No description available.

Piezoelectric actuators have been developed in various forms ranging from discrete layered composites to functionally graded composites. These composite actuators are usually made up of differentially poled piezoelectric ceramics. This study presents analyses of thermo-electro-mechanical response of piezoelectric actuators having combinations of metal and ceramic constituents with through thickness gradual variations of the metal and ceramic compositions. This is done in order to achieve better performance. The piezoelectric ceramic constituent allows for electro-mechanical coupling response and higher resistance to elevated temperatures while the metal constituent provides more ductile composites. The gradual variation in the ceramic and metal composition helps to avoid high stress concentrations at the layer interfaces in composites. A functionally graded composite is analyzed with discrete layers of piezoelectric ceramic/metal composite. Each layer in the functionally graded composite has a fixed ceramic/metal composition. The governing equation for such a piezoelectric functionally composite beam is presented based on a multi-layer Euler-Bernoulli beam model and the overall displacement response of the beam under thermal, mechanical and electrical stimuli is predicted. The variation of this response is studied with respect to functional grading parameter, number of layers, thermal and electrical and mechanical stimuli applied. It is found that the displacement due to thermal and mechanical effects can be mitigated to some extent by the application of an electric field. It is also observed that layers of varying thickness may be assumed to model the functional grading more accurately i.e. use thinner layers where the grading changes rapidly and thicker layers where the grading changes gradually. In addition to the above parametric studies, the change in the material properties with temperature is also studied. It is found that the temperature-dependent material parameters are important when the actuators are subjected to elevated temperatures.

Diss. med. dent. Zürich. / Literaturverz.

No description available.

This thesis contains two parts of materials characterization. Part I is a poly(butylene succinate) copolymer with minor amount of 2-methyl-propylene succinate. In the second part, six kinds of implant crowns made from five dental casting alloys and one Zircoina ceramic are studied. Copolyester was synthesized and characterized as having 89.0 mol% butylene succinate units and 11.0 mol% 2-methyl-propylene succinate units in a random sequence, revealed by NMR. Isothermal crystallization kinetics was studied in the temperature range (Tc) from 75 to 91 ¢XC using differential scanning calorimeter (DSC). The melting behavior after isothermal crystallization was studied by using DSC by varying the Tc, the crystallization time and the scanning rate. DSC curves showed triple melting peaks. Multiple melting behaviors indicate that the upper melting peaks are associated with the primary and the recrystallized crystals, or the crystals with different lamellar thickness. As the Tc increases, the contribution of recrystallization slowly decreases and finally disappears. A Hoffman-Weeks linear plot gives an equilibrium melting temperature of 118.4 ¢XC. The spherulitic growth rates of this copolyester were measured at Tc between 69 and 91 ¢XC using an optical microscope equipped with a CCD camera. The kinetic analysis of the growth rates gave a regime II-III transition temperature at about 77.2 ¢XC. Rectangular specimens of 10 ¡Ñ 9 ¡Ñ 4 mm were made of five kinds of casting alloys, separately. They were treated in the same procedures as crowns did. Their surfaces after oxidation were analyzed using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Rectangular specimens after applying porcelains were ~5.5 mm thick. The cross-section areas were studied by electron probe micro analyzer (EPMA). Standardized maxillary premolar crowns were fabricated with five different alloys and one Zircoina ceramic. The crown specimens were positioned in a custom testing apparatus and vertically loaded on the middle of the occlusal surface with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. Mean values of load at fracture were calculated in each alloy and compared with a one-way analysis of variance and Tukey test (£\=0.05). The fracture surfaces were examined using SEM. The results of XPS, SEM and EPMA indicate that on the surface there was an oxidation layer (or interface between metal and ceramic) of indium (or/and tin, zinc, etc.). The concentration of oxide metal increased, whereas that of precious metal decreased, from bulk to interface. The fracture strength and the fracture path of the crowns were correlated with the metal-ceramic interface of the rectangular specimens that was characterized using XPS, SEM and EPMA.

