Semicrystalline thermoplastic polyimides based upon bis(4-aminophenoxy)benzene and related "triphenyl ether" diamines were synthesized via the classical two step amic acid route. More specifically, polyimides were derived from para linked 1,4-bis(4-aminophenoxy)benzene, or TPEQ (triphenyl ether diamine- hydroquinone) and its meta isomer 1,3-bis(4-aminophenoxy)benzene, or TPER (triphenyl ether diamine-resorcinol). The reaction of these diamines with rigid or semi-rigid dianhydrides such as pyromellitic dianhydride (PMDA), biphenyl dianhydride (BPDA), and oxydiphthalic anhydride (ODPA) yields very thermally stable semi-crystalline polymers which have excellent resistance to organic liquids. Amorphous polyimides could be derived from hexafluoroisopropylidene-linked diphthalic anhydride (6FDA), but these systems were not extensively investigated. Importantly, molecular weight characterization of the semicrystalline systems at the soluble amic acid stage was successful by employing hydrodynamic volume calibrated, viscosity detector size exclusion chromatography (SEC). The experimental values were found to be within the targeted <M_n> range of 20-30,000 g/mole. Polyimide powders derived from these ether diamines were prepared by solution imidization at 180°C, to afford about 70% imidized structures as judged by dynamic thermal gravimetric analysis (TGA), before crystallization/precipitation occurred. Relatively small particle sizes ranging from 2 to 25 μm in size were generated, which would be appropriate for thermoplastic polymer matrix composites prepared by powder processing. All specimens showed excellent thermooxidative stability, consistent with the aromatic imide structure. The molecular design of the aromatic polyetherimide repeat unit was critical for the successful utilization of these semicrystalline high performance materials. The metba-linked TPER system when combined with the thermally stable s-biphenyl dianhydride (BPDA) produced a melting endotherm, T_m, at about 395°C, which was well within the thermal stability limitations of organic materials, i.e., less than or approximately 450°C. It was also demonstrated to be important to quantitatively endcap both ends of the chains at about 20-30,000 <M_n> with non-reactive phthalimide groups to achieve appropriate melt viscosities and good melt stability. This was done by off-setting the stoichiometry in favor of the diamine, reacting with a calculated amount of phthalic anhydride and imidizing in bulk above the Tg (≈210°C) at 300°C. These considerations allowed for remarkable melt stability in nitrogen at 430°C for at least 45 minutes, and importantly, repeated recrystallizations from the melt to afford tough, ductile semicrystalline films with excellent solvent resistance. If the macromolecular chains were not properly endcapped, it was demonstrated that viscosity increased rapidly at 430°C, suggesting reactions such as transimidization involving terminal amine end groups with in-chain imide segments and/or other side reactions, which quickly inhibited recrystallization, probably by reducing molecular transport processes. In contrast, polyimides based upon the more rigid para-linked TPEQ did not demonstrate melt or flow characteristics below 400°C, and degraded around the T_m at about 470°C! The less thermally stable TPEQ-ODPA based polyimide did melt around 409°C, and lower molecular weight samples, e.g., 10,000 M_n, recrystallized from the melt after short melt times, but cast films were brittle. It was hypothesized that the weak link may be the relatively electron rich arylene ether bond derived from the ODPA dianhydride. Several alkylated derivatives of TPER were synthesized in good yield by the reactions of alkylated resorcinol precursors with p-fluoronitrobenzene to produce dinitro compounds, which were subsequently reduced. These model diamines were then used to synthesize polyimides by the classical two step route. As expected, few of the polyimides derived from BPDA and these diamines displayed melting transitions (T_m), probably because of poor chain packing. However, they could have potential as new thermally stable membrane materials. Several amorphous polyimides prepared from 1,3-bis(p-aminophenoxy)-4-hexylbenzene were soluble in selected common organic solvents and could be cast into flexible films. / Ph. D.

