Orientadores: Mirela Sanae Shinohara, Mário Fernando de Góes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-21T23:51:52Z (GMT). No. of bitstreams: 1 Freitas_MarcelaSantiago_M.pdf: 38797129 bytes, checksum: 16869befa66eba198d1cb13ad5c9ac1d (MD5) Previous issue date: 2013 / Resumo: Estudos mostram que a resistência de união (RU) alcançada pelos sistemas adesivos autocondicionantes em superfície de esmalte pré-condicionado é significativamente maior se comparada aos valores obtidos em esmalte não condicionado. A partir destas evidências, este estudo teve como objetivo avaliar a RU e a morfologia da interface adesiva (MI) em esmalte e dentina de um adesivo autocondicionante de passo único multi-mode e um adesivo autocondicionante de dois passos com e sem pré-condicionamento ácido da superfície comparado a dois sistemas adesivos de condicionamento total, de dois e três passos. Terceiros molares humanos recém-extraídos foram seccionados para obtenção de superfícies planas em esmalte e dentina, as quais foram desgastadas com lixa SiC #600 para padronização da smear layer. Estas amostras foram divididas aleatoriamente em 6 grupos: (SBU) Scotchbond Universal; (SBUcond) SBU précondicionado; (CSE) Clearfil SE Bond; (CSEcond) CSE pré-condicionado; (SBMP) Scotchbond Multi-Purpose; e (EX) Excite F. Os grupos de condicionamento total e os autocondicionantes a serem avaliados com pré-condicionamento receberam a aplicação do ácido fosfórico por 15s em dentina e 30s em esmalte. Todos os sistemas adesivos foram aplicados de acordo com as recomendações dos fabricantes. Em seguida, um bloco de resina composta (Filtek Supreme Plus) foi construído incrementalmente sobre cada superfície preparada para o teste de RU, e para a MI, as superfícies foram restauradas com resina flow (Filtek Z-350 Flowable Restorative) formando um "sanduíche", de esmalte ou dentina. Após 24h, para avaliação da RU, as amostras foram seccionadas em palitos com área transversal de 0,8mm2 e submetidos ao teste de microtração com velocidade de 1,0mm/min. Os resultados foram analisados estatisticamente pelos testes one-way ANOVA e Fisher's PLSD (?=0.05) e os padrões de fratura analisados em Microscopia Eletrônica de Varredura (MEV). Para análise da MI, duas amostras de cada grupo foram incluídas em resina epóxica, polidas e observadas em MEV. Para esmalte, os resultados de RU mostraram que o SBUcond e CSEcond obtiveram os maiores valores, seguidos dos grupos SBMP, SBU e CSE que não apresentaram diferenças entre si. O grupo EX obteve os menores valores comparados aos outros grupos. Na análise da MI, os grupos SBUcond e CSEcond apresentaram nítidas extensões do adesivo penetrado no esmalte desmineralizado, semelhante aos sistemas de condicionamento total. Já para dentina, os resultados de RU mostraram que o condicionamento ácido prévio diminuiu significativamente os valores de RU dos sistemas autocondicionantes. Os maiores valores foram obtidos pelo SBU, CSE e SBMP, com valores de RU estatisticamente equivalentes entre si. Como em esmalte, o sistema adesivo EX obteve os menores valores. A análise em MEV da MI mostrou que o condicionamento prévio da dentina com adesivos autocondicionantes forma uma camada híbrida mais espessa com formação de tags resinosos, semelhantes aos sistemas adesivos de condicionamento total. Pode-se concluir que em esmalte, o condicionamento prévio aumentou significativamente os valores de RU para os sistemas autocondicionantes. Contudo, estes sistemas adesivos não apresentaram diferença estatística do adesivo convencional SBMP. E para dentina, o pré-condicionamento dos adesivos autocondicionantes diminuiu significativamente os valores de RU, entretanto, os valores de SBUcond não foram diferentes significativamente dos obtidos pelo sistema adesivo convencional SBMP / Abstract: Studies show that the bond strength (BS) achieved by self-etching adhesive systems on pre-etched enamel surface is significantly higher compared with the values obtained on unetched enamel. From this evidence, this study aimed to assess the BS and morphology of the adhesive interface (AI) on enamel and dentin of a one-step self-etching adhesive multi-mode and a two-step selfetching adhesive with and without pre-etching of surface compared with two totaletching adhesive systems, two and three steps. Recently extracted human third molars were sectioned to obtain flat surfaces in enamel and dentin, which were ground with #600 SiC sandpaper to standardize the smear layer. These samples were randomly assigned into 6 groups: (SBU) Scotchbond Universal; (SBU-et) SBU pre-etched; (CSE), Clearfil SE Bond, (CSE-et) CSE pre-etched; (SBMP) Scotchbond Multi-Purpose, and (EX) Excite F. The groups total-etching and selfetching to be evaluated with pre-etching received the application of phosphoric acid for 15s in dentin and 30s in enamel. All adhesive systems were applied according to manufacturers' recommendations. Then, a block of composite resin (Filtek Supreme Plus) was constructed incrementally on each surface prepared for BS testing. For AI, the areas were filled with flowable resin (Filtek Flowable Restorative Z-350) forming a "sandwich" of enamel or dentin. After 24 hours, to review the BS, the specimens were sectioned into sticks with cross-sectional area of 0.8mm² and submitted to microtensile test at a speed of 1.0mm/min. The results were statistically analyzed by one-way ANOVA test and Fisher's PLSD (?