Orientador: Alexandre Luiz Souto [Unesp] Borges / Resumo: Este estudo visou sintetizar e caracterizar mantas não tecidas de nanofibras (NFs) do acrilonitrila butadieno estireno (ABS), poliamida 6 (PA6) e poliestireno (PS), e avaliar sua capacidade de ser utilizada como reforço no polimetilmetacrilato (PMMA). O ABS foi dissolvido em diclorometano e acetona, a PA6 pelo 1,1,1,3,3,3-hexafluoro-2-propanol e o PS pela dimetilformamida, em uma concentração definida em estudo piloto. Após determinados os melhores parâmetros de eletrofiação (tensão contínua, razão de fluxo e distância agulha/anteparo) as amostras de cada grupo foram analisadas em microscopia eletrônica de varredura, análise de molhabilidade, análise de difratometria de raios X, espectroscopia de infravermelho por transformada de Fourier, diâmetro das fibras e resistência a tração. As NFs produzidas foram incluídas na área de tração dos corpos de prova em resina acrílica ativada termicamente (RAAT) conforme ISO1567, perfazendo 4 grupos (n=20), 1 controle (Grupo 1) e 3 experimentais (Grupo 2, RAAT+NF/ABS; Grupo 2, RAAT+NF/PA6; Grupo 4, RAAT+NF/PS), para ensaio de flexão três pontos para analisar suas propriedades mecânicas, como: módulos de elasticidade e resistência a flexão. De acordo com os testes de caracterização, as mantas se apresentaram hidrofóbicas, não houve mudança de sua estrutura polimérica, concluindo-se então que a técnica da eletrofiação foi promissora na síntese de mantas de NFs. A variação dos parâmetros afetou diretamente a morfologia, resultando em fibras u... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed to synthesize and characterize non-woven blankets of acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6) and polystyrene (PS) nanofibers (NFs), and to evaluate their ability to be used as reinforcement in polymethyl methacrylate (PMMA). ABS was dissolved in dichloromethane and acetone, PA6 by 1,1,1,3,3,3- hexafluoro-2-propanol and PS by dimethylformamide at a concentration defined in a pilot study. After determining the best electrospun parameters (continuous voltage, flow rate and needle/shield distance) the samples from each group were analyzed by scanning electron microscopy, wettability analysis, X-ray diffraction analysis, Fourier transform infrared spectroscopy, fiber diameter and tensile strength. The NFs produced were included in the tensile area of the thermally activated acrylic resin (RAAT) specimens according to ISO1567, making up 4 groups (n = 20), 1 control (Group 1) and 3 experimental (Group 2, RAAT+NF/ABS; Group 3, RAAT+NF/PA6 and Group 4 (RAAT+NF/PS), for three point bending test to analyze their mechanical properties, as: modules of elasticity and flexural strength. According to the characterization tests, the blankets were hydrophobic, there was no change in their polymeric structure, concluding that the electrospinning technique was promising in the synthesis of NFs blankets. The parameters variation affected directly in the morphology, resulting in uniform, bulky and without defects (beads) NFs blankets. The Groups 3 and 4 (NF/PA6+RA... (Complete abstract click electronic access below) / Mestre

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Recent theoretical and experimental studies, suggest that Carbon nanotubes are 10-100 times higher than the strongest steel at a fraction of the weight. There are two main types of CNTs that can have high structural perfection. Single-walled nanotubes (SWNTs) consist of a single graphite sheet seamlessly wrapped into a cylindrical tube. Multi-walled carbon nanotubes (MWNTs) comprise an array of such nanotubes concentrically nested like rings of a tree trunk. Denture base acrylics have been reinforced with different materials with limited success. No single reinforced material has showed a great statistical difference in mechanical improvement. The goal of this investigation was to study the effects of Single Walled Carbon Nanotubes reinforcement on the mechanical properties of commercially available denture base PMMA. Denture Base material was reinforced with Single-walled Carbon Nanotubes (SWNTs) at dispersion of 0.25 wt % (group 1), 0.50 wt % (group 2), 0.75 wt % (group 3) and 0.0 wt % (group 4, control). Samples from each group were evaluated for microhardness, flexural strength, flexural modulus, and fracture toughness. The samples were tested in two conditions, as manufactured (dry) and after storing at 37 C for 7 days (wet). Data from four experiments was analyzed by ANOVA. All control sample values were in the range of acceptance compared with previous studies. Higher values were obtained for the control groups for flexural strength and modulus compared with the experimental samples. (p < 0.05) There was no statistical difference regarding fracture toughness between control and experimental groups. A statistical difference was observed in Hardness. The experimental group showed higher values under compression.

