A Implantodontia proporciona tratamentos com alto grau de sucesso clínico nas reabilitações com próteses parafusadas ou cimentadas. A alta taxa de sobrevivência dos implantes, seu sucesso clínico significativo e a grande previsibilidade levaram a uma mudança de paradigma na Implantodontia atual. O uso de implantes, antes utilizados para a reposição de grandes perdas dentárias, é aplicado também para perdas parciais de dentes e até mesmo elementos unitários. Com isso a dificuldade técnica diminuiu ainda mais, consolidando o uso de próteses cimentadas sobre implantes. Desta forma a reversibilidade, que é o principal recurso das próteses parafusadas sobre implantes, não é mais decisiva na escolha do tipo de sistema de retenção. Entretanto, as próteses cimentadas apresentam desvantagens que podem levar a um fracasso do tratamento. Dentre elas o acúmulo do excesso de cimento, que pode levar a uma inflamação do tecido periimplantar com a possível perda do implante. Existem na literatura técnicas de cimentação que visam à redução do agente cimentante em excesso. Outro fator estudado é a influência da rugosidade da superfície do munhão protético na resistência ao arrancamento do elemento protético. O objetivo do estudo foi realizar uma análise da resistência ao arrancamento de coroas cimentadas sobre munhões protéticos polidos e asperizados, utilizando uma técnica experimental de cimentação. Foram confeccionados quarenta corpos de prova e formaram-se quatro grupos de estudo, de acordo com a técnica de cimentação utilizada (técnica controle e técnica experimental) e a rugosidade das paredes do munhão protético (polido e asperizado). As coroas foram cimentadas com o cimento de Fosfato de Zinco. A análise da resistência ao arrancamento foi realizada, após a ciclagem térmica dos quarenta corpos de prova, utilizando uma máquina de ensaio universal. Na análise das técnicas de cimentação pôde-se observar que não ocorreram diferenças estatisticamente significativas entre os grupos, com valores médios de resistência ao arrancamento de 157,83 N ± 22,16 N para o grupo técnica controle-superfície polida e 159,95 N ± 46,40 N para o grupo técnica experimental-superfície polida. A análise dos dados nos grupos técnica controle-superfície asperizada (626,23 N ± 34,80 N) e técnica experimental-superfície asperizada (642,62 N ± 94,00 N), também não indicaram diferenças significativas. Na análise dos grupos, comparando a rugosidade da superfície, pôde-se observar diferenças significativas, com valores de 157,83 N ± 22,16 N para o grupo técnica controle-superfície polida e 626,23 N ± 34,80 N para o grupo técnica controle-superfície asperizada. O mesmo foi observado no grupo técnica experimental-superfície polida com valores de 159,95 N ± 46,40 N e 642,62 N ± 94,00 N para o grupo técnica experimental-superfície asperizada. Conclui-se que, nas condições utilizadas neste estudo, a técnica de cimentação experimental não apresentou diferenças significativas com a técnica controle, em relação à resistência ao arrancamento, nas duas superfícies (polida e asperizada) utilizadas no estudo. A asperização das paredes axiais dos munhões levou a um aumento significativo da resistência ao arrancamento nas duas técnicas de cimentação estudadas. / The Implantology provides treatments with high clinical success rate in screw or cement retained rehabilitations. The high survival rate of the implants, its significant clinical success, and the great predictability led to a paradigm shift in current Implantology. The dental implant, previously used for replacing large teeth losses, is also applied to partial dental losses and even single tooth replacement. Therefore, technical difficulties have decreased even more, which consolidated the use of cement retained implant prosthesis. Thus the retrievability, which is the main resource of screw retained implant prostheses, is not the crucial point in the prosthesis retention selection. However, cement retained prostheses have disadvantages that can lead to treatment failure. One can mention the presence of residual excess cement, which may lead to an inflammation of the peri-implant tissue, or even a possible implant loss. There are in the literature cementation techniques that reduce the luting agent excess. Another studied factor is the influence of the prosthetic abutment surface roughness in the prosthetic element tensile strength. The aim of the study was to analyze the tensile strength of prosthetic crowns cemented on standard machined and sand blasted abutments using an experimental cementation technique. Forty specimens were fabricated and four experimental groups were formed, according to the cementation technique (control technique and experimental technique) and the prosthetic abutment roughness (standard machined and sand blasted). The crowns were cemented with zinc phosphate cement. The tensile strength analysis was performed, after the forty specimens thermal cycling, using an universal testing machine. In the cementation techniques analysis it was observed that there were no statistically significant differences between the groups, with mean tensile strength values of 157.83N±22.16N for the control technique- standard machined surface and 159.95N±46.40N for the experimental technique-standard machined surface. The data analysis of control technique-sand blasted surface group (626.23 N±34.80N) and experimental technique-sand blasted surface group (642.62 N±94.00N) also indicated no significant differences. In the group analysis, comparing the surface roughness, it was observed significant differences, with values of 157.83N±22.16N for the control technique-standard machined surface group and 626.23N±34.80N for the control technique-sand blasted surface group. The same was observed in the experimental technique-standard machined surface group with 159.95N±46.40N values and 642.62N±94.00N for the experimental technique-sand blasted surface group. It can be concluded that, under the study conditions, the experimental cementation technique showed no significant differences with the control technique, regarding tensile strength, in the two surfaces (standard machined and sand blasted) used in the study. The prosthetic abutments roughening led to a significant increase in tensile strength on the two studied cementation techniques.

