O objetivo deste estudo foi avaliar a estabilidade de cor e opacidade de cinco sistemas cerâmicos glazeados naturalmente e com pintura extrínseca, utilizando os espectrofotômetros Color Guide 45/0 (BYK-Gardner) e Easyshade (Vita), sob influência do envelhecimento artificial acelerado. Foram confeccionados 14 corpos de prova para cada grupo testado de cerâmica - metalocerâmica Ceramco 3 (Dentsply) (grupo 1), cerâmica pura Ceramco 3 (grupo 2), cerâmica pura EX -3 (Noritake) (grupo 3), Vitroceram (Angelus) recoberta com Allceram (Degudent) (grupo 4) e Vitroceram recoberta com Cerabien (Noritake) (grupo 5). Sete corpos de prova de cada grupo cerâmico foram glazeados naturalmente e sete foram submetidos à pintura extrínseca com pigmento Vita Chrom 712. Uma leitura inicial foi realizada em todos os corpos de prova utilizando o espectrofotômetro Color Guide, obtendo valores de opacidade e das coordenadas L*, a*, b* e E*; e utilizando o espectrofotômetro Easyshade, obtendo valores de L*, C*, h* e E*. Após o envelhecimento artificial de 500h, foram realizadas novas leituras nos espectrofotômetros. Os resultados encontrados foram submetidos à análise estatística e concluiu-se que os grupos 2, 3 e 4 foram influenciados estatisticamente pelo envelhecimento artificial acelerado quanto à opacidade; e que o grupo 5 foi o que obteve o pior desempenho de estabilidade de cor (E* = 3,32 - VTCE e E* = 2,68 = VTCEPE) para o espectrofotômetro Color Guide. Com o espectrofotômetro Easyshade os grupos 4 e 5 e as cerâmicas MC, CER, EX foram considerados ineficazes quanto à estabilidade de cor (p<0,05). / The aim of this study was to evaluate the color stability and opacity of five ceramic systems naturally glazed and with extrinsic porcelain colorant, under influence of accelerated aging, using two spectrophotometers Color Guide 45/0 (BYK-Gardner) and Easyshade (Vita) as a tool for color and opacity measurement. Fourteen samples were provided for each tested group of ceramics: metal-ceramic Ceramco3 (Dentsply) (Group 1), Ceramco3 (Group 2), EX3 (Noritake) (Group 3), Vitroceram (Angelus) with Allceram (Degudent) (Group 4) and Vitroceram with Cerabien (Noritake) (Group 5). Seven samples of each group were submitted to extrinsic colorant (Vita Chrom 712) and the other seven were naturally glazed. An initial measurement was performed and the values of opacity, L*, a*, b* and E* were obtained using the Color Guide spectrophotometer, and using Easyshade the values of L*, C*, h* and E* were obtained. After the process of 500h accelerated aging a new measurement was performed for all samples. The results were statistically analyzed and the conclusion was that the opacity of groups 2, 3 and 4 were statistically influenced by the accelerated aging and the group 5 had the worst assessment in color stability (E* = 3,32 - VTCE e E* = 2,68 - VTCEPE) with the Color Guide spectrophotometer. With Easyshade, groups 4 and 5 and MC, CER and EX ceramics were considered ineffective as for color stability (p<0,05).

