey (p<0,05), tendo como fator de variação, a temperatura. No frio, os dados foram submetidos à análise estatística 2-way ANOVA, Bonferroni (p<0,05), tendo como fatores de variação, o tempo e a temperatura. Verificou-se que houve alteração de cor dos materiais estéticos, tanto nas submissões ao calor quanto ao frio. Na resina composta, a rugosidade de superfície e a microdureza não se alteraram significantemente (p>0,05), independente da temperatura a que foram submetidos. No CIV, a rugosidade e a microdureza elevaram-se nos testes ao calor; e ao frio, não ocorreram alterações significativas (p>0,05) dessas propriedades. Para o amálgama houve alteração de rugosidade significante (p<0,05) no calor, nas submissões a 300°C; e a microdureza não se modificou. Ao frio não ocorreram mudanças significantes (p>0,05) na rugosidade nem na microdureza do amálgama. Concluiu-se que os materiais estéticos podem ser distinguidos, pela análise de cor, a partir de 200°C até 300°C e quando submetidos a (-80°C), tanto em 7 dias como em 30 dias. O tempo de congelamento não é significativo para a distinção dos materiais. Testes de rugosidade e microdureza podem distinguir os materiais estéticos, independentemente, da ação do calor ou do frio. / The purpose of this study was to evaluate the effect of the action of heat and cold on color stability, surface roughness and microhardness of composite resin (FiltekMR Z250 XT 3M ESPE®), glass ionomer cement (KetacTM Fil Plus 3M ESPE®) and silver amalgam capsules (gs-80 SDI®) restorations, in an attempt to simulate the behavior of these materials when present in dental elements of carbonized or killed by freezing victims. 180 bovine teeth were selected, prepared with a 6 x 6 mm 2 mm cavity and then separated into groups of 30 teeth, according to the type of restorative material. Then, initial color readings (Spectrophotometer VITA® Easyshade), surface roughness (Rugosimeter Mitutoyo® Surftest SJ-201P) and Knoop microhardness (Shimadzu Micro Hardness tester® HMV-2) readings were performed, which were considered the initial standards. Afterwards, the teeth were randomly divided into groups (n=10) according to the temperature used for freezing simulation (-80°C), (-20°C), (2,5°C); and carbonization simulation (100°C, 200°C, 300°C). Submission to high temperatures was performed by placing the restored teeth in an oven (ALUMINI Sinter Press EDG®), for 15 minutes and for low temperatures, a refrigerator (RFGE 700 GE®) at 2,5°C, a freezer (CVU18 Consul®) at (-20°C) and an ultra freezer (Ultra Freezer AL 374 - 80V American Lab®) at (-80°C) were used. After the teeth being submitted to the action of cold and heat for 7 and 30 days, the color, surface roughness and microhardness final readings were performed. For the heat evaluation, the color change (&Delta;E*, &Delta;L*, &Delta;a* e &Delta;b*) of the two aesthetic materials, and the surface roughness and microhardness of the three restorative materials, were subjected to statistical analysis (One-way ANOVA, Tukey, p<.05), with one variation factor, the temperature. For the cold evaluation, the data were statistically analyzed using 2-way ANOVA, Bonferroni, (p>.05) with two variation factors, time and temperature. Color alteration occurred for the aesthetic materials submitted to heat and cold. In the composite resin, the surface roughness and microhardness did not change (p>.05), regardless of temperature to which they were exposed. In CIV, the surface roughness and microhardness increased with the heat. After cold submission, there were no significant changes (p>.05) to these properties. For the amalgam, there was roughness change (p<.05) when submitted to heat at 300°C; the microhardness did not change. There were no significant changes in amalgam roughness or microhardness when teeth were submitted to cold (p>.05). It was concluded that the aesthetic materials can be distinguished by the color analysis, from 200°C to 300°C and when submitted to (-80°C), both after 7 days and 30 days. The freezing time is not significant for the distinction of materials. Roughness and microhardness tests can distinguish the aesthetic materials, regardless of the action of heat or cold.