=0.05) and fracture patterns were analyzed through Scanning Electron Microscopy (SEM). For analysis of AI, two samples from each group were embedded in epoxy resin, polished and observed through SEM. For enamel, the results of BS showed that SBU-et and CSE-et obtained the highest values, followed by SBMP groups, SBU and CSE with no differences among them. The EX group obtained the lowest values of all other groups. In the analysis of AI, and CSE-et and SBU-et groups showed sharp tag extensions of the adhesive penetrated in the demineralized enamel, similar to total-etching systems. As for dentin, BS results showed that acid etching significantly reduced the BS values of self-etching systems. The highest values were obtained by the SBU, CSE and SBMP with BS values statistically equivalent to each other. As in enamel, the adhesive system EX obtained the lowest values. SEM analysis showed that BS for pre-etched dentin with selfetching adhesive forms a thicker hybrid layer with resin tags formation, similar to total-etching adhesive systems. It can be concluded that on enamel, the preetching significantly increased BS for self-etching systems. However, these adhesive systems showed no statistical difference from conventional adhesive SBMP. And to dentin, pre-etching of sel-etching adhesives significantly reduced BS, however, SBU-et values were not significantly different from those obtained by the conventional adhesive system SBMP / Mestrado / Dentística / Mestra em Materiais Dentários

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A new generation of adhesive systems are currently available on market. They were reported on the literature as universal adhesives or multimode adhesives . These adhesives are versatile, as they can be use in either etch-and-rinse or self-etch strategy. However, only a few data is available about long-term bonding behavior of universal adhesive systems. Then, the aim of this study is to evaluate immediate and six months bond strength of different universal adhesive systems on sound and caries-affected dentin, either on etch-and-rinse or self-etch strategies. The adhesive systems tested were: Scotchbond Universal (3M ESPE), All-Bond Universal (Bisco), Prime & Bond Elect (Denstply Caulk), Adper Single Bond 2 (3M ESPE) and Clearfil SE Bond (Kuraray Noritake Dental). All adhesive systems were applied under manufacturer s instructions and a composite block was build up on dentin surfaces. Caries-affected dentin was artificially induced by pH-cycling (8h immersed on demineralizing solution and 16h on remineralizing solution, for 14 days). Stick shaped specimens (0,8 mm²) were obtained to be submitted to microtensile test at immediate time or after 6 months of storage. Bond strength data (MPa) were analyzed by three-way repeated measures ANOVA and post-hoc Tukey test (α= 5%). Analysis were performed for each substrate separately. On sound dentin, the etching strategy did not influence bond strength of universal adhesives and no significant statistical differences were found for bond strength values after 6 months of water storage. On caries-affected dentin, adhesive systems also showed similar results regardless etching strategies. However, significant reduction in bond strength values was found after six months. The etching strategy did not influence bond strength performance of universal adhesives on dentin substrate, although the long-term bond strength is decreased on caries-affected dentin. / Recentemente foram introduzidos no mercado uma nova geração de adesivos, reportados pela literatura como adesivos universais ou multi-modo . Esses adesivos são materiais versáteis, podendo ser utilizados tanto na técnica autocondicionante como na técnica com condicionamento ácido prévio. No entanto, pouco sabe-se ainda sobre o comportamento desses adesivos universais em relação à longevidade da adesão. Então, o objetivo deste estudo foi avaliar a resistência de união imediata e após 6 meses de diferentes adesivos universais em dentina hígida e afetada, usando as estratégias de condicionamento ácido prévio e autocondicionante. Os sistemas adesivos testados foram: Scotchbond Universal (3M ESPE), All-Bond Universal (Bisco), Prime & Bond Elect (Denstply Caulk), Adper Single Bond 2 (3M ESPE) e Clearfil SE Bond (Kuraray Noritake Dental). Todos os adesivos foram aplicados seguindo as recomendações dos fabricantes e um bloco de resina composta