Orientador: Maria Auxiliadora Junho de Araújo / Banca: Maria Auxiliadora Junho de Araújo / Banca: Lourenço Correr Sobrinho / Banca: Luiz Fernando Pegoraro / Banca: Estevão Tomomitsu Kimpara / Banca: Marco Antonio Bottino / Resumo: O objetivo deste trabalho foi avaliar a resistência à flexão de barras de In-Ceram Alumina e In-Ceram Zircônia sinterizadas, seccionadas de diferentes formas e posteriormente unidas e infiltradas por vidro fundido. Foram confeccionados duzentos corpos-de-prova, sendo cem do Grupo A (In-Ceram Alumina / ICA) - e cem do Grupo Z (In-Ceram Zircônia / ICZ). Todas as amostras foram confeccionadas segundo as recomendações do fabricante, com as dimensões de 25,0mm X 4,0mm X 3,0mm, e sinterizadas em um forno especial Inceramat III (Vita). As amostras foram dividas em cinco subgrupos: a) controle; b) corte reto central; c) corte diagonal 45º na região central; d) corte central com revestimento total; e) corte diagonal 45º na região de apoio. As amostras seccionadas foram unidas com o próprio material cerâmico, em dispositivo que manteve o alinhamento entre os segmentos cerâmicos, e novamente levadas ao forno, realizando novo ciclo de sinterização. Os corpos-de-prova foram submetidos ao ensaio de flexão de três pontos usando uma máquina de ensaios universal EMIC. Os resultados foram submetidos à análise de variância one-way e ao teste de Tukey (5%). Os resultados indicaram não haver diferença significativa entre os grupos controle dos materiais ICA controle (425,60l73,81MPa); ICZ controle (469,11l66,62MPa) e as amostras do subgrupo (GZ4) ICZ com corte diagonal 45º na região de apoio (416,39l54,64MPa) não apresentaram diferenças estatísticas significantes. A microscopia eletrônica de varredura para avaliação morfológica na região da fratura não apresentou diferenças marcantes entre os grupos analisados. Entretanto, foram observadas um maior número de lacunas entre o material cerâmico de união e a estrutura cerâmica, principalmente no subgrupo 3 - com corte na região central e recobrimento total. / Abstract: The aim of this work was to evaluate the flexural resistance of In-Ceram Alumina (ICA) and In-Ceram Zirconia (ICZ) bars, sinterized, cut in different shapes and afterwards jointed and infiltrated by glass. Two hundred samples were manufactured, being 100 of the group A (In-Ceram Alumina) and 100 of group Z (In-Ceram Zirconia). All the samples were made according to the manufacturer recommendations with the dimensions of 25,0mm X 4,0mm X 3,0mm, and fired in a special furnace (Inceramat III, Vita). The samples were divided in 5 sub-groups: a) control; b) central straight cut; c) diagonal cut 45º in the central region; d) central cut with total covering; e) diagonal cut 45º in the support region. The separated samples were then jointed with the same ceramic material in a device that kept the alignment between the segments and these were fired in a new e of sintering cycle. The samples were subjected to the three point bending test using a universal test machine EMIC. The results were submitted to the analysis of variance one-way and to the Tukey test (5%). There were no statistically significant differences (p<0,05) between the control groups: ICA control (425,60l73,81MPa); ICZ control (469,11l66,62MPa) and no statistically significant difference for the samples of sub-group (GZ4) ICZ diagonal cut 45º in the support region (416,39l54,64MPa). The electronic scanning microscopy showed no differences the morphology of the region of the crack in the analyzed groups. However, major gaps were observed between the ceramic union material and the ceramic structure, mainly in sub-group 3 - central cut with total covering. / Doutor