Orientador: Luana Marotta Reis de Vasconcellos / Coorientadora: Ivone Regina de Oliveira / Banca: Luciane Dias de Oliveira / Banca: Naira Correia Cusma Pelógia / Resumo: O aluminato de cálcio (CAC) como biomaterial tem sido avaliado em relação as suas propriedades físicas, mecânicas e de biocompatibilidade, sendo que suas características únicas de endurecimento e microestrutura, o tornam um biomaterial de destaque. Estudos relataram aplicação destes cimentos na ortopedia visando neoformação óssea devido a sua composição e coeficiente de expansão térmica semelhante ao osso humano. O objetivo neste estudo foi avaliar composições de blendas à base de cimento de aluminato de cálcio homogêneo (CACH) como substitutos em defeitos ósseos. Cinco composições de blendas (alumina, fosfato tricálcico, hidroxiapatita, quitosana, zircônia), além do cimento base CACH e de polimetilmetacrilato (PMMA), totalizando 07 grupos (n=5), foram avaliados quanto à neoformação óssea e formação de biofilme. Foi realizado um defeito ósseo monocortical de 3.0 mm nos fêmures direitos de 35 ratos Wistar, que foram preenchidos aleatoriamente com os materiais acima citados, sendo o grupo de PMMA utilizado como controle. Todos os animais foram eutanasiados após 30 dias a cirurgia. Posteriormente, foi realizada análise por microtomografia computadorizada para verificação da neoformação óssea na interface osso-biomaterial. Para avaliar a formação de biofilmes microbianos monotípicos, discos padronizados com 13,0 x 2,0 mm (n=6) dos 07 cimentos foram confeccionados. Cepas de referência de Staphylococcus aureus, Streptococcus mutans e Pseudomonas aeruginosa foram cultivadas sobre as... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Calcium aluminate as biomaterial has been evaluated for its physical, mechanical and biocompatibility properties. Calcium aluminate based materials exhibit, due to their unique hardening and microstructure characteristics, a great potential as a biomaterial. Studies have reported the application of these cements in orthopedics aimed at bone neoformation due to its composition and coefficient of thermal expansion similar to human bone. Thus, the aim of this study is to evaluate compositions of calcium aluminate cement based blends as substitutes for bone defects. Five compositions of blends (alumina, tricalcium phosphate, hydroxyapatite, chitosan, zirconia), in addition to the base cement consisting of homogeneous calcium aluminate (CACH) and polymethylmethacrylate (PMMA) cement are being evaluated for bone repair and biofilm formation. A monocortical bone defect of 3.0 mm was performed in the right femurs of 35 Wistar rats, these were randomly filled with the already mentioned materials, and the PMMA group was used as control, totaling 07 study groups (n=5). All animals were euthanized within four weeks. Subsequently, a computerized microtomography analysis was performed to verify bone repair. To evaluate the formation of monotypic microbial biofilms, standardized discs with 13.0 x 2.0 mm (n=6) of the seven types of cements evaluated were prepared. Reference strains of Staphylococcus aureus, Streptococcus mutans and Pseudomonas aeruginosa were cultured on the samples and subs... (Complete abstract click electronic access below) / Mestre