O objetivo deste trabalho foi avaliar a desmineralização do esmalte após períodos de 4, 7 e 10 dias de acúmulo de placa bacteriana in situ, além da influência de fatores salivares e microbiológicos no processo. Após a avaliação do fluxo salivar estimulado, capacidade tampão da saliva e níveis salivares de estreptococos do grupo mutans, 13 voluntários utilizaram dispositivos intrabucais palatinos contendo 4 blocos de esmalte bovino (4 X 4 X 2 mm) polidos, cobertos por uma tela plástica, durante 3 períodos cruzados de 4, 7 e 10 dias. Os voluntários utilizaram um dentifrício não fluoretado e gotejaram 10 vezes ao dia uma solução de sacarose a 20% sobre os blocos de esmalte. A microdureza superficial dos blocos foi determinada antes e após a desmineralização in situ, utilizando um penetrador Knoop e carga de 50 g por 5 s. Ao final de cada fase experimental, a placa bacteriana formada sobre os blocos foi coletada e a porcentagem de estreptococos mutans em relação ao número de bactérias totais foi determinada. Houve diferença estatisticamente significante, segundo o teste “t” pareado, entre a microdureza inicial e final nos três períodos estudados (p<0,05). A porcentagem de perda de dureza superficial (%PDS) foi em média de 13,8%, 19,3% e 48,3%, nos períodos de 4, 7 e 10 dias. Não houve diferença estatisticamente significante entre a %PDS com 4 e 7 dias, de acordo com a análise de variância e teste de Tukey (p<0,05). A correlação entre a %PDS e os fatores salivares e microbiológicos avaliados foi determinada por meio dos coeficientes de correlação de Pearson e Spearman, com p<0,05. Não foi encontrada correlação estatisticamente significante entre a %PDS e os fatores salivares avaliados inicialmente. Em aproximadamente metade das análises de placa bacteriana não foram detectados estreptococos mutans, embora tenha ocorrido desmineralização do esmalte. A porcentagem de estreptococos mutans na placa bacteriana não apresentou correlação com os níveis salivares dessas bactérias. Não foi encontrada correlação entre a %PDS e a porcentagem de estreptococos mutans na placa bacteriana formada sobre os blocos de esmalte. A %PDS nos blocos cobertos por placa bacteriana em que foram detectados estreptococos mutans foi estatisticamente maior do que nos blocos em que eles não foram detectados, apenas no período de 4 dias, de acordo com o teste de Mann-Whitney (p<0,05). Os resultados mostraram desmineralização do esmalte in situ após curtos períodos de acúmulo de placa bacteriana, não tendo sido encontrada relação com os fatores salivares avaliados ou com as contagens de estreptococos mutans na saliva e na placa. / The aim of this study was to evaluate the in situ enamel demineralization during 4, 7 and 10 days and some of the factors influencing the process. Before the beginning of the in situ phase, a stimulated whole saliva sample was collected from 13 volunteers for 5 min and the salivary secretion rate, buffering capacity and numbers of mutans streptococci were estimated. A palatal appliance containing 4 polished bovine enamel blocks (4 X 4 X 2 mm) covered by a plastic mesh was worn on 3 separate periods of 4, 7 and 10 days, throughout which time a non-fluoridated dentifrice was used. A 20% sucrose solution was dripped extra-orally onto the enamel blocks 10 times a day. All enamel blocks were evaluated by the analysis of enamel surface microhardness before and after in situ demineralization, using a 50 g, Knoop load for 5 s. At the end of each period, plaque covering the enamel blocks was collected and analyzed for the % of mutans streptococci of the total viable counts. Paired-t test showed that initial and final microhardness were statistically different at the three periods evaluated (p<0.05). Change in surface microhardness (%CSMH) was 13.8%, 19.3% and 48.3% during the 4, 7 and 10-day periods, respectively. There was no statistically significant difference on the %CSMH between 4 and 7 days, according to analysis of variance and Tukey’s test (p<0.05). Correlation between %CSMH and the salivary and bacteriological factors evaluated was determined using Pearson’s and Spearman’s coefficient of correlation (p<0.05). The %CSMH was not significantly correlated to the salivary factors determined initially. In about half of the plaque samples analyzed mutans streptococci were not detected, although the enamel showed some demineralization. The % of mutans streptococci in plaque samples was not correlated to its numbers in saliva. There was no statistically significant correlation between the %CSMH and the % of mutans streptococci in plaque over the enamel blocks. The presence of these bacteria in plaque significantly increased enamel demineralization when compared to the blocks where they were not detected only at 4 days, according to Mann-Whitney test (p<0.05). The results showed in situ enamel demineralization after short periods of plaque accumulation, which was not related to the salivary factors evaluated nor to the numbers of mutans streptococci in saliva or plaque.