Actin-based cell motility plays crucial role throughout the lifetime of an organism. While the dendritic nucleation model explains the initiation and organization of the actin network in lamellipodia, two questions need to be answered. In this study, I reconstructed cellular motility in vitro to investigate how actin filaments are organized to coordinate elongation and attachment to leading edge. Using total internal reflection fluorescence microscopy of actin filaments, we tested how profilin, Arp2/3, and capping protein (CP) function together to propel beads or thin glass nanofibers coated with N-WASP WCA domains. During sustained motility, physiological concentrations of Mg²⁺ generated actin filament bundles that processively attached to the nanofiber. Reduction of total Mg²⁺ abolished particle motility and actin attachment to the particle surface without affecting actin polymerization, Arp2/3 nucleation, filament capping, or actin shell formation. Addition of other types of crosslinkers restored both comet tail attachment and particle motility. We propose a model in which polycation-induced filament bundling sustains processive barbed end attachment to the leading edge. I lowered actin, profilin, Arp2/3, and CP concentrations to address the generation of actin filament orientation during the initiation of motility. In the absence of CP, Arp2/3 nucleates barbed ends that grow away from the nanofiber surface and branches remain stably attached to nanofiber. CP addition causes shedding of short branches and barbed end capture by the nanofiber. Barbed end retention by nanofibers is coupled with capping, indicating that WWCA and CP bind simultaneously to barbed ends. In pull-down assays, saturating CP addition only blocks WWCA binding to barbed end by half. Labeled WWCA bound to barbed ends with an affinity of 14 pM and unlabeled WWCA with an affinity of 75 pM. CP addition increased WWCA binding slightly at low CP concentrations and decreased WWCA binding to 50% at high CP concentrations. Molecular models of CP and WH2 domains bound respectively to the terminal and penultimate actin subunit showed no overlap and that CP orientation might blocks WWCA dissociation from the penultimate subunit. Simultaneous binding of CP and WWCA to barbed ends is essential to the establishment of filament orientation at the leading edge. / Ph. D.

A odontologia, atualmente, conta com uma nova abordagem terapêutica no campo da regeneração tecidual. Essa abordagem baseia-se no uso de moléculas bioativas, mais especificamente as BMPs (Bone Morphogenetic Proteins). A presente revisão propõe-se a apresentar alguns relatos, existentes na literatura, do uso das BMPs como medicamento, dando embasamento para realização de novos experimentos que possam sugerir abordagens terapêuticas inovadoras na área da regeneração tecidual. As BMPs são proteínas pleiotrópicas, que estão envolvidas no desenvolvimento de vários órgãos do corpo humano, e, também, estão presentes nas várias fases da morfogênese dentária, controlando e modulando as atividades celulares. As BMPs têm o potencial de serem usadas, tanto para a regeneração do complexo dentina-polpa quanto para a regeneração do periodonto (osso, cemento, ligamento, gengiva), podem ser empregadas em cirurgias craniofacial para correção de anomalias adquiridas ou herdadas, correção de seqüelas de trauma craniano, seqüelas de câncer, defeitos ósseos e reparo da cartilagem têmporomandibular. Deste trabalho pode-se concluir que a BMP: (1) tem importância na regeneração tecidual como elemento chave na engenharia de tecido; (2) oferece a vantagem de ser uma abordagem mais biológica, gerando um tecido idêntico ao perdido; (3) tem sido bem estudada em vários experimentos clínicos, com muito sucesso, inclusive em humanos; e (4) poderá estar disponível como uma alternativa de terapia a ser empregada no consultório odontológico. / Nowadays, odontology counts on a new therapeutic approach in the field of tissue regeneration. This approach is based in the use of bioactive molecules, specifically the BMPs (Bone Morphogenetic Proteins). The present revision has in view to know the BMPs and its applications as medicines, offering support to the accomplishment of experiments that could suggest new proposes of treatment in the field of tissue regeneration. The BMPs are pleiotropic proteins that are involved in the development of many organs of the human body and they are also present in the several phases of dental morphogenesis, controlling and modulating the cellular activities. The BMPs have the potential to be used to the regeneration of the dentin-pulp complex as much as to the regeneration of the periodontium (bone, cementum, ligament and gingiva), and can be used in facial and cranial surgeries to the correction of acquired or inherited anomalies, correction of cranial trauma consequences, bone defects and repair of the temporal- mandible cartilage. From this review, we can conclude some topics about the BMP: (1) it has importance in the tissue regeneration as a key element in tissue engineering; (2) the BMP offers the advantage of being a more biologic approach, generating a new tissue that is identic to the lost one; (3) it has been studied in several clinic experiments, with great success, even including humans; (4) it probably will be available as an alternative of therapy, that may be used in odontologic rooms in the future.