foi construído sobre a dentina. A dentina afetada foi obtida artificialmente através de ciclagem de pH (8 horas em solução desmineralizante e 16 horas em solução remineralizante, por 14 dias). Espécimes em forma de palitos foram obtidos (0,8 mm²) para serem submetidos ao teste de microtração imediatamente ou após 6 meses de armazenamento. Os dados obtidos em MPa foram analisados por análise de variância de 3 fatores e teste de contraste de Tukey (α= 5%). A análise foi realizada separadamente para cada substrato. Em dentina hígida, a estratégia de condicionamento não teve influência na resistência de união dos adesivos universais e não houve diferença estatisticamente significante entre a resistência de união imediata e após 6 meses. Em dentina afetada, os sistemas adesivos apresentaram resultados similares, independente da estratégia de condicionamento. No entanto, houve uma significativa redução na resistência de união após 6 meses. Assim, a estratégia de condicionamento não influencia a resistência de união dos adesivos universais em dentina, porém a resistência de união a longo prazo é reduzida em dentina afetada.

The current trends in the road transport sector show a growth in axle loads as well as vehicle numbers on all types of roads in highly industrialised countries as well as in developing countries. This increase in axle loads and numbers has forced road agencies to amend their design standards adopting designs that provide roads with higher load bearing capacity. However, the rapid depletion of natural road construction gravel, as well as strict environmental conservation laws have resulted in many agencies in-charge of road construction and maintenance to resort to use of alternative materials that will be economically feasible and environmental friendly. The use of natural pozzolans for stabilising pavement layers fulfils this requirement. This research study was performed with the aim of evaluating the engineering properties of aggregate-lime-natural pozzolan (ALP) mixtures at varying compaction degrees of saturation and to compare them with conventional cement-stabilized aggregates. Two types of pozzolans found in Tanzania were used. The laboratory investigation was carried out in two parts, namely a pilot investigation where the strength behaviour with time, shrinkage and CBR were determined at three degrees of saturation for a washed river sand specimen followed by the main investigation using two different types of sands at four varying degrees of saturation. The study showed that the compaction degree of saturation for ALP mixes plays an important role in their tensile and compressive strengths development regardless of their optimum moisture contents. The ratio between tensile and compressive strengths for ALP mixes was also found to closely obey the relation given by Fulton (2001) for concrete. The ALP mixes were also observed to develop their strength similar to cement mixes with the formation of tobermorite crystals with the additional of water and appropriate activator. Both pozzolan mixes developed significant tensile and compressive strength after 28 days of curing similar to cement mixes. High CBR values for the two ALP mixes were obtained in mixes moulded at degrees of saturation lower than that corresponding to their optimum. Similarly, the shrinkage of the mixes was found to decrease with a decrease in the degrees of saturation. The CBR and shrinkage of the ALP mixes were found to show similar trend to that of the control cement mixes. The ALP mixes showed no significant strength loss with an increase in the fines content in unwashed sand mix in comparison with that of washed sand mixes. No significant strength loss was observed in the ALP mixes as in the control cement mixes at all moulding degrees of saturation. Finally the study concluded that the ALP mixes could be used in stabilization of pavement layers. However, care must be taken in deciding the compaction degrees of saturation as the specifications used in conventional cement stabilization does not necessarily yield desirable strength development in ALP mixes. / Dissertation (MEng (Transportation))--University of Pretoria, 2006. / Civil Engineering / unrestricted