Este trabalho in vitro teve objetivo de avaliar a superfície dentinária remanescente após remoção de tecido dentinário cariado, com instrumento cortante rotatório em baixa rotação e dois métodos químico-mecânicos (Papacárie® e Carisolv®) através da fluorescência laser (DIAGNOdent), microdureza e microscopia eletrônica de varredura. Na primeira fase do estudo, trinta incisivos decíduos com lesão de cárie em uma das faces proximais provenientes do Banco de Dentes Humanos da FOUSP foram avaliados antes e após a remoção do tecido cariado, pela fluorescência laser, sendo posteriormente preparados avaliação da microdureza . O teste de microdureza foi realizado em diferentes distâncias abaixo da dentina tratada após remoção do tecido cariado (50, 100, 150, 200, 300, 400 e 500µm) e do lado hígido (100, 150, 200, 300, 400, 500, 1000 e 1500 µm). Posteriormente, mais 30 dentes decíduos cariados foram divididos em três grupos de acordo com os diferentes tipos de tratamento para análise em MEV, sendo 15 dentes para análise do substrato e 15 dentes para observação de réplicas. Para obtenção destas, os dentes foram restaurados com o adesivo Single Bond (3M) e resina Filtek Z100 (3M) para avaliação de tags (15). Concluiu-se que houve diferença estatisticamente significante nos valores de fluorescência laser da dentina cariada e da dentina após a remoção do tecido cariado, não havendo influência dos tipos de tratamento utilizados. A análise estatística da microdureza mostrou que a dureza da dentina remanescente após remoção do tecido cariado foi menor que aquela obtida do lado hígido, não havendo diferença entre os grupos tratados: Instrumento cortante rotatório, Papacárie® e Carisolv®. Na análise em MEV pode-se observar com uso do Papacárie® e Carisolv® presença de uma camada amorfa semelhante a smear layer e poucas áreas com túbulos dentinários expostos; e no grupo do instrumento rotatório constatou-se superfície uniforme e lisa com smear layer característica e exposição de túbulos dentinários. Todos os grupos apresentaram acentuada formação de tags / The purpose of this in vitro study was to analyze the residual dentinal surfaces following caries removal using rotatory instruments and two chemomechanical methods (Papacárie® and Carisolv®), by laser fluorescence (DIAGNOdent), microhardness test and scanning electron microscopy (SEM). Thirty primary incisives, from the Human Bank Teeth of FOUSP, with carious cavities on one of the proximal surfaces were evaluated, before and after caries removal, by laser fluorescence, and then, prepared for the microhardness test. Microhardness was measured in different distances bellow the carious cavity side (50, 100, 150, 200, 300, 400 e 500µm) and on sound dentine of the other proximal side (100, 150, 200, 300, 400, 500, 1000 e 1500 µm). Next, other 30 primary incisives were divided in three groups, according to the caries removal method used, and their residual dentine was examined under SEM (15). After caries removal, 15 of these teeth were restored with Single Bond (3M) adhesive system and Z100 Filtek composite resin (3M). The tags of the replicas were observed under SEM. In conclusion, the laser fluorescence measurements observed before and after caries removal showed statistically significant difference in all groups; however, there was no difference among the caries removal methods used. The microhardness values of the residual dentinal surfaces were significantly lower than the ones found on sound dentine. No difference was found among the three caries removal methods regarding the microhardness values of residual dentine. Under SEM, the chemomechanical caries removal methods (Papacárie® and Carisolv®) formed an amorphous layer, similar to the smear layer and few exposed dentinal tubules; the conventional caries removal method produced a smooth and regular dentinal surface, with typical smear layer and exposed dentinal tubules. All groups showed abundant tag formation

