Orientador: Lídia Parsekian Martins / Banca: Gandini Junior, Luiz Gonzaga / Banca: Vaz, Luis Geraldo / Banca: José Tarcísio Lima Ferreira / Resumo: Determinar in vivo e in vitro o efeito do tempo sobre as propriedades mecânicas de molas helicoidais fechadas de níquel-titânio. Métodos: Três artigos científicos foram redigidos e utilizados para a avaliação dos propósitos apresentados. Resultados: No artigo 1 (in vivo), o tempo e a ativação influenciaram significantemente a taxa de superelasticidade (SE) e a força média do platô clínico superelástico (FP) quando o perfil total das molas foi avaliado (p<0,001). Foi detectada uma interação significante entre tempo e ativação nas variáveis taxa de SE (p<0,001) e FP (p=0,013). No artigo 2 (in vitro), o tempo influenciou significantemente a FP e a taxa de SE quando o perfil total das molas foi avaliado (p<0,001). A ativação influenciou significantemente a taxa de SE (p<0,001), não influenciando a FP (p=0,218). Foi detectada uma interação significante entre tempo e ativação na variável taxa de SE (p=0,020), o que não ocorreu na variável FP (p=1,00). No artigo 3 (in vivo), o uso clínico e a ativação influenciaram significantemente a deformação das molas (p<0,001). Foi detectada interação significante entre os fatores tempo e ativação na variável deformação (p<0,001). Conclusões: Após 6 meses de uso clínico, as molas apresentaram diminuições significantes nas taxas de SE em até 52%, nas FP em até 88% e aumento da deformação em até 1,26 mm. Laboratorialmente, os efeitos nas FP foram maiores nos dois primeiros meses e depois se estabilizaram, já as taxas de SE não apresentaram diferenças nos dois meses iniciais, aumentando nos seguintes. Desta forma, a reutilização das molas avaliadas neste estudo seria desaconselhada. / Abstract: Determine in vivo and in vitro the time effect on the mechanical properties of nickel-titanium closed coil springs. Materials and Methods: Three research papers were written and analyzed for the evaluation of the aims presented. Results: In first paper (in vivo), time and the activation significantly affected superelasticity (SE) rate and the average force of the superelastic clinical plateau (FP) when the total profiles of the springs were evaluated (p<0,001). A significant interaction between time and activation was detected for the SE rate (p<0,001) and FP (p=0,013) variables. In second paper (in vitro), time significantly affected FP and SE rate when the total profiles of the springs were evaluated (p<0,001). Activation significantly affected the SE rate (p<0,001), but not the FP (p=0,218). A significant interaction between time and activation was detected for the SE rate variable (p=0,020), but not for the FP variable (p=1,00). In third paper (in vivo), the clinical use and activation significantly affected the springs deformation (p<0,001). A significant interaction between time and activation was detected for the deformation variable (p<0,001). Conclusions: After six months of active clinical use, the analyzed springs presented a significant decay on their SE rates up to 52%, on FP up to 88% and increase in deformation up to 1,26 mm. In the in vitro study, the effects on FP were higher in the first two months and then stabilized, and the SE rates didn't differ in the two initials months, increasing in the following. This way, reuse of the springs evaluated in this study would be inadvisable. / Doutor

Orientador: Carlos Alberto de Souza Costa / Coorientador: Pedro Paulo Chaves de Souza / Banca: Raphael Freitas de Souza / Banca: Francisco de Assis Mollo Junior / Resumo: A osseointegração, requisito indispensável para o sucesso dos implantes dentários, é um processo lento, caracterizado, sequencialmente, pelas etapas de adesão, diferenciação e proliferação celular, bem como pela aposição e mineralização da matriz óssea depositada por osteoblastos. Acelerar o processo de osseointegração significa reduzir o tempo de espera para a aplicação segura de uma carga funcional sobre os implantes de titânio (Ti). Sabe-se que vários fatores, tal como a topografia da superfície do Ti, influenciam diretamente o processo de osseointegração. Assim, desde que foi demonstrado que alguns padrões específicos de superfície do Ti são capazes de bio-estimular osteoblastos, favorecendo e acelerando a osseointegração, diversas