Orientador: Carlos Alberto dos Santos Cruz / Banca: Luís Geraldo Vaz / Banca: Paulo Vicente Barbosa da Rocha / Resumo: O objetivo deste trabalho foi avaliar a resistência à flexão, a resistência à tração diametral e a dureza das cerâmicas feldspáticas AllCeram (processada por sinterização) e Cergogold (processada por injeção à vácuo) e Ceramco 2 (processada por sinterização convencional e por injeção). Foram confeccionadas dez amostras de cada grupo experimental para o ensaio de resistência à flexão (em forma de barra, 25mm de comprimento, 5mm de largura, 2mm de espessura - ISO 6872) e 15 amostras para o ensaio de resistência à tração diametral (em forma de disco, 6mm de diâmetro, 3mm de espessura). Os testes foram realizados em equipamento MTS 810 (Material Test System, EUA), com célula de carga de 10kN e velocidade de 0,5mm/minuto, gerenciado por programa Test Star II (IBM, EUA). Para o ensaio de dureza, na escala Vickers, cinco fragmentos de cada grupo foram incluídos em resina acrílica autopolimerizável, polidos e submetidos ao teste no durômetro Buheler (EUA), com carga de 1,0kgf por 30 segundos. Dento da técnica de processamento indicada pelo fabricante, nos ensaios de resistência à flexão e dureza, os resultados apontaram igualdade estatística entre os materiais Ceramco 2 (73,75MPa / 478,8VNH) e Cergogold (68,96MPa / 495,3VHN); a seguir, com valores estatisticamente inferiores está a cerâmica All-Ceram (50,51MPa / 451VHN). No ensaio de resistência à tração diametral, houve igualdade estatística entre os 3 materiais: Ceramco 2 (34,15MPa), Cergogold (33,95MPa) e AllCeram (29,74MPa). Para a cerâmica Ceramco 2, o método de processamento sinterização ou injeção à vácuo não interferiu na resistência mecânica, apresentando valores com igualdade estatística para as três propriedades estudadas: respectivamente, resistência à flexão (73,75MPA, 77,88MPa), resistência à tração diametral (34,15MPa, 33,52MPa) e dureza ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to compare flexural strength, diametral tensile strength and hardness of ceramics AllCeram (convencional fusing), Cergogold (heat-pressed) and Ceramco 2 (convencional fusing and heat-pressed). Ten especimens were made for flexural test (25mm length; 5mm width; 2mm thick - ISO 6872), and 15 especimens for diametral test (6mm diameter, 3mm thick). The tests were done in a MTS 810 machine (Material Test System - USA), with load cell of 10kN and crosshead-speed of 0.5mm/minute, managed by Test Star II software (IBM, USA). Five samples of each ceramic were included in autocured resin JET (Artigos odontológicos Clássico, Brazil), polished and submitted to Vickers hardness test in duromer Buheler (USA), with load of 1.0kgf for 30 seconds. Manuffacturer' processing technique the mean flexural stengths and hardness was significantly similar for Ceramco 2(73,75MPa / 478,8VNH) and Cergogold (68,96MPa / 495,3VNH), and significantly stronger than AllCeram (50,51 / 451VNH). All materials did not differ for diametral tensile (AllCeram 29,74MPa; Cergogold, 33,95MPa; Ceramco 2, 34,15MPa). Effects of processing method (convencional fusing and heat-pressed) did not influenced on flexural strength (73,75MPa / 77,88MPa), diametral tensile strength (34.15 MPa / 33,52 MPa) and hardness (478,8VHN / 471,5VHN) of Ceramco 2. However, for Ceramco 2 (heat-pressed) flexural strength (77,88MPa) became significantly higher and hardness (471,5VHN) became significantly lower than Cergogold (68,96MPa, 495,3VHN). / Mestre