O hidróxido de cálcio (HCa), o agregado de trióxido mineral (MTA) e o óleo-resina de copaíba (COP) isoladamente apresentam características biológicas do material de capeamento pulpar direto mais apropriado. Com o pressuposto que associados poderiam originar materiais mais apropriados para serem aplicados em capeamento pulpar direto, este estudo objetivou analisar in vitro proliferação, diferenciação e migração de células-tronco de polpa de dente decíduo humano esfoliado (SHEDs) em resposta a substâncias liberadas pelo COP isolado ou associado ao HCa ou ao MTA. Proliferação, diferenciação e migração de SHEDs (Linhagem PDH3) foram analisadas através do ensaio de redução do MTT; da atividade de fosfatase alcalina (ALP), formação de nódulos mineralizados pelo ensaio de Vermelho de Alizarina e expressão dos genes (BGLAP, DSPP, DMP1 e HSP-27) pelo qRT-PCR; e, do ensaio do Scratch, respectivamente. As células foram submetidas à ação de meios condicionados pelos biomateriais, de acordo com os seguintes grupos experimentais: COP isolado (COP); HCa isolado (HCa); HCa associado ao COP (HCa+COP); MTA isolado (MTA) e MTA associado ao COP (MTA+COP). Células crescidas em meio de cultura fresco serviram de controle. Os dados foram comparados utilizando ANOVA complementado pelo teste de Tukey (p 0,05). O grupo HCa apresentou número de células viáveis significativamente menor que o dos demais grupos, inclusive o do grupo HCa+COP (p<0,01) em todos os tempos experimentais. A atividade de ALP em 14 dias foi similar em todos os grupos experimentais. Em 21 dias, o grupo COP apresentou quantidade maior de mineralização que os demais grupos (p<0,01) e o grupo HCa+COP maior que o grupo HCa (p<0,01). O gene DMP1 não foi expresso pelas células em nenhum grupo experimental. O grupo COP apresentou as menores expressões dos genes BGLAP, DSPP e HSP-27. As SHEDs do grupo MTA+COP apresentaram superexpressão dos genes BGLAP, DSPP e HSP-27, e as do grupo HCa+COP superexpressão dos genes BGLAP e HSP-27. O grupo HCa foi o único que não apresentou células em migração em todos os tempos experimentais. Os demais grupos apresentaram migração similar à do grupo Controle, exceto o grupo MTA em 12 e 24 horas. As SHEDs dos grupos HCa+COP e MTA+COP migraram significativamente mais que as dos grupos HCa e MTA, respectivamente. O COP, isolado ou em associação aos demais biomateriais, não interfere na proliferação de SHEDs e quando associado ao HCa é capaz de anular a citotoxicidade deste biomaterial isolado. O COP, isoladamente ou em associação, não interfere na atividade de fosfatase alcalina. Isoladamente, o COP induz a maior diferenciação funcional e quando associado ao HCa melhora substancialmente a diferenciação induzida por este biomaterial isolado. Os biomateriais isolados ou associados não são capazes de induzir expressão de DMP1. O COP associado aos biomateriais induz superexpressão de genes relacionados à formação de matriz extracelular e de diferenciação odontoblástica. O COP isoladamente não interfere na migração celular e, quando associado ao HCa, anula por completo a inibição de migração causada por esse biomaterial isolado. Quando associado ao MTA, o COP aumenta a velocidade de migração das células em relação ao MTA isolado. Óleo-resina de copaíba (COP) promove proliferação, diferenciação e migração de células-tronco de polpa dental sendo uma proposta de um biomaterial para capeamento pulpar. / The calcium hydroxide (CaH), the mineral trioxide aggregate (MTA) and the oil-resin copaiba (COP) by themselves have biological characteristics of the ideal direct pulp capping material. With the assumption that when associated they could originate materials more appropriated for direct pulp capping, this study aimed to analyze the in vitro proliferation, differentiation and migration of stem cells from human exfoliated deciduous teeth (SHEDs) in response to substances leached from COP alone or associated with CaH or MTA. Proliferation, differentiation and migration of SHEDs (PDH3 lineage) were analyzed through the MTT reduction assay; alkaline phosphatase (ALP) activity, mineralized nodules formation using the Alizarin Red assay and gene expression (BGLAP, DSPP, DMP1 e HSP-27) using qRT-PCR; and the Scratch assay, respectively. The cells were submitted to the culture medium conditioned by the biomaterials according to the following experimental groups: COP alone (COP); CaH alone (CaH); CaH associated to COP (CaH+COP); MTA alone (MTA) and MTA associated to COP (MTA+COP). Cells grown in fresh culture medium served as control. Data were compared by ANOVA complemented by the Tukey´s test (p 0.05). The CaH group presented number of viable cells significantly smaller (p<0.01) than those of all other experimental groups, including the CaH+COP, during whole experimental time. The ALP activity in 14 days was similar in all experimental groups. In 21 days, the COP group presented the amount of mineralization higher (p<0.01) than those of all other groups. The gene DMP1 was not expressed by