[Truncated abstract] Characterising the behaviour of calcareous sediments that possess some degree of bonding between their constituents has attracted worldwide research interest in recent years. Although many recent studies have made significant contributions in delineating the behaviour of these sediments, there is still paucity of information particularly on the cyclic behaviour of cemented calcareous soils. This thesis describes in detail the characteristic features of cemented calcareous soils and proposes methods for characterising their cyclic behaviour. Two different calcareous soils Goodwyn (GW) and Ledge Point (LP) soils representing extreme depositional environments were examined in this study. Artificially cemented sample were created using the CIPS (Calcite Insitu Precipitation Systems) technique, considering its superiority over other most commonly available cementation techniques in replicating the natural pattern of cementation, and the behaviour of natural calcarenite under monotonic loading conditions. The experimental program involved triaxial testing of both uncemented and calcite-cemented calcareous soils under different loading conditions, i.e. isotropic compression tests to high-pressure (16 MPa), monotonic shearing tests, undrained cyclic shearing tests and undrained monotonic post-cyclic shearing tests. Significant emphasis has been placed on the cyclic behaviour of these soils. Internal submersible LDVTs were used for the accurate and continuous measurement of strain down to about 10-5

Includes bibliographical references (leaves 153-157). Petrographic image analysis proved particularly useful in determining the parameters for statistical analysis for the simple mineralogies displayed in the samples from the Hutton Sandstone. Concentrates on establishing techniques for statistical study of data collected by PIA to subdivide the framework grains from the porosity or cement.

In this study, various techniques of hydrometallurgy and ultrasound-assisted solvent extraction were used to recover the platinum group metals (PGM¡¦s) from a composite sample of honeycomb-type autocatalysts. After they were removed from the converter casings, the autocatalyst substrates were first crushed and then ground by a ball mill. The recovery procedures employed are shown as follows: (1) dissolve PGM¡¦s from ground spent autocatalyst by aqua regia leaching; (2) separate PGM¡¦s from base metals in the aqua regia leachate by metal cementation using zinc powder so that PGM¡¦s can be precipitated out; (3) the PGM¡¦s precipitate was first dissolved by aqua regia, then proceed to remove nitrate and hydrochloride within. The residue was further dissolved in hydrochloride acid as a preparation step for solvent extraction; (4) the PGM¡¦s pregnant solution of hydrochloride acid was treated by solvent extraction and stripping to separate and purify each component of PGM¡¦s. Effects of ultrasound agitation on the efficiency of solvent extraction was also evaluated in this work. Results of aqua regia leaching experiments have shown that the quantity of dissolved PGM¡¦s increased as the solid-to-liquid ratio decreased. The maximum dissolved quantity of PGM¡¦s could be obtained by a 3-hr leaching time. At this stage, the PGM¡¦s recoveries are 80-90% for platinum and rhodium and greater than 99% for palladium. The result of a preliminary test has indicated that acetic acid can not effectively separate the PGM¡¦s and base metals. Thus, the method of cementation by zinc powder was employed to separate PGM¡¦s from base metals. Before cementation, the aqua regia leachate was diluted and pH-adjusted to greater than 2. In so doing, an almost complete cementation (>99%) could be obtained by the least quantity of zinc powder. In addition, the base metals occurred with the PGM¡¦s precipitate have been minimized except lead and zinc. While palladium was extracted by di-n-octyl sulfide (DOS), ultrasound assistance has rendered a complete extraction within a few minutes. At this stage, the extraction efficiency was found to be independent of the HCl concentration. It was found that platinum and rhodium were not extracted by DOS. When platinum was extracted by tri-n-octylamine (TOA) and assisted by ultrasound, rhodium will be extracted at the HCl concentration higher than 4M. Thus, TOA is not an effective chemical for selective extraction of platinum. TOA was then replaced by tributyl phosphate (TBP). Experimental results have indicated that the extraction of platinum using TBP was affected by the HCl concentration. The best result was obtained when the HCl concentration was 5M. Extraction by TBP was found to be fast. It took only 20-30 seconds to reach the equilibrium even with no ultrasound assistance. But multi-stage extractions are generally required to extract platinum completely. Rhodium was found to be not extracted by TBP. After palladium and platinum were extracted, only rhodium was remained in the reffinate. In summary, solvent extraction using DOS and TBP has made it possible to separate palladium, platinum, and rhodium effectively. In the palladium stripping solution almost no base metals was determined. However, zinc and lead were found in the platinum stripping solution and the rhodium-containing raffinate. These base metals should be removed to achieve a better purity for each precious metal. The TCLP (i.e., a leaching test for toxicity) result of the autocatalyst substrate after aqua regia leaching has found to be non-hazardous. However, several streams of wastewater and acid gas generated in the recovery process should be properly managed to avoid the secondary pollution.