OBJECTIVE: The purpose of this study is to evaluate the experimental properties of zirconia-based ceramics. METHODS: Zirconia bars were veneered to 2mm total thickness. Veneering-method groups included: 1.Hand-layered feldsparthic porcelain (VM=VitaVM9,Vident) and fluorapatite glass-ceramic (CR=IPSe.maxCeram,IvoclarVivadent); 2.Pressed feldspathic porcelain (PM=VitaPM9,Vident) and fluorapatite glass-ceramic (ZP=IPSe.maxZirPress,IvoclarVivadent); 3.CAD/CAM milled feldspathic ceramic (TF=VitablocsTriluxeForte,Vident) and lithium-disilicate glass-ceramic (CAD=IPSe.maxCAD,IvoclarVivadent). CAD/CAM veneers were either cemented with resin cements (P=Panavia21,KurarayDental), (R=RelyXUltimate,3M ESPE), (M=MultilinkAutomix,IvoclarVivadent) or fused with fusion glass-ceramic (C=CrystalConnect,IvoclarVivadent). A Three-point-bending test was performed. For group VM,PM,TF-M,TF-C,CAD-M,CAD-C, ten more bars were prepared and aged with cyclic loading and thermocycling before testing. Zirconia bars (PrettauZirconia,Zirkonzahn;inCorisTZI,Sirona;ZirluxFC,PentronCeramics) specimens were prepared and polished. The specimens were divided into 3 groups: control, self-glaze fired, and glazed groups. A Three-point bending test was performed. Veneered zirconia crowns were made. Feldspathic porcelain was applied to zirconia coping. Bevel cut on porcelain was made to simulate porcelain chipping. The crowns were then divided into 4 different groups according to repair materials including: 1.Conventional-resin composite (TetricEvoCeram,IvoclarVivadent) 2.Flowable-resin composite (G-aenialUniversalFlo,GCamerica) 3.Cemented CAD/CAM milled feldspathic ceramic (VitaTriluxForte,Vident) 4.Cemented CAD/CAM milled lithium-disilicate glass-ceramic (IPSe.maxCAD,IvoclarVivadent). Each crown underwent thermocycling. The test was performed by loading force on the center of repaired part to record load-to-failure. RESULTS: There were significant differences in the failure loads of non-aged bilayered veneer-zirconia bars. Aging experiment revealed a significant difference in failure load between non-aged and aged bars in groups VM and PM, but not in the groups with CAD/CAM milled veneers. There was significant influence of surface treatments on flexural strength of zirconia specimens. Post-hoc test showed that glazed group had significant lower flexural strength than other groups. Crowns repaired with CAD/CAM ceramics showed significant higher failure load than resin composite. Repairing with lithium-disilicate glass ceramic yielded the highest load-to-failure of the specimens. CONCLUSIONS: - Veneer materials, veneering methods, and cement materials have a significant effect on the failure load of bilayered veneer- zirconia. CAD/CAM veneer-zirconia is not susceptible to aging performed in this study. - Glazing decreased the flexural strength of high translucent zirconia. - Veneered zirconia crowns repaired with CAD/CAM ceramic materials have significantly higher load-to-failure than veneered crowns repaired with resin composite. / 2018-09-28T00:00:00Z

The dissertation follows the trajectory of one of the commodities of the transpacific trade, Chinese porcelain, from the city of Jingdezhen where it was produced, to Manila where it was sold to Spanish merchants, on to Mexico, where it was adopted by the colonial society. The study ends in the city of Puebla where potters drew inspiration from Chinese porcelain for the invention of a new ceramic style known as loza poblana. The methodology of following the trajectory of Chinese porcelains through various sites reveals a new kind of history, one where the tactile aspects of the circulation of goods become salient. The places, contexts, and transactions that the commodities passed through are more prominent--the trade is no longer an abstract exchange between different parties or an endeavor driven purely by imperial greed. Instead it emerges as a process that developed from an interaction between global material forces and local histories and contingencies. Such a tactile history also provides details about the movement and transfer of aesthetics in the early modern period, as seen in the case of the design of the Chinese guan, a jar form, that was adapted to make the Mexican chocolatero.