the cells in all experimental groups. The COP group presented the smallest expression (p<0.01) of BGLAP, DSPP and HSP-27 genes. The SHEDs of the MTA+COP group presented superexpression of the BGLAP, DSPP and HSP-27 genes, and in the CaH+COP group the cells superexpressed the BGLAP and HSP-27 genes. The CaH group was the only one where there was no cell migration during whole experiment. Migration of all other groups was similar to that of the control group, except by the MTA group in 12 and 24 hours. The CaH+COP and MTA+COP migrated significantly more than the CaH and MTA groups, respectively. COP, alone or in association to the other biomaterials, does not interfere with the proliferation of the SHEDs, and when associated to CaH is able to annul the cytotoxicity of the CaH alone. The COP, alone or in association to the other biomaterials, does not interfere with the ALP activity. The COP alone induces the highest functional differentiation of the SHEDs and when associated to the CaH substantively improves this differentiation. The biomaterials, alone or in association, are not able to induce the expression of the DMP1 gene. The COP associated to the biomaterials induces superexpression of the genes related to the extracellular matrix formation and odontoblastic differentiation. The COP alone does not interfere with the cell migration and, when associate to CaH, completely annuls the inhibition of migration caused by this material alone. When associated to MTA the COP increases the cell migration speed compared to the effect of the MTA alone. Oil-resin copaiba (COP) promotes proliferation, differentiation and migration of stem cells from dental pulp with a proposal for a biomaterial for pulp capping.

O sucesso no tratamento odontológico tem sido incansavelmente buscado, seja através da melhoria das técnicas ou dos materiais. Contribuindo com essa realidade, o objetivo deste trabalho foi, por meio de uma metodologia inédita, verificar e comparar a densidade óptica do hidróxido de cálcio, cimento de ionômero de vidro e de um vidro bioativo, correlacionando-as com a densidade óptica de estruturas dentais. Foi desenvolvido e confeccionado um dispositivo padronizador, que simula a situação clínica onde o material é utilizado, composta por orifícios, onde o material era depositado, e por degraus, que representavam as diferentes espessuras dos materiais, além do penetrômetro de alumínio, para que fosse obtida uma curva de padronização. Foram obtidas imagens radiográficas em tempos de exposição de 0,3; 0,4 e 0,5s. Após a leitura dos valores da densidadeópticas das imagens radiográficas em fotodensitômetro, os dados obtidos foram submetidos à análise estatística (teste 3-way ANOVA, Bonferroni, nível de significância de 95%) que permitiu verificar que houve diferença na densidade óptica dos materiais, tanto em tempo, quanto em espessuras diferentes, sejam comparados entre si ou com as estruturas dentais. Os maiores valores foram obtidos com o hidróxido de cálcio, no tempo de 0,5s com 2,0mm de espessura, enquanto que o menor valor foi apresentado pelo esmalte com 3,0mm em tempo de 0,3s. Com os resultados obtidos, concluiu-se que todos os materiais apresentaram valores menores que as estruturas dentais, sendo mais radiolúcidos. / The success of dental treatment has been continuously searched by the improvement of both the techniques and materials. In order to contribute with this reality, the purpose of this study was to verify and compare, by means of an inedited methodology, the optical densities of calcium hydroxide, glass ionomer cement and a bioactive glass, correlating them with the optical density dental tissues. A standardizing device was developed and constructed, which simulates the clinical situation in which the material is used. This device was composed of orifices in which the material was inserted and steps that represented the different thicknesses of the materials, in addition to an aluminum penetrometer to provide a standardization curve. Radiographic images were obtained using exposure times of 0.3, 0.4 and 0.5 s. After reading of the optical density values of the radiographic images in a photodensitometer, the gathered data were submitted to statistical analysis by 3-way ANOVA and Bonferroni correction at 5% significance level. There was statistically significant difference in the optical density of the material regarding both the exposure times and the thicknesses, comparing to each other as well as to the dental tissues. The greatest values were obtained for calcium hydroxide at 0.5-s exposure time and 2.0 mm thickness, whereas the lowest value was obtained for enamel with thickness of 3.0 mm and exposure time of 0.3 s. Based on the obtained results, it may be concluded that all materials presented lower optical density values than the dental structures, being more radiolucent, in addition to the suggestion of adding to the materials? instructions for use information regarding the ideal exposure time and type of x-ray equipment.