<p>U uvodnom delu doktorske disertacije opisuje se kompleksnost problematike kori&scaron;ćenja polimera za bazu zubne proteze, sa osvrtom na njihove op&scaron;te osobine, stepen biokompatibilnosti i njihove mehaničke karakteristike. Detaljno je opisana problematika ispitivanja stomatolo&scaron;kih materijala i napravljeno je poređenje i korelacija između in vitro i in vivo načina ispitivanja biokompatibilnosti. Drugi deo obuhvata ispitivanje čvrstoće polimera za bazu zubne proteze i analizu uticaja osobina materijala u odnosu na biolo&scaron;ku sredinu u kojoj obavljaju svoju funkciju, i u odnosu na sile kojima su tokom funkcije materijali izloženi. Cilj doktorske disertacije je utvrđivanje stepena biokompatibilnosti i mehaničkih karakteristika toplopolimerizujućih, hladnopolimerizujućih i termoplastičnih akrilata za bazu zubne proteze. Istraživanje je obuhvatilo 3 komercijalna materijala iz grupe akrilata, koji se razlikuju po hemijskom sastavu i načinu polimerizacije. Ispitivanje biokompatibilnosti rađeno je u in vitro i in vivo uslovima. Ispitivanje na ćelijskim kulturama obuhvatalo je dve ćelisjke linije (MRC 5 i L929) sa dva načina kontakta između ćelija i materijala (direktan, indirektan) i dva načina određivanja biolo&scaron;kog ishoda (MTT test, Agar difuzioni test). Istraživanje urađeno in vivo obuhvatalo je test subkutane implantacije, na animalnom modelu pacova, i test iritacije oralne sluzokože na animalnom modelu hrčka. Oba testa rađena su u skladu sa standardom ISO 10993. Cilj in vivo istraživanja bio je ispitivanje reakcije tkiva na implantirani materijal, računajući i zavr&scaron;nu integraciju ili dezintegraciju implantiranog materijala. Prednost in vivo istraživanja nalazi seu analizi uticaja materijala na sterilno živo tkivo, uz praćenje imunolo&scaron;ke reakcije, kao dopuna prethodnom istraživanju na ćelijskim kulturama. Dopunski deo in vivo ispitivanja biokompatibilnosti određen je prema kliničkoj upotrebi ispitivanih materijala, zbog čega je odabran test oralne iritacije sluzokože. Sluzokoža bukalne kesice sirijskog hrčka sastoji se od pločasto slojvitog epitela sa orožavanjem, &scaron;to je predstavljao dobar model za ispitivanje polimera za bazu zubne proteze, po&scaron;to zubna proteza naleže na sluzokožu nepca i rezidualnog alveolarnog grebena koja takođe orožava. Drugi deo disertacije obuhvatao je ispitivanje mehaničkih karakteristika, pri čemu su urađeni test zatezne čvrstoće, test savojne čvrstoće, test čvrstoće loma i mikrotvrdoće, uz dopunsku analizu pratećih parametara. Rezultati ispitivanja biokompatibilnosti pokazali su da su testovi biokompatibilnosti osetljivi na upražnjeni metodolo&scaron;ki postupak. Ispitivanjem na ćelijskim kulturama nisu utvrđene značajne razlike u citotoksičnosti između toplopolimerizujućih, hladnopolimerizujućih i termoplastičnih akrilata. Takođe, rezultati su se razlikovali u odnosu na tip ćelijske kulture i način provere biolo&scaron;kog ishoda, &scaron;to se slaže sa prethodnim navodima o kompleksnoj problematici njihovog međusobnog poređenja. Ispitivanjem biokompatibilnosti subkutanom implantacijom praćen je inflamatorni odgovor tkiva u vremenskom intervalu od 90 dana. Reakcija organizma na implantirani materijal posmatrana je kroz ćelijske i tkivne parametre, u skladu sa ISO 10993. Dodatno je urađena i analiza hrapavosti implantiranih materijala. Histolo&scaron;kom analizom utvrđena je razlika u inflamatornom odgovoru u odnosu na kori&scaron;ćeni materijal, kao i prema vremenskom intervalu implantacije. Test oralne iritacije sluzokože nije se pokazao kao dovoljno senzitivan za ispitivanje ovih vrsta materijala. Ispitivanjem mehaničkih karakteristika utvrđene su razlike između toplopolimerizujućih, hladnopolimerizujućih i termoplastičnih akrilata. Najveći stepen čvrstoće utvrđen je kod toplopolimerizujućih akrilata dok je najveća konzistentnost rezultata bila u grupi termoplastičnih akrilata. Prezentovano istraživanje predstavlja prvu detaljnu analizu biokompatibilnosti i mehaničkih karaktestistika polimera za bazu zubne proteze.</p> / <p>The introduction describes the complexity of use of denture base materials, with regard to their general characteristics, biocompatibility and mechanical properties. Issues related to the testing of dental materials is described in detail and comparison is made between in vitro and in vivo methods of biocompatibility testing. The second part further covers the determination of strength of previously used materials, in relation to biological environment in which their function is conducted and in relation to the influence of masticatory forces which can contribute to their mechanical failure. The aim of the presented research was to assess the degree of biocompatibility and mechanical properties of cold curing, hot curing and thermoformed denture base materials. The