Leung Yuen-fun Rachel. / Thesis submitted in: May 2004. / One leaflet mounted. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Abstracts in English and Chinese. / Chapter Chapter One: --- Historical Background / The discovery of the kiln sites --- p.1 / The naming of Changsha ware --- p.3 / The beginning of production --- p.5 / Chapter Chapter Two: --- Development of Changsha ware / Duration of operation --- p.10 / Stages of development --- p.11 / Reasons for decline --- p.15 / Chapter Chapter Three: --- Glaze and Kiln Characteristics of Changsha ware / Body --- p.18 / Shaping method --- p.19 / Glazes --- p.19 / Kiln --- p.21 / Chapter Chapter Four: --- Classification of Changsha ware in the Art Museum collection / Introduction --- p.24 / Daily household wares --- p.25 / Cultural and scholar's articles --- p.44 / Toys --- p.47 / Potter's tool --- p.51 / Chapter Chapter Five: --- Decoration of Changsha ware in the Art Museum collection / Introduction --- p.53 / Decorative technique --- p.54 / Decorative motif --- p.59 / Chapter Chapter Six: --- Changsha ware as reflections of daily life / Custom and religion --- p.78 / Games --- p.94 / Childhood education --- p.98 / Cross cultural Communication --- p.100 / Chapter Chapter Seven: --- Conclusion --- p.102

O estudo da dispersão e estabilização de barbotinas de porcelana de cinza de ossos é uma etapa muito importante no processo de conformação de peças cerâmicas, assim como também a etapa de obtenção da sua principal matéria-prima que é a cinza de ossos, devido a que constitui 50% em peso da porcelana e por ser uma matéria-prima renovável, reciclável e com alto valor agregado na fabricação de porcelana. Neste trabalho se investigou a influência das temperaturas de calcinação dos ossos (700, 800, 900 e 1000 °C) moídos e lavados, no seu tamanho, forma das partículas, composição química, comportamento elétrico superficial das partículas com o meio líquido, grupos funcionais e possíveis contaminantes nas superfícies das partículas dos ossos calcinados, que poderiam prejudicar a preparação de barbotinas de porcelana de ossos. Mostra-se também a dispersão, preparação e a estabilização da mistura de porcelana de ossos (50% cinza de ossos, 25% de caulim, 25% de feldspato) por meio dos ensaios de viscosidade e mobilidade eletroforética, conseguindo dispersar, homogeneizar e estabilizar as suspensões de porcelana de ossos aplicando tempos de envelhecimentos apropriados. / The study of the dispersion and stabilization of slip casting of bone porcelain is a very important stage in the process of preparation of suspensions ceramic, as well as the obtaining of its main material, that it is the bone ash, so that it constitutes 50% in weight of dry mass, and also that is one raw material renewable, recyclable and with high value added in the porcelain production. In the present research, the influence from the calcination of bovine bones to different temperatures (700, 800, 900 and 1000 °C) was investigated besides the size and form of the particles, variation in its chemical compositions, variations in its electric superficial behavior of the particles in contact with the liquid medium and also the groups present functional in the particles of ash of bones, kaolin and feldspar. Reveals the behavior of the particles during the dispersion and stabilization of the bone porcelain (50% ash of bones, 25% kaolin, 25 % feldspar) by means of the tests of viscosity and electrophoretic mobility, being able to disperse, to homogenize and to stabilize the suspensions of bone china with appropriate ageing time.