Evaluation of the effect of particle cementation on the stiffness of uniform sand was carried out by measuring compression wave velocities (VP) and shear wave velocities (VS) on both clean and artificially cemented specimens. Piezoelectric transducers (PT) were used to perform the majority of the measurements. Shear wave velocity (VS), shear moduli (G) and material damping ratio (D) of clean and artificially cemented specimens were also determined using resonant column (RC) testing. Linear (shearing strains ≤ 0.001%) and nonlinear (shearing strains > 0.001%) behavior of the specimens were evaluated in the resonant column tests. The sand selected for this investigation is commonly known as Hickory sand, from the Hickory formation, western Llano uplift, Texas. This material was selected for its grain geometry and gradation; it consists of uniformly graded sand with rounded particles. The sand specimens were artificially cemented with a solution of hydrated sodium silicate and water. Sodium silicate is an alkaline compound obtained from the reaction of sodium hydroxide and silica. All artificially cemented specimens and uncemented hickory sand specimens were formed by pluviation through air. The microstructure of the specimens was visually assessed with images obtained from both optical and scanning electron (SEM) microscopes. These images confirmed that the procedure used to form artificially cemented specimens provides cementation around the contacts while some grain-to-grain contact appears to be preserved. Seismic and drained strength measurements on Hickory sand specimens were obtained from different cement concentrations and compared with results from clean sand specimens. Among the findings of this investigation are: (1) the procedure to artificially cement sand specimens in the laboratory was successful, (2) the slopes (nP and nS) obtained from the relationships between compression and shear wave velocities with effective isotropic confining pressure in log-log scale decrease as the cement content increases, and (3) as increasing amounts of cement are added to the sand particles, the nonlinearity of the specimens increases up to certain amount of cement, after which the nonlinearity of the specimen decreases and tends towards rock-like behavior. / text

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The aim of this thesis is to study water saturation models available in the literature and to apply a proper one to a real field case. Archie equation is the most well-known water saturation model. However, it is formulated on some assumptions and is applicable to only clean sands. Archie equation cannot be used for shaly formation. There are many shaly water saturation models that account for shale effect for water saturation estimation. In this study, 3 wells, namely Well-01, Well-02 and Well-03 are studied. These wells lie in a fractured carbonate reservoir located in Southeastern part of Turkey. From well log recordings, the production formation is seen almost clean. In other words, the shale amount of the formation is so small that it can be neglected. Thus, to calculate the water saturation in those wells, the well-known Archie water saturation equation is used. Since the formation is fractured carbonate, the cementation factor (m ) and saturation exponent (n ) of conventional value of 2 each cannot be used for the water saturation calculation. Instead, these parameters are obtained from generalized crossplot of log-derived porosity and resistivity technique. Finally, each well is divided into zones using porosity data. Zonation is conducted based on statistical method, ANOVA (analysis of variance). Well-01 and Well-02 are both divided into two zones. On the other hand, the statistical method was initially divided Well-03 into three zones. However, Well-03 is better described as a whole zone, depending on the geological analysis and engineering judgment. After the zonation, the zones are correlated from well to well. The water saturations in significantly correlated zones are examined. Also, using the same statistical method, the water saturation zones are identified. However, these zones do not coincide with the porosity zones. This difference is attributed to pore size distribution and wettability which affect saturation distribution.

[Truncated abstract] Characterising the behaviour of calcareous sediments that possess some degree of bonding between their constituents has attracted worldwide research interest in recent years. Although many recent studies have made significant contributions in delineating the behaviour of these sediments, there is still paucity of information particularly on the cyclic behaviour of cemented calcareous soils. This thesis describes in detail the characteristic features of cemented calcareous soils and proposes methods for characterising their cyclic behaviour. Two different calcareous soils Goodwyn (GW) and Ledge Point (LP) soils representing extreme depositional environments were examined in this study. Artificially cemented sample were created using the CIPS (Calcite Insitu Precipitation Systems) technique, considering its superiority over other most commonly available cementation techniques in replicating the natural pattern of cementation, and the behaviour of natural calcarenite under monotonic loading conditions. The experimental program involved triaxial testing of both uncemented and calcite-cemented calcareous soils under different loading conditions, i.e. isotropic compression tests to high-pressure (16 MPa), monotonic shearing tests, undrained cyclic shearing tests and undrained monotonic post-cyclic shearing tests. Significant emphasis has been placed on the cyclic behaviour of these soils. Internal submersible LDVTs were used for the accurate and continuous measurement of strain down to about 10-5

Thesis (Ph.D.)--Memorial University of Newfoundland. / Typescript. Restricted until November 1996. Bibliography: leaves 253-274. Also available online.