research included three denture base materials, which differed according to their chemical composition and polymerization protocols. The biocompatibility testing was carried out in in vitro and in vivo conditions. The in vitro experiments covered two different cell lines (MRC 5 human lung fibroblasts and L929 mouse fibroblasts) with two types of contact (direct, indirect) and two different types of quantification of biological outcome (MTT assay and Agar overley test). The in vivo assessment of biocompatibility covered the subcutaneous implantation test, on the animal model of Wistar rat, and oral mucosa irritation test, on the animal model of sirian hamster. Both tests were conducted according to the ISO 10993. The aim of the in vivo investigation was to evaluate tissue reactions to the implanted materials, including the final integration or disintegration of the tested materials. The advantage of in vivo investigation included the possibility of monitoring the materials influence on living tissues, with the analysis of imunological response as an addition to the previously conductedresearchon cell cultures. The supplemental part of in vivo investigation was chosen according to the clinical use of the tested materials, which included the oral mucosa irritation test.The mucosa of hamster buccal pouch consists of stratified squamos epithelium, which is considered to be an adequate replacement for the human denture supporting tissues, which also consist of the same type of epithelium. The second part of thesis includes the determination of mechanical properties of denture base materials. It consists of four types of tests: tensile strength test, bending strength test, fracture toughness test and microhardness tests, followed by the analysis of corresponding parameters. The results of the biocompatibility tests showed that the biological outcome of the applied method is highly depended on the methodological procedure. The investigation conducted in vitro, on two different cell lines, did not show significant difference in cytotoxicity between hot curing, cold curing and thermoformed denture base materials. Also, the results were influenced by the type of cell culture and the evaluation method of biological outcome, which agrees with the previous allegations about the complexicity of their mutual comparison. The subcutaneous implantation test covered the inflammatory response in the time period of 90 days. The organism reaction to the implanted material was determined through the cell and tissue parameters of organism response, evaluation of which was conducted according to the ISO 10993. Additionally, the surface roughness of the implanted specimens of materials was also measured. The inflammatory response of the ogranism was influenced by the type of the implanted material and the time interval of implantation. The oral mucosa irritation test has proven not to be sufficiently sensitive for testing of this type of materials. Testing of the mechanical properties od denture base materials, revealed the difference between the cold curing, hot curing and thermofomed denture base materials. The highest strength was observed in hot curing materials, while the highest consistency of the results was observed in thermoformed resins. The presented investigation presents the first detail analysis of the biocompatibility and mechanical properties of the denture base materials, and as such presents a novelty in the field of dental materials characterization.</p>

Este estudo teve o objetivo de avaliar in vitro a influência da alteração dimensional de resinas acrílicas para base de prótese total submetidas a diferentes formas de processamento sobre a posição da cabeça da mandíbula, buscando estabelecer uma possível relação com a etiologia das disfunções crânio-mandibulares nos pacientes usuários desse tipo de prótese. Foram duas etapas: a primeira parte enfocou o papel do tipo de prensa (Getom ou de cozimento) e da força de prensagem para fechamento da mufla (1000 ou 1500 kgf) utilizados no processamento de duas resinas: Lucitone 550 e QC–20 e somente da força de prensagem para a resina Acron MC. Já a segunda parte do estudo teve o intuito de avaliar a influência dos ciclos de polimerização curtos e longos na alteração dimensional de cinco resinas: as mesmas três da primeira parte, além da Clássico e Ondacryl. As próteses superiores acrilizadas foram remontadas em articulador totalmente ajustável, tendo como referência a posição de máxima intercuspidação (MIC). Nessa posição de maior estabilidade oclusal, foi vazado gesso tipo IV no espaço entre as esferas condilares do articulador e as paredes dos estojos condilares. Após a cristalização, esses corpos-de-prova de gesso foram removidos do estojo condilar e suas dimensões medidas e submetidas à análise estatística por meio de um