O objetivo desse trabalho foi verificar a influência do tratamento ácido realizado em superfície metálica de cobalto-cromo sobre a resistência de união metalocerâmica (RUMC), que é um dos critérios fundamentais para o sucesso da restauração protética. A partir de uma matriz de teflon, foram confeccionadas 120 tiras em resina acrílica Duralay (25 mm x 3,0 mm x 0,5 mm), que foram em três grupos experimentais, de acordo com a liga de cobalto-cromo (Keragen, Remanium 2001 e StarLoy C) utilizada na fundição. Em seguida, as tiras metálicas obtidas foram usinadas e jateadas com óxido de alumínio 100 µm. e subdivididas em quatro grupos (n=10), de acordo com o tratamento de superfície realizado, totalizando 12 grupos experimentais. Para o grupo controle (C), nenhum tratamento adicional foi realizado. O grupo T1 foi tratado adicionalmente com ácido clorídrico a 37% (HCl 37%) por 10 minutos, T2 com HCl 37% por 20 minutos e T3 com HCl 37% por 30 minutos. Após a realização do tratamento, os espécimes foram imersos em álcool isopropílico, limpos em ultrassom e secos em temperatura ambiente. Na sequência foi aplicada a cerâmica (IPS inline), composta por duas camadas de opaco e duas de dentina. Os espécimes foram submetidos ao teste de flexão de três pontos, em máquina de ensaios mecânicos para obtenção dos valores de carga de ruptura (MPa). Dada a distribuição normal dos dados, foi realizada análise estatística por meio da Análise de Variância de dois fatores, seguida pelo teste de Bonferroni (=0,05). Entre as ligas metálicas, não houve diferença significante (p=0,088). Entre os tratamentos (p=0,023) o grupo T3 (61,57 ± 12,19) apresentou valores estatisticamente maiores que o grupo controle (51,96 ± 13,54). Não houve diferenças entre os grupos T1 (57,82 ± 13,22) e T2 (57,91 ± 10,08). Também não houve interação entre a liga metálica e o tratamento de superfície realizado (p= 0,106). Dessa forma, pode-se concluir que o tratamento da superfície metálica com ácido clorídrico a 37% por 30 minutos favoreceu a união da cerâmica às ligas de Co-Cr / The aim of this study was to assess the influence of the acid treatment performed on the metallic surface of cobalt-chromium on metal ceramic bond strength (MCBS), which is one of the fundamental criteria for prosthetic restorations success. One-hundred and twenty strips of Duralay acrylic resin (25 mm x 3.0 mm x 0.5 mm) were made from a Teflon matrix, which were cast into three different cobaltchromium alloys (Keragen, Remanium 2001 and StarLoy C) and subdivided into four groups (n = 10), according to the surface treatment performed. Afterwards, the metal strips obtained were machined and sandblasted with 100 m aluminum oxide. For control group (C), no additional treatment was performed. The T1 group was further treated with 37% hydrochloric acid (37% HCl) for 10 minutes, T2 with 37% HCl for 20 minutes and T3 with 37% HCl for 30 minutes. After the acid treatment, specimens were immersed in isopropyl alcohol, cleaned in ultrasound and dried at room temperature. Posteriorly, ceramic (IPS inline) was applied, composed of two layers of opaque and two layers of dentin. Specimens were submitted to three-point bending test in a mechanical test machine to obtain rupture loading values (MPa). The results were analyzed using 2-way ANOVA (=0.05) and Bonferroni post-hoc test. Among dental alloys, there was no significant difference (p=0.088). Among treatments (p=0.023), T3 group (61.57 ± 12.19) had values statistically higher than control group (51.96 ± 13.54). There were no differences between T1 (57.82 ± 13.22) and T2 (57.91 ± 10.08) groups. There was also no interaction between dental alloy and the surface treatment performed (p=0.106). In conclusion, metal surface treatment with 37% hydrochloric acid for 30 minutes favored bonding between ceramic and Co-Cr alloys

A adaptação marginal e a rugosidade de superfície são parâmetros fundamentais para o sucesso clinico e longevidade das coroas metalocerâmicas. O primeiro permite o selamento das bordas do preparo, prevenindo contra problemas relacionados a exposição do preparo aos fluidos orais e a placa bacteriana e o segundo, remete ao auxilio de uma boa adaptação a fatores mecânicos e biológicos importantes a qualidade da restauração final. Visto que ambos os aspectos são diretamente relacionados a temperatura em que as ligas são submetidas, o objetivo deste trabalho foi avaliar o desajuste marginal, por meio de microscopia óptica, e rugosidade de superfície, por meio de microscopia confocal, de copings metálicos obtidos com as ligas metalicas