Orientador: Marcelo Giannini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-22T02:35:57Z (GMT). No. of bitstreams: 1 Ayres_AnaPaulaAlmeida_M.pdf: 3452977 bytes, checksum: c1245f8af84e3e9b42ae18f3eb096ed8 (MD5) Previous issue date: 2013 / Resumo: O objetivo desse estudo foi avaliar a resistência de união à dentina de sistemas restauradores contendo ou não fluoretos em sua composição e o comportamento do esmalte e da dentina adjacentes às restaurações, quando submetidos ao desafio cariogênico in vitro. Adicionalmente, durante o desafio cariogênio foi mensurada a liberação de fluoreto dos adesivos. Para o estudo foram utilizados 64 dentes terceiros molares humanos e quatro sistemas restauradores: FL-Bond II/Beautifil II, Bond Force/Estelite Sigma, GC Fuji II LC e Adper Easy Bond/Filtek Z350 XT. No estudo de resistência da união à dentina, utilizou-se a dentina coronária, onde foram aplicados os materiais restauradores (n=8). Os dentes foram seccionados para obtenção dos espécimes e o teste de microtração foi realizado em dois tempos: imediato e após um ano de armazenamento em saliva artificial. Para o estudo da microdureza longitudinal, foram confeccionadas cavidades na região cervical, as quais foram restauradas com os quatro sistemas propostos, de acordo com as recomendações dos fabricantes (n=8). Os dentes restaurados foram submetidos à ciclagem térmica (3.000 ciclos) e, posteriormente, à ciclagem de pH durante oito dias. A mensuração da microdureza subsuperficial foi realizada em esmalte e em dentina, em três distâncias da parede cavitária e em seis profundidades em relação à superfície submetida à ciclagem de pH. As soluções desmineralizantes e remineralizantes utilizadas nessa ciclagem foram utilizadas para análise de concentração catiônica de flúor. A análise estatística de resistência de união dentinária mostrou que os valores médios não foram afetados após um ano de armazenamento em saliva artificial para nenhum dos sistemas restauradores. Os resultados de microdureza longitudinal em esmalte apresentaram diferença estatística significativa apenas para a distância 50 ?m. Mas os valores médios de microdureza Knoop em esmalte foram semelhantes para os quatro sistemas restauradores quando avaliados nas mesmas distâncias e profundidades. O mesmo padrão de resultado foi encontrado na dentina, mas os valores médios de microdureza não apresentaram diferença estatística entre as distâncias da restauração. A análise catiônica de flúor detectou liberação de fluoreto nos espécimes restaurados com GC Fuji LC II e FL-Bond II/Beautifil II. A partir dos resultados desse estudo in vitro é possível afirmar que os sistemas restauradores avaliados apresentaram estabilidade da união por um ano, porém apresentaram pouca capacidade de inibição de cárie secundária em esmalte e em dentina, independentemente da liberação ou não de fluoretos / Abstract: The aim of this study was to evaluate the bond strength to dentin of restorative systems containing or not fluoride in their compositions and the performance of enamel and dentin around the restorations, when submitted to cariogenic challenge in vitro. Additionally, the fluoride released was measured during the pH cycling. This study used 64 third molars human teeth and four restorative systems were selected: FL-Bond II/Beautifil II, Bond Force/Estelite Sigma, GC Fuji II LC and Adper Easy Bond/Filtek Z350 XT. For the bond strength evaluation, it was used oclusal dentin in which the restorative materials were applied (n=8). The "restored" teeth were sectioned for obtaining bonded beam specimens and the microtensile test was performed in two times: imediate and after one year of storage in artificial saliva. For the cross-sectional microhardness test, cervical cavities were prepared and filled with the restorative systems according to the manufacturer's instructions (n=8). The restored teeth were submitted to thermo cycling (3.000 cycles) and subsequent pH-cycling during eight days. The cross-sectional microhardness analysis was performed in enamel and dentin, at three distances from cavity wall and at six depths regarding the surface submitted to pH-cycling. The desmineralizing and remineralizing solutions of this pH-cycling regimen was used for fluor cationic concentration analysis. The statistical analysis of bond strength to dentin showed that means were not reduced after one year of storage in artificial saliva for no restorative systems. The results of cross-sectional microhardness measurements in enamel presented significant statistical difference only at the distance of 50 ?m. However, means of Knoop microhardness measurements were similar for the four restorative systems when compared to the same distances and depths. The same pattern of results was found in dentin, but the means of microhardness measurements showed no significant statistical differences between the distances from the restorations. Fluor cationic concentration analysis detected fluoride releasing by the specimens restored GC Fuji LC II and FL-Bond II/Beautifil II. The results of this in vitro study suggest that the restorative products tested presented bond stability after one year, but showed little ability to inhibit secondary caries around restoration, independently on fluoride releasing or not / Mestrado / Dentística / Mestra em Clínica Odontológica