modelo de análise de variância com medidas repetidas que permitiu concluir que houve variações na posição da “cabeça da mandíbula" em 625 das 630 medidas efetuadas; as médias de movimentação condilar variaram de 0,118 (DP = 0,0968) a 1,956 mm (DP = 0,414) e ocorreram principalmente no sentido posterior do lado esquerdo; na maioria dos casos em que a força de prensagem agiu como fator devariação, os deslocamentos obtidos com 1500 kgf foram menores do que aqueles obtidos com 1000 kgf; nos casos em que o tipo de prensa agiu como fator de variação, ora os menores deslocamentos foram obtidos com a prensa de cozimento, ora com a Getom; o ciclo empregado na polimerização não influenciou significativamente na estabilidade dimensional das próteses totais e a única diferença encontrada envolveu a resina Clássico, que levou aos maiores deslocamentos no sentido posterior do lado esquerdo. / The purpose of this study was to evaluate in vitro the influence of dimensional changes in denture base acrylic resins submitted to different processing methods on the position of the mandibular condyle. This was done to establish a relation between these dimensional changes and the etiology of temporomandibular disorders in complete denture wearers. This research was divided into two parts. The first part focused on the type of press (conventional water bath or Getom), on the pressing force for flask closure (1000 or 1500 kgf) when processing Lucitone 550 and QC-20 resins, and on the pressing force when processing Acron MC resin. The purpose of the second part was to evaluate the influence of polymerization time on the dimensional stability of five resins, namely Lucitone 550, QC-20, Acron MC, Clássico and Ondacryl. The polymerized upper prostheses were remounted on a fully adjustable articulator, using the maximal intercuspal position (MIP) as reference. Type IV dental stone was poured into the space between the condylar spheres and the condylar walls. After the dental stone dried, the samples were removed from the articulator and their dimensions were measured and submitted to analysis of variance with repeated measures. The following conclusions were drawn: 625 from 630 measurements done showed changes in the position of the “mandibular condyle" and mean values for condylar movement ranged from 0.118 (SD = 0.0968) to 1.956 mm (SD = 0.414) and occurred mainly in the posterior direction on the left side; in most cases where the pressing force influenced the condylar position, the changes were smaller in 1500 kgf group than in the 1000 kgf group; in the cases where the type of press influenced the changes in condylar position, the smallest values were found in both groups, sometimes with Getom and other times with conventional water bath press; polymerization time did not significantly affect the dimensional stability of the dentures and the greatest changes occurred in the posterior direction on the left side with Clássico resin.

Une nouvelle méthode de détection sans marquage des interactions biomoléculaires a été développée. Elle est basée sur la conception d’une couche sensible supportée innovante réalisée par la technique de Langmuir‐Blodgett. Cette couche est composée d'un lipide à tête polaire immobilisant un cation métallique divalent capable (i) de chélater une molécule possédant une affinité pour ce type de cation et (ii) de catalyser la réaction de chimiluminescence du luminol. L'intensité du signal chimiluminescent est modulée par la présence de biomolécules fixées en surface de la couche sensible, qui modifient l'environnement immédiat du cation métallique. La variation du signal chimiluminescent (issu de la catalyse par le cation immobilisé) a pu être quantifiée et corrélée à une gamme de concentration d’histamine et d’anticorps. Les potentialités de cette approche ont finalement été exploitées pour développer une puce de PMMA de type macropuce immobilisant la monocouche de lipides. / A new label‐free detection method for biomolecular interactions was developed. It is based on the development of an original sensitive layer performed with the Langmuir‐ Blodgett technique. This layer is composed of a lipid which immobilized a bivalent metallic cation on his polar head, able (i) to chelate a molecule which has an affinity for this cation and (ii) to catalyze the luminol chemiluminescent reaction. The chemiluminescent signal intensity is modulated by the presence of immobilized biomolecules on the sensitive layer surface, which modifies the immediate environmentof the metallic cation. The chemiluminescent signal variation (from catalysis by the metallic cation) has been quantified and correlated to a histamine and antibody concentration range. The potentialities of this approach have finally been employed to achieve a PMMA chip (macroarray type), immobilizing the lipid monolayer.