de Ni-Cr [Verabond II e experimental (SR)] e Co-Cr (Keragen) injetadas no molde de revestimento a duas diferentes temperaturas de estufagem (900°C e 700°C), de forma a avaliar se a redução da temperatura de estufagem possa causar o melhoramento do resultado das fundições, minimizando os efeitos das altas temperaturas. As leituras foram realizadas em copings confeccionados a partir da fundição de casquetes de munhão calcináveis. Cada coping foi cimentado a uma matriz (munhão) por meio de um padronizador da pressão de assentamento e levado aos respectivos microscópios para leitura de desajuste marginal e rugosidade de superfície. Para a avaliação do desajuste marginal foi calculada a media das distancias da borda da restauração a borda do preparo a partir de um ponto inicial aleatório selecionado sobre a margem cervical do coping. Duas leituras eram realizadas a cada &frac14; de volta, totalizando 8 leituras por coping. Para os dados obtidos, que tiveram distribuição não normal, foi utilizado o teste não paramétrico de Kruskal Wallis e foi observado que a liga VB apresentou menor desajuste marginal (56,92&micro;m) quando comparado a liga Keragen (66,75 &micro;m) com p<0,05 e a liga SR apresentou resultado intermediário (49,87&micro;m), sem diferença estatística entre as demais. Para comparação das temperaturas foi utilizado o teste Mann-Whitney e a fundição a 700 °C resultou em melhor adaptação marginal que a 900 °C (50,75 &micro;m e 66,75 &micro;m, respectivamente) com p=0,045. Para a avaliação da rugosidade foi selecionada uma área do coping distante 100 m da borda cervical da peca e realizada a leitura. Os dados de rugosidade de superfície seguiram distribuição normal, sendo utilizado um teste paramétrico (ANOVA), seguindo pelo teste de Bonferroni. Ao se compararem as Ligas, SR apresentou menor rugosidade que Keragen (p=0,002) e que Vera Bond (p=0,001); ao se compararem as temperaturas a fundição a 700 °C resultou em menor rugosidade que a 900 °C (p=0,045). O que se concluiu com a presente metodologia apresentada foi que o comportamento das ligas as diferentes temperaturas varia de acordo com a sua composição tanto em relação a superfície quanto a adaptação marginal e que a fundição a 700 °C proporcionou obtenção dos melhores resultados em ambas as variáveis, sendo possível a otimização da superfície da peca fundida sem o comprometimento da adaptação marginal por meio da redução da temperatura de injeção da liga no molde, favorecendo o resultado final das restaurações. / A proper marginal fit and surface roughness are fundamental aspects for the clinical success of metal-ceramic crowns. The first parameter allows to preserve the margins adaptation accuracy of the restaurations, thus preventing issues related to an improper exposition of the dental tissues into the oral fluids and biofilm. The second parameter is related to mechanical and biological important aspects for the restoration quality and is also able to optimize the piece final adaptation. Both parameters are associated to temperature levels and the understanding of their behavior is convenient for the improvement of the Fixed Prostheses, therefore the aim of this study was to mensure the maginal gap by using the optical microscopy and evaluate the surface roughness by confocal microscopy of metallic copings fused with Nickel-Chromium alloys [Verabond II e experimental (SR)] and Cobalt- Chromium (Keragen) under two distinct mold temperature for the alloy injection: 700°C and 900°C. Performing those analysis represents a way to find out if the temperature reduction of the mold can be convenient to increase the quality of the casting patterns`s surface without affect the marginal fidelity, thus minimizing the overheat casting problems. The mensurements were performed in copings fused from resin cylinders for casting and each one, after fused, was cimented in a abutment cylinder analogue with standardized pression and placed under the respective microscopes for marginal fit and surface analyses. For the marginal fit mensurement were selected two equidistant points in a metal coping that representing &frac14; turn on the measurement device, in a total of 8 measurements for coping in each step that results in a misfit average. Once it was found a non-normal distribution, the non-parametric Kruskal Wallis test was performed for the data and was observed that the allow VBII conferred lower values of marginal fit (56,92 &micro;m) when compared to Keragen alloy (66,75 &micro;m), p<0,05, and SR conferred average values between the others (49,87 &micro;m),with