técnicas de baixo custo, rápida execução e altamente reproduzíveis, tem sido propostas para tratar a superfície dos implantes. Desta maneira, o objetivo da presente pesquisa foi avaliar a capacidade de superfícies de Ti, modificadas com laser pulsado de alta potência (L) ou usinadas (U), de estimular a diferenciação e maturação de células obtidas de calvária de camundongos cultivadas sobre elas. Para isto, foram realizados ensaios laboratoriais para determinar a atividade mineralizadora das células (coloração com vermelho de alizarina e fosfatase alcalina), o metabolismo (MTT assay) e morfologia celular (MEV). A fim de melhor caracterizar a diferenciação de osteoblastos, foi realizada a reação de polimerização em cadeia (PCR) quantitativa em tempo real para analisar a expressão, pelas células cultivadas sobre as superfícies de Ti, de genes que codificam os fatores de transcrição Runx2 e Sp7 e proteínas específicas da matriz extracelular mineralizada... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The osseointegration, which plays a fundamental role in the dental implantation success, is characterized by cell adhesion, differentiation, proliferation as well as deposition and mineralization of of bone matriz by osteoblasts. To make the osseointegration process faster means reducing the period to apply a safe functional stress on the titanium (Ti) implants. A number of factors, such as the topographical surface of Ti enhances the osseointegration process. Different Ti surface treatments capable of bio-estimulating osteoblasts to accelerate the osseointegration have been evaluated. Current studies have shown that osseointegration of Ti devices is enhanced by surface roughness. In this way, the aim of the present investigation was to assess the capacity of Ti surfaces irradiated with high potency laser (L) or polished (U) to stimulate the differentiation and maturation of cells obtained from calvarian bone of mouse. Then, laboratorial protocols to evaluate the mineralizing cell activity (alizarin red assay), cell metabolism (MTT assay) as well as the morphology (SEM) of cells cultured on the Ti surfaces were carried out. To better characterize the osteoblast differentiation, the real time qPCR for expression of genes that code to the transcription factors Runx2 and Sp7 were performed. Additionaly, this protocol was also used to assess specific proteins of extracellular matrix (Spp1, Alpl, e Col1a1). The numeric data were subjected to statistical analysis. Our data demonstrated that the Ti surface L improved the osteoblast maturation capacity of calvarial osteoblasts grown over this surface. Scanning electron microscopy (SEM) revealed spheres and protrusions created by laser treatment. Laser profilometry showed a disordered surface with micrometric and/to nanometric scales features (Ra = 10.57μm). When compared to polished... (Complete abstract click electronic access below) / Mestre

Orientador: Mauro Antonio de Arruda Nobilo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-06T16:55:24Z (GMT). No. of bitstreams: 1 Baboni_ClaudiaRahal_M.pdf: 1352784 bytes, checksum: a34de1b55cf421a9f8fc3a659dac35bc (MD5) Previous issue date: 2006 / Resumo: O presente estudo avaliou através de análise fotoelástica a passividade de infra-estrutura fundida em titânio, antes e após a aplicação de eletroerosão. Foi confeccionada uma matriz metálica simulando uma mandíbula humana onde foram implantados cinco análogos de pilares Micro-Unit (Conect ¿ AR, Conexão Sistemas de Prótese). A partir de um molde de silicone de duplicação foi confeccionado um modelo em resina fotoelástica com cinco implantes osseointegrados incorporados e pilares Micro-Unit. Sobre a matriz metálica foram realizados os procedimentos de enceramento de seis estruturas metálicas, inclusão, fundição em titânio comercialmente puro e acabamento das mesmas. Em todas as amostras foi realizada a soldagem a laser de cilindros de titânio e posterior avaliação em microscópio mensurador com precisão de 0,0005mm. A estrutura com melhor adaptação foi selecionada e submetida a análise fotoelástica conduzida pelo aperto dos parafusos em três seqüências preconizadas (1,2,3,4,5/ 5,4,3,2,1/ 3,2,4,1,5). A mesma estrutura foi submetida ao refinamento de adaptação pela técnica da eletroerosão (EDM) e subseqüente análise fotoelástica. Os resultados