Made available in DSpace on 2014-08-20T14:30:17Z (GMT). No. of bitstreams: 1 Dissertacao_Daniela_Venturini.pdf: 913438 bytes, checksum: e17fa4ddbe1c025e3411319cac841d1e (MD5) Previous issue date: 2006-06-30 / This study evaluated the effects of immediate and delayed polishing on surface roughness (Ra), microhardness (KHN) and microleakage of a microfilled composite (Filtek A110) and a hybrid composite (Filtek Z250) restorations after one-year storage. Standardized cavities preparations were made in the buccal surface of 256 bovine teeth; half were restored with each composite. Immediately after photo activation finishing was carried out with #280 grit sandpaper. For each composite, the specimens were randomly allocated for two sub-groups. The first group (IM) was immediately polished, using three different systems (n=16): A- Sof-Lex; B- Flexicups; and C- a sequential technique using Flexicups, Jiffy Polishing Brush and Flexibuffs. The specimens were stored in saline solution at 37ºC. The second group (DE) was stored for two weeks and then polished with the same systems. Part of the specimens had their surface properties analyzed at the baseline, and the remaining specimens were stored for one-year in distilled water at 37ºC. Five readings per specimen were taken for each specimen regarding surface roughness and microhardness. After immersion in basic fuchsin, microleakage was evaluated (X40) using standardized scores. Data were analyzed at significance level of 0.05 with analysis of variance and a SNK test (surface roughness and microhardness) or with Mann-Whitney and Kruskal-Wallis (microleakage). For comparison between baseline and one-year Student´s t test (Ra) and Mann-Withney (microleakage) were carried out. After one-year, in general microfilled composite specimens showed lower roughness and hardness. No difference regarding microleakage was observed among different groups, but better sealing was observed in enamel margins. The sequential technique provided the lowest roughness and the Sof-Lex the lowest hardness in the most of the experimental conditions. Aging increased composite roughness. Immediate polishing showed similar or better performance than delayed polishing for microleakage and surface roughness, but this was not observed for microhardness, except in sequential technique groups / Este estudo avaliou os efeitos do polimento imediato e mediato na rugosidade média superficial (Ra), dureza Knoop (KHN) e microinfiltração de um compósito microparticulado (Filtek A110) e um híbrido (Filtek Z250), após um ano de armazenagem dos espécimes. Preparos padronizados de 3mm mesio-distais, 3mm inciso-cervicais e 2mm de profundidade foram realizados na face vestibular de 256 incisivos bovinos, metade destes foi restaurada com cada tipo de compósito. Imediatamente após a fotoativação realizado o acabamento com lixa d água de granulação 280. Os espécimes restaurados com cada compósito foram divididos em dois grupos. O primeiro grupo (IM) foi polido imediatamente após o acabamento, usando três sistemas diferentes (n=16): A- Sof-Lex (3M-ESPE), B- FlexiCups (Cosmedent), C- (técnica seqüencial)- a seqüência de FlexiCups, Jiffy Polishing Brush (Ultradent) e FlexiBuffs (Cosmedent). Os espécimes foram então armazenados em solução salina a 37ºC. O segundo grupo (ME) foi armazenado por duas semanas e então polido com os mesmos sistemas. Parte dos espécimes foi analisada numa primeira etapa do experimento e o restante ficou armazenado por um ano em água destilada a 37ºC. Cinco leituras por espécimes foram realizadas para Ra e KHN. Após imersão em fucsina básica realizou-se o teste de penetração de corante sendo após analisado sob aumento (40x) usando escores padrão. Os dados foram verificados através de Análise de Variância e teste SNK (Ra e KHN). Também foram utilizados os testes de Mann-Whitney ou Kruskal-Wallis (microinfiltração). Para comparação com os dados baseline foram utilizados os testes t de Student (Ra) e Mann-Withney (infiltração marginal). Todos os testes foram executados com significância de 5%. Após um ano de armazenagem os espécimes do compósito A110 apresentaram significativamente menor rugosidade e menor dureza. A técnica seqüencial promoveu a menor rugosidade e os discos Sof-Lex a menor dureza, essas diferenças foram estatisticamente significantes. Os escores de infiltração marginal foram semelhantes entre os grupos. Após um ano de armazenagem os espécimes apresentaram um aumento significativo na rugosidade. O polimento IM mostrou-se igual, ou melhor, que o ME tanto para a infiltração marginal como para a rugosidade superficial para a maioria dos grupos analisados, no entanto tal fato não foi observado quanto à dureza superficial, exceto quando foi utilizada a técnica seqüencial