Orientador: Luís Alexandre Maffei Sartini Paulillo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-24T07:41:05Z (GMT). No. of bitstreams: 1 Coppini_ErickKamiya_M.pdf: 3349153 bytes, checksum: e0323d6512c30cee2e8ea17128a4c6e6 (MD5) Previous issue date: 2013 / Resumo: The aim of this study was to evaluate the cavosuperficial enamel acid-etching influence in class I cavities, filled with composites on microtensile bond strength, Knoop microhardness and nanoleakage after thermomechanic ageing. It was selected 76 sound molar splitted on: 32 teeth to microtensile test (n=8); 32 teeth to Knoop microhardness (n=8); and 12 teeth (n=3) to nanoleakage analysis. The cavities were prepared on a standard cavity preparation machine. Half of the teeth had the cavosuperficial enamel etched with 35% phosphoric acid and restored with a Silorane restorative system or a Methacrylate restorative system. After the conclusion of the restoration procedures, the teeth were taken to a thermomechanic cycling machine where the artificial ageing was performed with 200.000 mechanical cycles with an 80 N load in a 2HZ frequency and thermocycling by filling the chambers for 30 seconds and 15 seconds drainage with the temperatures varying between 5ºC and 55ºC. The samples were submitted to the microtensile bond strength test, Knoop microhardness and nanoleakage evaluation. To statistical analysis it was performed the ANOVA two-way and Tuckey test (p ? 0,05). The group restored with methacrylate without acid-etching showed the lowest values of microtensile bond strength and it was statistically different to the other groups that have no difference between them. The methacrylate composite presented statistically higher values on Knoop microhardness compared to silorane composite. The nanoleakage analysis showed low infiltration to silorane restorative system and moderate infiltration to the methacrylate restorative system. The methacrylate group restored without enamel acid-etching showed the formation of Water Trees. It can be concluded that the acid-etching improved the bond strength to the methacylate system. The methacrylate composite has bigger Knoop microhardness than silorane composite. The methacrylate restorative system showed moderate infiltration on nanoleakage analysis / Abstract: The aim of this study was to evaluate the cavosuperficial enamel acid-etching influence in class I cavities, filled with composites on microtensile bond strength, Knoop microhardness and nanoleakage after thermomechanic ageing. It was selected 76 sound molar splitted on: 32 teeth to microtensile test (n=8); 32 teeth to Knoop microhardness (n=8); and 12 teeth (n=3) to nanoleakage analysis. The cavities were prepared on a standard cavity preparation machine. Half of the teeth had the cavosuperficial enamel etched with 35% phosphoric acid and restored with a Silorane restorative system or a Methacrylate restorative system. After the conclusion of the restoration procedures, the teeth were taken to a thermomechanic cycling machine where the artificial ageing was performed with 200.000 mechanical cycles with an 80 N load in a 2HZ frequency and thermocycling by filling the chambers for 30 seconds and 15 seconds drainage with the temperatures varying between 5ºC and 55ºC. The samples were submitted to the microtensile bond strength test, Knoop microhardness and nanoleakage evaluation. To statistical analysis it was performed the ANOVA two-way and Tuckey test (p ? 0,05). The group restored with methacrylate without acid-etching showed the lowest values of microtensile bond strength and it was statistically different to the other groups that have no difference between them. The methacrylate composite presented statistically higher values on Knoop microhardness compared to silorane composite. The nanoleakage analysis showed low infiltration to silorane restorative system and moderate infiltration to the methacrylate restorative system. The methacrylate group restored without enamel acid-etching showed the formation of Water Trees. It can be concluded that the acid-etching improved the bond strength to the methacylate system. The methacrylate composite has bigger Knoop microhardness than silorane composite. The methacrylate restorative system showed moderate infiltration on nanoleakage analysis / Mestrado / Dentística / Mestre em Clínica Odontológica

Orientadores: Simonides Consani, Lourenço Correr Sobrinho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-28T00:04:36Z (GMT). No. of bitstreams: 1 Dantas_LucasCostadeMedeiros_D.pdf: 1456971 bytes, checksum: 92555fabf5fb3ce889e0f529fd098830 (MD5) Previous issue date: 2015 / Resumo: Diferentes métodos de ensaio para verificação da resistência de união entre materiais odontológicos são descritos na literatura como meios de predizer o comportamento destes materiais em meio oral. Entre os métodos utilizados, os mais mencionados são os de microtração e microcisalhamento. Apesar de amplamente estudados, existe uma grande variação nos protocolos de confecção de espécimes e de ensaio mecânico, dificultando a comparação entre os estudos. O objetivo neste estudo foi avaliar o comportamento da interface de união entre cerâmica odontológica e