O sucesso no tratamento odontológico tem sido incansavelmente buscado, seja através da melhoria das técnicas ou dos materiais. Contribuindo com essa realidade, o objetivo deste trabalho foi, por meio de uma metodologia inédita, verificar e comparar a densidade óptica do hidróxido de cálcio, cimento de ionômero de vidro e de um vidro bioativo, correlacionando-as com a densidade óptica de estruturas dentais. Foi desenvolvido e confeccionado um dispositivo padronizador, que simula a situação clínica onde o material é utilizado, composta por orifícios, onde o material era depositado, e por degraus, que representavam as diferentes espessuras dos materiais, além do penetrômetro de alumínio, para que fosse obtida uma curva de padronização. Foram obtidas imagens radiográficas em tempos de exposição de 0,3; 0,4 e 0,5s. Após a leitura dos valores da densidadeópticas das imagens radiográficas em fotodensitômetro, os dados obtidos foram submetidos à análise estatística (teste 3-way ANOVA, Bonferroni, nível de significância de 95%) que permitiu verificar que houve diferença na densidade óptica dos materiais, tanto em tempo, quanto em espessuras diferentes, sejam comparados entre si ou com as estruturas dentais. Os maiores valores foram obtidos com o hidróxido de cálcio, no tempo de 0,5s com 2,0mm de espessura, enquanto que o menor valor foi apresentado pelo esmalte com 3,0mm em tempo de 0,3s. Com os resultados obtidos, concluiu-se que todos os materiais apresentaram valores menores que as estruturas dentais, sendo mais radiolúcidos. / The success of dental treatment has been continuously searched by the improvement of both the techniques and materials. In order to contribute with this reality, the purpose of this study was to verify and compare, by means of an inedited methodology, the optical densities of calcium hydroxide, glass ionomer cement and a bioactive glass, correlating them with the optical density dental tissues. A standardizing device was developed and constructed, which simulates the clinical situation in which the material is used. This device was composed of orifices in which the material was inserted and steps that represented the different thicknesses of the materials, in addition to an aluminum penetrometer to provide a standardization curve. Radiographic images were obtained using exposure times of 0.3, 0.4 and 0.5 s. After reading of the optical density values of the radiographic images in a photodensitometer, the gathered data were submitted to statistical analysis by 3-way ANOVA and Bonferroni correction at 5% significance level. There was statistically significant difference in the optical density of the material regarding both the exposure times and the thicknesses, comparing to each other as well as to the dental tissues. The greatest values were obtained for calcium hydroxide at 0.5-s exposure time and 2.0 mm thickness, whereas the lowest value was obtained for enamel with thickness of 3.0 mm and exposure time of 0.3 s. Based on the obtained results, it may be concluded that all materials presented lower optical density values than the dental structures, being more radiolucent, in addition to the suggestion of adding to the materials? instructions for use information regarding the ideal exposure time and type of x-ray equipment.