In the present work, a new generation opaque polymer pigment with multihollow structure was synthesized by suspension polymerization of &ldquo / Water-in-Oil-in-Water&rdquo / (W/O/W) emulsion system. Oil phase was methyl methacrylate and ethylene glycol dimethacrylate monomer mixture at 1:1 weight ratio. The dimension and distribution of hollows inside polymer particles are dependent on the size of water droplets which are encapsulated in micelles. For Water-in-Oil (W/O) assembly, a hydrophobic surfactant and hydrophilic co-surfactant (Span 80-Tween 80) combination with a hydrophilic/lipophilic balance (HLB) value between 5-8 was used. The effects of surfactant and co-surfactant composition on the stability of the W/O emulsion and also on the size of water droplets were studied. In addition, the effect of the ultrasonication on the average size of water droplets was investigated. The hollow size distribution which may possibly give the maximum scattering efficiency was predicted by a mathematical model based on the Mie scattering. The optimum size distribution for W/O emulsion was obtained at the monomer/surfactant/water ratio of 75.5/9.4/15.1 after ultrasonication for 30 seconds at 80 W power. The W/O/W emulsion was prepared by dispersing the W/O emulsion in aqueous solution of hydrophilic Triton X-405. The influence of surfactant concentration and mechanical mixing on monomer droplets was investigated by size measurement and optical microscopy. After stabilizing with 1 %w/w polyvinylpyrrolidone (PVP) solution, the W/O/W emulsion was polymerized at 55 &deg / C for 20 h. The surface morphology of synthesized polymer pigments was analyzed by scanning electron microscopy (SEM) and the inner hollow structure was confirmed by transmission electron microscopy (TEM). The analysis indicated that multihollow opaque polymer pigments were successfully synthesized. The opacity, the L*a*b* color, and the gloss properties of polymer pigments were examined by spectrophotometer and glossmeter. The opacity values were assessed by contrast ratio measurements, and the synthesized polymer pigments provided up to 97.3 % opacity (50 %v/v solid content). In addition, the pigments exhibited low gloss values, and yielded matt films.

Sub-surface modification using a frequency doubled Ti: Sapphire femtosecond (fs) laser at 1kHz repetition rate, producing 100-fs pulse duration at 400nm, is studied in order to fabricate optical components within non-photosensitised polymethyl methacrylate (PMMA). This thesis explores the feasibility of producing three-dimensional optical devices in bulk polymers and polymer optical fibre (POF) using fs laser direct-writing techniques. For effective and optimal structuring, the laser writing parameters and focusing conditions, such as focusing depth, translation speed, and accumulated fluence are investigated by means of photo-modification thresholds; structural changes in dimensions and morphologies; and the magnitude of the refractive index modulation. The highest refractive index change is 3.2x10^(-3) achieved by using a dry (non-immersion) 0.45-NA objective for a single laser scan. Variations in damage threshold with focusing depths are attributed to a combination of material absorption or surface scattering of light due to contamination or surface imperfections, as well as oxygen diffusion and spherical aberration. Distortion of the laser-induced feature size and shape due to spherical aberrations is controlled and compensated by adjusting the laser power near the damage threshold. Permanent refractive index structures with cross-sectional dimensions of 2μm by 0.9μm and 3μm by 1.4μm are demonstrated at depths of 300μm and 500μm below the surface, resulting in the axial/ lateral ratio of 2.2 and 2.1, respectively. A novel phenomenon relevant to effects of translation speed on the fs laser modification is observed for the first time. As translation speeds reduce from 1.2 to 0.6mm/s, the optical damage threshold power decreases by 6μW, whilst other writing conditions remain constant. However, the damage threshold increases by 74μW with decreasing speeds from 0.6 to 0.35mm/s. This significant increase in threshold power enables inscription of refractive index gratings <5μm below the surface, because irradiation on the surface or near the surface initiates ablation rather than refractive index changes, and this forms a limit for writing useful structures. Compensating for this limit by using appropriate writing parameters highlights the potential of fabricating three-dimensional integrated optical circuits in thin (100μm) polymer substrates. Finally, highly localised fabrication of long period gratings into step-index single mode polymer fibres is demonstrated by removing distortion effects due to the curved surface. The distortion is compensated by sandwiching the fibre with two flat PMMA sheets, between which index-matching oil (n=1.5) is injected. This arrangement enables precise laser micro-structuring with flat interfaces and continuous inner material. The first demonstration of a 250-μm-period fibre grating, resulting in attenuation bands in the visible spectral region at 613, 633, 728, 816, 853, 877 and 900nm, is presented.