dois cimentos resinosos sob influência de diferentes ensaios de resistência de união, potências de fotoativação e realização de ciclagem térmica. Utilizando o método de elementos finitos, no capítulo 1, dois modelos, um simulando o ensaio de microcisalhamento e o outro o ensaio de microtração, foram analisados quanto à distribuição de tensões na região de união dos espécimes. Assim, no capítulo 2, o ensaio de microcisalhamento foi utilizado para avaliar a resistência de união entre dois cimentos resinosos e uma cerâmica odontológica variando a potência do aparelho fotoativador, e a simulação de envelhecimento por meio de ciclagem térmica. Por meio de teste in vitro, os ensaios de microtração e microcisalhamento foram utilizados para avaliar a resistência de união entre os mesmos materiais e com os mesmos protocolos de confecção, variando o tipo de cimento resinoso e a potência do foto ativador. O método de elementos finitos revelou a presença de uma tensão uniaxial para o modelo de microtração. Nos ensaios laboratoriais o ensaio de microcisalhamento resultou em maiores valores de resistência de união. O método de envelhecimento de amostras diminuiu a resistência de união. Desta forma, conclui-se que a utilização da baixa potência de fotoativação favoreceu o resultado de resistência de união imediato e que o ensaio de microtração performado neste estudo apresentou tensões melhores distribuídas indicando melhor utilização no ensaio / Abstract: Different test methods to verify the bond strength of dental materials are described in the literature as a means to predict the behaviour of these materials in the oral environment. Among the methods used, the most mentioned are the microtensile and microshear. Although widely studied, there is a large variation in the preparation of specimens and mechanical testing protocols, making it difficult to compare studies. The aim of this study was to evaluate the behaviour of the adhesive interface with two resin cements and curing powers and performing thermal cycling, assessed by two different tests of bond strength. Using the finite element method, in chapter 1, two models were made, one simulating the test microshear and the other microtensile test were analysed for the stress distribution in the adhesive region of the specimens. Thus, microshear test, in chapter 2, was used to evaluate the bond strength of two resin cements and dental ceramics by varying the power of curing unit device and the simulation of ageing by thermal cycling. By the means of in vitro assay tests microtensile and microshear were used to evaluate the bond strength of the same materials and with the same protocols of specimens preparation by varying the type of resin cement and the power of the photoactivator. The finite element analysis revealed the microtensile model a uniaxial stress. In laboratory, microshear results in higher values of bond strength. The ageing method promoted reducing in bond strength values, while the low power of photoactivation increases these values. It may be concluded, that low intensity of photoactivation leads to an immediately higher bond strength and microtensile bond strength test performed in this study showed the stresses distributed in correct axis indicating better use to bond strength evaluation / Doutorado / Materiais Dentarios / Doutor em Materiais Dentários

In order to study the mechanical performance of dry-cast synthetic fiber reinforced concrete (SynFRC), samples of varying geometry, fiber content, and environmental exposure were developed and tested using the modified indirect tensile test. The samples created consisted of three different thicknesses (with two different geometries), and six different fiber contents that differed in either type, or quantity, of fibers. Throughout the duration of this research, procedures for inflicting detrimental materials into the concrete samples were employed at a number of different environments by implementing accelerated rates of deterioration using geometric adjustments, increased temperature exposure, wetting/drying cycles, and preparation techniques. The SynFRC samples studied were immersed in a wide range of environments including: the exposure of samples to high humidity and calcium hydroxide environments, which served at the control group, while the sea water, low pH, and barge conditioning environments were used to depict the real world environments similar to what would be experienced in the Florida ecosystem. As a result of this conditioning regime, the concrete was able to imitate the real-world effects that the environments would have inflicted if exposed for long durations after an exposure period of only 20-24 months. Having adequately conditioned the samples in their respective environments, they were then tested (and forensically investigated) using the modified indirect tensile testing method to gather data regarding each sample’s toughness