no statistic difference. In the comparison between the mold temperatures the Mann-Whitney test was implemented and the temperature at 700°C reveled better results of marginal fit than the 900 °C temperature (50,75 &micro;m e 66,75 &micro;m, respectively) with p=0,045.For the surface analysis was selected an anatomic reference line in each coping and was set up a distance of 100 &micro;m from this point to make the quantification. For the surface roughness data, with normal distribution, comparisons were performed using a parametric test for independent data (ANOVA), followed by Bonferroni test. The level of significance was set at 5%. At the comparison of alloys, the SR granted lower values of roughness in its patterns than Keragen (p=0.002) and Verabond II (p=0,001). Comparing the temperatures, the values of roughness of the patterns fused under 700° were lower than those fused under 900° (p=0,045). There was no significant difference for interaction between alloy X temperature (p=0,280). The conclusion of the present study was that the behavior of the alloys regarding the marginal fit and surface roughness vary depending of its composition and the Mold temperature and Pieces injected at 700°C in the mold conferred better results in both parameters, therefore being possible to optimize the fixed photesis casting patterns surfaces without marginal fit commitment by reducing the mold temperature for the alloy injection, thus Contributing to the quality of the metal ceramic restorations.

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2005Bitstream added on 2014-06-13T19:16:39Z : No. of bitstreams: 1 rodrigues_fp_me_guara.pdf: 4184618 bytes, checksum: edb4c6c9b5b186971c9e548252d87136 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Problemas com a resistência de união metal-cerâmica têm sido encontrados quando o titânio é utilizado em Odontologia. A proposta deste estudo foi aumentar a resistência na interface titânio-cerâmica pela aplicação de um filme fino de platina na superfície do titânio, por meio da utilização da técnica de deposição por pulverização catódica. Dez padrões (1.0 x 4.0 x 30 mm) foram obtidos por meio de cortes de placas de resina acrílica e incluídos em um revestimento à base de zircônia. As fundições de titânio para preenchimento dos moldes foram realizadas em uma máquina de fundição centrífuga. As amostras foram lixadas até as dimensões finais (0.50 x 3.0 x 30 mm) para a remoção da camada -case e jateadas com pó de alumina (grupo controle) e de dióxido de titânio (grupo experimental). Uma cerâmica de ultrabaixa temperatura de fusão foi aplicada no centro da superfície (8.0 x 1.0 x 3 mm). A resistência de união foi determinada pelo teste de flexão de três pontos em uma máquina universal de ensaios com uma velocidade de 0,5mm/min. As amostras foram analisadas por meio de microscopia óptica e microscopia eletrônica de varredura antes e após os ensaios mecânicos. Os resultados revelaram valores maiores de união entre o titânio e a cerâmica quando o filme de platina foi aplicado (25,70 l 4,54 MPa), mas não houve diferença estatística significante em relação ao grupo controle (24,32 l 3,11 MPa), o que indica que o primeiro grupo também possui uma resistência de união suficiente para uso clínico. / Problems with metal-ceramic bond strength have been encountered when titanium is used in prosthetic dentistry. The purpose of this study was increase the bond strength of titanium-ceramic interface applying a platinum film on the titanium surface using DC-sputtering deposition technique. Ten 1.0 x 4.0 x 30 mm patterns were cut from sheet of acrylic resin and invested in a zirconia-based investment material. Titanium castings were made using a centrifugal casting machine. Specimens were grinded to final dimensions (0.50 x 3.0 x 30 mm) to remove the -case layer and blasted with alumina (control group) and titanium dioxide (experimental group) powders. An ultra low-fusing dental ceramic was applied to the center of the surface (8.0 x 1.0 x 3 mm). The bond strength was determined by three-point bending test. at a universal testing machine with a loading rate of 0,5mm/min.The samples were analyzed using Optical Microscopy and Scanning Electron Microscopy before and after the mechanical testing.The results showed greater values of adherence between titanium and ceramic when the platinum film was applied (25,70 l 4,54 MPa), but there were no statistic differences to those of the controls (24,32 l 3,11 MPa) that indicates that the first one has also sufficient bond strength for clinical use.