Made available in DSpace on 2017-07-10T14:57:33Z (GMT). No. of bitstreams: 1 Lucio_ paulo.pdf: 1888833 bytes, checksum: 7e440f531baf7b1f6f7f1d8c2cd63b02 (MD5) Previous issue date: 2016-02-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The direct pulp capping aims to protect the pulp by a bioactive material, allowing the maintenance of pulp vitality and the formation of mineralized barrier. The objective of this study was histologically comparing the pulp response of different materials, for continuity and morphology of the mineralized structure. It was 108 (one hundred and eight) teeth of 54 (fifty-four) male Wistar rats, eight (8) weeks old. Circular cavities were prepared in mesio-occlusal surface of the upper first molars and capped in accordance with the Group, which included the animal: group 1 with calcium hydroxide (CH); Group 2: MTA and group 3: Biodentine®. All cavities were sealed with cement resin modified glass ionomer cement (3M Vitremer -ESPE) and the animals euthanized at predetermined periods of seven (7), fourteen (14) and 21 (twenty one) days. The jaws were removed and fixed slides prepared and stained with HE (hematoxylin and eosin) for descriptive histological evaluation of inflammation and the formation of mineralized barrier. The results showed that the MTA and the Biodentine® exhibit less intense inflammatory reactions when compared to the CH, and the statistical comparison (Kruskal-Wallis) of formation and quality of the formed dentin barrier statistically different at 21 days between the CH groups for MTA and Biodentine, which were similar to each other. It can be concluded that the MTA and Biodentine® induce mineralized architecture of a more continuous and uniform barrier and less intense when compared to pulp response to CH. / O capeamento pulpar direto visa à proteção da polpa por um material bioativo que permita a manutenção da vitalidade pulpar e a formação de barreira mineralizada. Assim, o objetivo deste estudo foi comparar histologicamente a resposta pulpar frente a materiais dentários, quanto à continuidade e morfologia da estrutura mineralizada. Foram utilizados 108 (cento e oito) dentes de 54 (cinquenta e quatro) ratos Wistar, machos com 8 (oito) semanas de idade. Cavidades circulares foram preparadas na face mesio-oclusal dos primeiros molares superiores e capeadas de acordo com o grupo ao qual pertencia o animal: grupo 1: com hidróxido de cálcio (CH); grupo 2: MTA e grupo 3: Biodentine®. Todas as cavidades foram seladas com cimento de ionômero de vidro modificado por resina (Vitremer 3M ESPE) e os animais eutanasiados em períodos predeterminados de 7 (sete), 14 (quatorze) e 21(vinte e um) dias. Posteriormente as maxilas removidas, fixadas e confeccionadas lâminas coradas H.E. (Hematoxilina e Eosina) para avaliação histológica descritiva da inflamação e da formação da barreira mineralizada. Os resultados demostraram que o MTA e o Biodentine® promovem reações inflamatórias menos intensas quando comparados ao CH. A comparação estatística (Kruskal-Wallis) da formação e da qualidade da barreira de dentina formada demonstrou diferença estatística aos 21 dias entre os grupos de CH para o MTA e Biodentine, e estes dois últimos similares entre si. Pode-se concluir que o MTA e o Biodentine® induzem a arquitetura de uma barreira mineralizada mais contínua e uniforme e a uma resposta pulpar menos intensa quando comparados ao CH.