and load handling capability. By analyzing the results from each sample, the toughness was calculated by taking the area under the force displacement curve. From these toughness readings it was found that possible degradation occurred between the fiber-matrix interface of some of the concrete samples conditioned in the Barge environment. From these specimens that were immersed in the barge environment, a handful of them exhibited multiple episodes of strain softening characteristics within their force displacement curves. In regard to the fibers used within the samples, the PVA fibers tended to pull off more while the Tuff Strand SF fibers had the highest tendency to break (despite some of the fibers showing similar pull off and breaking failure characteristics). When it comes to the overall thickness of the sample, there was clear correlation between the increase in size and the increase in sample toughness, however the degree to which it correlates varies from sample to sample. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Orientador: Rebeca [Unesp] Di Nicoló / Resumo: O objetivo desse estudo foi avaliar as propriedades de um sistema adesivo modificado com a incorporação de partículas de vidro bioativas (SCHOTT Bioactive Glass) em duas diferentes concentrações (0,5 e 1%). Foram avaliados a resistência de união da interface adesiva, o grau de conversão e a atividade antibacteriana, além da análise por meio do Estereomicroscópio e Microscópio Eletrônico de Varredura (MEV). Os adesivos foram divididos em três grupos: ASB - Adesivo Single Bond 2 (3M-ESPE) sem a incorporação de partículas bioativas, ASB0,5 – Adesivo Single Bond 2 com a incorporação de partículas bioativas na concentração de 0,5% e ASB1 – Adesivo Single Bond 2 com a incorporação de partículas bioativas na concentração de 1%. Para o teste de resistência de união foram utilizados 30 molares humanos hígidos (n=10) que posteriormente foram observados em Estereomicroscópio para análise do padrão da fratura. O grau de conversão foi feito no FTIR, onde foram feitas três leituras das gotas do adesivo dos diferentes grupos. A atividade antibacteriana foi feita através dos testes de difusão em ágar e contagem da unidade formadora de colônia (UFC), onde foram utilizados discos de adesivos polimerizados dos diferentes grupos. Os testes antibacterianos foram repetidos por três vezes. Os dados foram analisados estatisticamente quanto à sua normalidade. Como estes apresentaram distribuição normal, realizou-se o teste de análise de variância (ANOVA) paramétrica um fator (sistema adesivo) e o tes... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

With the rapid increase in utilization of the cheap and user friendly Fused Filament Fabrication, FFF 3D printer, a deeper knowledge about the technique is needful. The frame restricting the 3D printers for prototyping purposes is fading and a new phase of endless application possibilities is emerging. To bridge the gap in possible applications from prototypes to real products it is key to know and improve the factors affecting durability. With over a hundred settings and parameters to tweak the FFF 3D printing process there are a lot of opportunities, opportunities to optimize for durability.The tensile properties of some of the most used FFF 3D printing materials together with a few nylon based materials are examined, which are popular in engineering applications. The materials tested are ranging from rigid to flexible, rubber like materials. The most common failure scenario of a FFF 3D printed product is layer bonding failure. The factors affecting layer bonding performance are studied.The measurements are carried out using tensile testing equipment at Blekinge Institute of Technology. All tested specimens are manufactured at Creative Tools AB Halmstad with the FFF 3D printers Flashforge Dreamer and Makerbot Replicator 2X.The tensile strength of 3D printed PLA is found to be 51 MPa. PET has a tensile strength of 40 MPa and ABS 34 MPa. Stress-strain behavior of the materials shows that ABS is slightly softer than PLA and PET are slightly softer than ABS. PLA being the hardest material in the test. ISO 527-2 tensile testing standard is used but the tests diverge from the standard in several ways. The measurement data presented in this study can be very useful to guide the design engineer to choose the most durable plastic for the unique application.Five basic 3D printing settings are evaluated for layer bonding performance, by measuring the load capacity of a PLA specimen loaded transversally relative to the layers. Four of the settings show to possibly affect the layer bond’s load capacity by 50 % or more individually.The results of this study are presented in graphs, diagrams and pictures. These may help the 3D printer user to tweak basic settings to increase layer bonding performance and ultimately the durability of the product significantly.