O tratamento ortodôntico em adultos, nos últimos tempos, tem ganhado popularidade na tentativa de melhorar a estética e a função. No entanto, é uma característica comum nestes pacientes, ter os dentes restaurados com facetas de resina, coroas metalo-cerâmicas e/ou porcelana pura. Neste contexto, o ortodontista se defronta com o desafio de colar braquetes em diferentes sistemas cerâmicos, de capacidade desconhecida de resistir às forças de cisalhamento. Portanto, os objetivos deste trabalho foram: 1) Verificar se a força de cisalhamento em braquetes colados em superfícies de porcelana feldspática e AllCeram é afetada por diferentes tempos de ataque com ácido hidrofluorídrico e 2) Observar se existe uma relação direta entre os valores obtidos da força de cisalhamento e o índice remanescente de adesivo (IRA). Sessenta espécimes de porcelana em formato cilíndrico foram aleatoriamente divididos em 3 grupos de 20 espécimes de acordo com o tempo de ataque do ácido hidrofluorídrico de 1 minuto, 30 segundos e 15 segundos (grupos 1, 2 e 3 respectivamente). Outros sessenta espécimes de porcelana AllCeram, com o mesmo formato e divididos da mesma maneira de acordo com o tempo de ataque ácido (grupos 4, 5 e 6 respectivamente). A colagem dos braquetes na superfície cerâmica incluiu aplicação de silano, colocação de resina fotoativada sobre a base do braquete e cimentação com força padronizada de 500g. Vinte e quatro horas após a cimentação, os espécimes foram submersos em água destilada a 37OC e submetidos ao teste de resistência ao cisalhamento em uma máquina de ensaio universal, com velocidade de 0,5 mm/min, cujos valores registrados em Kgf e convertidos em MPa. O tipo de falha também foi egistrado usando o IRA através de um estereoscópio com magnificação de 4x. A força de cisalhamento mais alta foi registrada no grupo 1 (21.21 MPa), que foi significativamente diferente dos grupos 2, 3, 4, 5 e 6 (11.01, 10.64, 14.31, 10.59, 10.39 MPa, respectivamente). Os valores mais baixos encontrados nos grupos remanescentes não diferiram entre si. A mediana dos escores do IRA para os grupos 1, 2, 3, 4, 5 e 6 foi 2, 3, 3, 0, 3, e 3, respectivamente. O grupo 1 (porcelana feldspática 1 minuto) foi afetado pelos diferentes tempos de ataque com ácido hidrofluorídrico, quando comparado aos grupos 2 e 3, ao passo em que os grupos 4, 5 e 6 de porcelana AllCeram não foram. Não houve relação direta entre o escore do IRA e os valores da força de cisalhamento. / Orthodontic treatment in the adult population has lately gained popularity in an attempt to improve esthetic and function. It is, however, a common feature in these patients, that their dentition is restored by resin veneers, porcelain fused to metal and all ceramic crowns. In this context, the orthodontist faces the challenge of bonding brackets to different porcelain based materials, of unknown ability to resist shear forces. Thus, the aim of this investigation was: 1) to test the null hypothesis that shear strength of brackets bonded to feldspathic and AllCeram porcelain surfaces is not affected by different hydrofluoridric etching times and 2) to test the null hypothesis that there is no direct relation between shear strength values and the adhesive remanescent index (ARI). Sixty feldspathic porcelain disc shaped specimens were randomly divided into 3 groups of 20 each, according to hydrofluoridric acid etching time of either 15, 30 seconds and 1 minute (groups 1, 2 and 3, respectively). Another 60 AllCeram specimens of the same shape were subjected to the same division, according to etching time (groups 4, 5, and 6 respectively). Bonding the brackets to the porcelain surfaces included silane coating, an overlying photoactivated resin and a standardized 500g cementation force. Twenty-four hours after cementation, at 37oC in destilled water, specimens were subjected to a shear force in a universal testing machine at a cross-head speed of 0,5mm/min and shear values registered in Kgf and then converted to MPa. Type of failure was lso recorded using ARI by means of a stereoscope at 4x augmentation. The highest shear strength was found for group 1 (21.21 MPa), which was significantly different than groups 2, 3, 4, 5, and 6 (11.01, 10.64, 14.31, 10.59, 10.39 MPa). The lower values found in the remaining groups were not different among each other. Median ARI scores for groups 1, 2, 3, 4, 5, and 6 were 2, 3, 3, 0, 3, and 3, respectively. The first hypothesis must be partially rejected since only feldspathic porcelain group 1 was affected by different hydrofluoric etching times, when compared to groups 2 and 3, while AllCeram groups 4, 5, and 6 were not. On the other hand, the second null hypothesis must be accepted since no direct relation between ARI score and shear strength values could be determined.