A la suite d’une lésion carieuse ou traumatique du complexe pulpo-dentinaire, une inflammation locale est initiée. Cette inflammation peut être délétère car la pulpe dentaire est localisée au sein de parois dentinaires rigides, elle doit donc être résolue pour initier la régénération.Lors de lésions juxta-pulpaires, le praticien réalise un coiffage pulpaire direct afin de conserver la vitalité de la dent. Un biomatériau est placé au contact des tissus pulpaires afin de maintenir l’intégrité de la pulpe, en promouvant les processus de guérison tout en la protégeant du milieu buccal hostile.Les silicates de calcium sont aujourd’hui les matériaux de choix pour ces actes thérapeutiques. Des modifications de leur formulation visant à réduire leur temps de prise ont conduit au développement de silicates tricalciques photo-polymérisables. Cependant, la présence importante de résines dont la toxicité pulpaire est connue, soulève des questions. Cette thèse a pour objectif d’évaluer l’effet de différents biomatériaux de coiffage pulpaire sur l’inflammation et la régénération, au niveau cellulaire et tissulaire et d'étudier les conséquences de l'ajout de résines. Nos résultats démontrent que les matériaux de coiffage pulpaire affectent les étapes précoces de l'inflammation et de la régénération pulpaire. Alors que les silicates tricalciques modifient l'équilibre vers le processus de régénération, les biomatériaux contenant de la résine déplacent cet équilibre vers une réaction inflammatoire. Ce travail met en évidence l'importance capitale du choix du biomatériau de coiffage et restreint l'utilisation de biomatériaux contenant de la résine pour le coiffage pulpaire indirect. / Deep carious or physical lesions may lead to dental pulp injuries. Subsequently, both infiltrating bacteria and injured tissues initiate an inflammatory reaction. This may be detrimental to the healing process within the pulp inextensible environment.Clinically, during juxta-pulpal lesions, the practitioner performs a direct pulp capping in order to preserve the tooth vitality. A biomaterial is placed directly in contact with the pulp tissues to maintain pulp integrity, promoting the healing processes and protecting it from the hostile oral environment. Tricalcium silicates are now considered as the biomaterials of choice for vital pulp therapy. Modifications of this type of biomaterials aiming at reducing their setting time led to the development of light-cured tricalcium silicates. However, the presence of a high percentage of resins in this material raises questions about its possible effects on the pulp inflammatory reaction due to its reported toxicity. This aim of this thesis was to determine the influence of tricalcium silicate-based capping biomaterials on the initial steps of pulp inflammation and healing and to investigate the consequences of adding resins.Our results demonstrate that pulp capping biomaterials affect the early steps of pulp inflammation and healing. While tricalcium silicates shift the balance towards the healing process, resin-containing biomaterials drive this balance towards an inflammatory reaction. Overall, this work highlights the fact that the choice of pulp capping biomaterial is of prime importance in direct pulp capping procedures and does not support using resin containing biomaterials for direct pulp capping.

In order to better predict the aggregation state of nanomaterials, the factors that influence aggregation must be understood. The combined effects of natural and engineered coatings have been shown to factor into nanoparticle aggregation behavior in preliminary research. In this study, aggregation behaviors of gold nanoparticles with two different engineered coatings were investigated in the presence of the monovalent electrolyte KCl and the divalent electrolyte CaCl���. Aggregation studies were conducted using dynamic light scattering to determine the relative stability of the NMs in environments of varying ionic strength in the absence and presence of Suwannee River Natural Organic Matter (SRNOM). Coatings which provided primarily electrostatic stabilization were found to adhere closely to DLVO theory, while coatings which provided steric stability inhibited aggregation over a wide range of ionic strengths for both electrolytes. The presence of SRNOM was found to provide some electrostatic stability in the presence of KCl, but appeared to form agglomerates with calcium ions, especially at higher SRNOM concentrations. / Graduation date: 2013

The use of geosynthetics in landfill construction introduces potential planes of weakness. As a result, there is a requirement to assess the stability along the soil/geosynthetic and geosynthetic/geosynthetic interfaces. Stability is governed by the shear strength along the weakest interface in the system. Repeatability interface shear strength testing of a geomembrane/geotextile interface at low normal stresses suitable for capping systems showed considerable variability of measured geosynthetic interface shear strengths, suggesting that minor factors can have a significant influence on the measured shear strength. This study demonstrates that more than one test per normal stress is necessary if a more accurate and reliable interface shear strength value is to be obtained. Carefully controlled inter-laboratory geosynthetic interface shear strength comparison tests undertaken on large direct shear devices that differ in the kinematic degrees of freedom of the top box, showed the fixed top box design to consistently over estimate the available interface shear strength compared to the vertically movable top box design. Results obtained from measurement of the normal stress on the interface during shear with use of load cells in the lower box of the fixed top box design, raise key questions on the accuracy, reliability and proper interpretation of the interface shear strength data used in landfill design calculations. Tests on the geocomposite/sand interface have shown the interface friction angle to vary with the orientation of the geocomposite's main core, in relation to the direction of shearing. Close attention needs to be paid to the onsite geocomposite placement in confined spaces and capping slope corners, as grid orientation on the slope becomes particularly important when sliding is initiated. Attempts to measure the pore water pressure during staged consolidation and shear along a clay/geomembrane interface in the large direct shear device suggest that this interface is a partial drainage path.