Maintenance and rehabilitation of existing masonry and reinforced concrete structures are of great importance in the field of civil engineering. Due to deterioration and severe environment, numerous structures fail to meet functional or safety requirements, and as a result, they should be strengthened. Several methods have been utilized to repair the structures, including steel plate bonding, cable post-tensioning, and section enlargement. However, these methods bring disadvantages, such as significant added dead load and high labour cost. Therefore, externally bonding with composite materials has attracted considerable attention recently. Externally bonded fibre-reinforced polymer (FRP) sheets have been widely used to strengthen reinforced concrete and masonry structures. FRP has been a common method to provide a higher service life for structures for several decades. However, strengthening structural members with FRP introduces certain drawbacks, such as their poor performance in fire scenarios caused by the rapid softening of the polymer-based resin. An alternative strengthening system known as a fabric-reinforced cementitious matrix (FRCM) has been developed to address this issue by replacing resin-based material with an inorganic cementitious-based matrix. Nonetheless, the performance of FRCM at high temperatures has not been investigated sufficiently so far. Hence, this research focused on the mechanical behaviour of FRCM at high temperatures. This experimental research investigates the tensile performance of carbon FRCM at high temperatures. First, the temperature distribution within the specimens during heating was studied using nine specimens with one, two, or three layers to reveal the required time for the inner fabric to reach a steady temperature. Then, the tension and stiffness degradation of FRCM coupons were studied at different temperatures. A total of 84 FRCM coupons were fabricated and tested in tension; 60 of the tests were conducted at steady-state conditions in which temperature was held constant and load increased, and 24 specimens were carried out in transient-state tests, in which load was constant, and temperature grew. In order to provide a more comprehensive knowledge concerning the FRCM composite, some key variables were included in this research. These parameters are the number of layers (1, 2, 3) leading to different thicknesses (20, 30, 40 mm), the orientation of the fabric layer (unidirectional and bidirectional), target temperature (ambient, 100, 200, 300, 400°C), and heating condition (steady-state, transient state). These tests aimed to reveal the primary mechanical characteristics such as ultimate strength and cracked elastic modulus at different temperatures and compare them with control specimens tested at room temperature. With the increase in the number of fabric grids from one to two and three, the stress at failure decreased by about 11 and 18%, respectively. With regards to cracked elastic modulus two and three-layered specimens showed 18 and 20% reduction in value. It is also noteworthy to mention that overall load capacity of specimens rose with the increase in number of layers; however, due to the more significant increase in area, the stress was reduced. The same decreases in the cracked elastic modulus and ultimate strength were observed as the target temperature increased. Increasing the temperature to 400°C led to a decrease in ultimate strength and cracked elastic modulus of approximately 60 to 70%. Furthermore, the bidirectional specimens showed a better behaviour than unidirectional specimens in terms of ultimate strength; however, their cracked elastic moduli were almost the same. With regards to the transient-state tests, as the material became thicker, the failure temperature increased considerably. For instance, a 20-mm specimen failed at 467°C with a 20% sustained load, while a 30-mm specimen failed at 558°C. Another vital parameter studied in transient-state tests was the decrease in temperature with the increase in sustained load. An example of this is the 20-mm specimens which failed at 352 and 258°C, while they were preloaded to 40 and 60% of their capacities. The conclusions of this study suggest that FRCM materials do retain a non-negligible strength capacity at high temperatures. However, further investigations to reveal FRCM bond behaviour and retrofitted structural members at high temperatures are still required to provide comprehensive knowledge.