Orientador: Guilherme de Siqueira Ferreira Anzaloni Saavedra / Coorientadora: Anelyse Arata / Banca: Dolores Ribeiro Ricci Lazar / Banca: João Paulo Barros Machado / Banca: Renata Marques de Melo Marinho / Banca: Estevão Tomomitsu Kimpara / Resumo: Neste estudo avaliou-se por caracterização mecânica e microestrutural, a degradação em meio bucal e in vitro da cerâmica Y-TZP sinterizada por energia de micro-ondas em comparação ao método convencional. Foram confeccionados noventa e seis discos por CAD-CAM (ISO 6872), sinterizados de modo convencional (C) 1530°C/120 minutos e por energia de micro-ondas (M) 1450°C/15 minutos. E submetidos à degradação hidrotérmica em reator pressurizado (E) (1,5h/150°C/3 bar) e à degradação in situ (B) (240 horas em meio bucal), formando-se 8 grupos (n = 12): M, C, ME, CE, MB, CB, MEB e CEB. Foram realizadas análises de contração volumétrica, difração de raios-X (DRX), rugosidade superficial (Ra e Rz), ângulo de contato, microscopia eletrônica de varredura (MEV), quantificação do biofilme por UFC/mL e análise de resistência mecânica por flexão biaxial. Os resultados obtidos foram analisados estatisticamente por t-Student, Anova dois e três fatores, e teste de Tukey (5%). Por DRX observou-se transformação de fase tetragonal para monoclínica (t-m) nos grupos envelhecidos, exceto para o grupo MB. Não foram observadas diferenças significantes na contração volumétrica (p=0,274), na rugosidade Ra (p=0,137) e Rz (p=0,187), assim como nos valores de ângulo de contato entre os métodos de sinterização (p=0,669). Por MEV observou-se a presença de formação de biofilme inicial e na contagem de Unidades Formadoras de Colônias (UFC/mL) foi maior quando os espécimes foram previamente envelhecidos in vitro (... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this study ir was evaluated the effect of in situ low temperature degradation of yttrium oxide stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics sintered by microwave energy in comparison to the conventional method. Ninety-six discs milled by CAD/CAM (ISO 6872) were divided in: conventionally sintered (C) at 1530 ° C / 120 minutes and microwave energy (M) 1450°C / 15 minutes. Specimens were submitted to hydrothermal degradation in a pressurized reactor (E) (1.5h / 150°C / 3 bar) and in situ degradation (B) (240 hours in the buccal medium), forming eight groups (n=12): M, C, ME, CE, MB, CB, MEB and CEB. Specimens were evaluated through analysis of volumetric contraction, X-ray diffraction (XRD), surface roughness (Ra and Rz), contact angle, scanning electron microscopy (SEM), biofilm quantification by CFU / mL and biaxial flexural strength. Results were statistically analyzed through t-Student, two, three-way Anova and Tukey tests (5%). By XRD, tetragonal to monoclinic phase transformation (t-m) was observed in the aged groups, except for the MB group. No significant differences were observed in the volumetric contraction (p = 0.274), Ra roughness (p = 0.137) and Rz (p = 0.187), as well as contact angle values between sintering methods (p = 0.669). SEM images showed that the initial biofilm formation was observed after 8 hours in situ, an increase of CFU / mL occurred when the specimens were previously aged in vitro (p = 0.001). Regarding biaxial flexural strength... (Complete abstract click electronic access below) / Doutor

<p>Clay, quartz and feldspar are widely available in Uganda. The location and properties of various clay deposits are reported in the literature, but little is reported on feldspar and quartz deposits. In this work an extended literature on ceramics and porcelains in particular, is documented. Samples from two deposits of feldspar and two deposits of quartz are characterised and found to possess requisite properties for making porcelain insulators. Sample porcelain bodies are made from materials collected from selected deposits using different mixing proportions of clay, feldspar and quartz. Their properties in relation to workability, firing temperature, dielectric and bending strengths are studied. It is found that a mixture consisting of 30% Mutaka kaolin, 15% Mukono ball clay, 30% Mutaka feldspar and 25% Lido beach flint yields a body with highest mechanical strength (72MPa) and dielectric strength (19kV/mm) when fired at 1250°C. The strength (both mechanical and dielectric) is found to decrease with increasing firing temperature. At high firing temperatures, the undissolved quartz in the body decreased, the glass content increases and pores are formed. Mullite content on the other hand does not change at temperatures above 1200°C but there are significant differences in the morphologies of the mullite crystals in the samples. Optimum mechanical and electrical properties are found at maximum virtification and a microstructure showing small closely packed mullite needles.</p>