Abstract The effect of austenite pancaking in the non-recrystallisation regime on microstructure and mechanical properties, especially bendability, was investigated in direct-quenched ultrahigh-strength strip steels with martensitic-bainitic microstructures. Lowering the finishing rolling temperature (FRT) increased total reduction in the non-recrystallisation region (R tot). Niobium microalloying increased Rtot while variations in C, Mn and Mo did not affect Rtot to the same extent as Nb. A decrease in the FRT increased the incidence of softer microstructures such as ferrite and granular bainite in the subsurface layers. The microstructures at the centreline were comprised of auto-tempered martensite with some bainite. An increase in Rtot strengthens the intensities of the ~{554}&lt;225>α and ~{112}&lt;110>α texture components at the centreline and the components ~{112}&lt;111>α and ~{110}&lt;112>α - {110}&lt;111>α at the strip subsurface. Bendability is poorer with the bend axis perpendicular rather than parallel to the rolling direction (RD) and is further impaired with increasing hardness below the sheet surface. An intense ~{112}&lt;111>α shear texture combined with upper bainite containing MA islands in the subsurface region is shown to be detrimental to bendability when the bend axis is perpendicular to the RD. This anisotropy of bendability can be explained by the appearance of geometric softening in grain clusters belonging to this texture component when the bend axis is perpendicular to the RD. Shear localisation is prevented, however, by the presence of a sufficiently thick subsurface microstructure having adequate work hardening capacity, i.e., ferrite + granular bainite rather than ferrite + upper bainite. The strain required to initiate strain localisation can be increased and good bendability thereby achieved—even in the presence of detrimental texture components—by ensuring the presence of a sufficiently soft subsurface layer extending to a depth of approximately 5% of the total sheet thickness. The above beneficial microstructures can be obtained and good bendability ensured in direct-quenched strip steel with a yield stress above 900 MPa together with good impact toughness, provided a suitable combination of chemical composition and processing parameters is selected and sufficient attention is paid to steelmaking operations to obtain a proper inclusion structure. / Tiivistelmä Austeniitin muokkauksen vaikutusta mikrorakenteeseen ja mekaanisiin ominaisuuksiin, erityisesti särmättävyyteen, tutkittiin suorasammutetuilla martensiittis-bainiittisilla suurlujuusnauhateräksillä. Kuumavalssauksen lopetuslämpötilan lasku kasvatti austeniitin kokonaisreduktiota ei-rekristallisaatioalueella. Mikroseostus niobilla kasvatti myös kokonaisreduktiota, kun taasen muutokset C-, Mn- ja Mo -pitoisuuksissa eivät vaikuttaneet yhtä voimakkaasti. Valssauksen lopetuslämpötilan lasku kasvatti pehmeämpien mikrorakenteiden, kuten ferriitin ja granulaarisen bainiitin, määrää nauhan pintakerroksessa. Terästen keskilinjan mikrorakenteet koostuivat pääasiassa itsepäässeestä martensiitista sekä pienestä määrästä bainiittia. Kokonaisreduktion kasvu voimisti ~{554}&lt;225>α - ja ~{112}&lt;110>α -tekstuurikomponentteja keskilinjalla sekä ~{112}&lt;111>α- ja ~{110}&lt;112>α - {110}&lt;111>α -komponentteja nauhan pintakerroksessa. Särmättävyys oli huonompi särmän ollessa poikittain valssaussuuntaan nähden kuin pitkittäin. Pintakerroksen kovuuden kasvu heikensi särmättävyyttä. Pintakerroksen voimakas ~{112}&lt;111>α -leikkaustekstuuri, yläbainiitin ja MA-saarekkeiden läsnä ollessa, osoittautui haitalliseksi särmän ollessa poikittain valssaussuuntaan nähden. Särmättävyyden anisotrooppisuus voidaan selittää geometrisella pehmenemisellä rakeissa, joissa kyseinen tekstuurikomponentti on voimakas. Leikkausmyötymän paikallistuminen estyy, kun pinnassa on riittävän paksu hyvän muokkauslujittumiskyvyn omaava kerros, mikä sisältää esim. ferriittiä ja granulaarista bainiittia, mutta ei ferriittiä ja yläbainiittia. Särmättävyys osoittautui pysyvän hyvänä huolimatta haitallisesta tekstuurikomponentista, kun pehmeä pintakerros ulottui noin 5 % syvyydelle levyn paksuudesta. Edellä mainitut mikrorakenteet ja hyvä särmättävyys voidaan saavuttaa suorasammutetuilla yli 900 MPa myötölujuuden nauhateräksillä yhdessä hyvän iskusitkeyden kanssa, kunhan valitaan sopiva kemiallisen koostumuksen ja valmistusparametrien yhdistelmä sekä kiinnitetään huomiota teräksen sulkeumapuhtauteen.