Made available in DSpace on 2014-06-11T19:28:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-12-01Bitstream added on 2014-06-13T20:37:52Z : No. of bitstreams: 1 santos_jg_me_arafo.pdf: 726799 bytes, checksum: ba399d198e118a915d5001ecb642c403 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O reparo em próteses metalocerâmicas é um procedimento útil em determinadas situações clínicas. Recentemente surgiram no mercado alguns materiais designados para tal finalidade que, segundo seus fabricantes, são promissores. Neste trabalho foi avaliada a resistência ao cisalhamento de determinados sistemas de reparo para metalocerâmicas. Foram confeccionadas amostras cilíndricas em liga de NiCr (Vera Bond II) e em porcelana feldspática (Noritake). Após inclusão destas em anel de PVC, suas superfícies foram lixadas (320) e, com auxílio de matriz bi-partida (5 mm diâmetro e 2 mm altura), receberam um dos seguintes tratamentos (n=10): 1) sistema Clearfil SE Bond/Clearfil AP-X (Kuraray), 2) sistema Bistite II DC/Palfique (Tokuyama), 3) sistema Cojet Sand/Z100 (3M-ESPE), 4) jateamento com Al2O3 e sistema Scotchbond Multi Uso Plus/Z100 (3M-ESPE) (grupo controle), e 5) jateamento com Cojet Sand e sistema Scotchbond Multi Uso Plus/Z100. Os corpos-de-prova foram armazenados por 24 horas em água destilada a 37ºC, termociclados (1.000 ciclos - 5º a 55ºC) e, então, deixados nas condições descritas acima por mais 8 dias. O ensaio foi realizado em máquina MTS 810 com velocidade de 0,5 mm/min. Os valores originais foram submetidos à análise de variância (ANOVA) e teste de Tukey. No metal, as médias de resistência dos grupos de 1 a 5 foram respectivamente de 18,40 MPa (B), 8,57 MPa (D), 25,24 MPa (A), 16,26 MPa (BC) e de 13,11 MPa (C) (valor crítico 3,2). Em porcelana, foram de 16,91 MPa (B), 18,04 MPa (AB), 19,54 MPa (AB), 21,05 MPa (A) e de 16,18 MPa (B) (valor crítico 3,7). A melhor opção mediante exposição em metal foi o sistema Cojet Sand. Em porcelana, os sistemas Scotchbond Multi Uso Plus associado ao jateamento com Al2O3, Cojet Sand e Bistite II DC apresentaram os melhores resultados. / Fracture of porcelain in metal-ceramic restorations is a common clinical problem and sometimes the repair is a useful solution. Recently some new repair materials with promising results according to their manufactures are available. The aim of this study was to evaluate the shear bond strengths of porcelain repair systems. Fifty disks in NiCr alloy (Vera Bond II) and in feldspatic porcelain (Noritake) were made. The specimens were included in acrylic resin and the surfaces were ground with 320-grit silicon carbide paper. Metal and porcelain specimens were divided into five groups of ten each and the bonding sites received one of the following treatments: 1) Clearfil SE Bond/Clearfil AP-X (Kuraray), 2) Bistite II DC/Palfique (Tokuyama), 3) Cojet Sand System/Z100 (3M-ESPE), 4) air-abrading with Al2O3 and Scotchbond Multi Purpose/Z100 (3M-ESPE) (control group) and 5) air-abrading with Cojet Sand and Scotchbond Multi Purpose/Z100. After storage for 24 hours in distilled water at 37°C, thermocycling (1.000 cycles - 5º and 55ºC) and storage for more 8 days at the same conditions above, the shear bond strength test was performed in a testing machine MTS 810 at a crosshead speed of 0.5mm/min until fracture. Statistical analysis of the data was accomplished by analysis of variance (ANOVA) and Tukey's test. In metal, the bond strengths of groups 1 to 5 were, respectively 18,40 MPa (B), 8,57 MPa (D), 25,24 MPa (A), 16,26 MPa (BC) and 13,11 MPa (C). In porcelain, the bond strengths of the five groups were 16,91 MPa (B), 18,04 MPa (AB), 19,54 MPa (AB), 21,05 MPa (A) and 16,18 MPa (B). The best option when occurs metal exposure is Cojet Sand System. In porcelain, air-abrading with Al2O3 and Scotchbond Multi Purpose, Cojet Sand System and Bistite II DC showed the best results.