Este estudo teve o objetivo de avaliar in vitro a influência da alteração dimensional de resinas acrílicas para base de prótese total submetidas a diferentes formas de processamento sobre a posição da cabeça da mandíbula, buscando estabelecer uma possível relação com a etiologia das disfunções crânio-mandibulares nos pacientes usuários desse tipo de prótese. Foram duas etapas: a primeira parte enfocou o papel do tipo de prensa (Getom ou de cozimento) e da força de prensagem para fechamento da mufla (1000 ou 1500 kgf) utilizados no processamento de duas resinas: Lucitone 550 e QC–20 e somente da força de prensagem para a resina Acron MC. Já a segunda parte do estudo teve o intuito de avaliar a influência dos ciclos de polimerização curtos e longos na alteração dimensional de cinco resinas: as mesmas três da primeira parte, além da Clássico e Ondacryl. As próteses superiores acrilizadas foram remontadas em articulador totalmente ajustável, tendo como referência a posição de máxima intercuspidação (MIC). Nessa posição de maior estabilidade oclusal, foi vazado gesso tipo IV no espaço entre as esferas condilares do articulador e as paredes dos estojos condilares. Após a cristalização, esses corpos-de-prova de gesso foram removidos do estojo condilar e suas dimensões medidas e submetidas à análise estatística por meio de um modelo de análise de variância com medidas repetidas que permitiu concluir que houve variações na posição da “cabeça da mandíbula” em 625 das 630 medidas efetuadas; as médias de movimentação condilar variaram de 0,118 (DP = 0,0968) a 1,956 mm (DP = 0,414) e ocorreram principalmente no sentido posterior do lado esquerdo; na maioria dos casos em que a força de prensagem agiu como fator devariação, os deslocamentos obtidos com 1500 kgf foram menores do que aqueles obtidos com 1000 kgf; nos casos em que o tipo de prensa agiu como fator de variação, ora os menores deslocamentos foram obtidos com a prensa de cozimento, ora com a Getom; o ciclo empregado na polimerização não influenciou significativamente na estabilidade dimensional das próteses totais e a única diferença encontrada envolveu a resina Clássico, que levou aos maiores deslocamentos no sentido posterior do lado esquerdo. / The purpose of this study was to evaluate in vitro the influence of dimensional changes in denture base acrylic resins submitted to different processing methods on the position of the mandibular condyle. This was done to establish a relation between these dimensional changes and the etiology of temporomandibular disorders in complete denture wearers. This research was divided into two parts. The first part focused on the type of press (conventional water bath or Getom), on the pressing force for flask closure (1000 or 1500 kgf) when processing Lucitone 550 and QC-20 resins, and on the pressing force when processing Acron MC resin. The purpose of the second part was to evaluate the influence of polymerization time on the dimensional stability of five resins, namely Lucitone 550, QC-20, Acron MC, Clássico and Ondacryl. The polymerized upper prostheses were remounted on a fully adjustable articulator, using the maximal intercuspal position (MIP) as reference. Type IV dental stone was poured into the space between the condylar spheres and the condylar walls. After the dental stone dried, the samples were removed from the articulator and their dimensions were measured and submitted to analysis of variance with repeated measures. The following conclusions were drawn: 625 from 630 measurements done showed changes in the position of the “mandibular condyle” and mean values for condylar movement ranged from 0.118 (SD = 0.0968) to 1.956 mm (SD = 0.414) and occurred mainly in the posterior direction on the left side; in most cases where the pressing force influenced the condylar position, the changes were smaller in 1500 kgf group than in the 1000 kgf group; in the cases where the type of press influenced the changes in condylar position, the smallest values were found in both groups, sometimes with Getom and other times with conventional water bath press; polymerization time did not significantly affect the dimensional stability of the dentures and the greatest changes occurred in the posterior direction on the left side with Clássico resin.