In the modern era of metal-free minimally-invasive dentistry, there is a growing tendency toward using metal-free restorative alternatives that provide not only excellent aesthetics but also enable superior durability. Fibre-reinforced composite (FRC) is one cost-effective alternative that fulfils the requirements of aesthetics and durability, and offers favourable physico-mechanical properties. Many FRC applications are well-documented in the literature, such as crowns and fixed partial dentures (FPD); however, their clinical implementation is still limited, owing to the lack of significant knowledge about their longevity, deterioration signs, optimum design and overall performance. This in-vitro research aimed to address these uncertainties by investigating the performance of FRC restorations, and the influence of fibre reinforcement on particular physcio-mechanical properties, including surface hardness, edge-strength, shear bond strength, fatigue and wear resistance. Basic testing models were used to investigate the effect of incorporating differently-oriented FRCs on the surface hardness, edge-strength and shear bond strength of particulate-reinforced composite (PRC). The results revealed that the incorporation of FRC significantly enhanced surface hardness (by 12 - 19 %) and edge-strength (by 27 -75 %). However, this incorporation significantly reduced the shear bond strength (SBS) between PRC and other restorative materials, including lithium disilicate ceramic (10.9±3.1 MPa) and Co-Cr metal alloy (12.8±2.3 MPa), compared to the control (15.2±3.6 MPa, 15.0±3.7 MPa). The orientation of FRC was also found to affect the efficiency of reinforcement as bidirectional FRCs exhibited significantly higher hardness (76.8±1.2 VHN), edge-strength (67.7±8.2 N) and SBS (14.1±3.9 MPa) values than unidirectional FRCs (72.4±1.2 VHN, 56.8±5.9 N, 9.8±2.3 MPa).Clinically-relevant testing models, employing accelerated aging techniques, were performed to investigate the fatigue and wear behaviours of anatomically-shaped FRC restorations in-vitro. Direct inlay-retained FRC-FPDs with two framework designs, were tested for their fatigue behaviour and load-bearing capacity. Type-I design (with an additional bidirectional FRC layer incorporated perpendicular to the loading direction) yielded significantly higher fatigue resistance (1144.0±270.9 N) and load-bearing capacity (1598.6±361.8) than Type-II design (with a woven FRC embedded around the pontic core) (716.6±72.1 N, 1125.8±278.2 N, respectively). However, Type-19II design exhibited fewer delamination failures. Both framework design and dynamic fatigue were found to have a significant influence (p < 0.05) on the load-bearing capacity of FRC-FPDs. Additionally, the in-vitro fatigue and wear behaviours of FRC crowns, fabricated conventionally from bidirectional FRC and indirect PRC (Sinfony), were compared with those made of two CAD/CAM alternatives, namely Lava Zirconia (LZ) and Lava Ultimate (LU). A chewing simulator was employed to induce some fatigue wear in crowns, while an intraoral 3D scanner was used to quantify the resultant morphological changes. The results showed that FRC crowns had significantly lower mean cumulative wear (233.9±100.4 μm) than LU crowns (348.2±52.0 μm), but higher than LZ crowns (16.4±1.5 μm). The mean load bearing-capacity after fatigue simulation was also the highest for LZ crowns (1997.8±260.2 N) compared with FRC (1386.5±258.4 N) and LU crowns (756.5±290.9 N).Accordingly, the incorporation of FRC in resin-composite restorations is advocated since it increases surface hardness and marginal integrity, improves fatigue and wear behaviours, and enhances load-bearing capacity and overall performance.

The titanium alloy, Ti-6Al-4V, is vastly studied and used in many applications because it has a transformation microstructure, which can be tailored for apt properties that are consistent up to 500°C. Compared to conventional steels, this alloy favours certain applications due to its high specific strength, hardenability, corrosion resistance, biocompatibility and weldability. Its weldability makes the alloy a good candidate for additive manufacturing (AM). Ti-6Al-4V parts are widely built by the AM process of electron beam melting (EBM). However, heat transfer remains crucial in EBM process. The high intensity localized, moving, electron beam heat source and the rapid self-cooling are critical, especially in thin parts/ sections. When thin sections are built by the EBM process, there will be microstructural variation in their build direction, which can lead to the variation of their mechanical properties. It is necessary to understand the microstructure and mechanical properties of thin sections when they are used as functional parts in various applications in aerospace, automotive, medical, etc. industries. The microstructure, tribological behaviour and mechanical properties of Ti-6Al-4V, as-built EBM thin plates were studied by means of various hardness, scratch and tensile testing. The hardness and scratch tests were performed on the thin plates to correlate the microstructural variation. In-situ micro tensile test was performed inside the scanning electron microscope (SEM), to see the sample’s deformation behaviour. Microstructural characterization revealed equiaxed grains in the transverse section and the longitudinal surface exhibited columnar grains elongated along the build direction. The size of the equiaxed grains are found to vary across the thickness of the plate. The indentation and scratch hardness also vary in correlation with the varying grain size across the plate’s thickness. The micro tensile results reveal that the tensile properties of the thin plate are comparable to that of its bulk Ti-6Al-4V counterpart.