Orientador: Renata Garcia Fonseca / Banca: Carlos Alberto dos Santos Cruz / Banca: Mauro Antonio de Arruda Nobilo / Resumo: O reparo de restaurações metalocerâmicas fraturadas pode ser considerado um desafio, principalmente quando grande quantidade de metal é exposta. O estabelecimento de uma união forte e durável entre material reparador e substrato da restauração fraturada é essencial para o sucesso do reparo. Este estudo avaliou a resistência ao cisalhamento entre diferentes sistemas de reparo e liga de NiCr e a durabilidade desta união após armazenamento em água por um longo período. Foram confeccionados 100 discos (9 OE 3 mm) em liga de NiCr. Esses foram incluídos em anel de PVC com resina acrílica e tiveram suas superfícies regularizadas com lixas (120, 220 e 320) em politriz. Cada espécime recebeu um dos seguintes tratamentos: 1) Clearfil SE Bond, 2)Bistite II DC, 3)Cojet, 4) Scotchbond Multi Uso Plus (Grupo controle), e 5) uma variação do Grupo controle, na qual foram empregadas partículas de sílica do sistema Cojet Sand em substituição às de óxido de alumínio. Os espécimes foram armazenados água destilada a 37ºC por 24 horas, termociclados (1.000 ciclos - 5º e 55ºC) e, então, armazenados nas mesmas condições descritas anteriormente, por um período adicional de 24 horas ou 6 meses. O ensaio de cisalhamento foi realizado em máquina de ensaios Material Test System 810 com velocidade de 0,5 mm/minuto. Para cada período de armazenamento, os resultados foram analisados por meio de análise de variância (ANOVA) e teste de Tukey. Para cada sistema, os valores obtidos às 24 horas foram comparados aos encontrados após 6 meses empregando-se teste t de Student não pareado. (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: When clinical fractures of metal-ceramic prostheses occur, exposing the metal substructure, repair may be considered a challenge. The clinical success of repair depends on establishing a strong and long-term durable bond between the repair material and the metal surface of the failed restoration. This study evaluated shear bond strength of different repair systems to NiCr alloy and bond durability after long-term water storage. One hundred cylindrical specimens (9 OE 3 mm) were fabricated in a nickel-chromium alloy. The NiCr cylinders were embedded in a PVC ring and all specimen bonding surfaces were smoothed with silicon carbide papers (120, 220, and 320 grit) using a polisher. Specimens were divided into 5 groups of 20, which received one of the following bonding and resin composite repair systems (n=10): 1) Clearfil SE Bond/Clearfil AP-X, 2) Bistite II DC/Palfique, 3) Cojet /Z100, 4) Scotchbond Multipurpose Plus /Z100 (control group), and 5) Cojet Sand plus Scotchbond Multipurpose Plus /Z100. The specimens were stored in distilled water for 24 hours at 37ºC, thermal cycled (1,000 cycles - 5º to 55ºC) and stored in distilled water at 37ºC for either 24 hours or 6 months. Shear bond tests were performed in a mechanical testing machine with a crosshead speed of 0.5 mm/minute. Data (MPa) were analyzed using 1-way ANOVA and Tukey HSD test (a=.05) for each storage time. The results obtained at 24 hours for each repair system were compared with those found at 6 months using Student's t-test. Each specimen was examined under a stereoscopic lens with OE30 magnification, and mode of failure was classified as adhesive, cohesive or combination. (Complete abstract, click electronic access below) / Mestre