Indentation hardness, H, has been widely used to characterize the mechanical properties of materials for more than a century because of the following advantages of this technique; (1) it requires small sample and (2) the test is non destructive in nature. Recent technological advances helped in the development of instrumented indentation machines which can record the load, P, vs. displacement, h, data continuously during indentation with excellent load and displacement resolutions. From these, H and the elastic modulus, E, of the indented material can be obtained on the basis of the ‘contact area’ of the indentation at the maximum load. The estimation of true contact area becomes difficult during ‘pile-up’ and ‘sink-in’, commonly observed phenomena while indentation of a low and high strain hardened materials. In order for the better understanding of these phenomena it is important to understand the plastic flow distribution under indenters. It is also important for the prediction of elastic-plastic properties from the P-h data. Recently, there have been considerable theoretical and simulation efforts on this front with a combination of dimensional analysis and finite element simulations. One of the important input parameter for the dimensional analysis is the ‘representative strain’ under the indenter, which is a strong function of the indenter geometry. However there is no comprehensive understanding of the representative strain under the indenter despite several studies till date. One objective of the present thesis is to conduct an experimental analysis of the plastic flow during the sharp indentation. The plastic zone size and shape under conical indenters of different apex angles in a pure and annealed copper were examined by employing the subsurface indentation technique to generate the hardness map. From these isostrain contours are constructed joining the data having similar strain values. The following are the key observations. (1) The plastic strain contours are elliptical in nature, spreading more along the direction of the indenter axis than the lateral direction. (2) The magnitude of the plastic strain in the contact region decreases with increasing the indenter angle. (3) The strain decay in the indentation direction follow a power-law relation with the distance. The estimated representative strains under the indenters, computed as the volume average strain within the elastic-plastic boundary, decreases with increasing indenter angle. We also performed finite element simulations to generate plastic flow distribution under the indenter geometries and compared with the experimental results. The results suggest that the experimental and computed average strains match well. However, the plastic strain contours do not, suggesting that further detailed understanding of the elasto-plastic deformation underneath the sharp indenter is essential before reliable estimates of plastic properties from the P-h curves can be made routinely. The second objective of this thesis is to understand plastic flow in amorphous alloys. It is now well established that plastic deformation in metallic glasses is pressure sensitive, owing to the fundamentally different mechanisms vis-à-vis the dislocation mediated plastic flow in crystalline metals alloys. Early work has shown that the pressure sensitivity of amorphous alloys gets reflected as high constraint factor, C (hardness to yield stress ratio), which sometimes exceed 3.0. In this thesis, we study the temperature dependence of pressure sensitive plastic flow in bulk metallic glasses (BMGs) using C as the proxy for the pressure sensitivity. Experiments on three different BMGs show that C increases with temperature hence the pressure sensitivity. In addition we have carried out finite element simulations to generate P-h curves for different levels of pressure sensitivities and match them with the experimental curves that are obtained at different temperatures. Simulations predict that higher pressure sensitivity index values are required to match the experimental curves at high temperatures confirming that the pressure sensitivity increases with increasing temperature. The fundamental mechanisms responsible for the increase in pressure sensitivity are discussed in detail. Finally we pose a question, is the increase in pressure sensitivity with temperature is common to other amorphous materials such as strong amorphous polymers? In order to answer this question we have chosen PMMA, a strong amorphous polymer. In this study also we have taken C as a proxy to index the pressure sensitivity. Indentation stress-strain curves are constructed at different temperature using spherical indentation experiments. The C values corresponding to different temperatures are determined and plotted as a function of temperature. It is found that C increases with temperature implying that the pressure sensitivity of amorphous polymers also increases with temperature. The micro-mechanisms responsible for the increase in pressure sensitivity are sought.