mostraram menor formação e intensidade das franjas fotoelásticas após o refinamento por eletroerosão em todas as seqüências de aperto dos parafusos. A seqüência (3,2,4,1,5), mostrou melhores resultados e a maior quantidade de tensões foram observadas ao redor dos implantes mediais em todas as seqüências em ambos os grupos. Pode-se concluir que o processo de eletroerosão melhora a adaptação marginal da infra-estrutura sendo eficaz para o alcance do assentamento passivo / Abstract: Through the photoelastic analysis, the present study evaluated the passive fit of titanium cast laser welding frameworks before and after the spark erosion procedure (Electrical Discharge Machining). A metallic matrix was made simulating a human mandible and, on top of it, 5 Micro-Unit abutment analogs had been implanted. A impression material mold was made and from it a photoelastic matrix had been created with 5 incorporated osseointegrated implants (Conect AR ¿ Conexão Sistemas de Prótese, São Paulo, Brazil) and with Micro-Unit abutment. Based on the metallic model, the following procedures were tested: closing 6 frameworks, embedding, casting in pure commercial titanium and finishing on them. A laser welding followed by an evaluation with microscope measurement with precision of 0.0005mm has been applied in all samples. The frameworks with best results had been selected and submitted to a photoelastic analysis followed by pressing the screws in 3 predisposed sequences (1,2,3,4,5/ 5,4,3,2,1/3,2,4,1,5). The same framework has been submitted to the adaptation refinement by spark erosion technique followed by the photoelastic analysis. The results demonstrated less photoelastics fringes in quantity and intensity after the spark erosion application in all screw pressing sequences. The sequence (3,2,4,1,5) achieved better results in both groups. A higher quantity of fringes had been observed around the medium implants in all sequences and in both groups. We can conclude that the titanium cast laser welded frameworks processes added to an spark erosion procedure improves significantly the marginal frameworks adaptation, which is effective for the passive fit of it / Mestrado / Protese Dental / Mestre em Clínica Odontológica

Orientadores: Marcelo Ferraz Mesquita, Juliana Maria Costa Nuñez-Pantoja / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-24T18:20:55Z (GMT). No. of bitstreams: 1 Zen_BrunoMassucato_M.pdf: 1546130 bytes, checksum: fc57f5ffe80d1ffb71f0ca849815f9ad (MD5) Previous issue date: 2014 / Resumo: O assentamento passivo de infraestrututuras protéticas é considerado essencial para a longevidade do tratamento reabilitador sobre implantes dentários. O objetivo neste estudo foi analisar o desajuste vertical decorrente da fundição em Ti cp de barras de Overdentures; avaliar as tensões induzidas e torque de afrouxamento do parafuso protético, em infraestruturas protéticas passivas e não-passivas. Foram fundidas vinte barras em Ti cp, retidas por dois implantes, utilizando-se dois tipos de pilares (UCLA e MP), sobre as quais foram avaliadas, utilizando-se microscópio óptico, as desadaptações marginais inerentes à fundição. A quantificação do desajuste seguiu o protocolo do teste do parafuso único (32 Ncm e 10 Ncm). Foram confeccionados 20 index(10 para cada pilar).Os desajustes foram padronizados com a interposição de um anel metálico de 200 µm entre o análogodo pilar A e o cilindro protético. Nesses index, foram avaliados os níveis de desajuste marginal, seguindo o mesmo protocolo utilizado para análise dos desajustes pós-fundição. As aferições das tensões foram realizadas através de extensômetros elétricos fixados aos análogos, após o retorque dos parafusos protéticos. A força necessária para o torque de afrouxamento dos parafusos protéticos de titânio foi medida com torquímetro digital de precisão de 0,1 Ncm. Os resultados foram analisados estatisticamente (ANOVA, teste t (? = 0,05), Correlação de Pearson). Foi encontrada diferença estatística entre os grupos passivos e não-passivos para: porcentagem do torque de afrouxamento (UCLA, p = 0,0087; MP, p = <0,0001); tensão média (MP, p = 0,0192) independente da adaptação e entre as barras desadaptadas (p = 0,0001) qualquer que fosse o pilar utilizado. A correlação de Pearson indicou correlação positiva entre: desajuste x destorque (UCLA, r = 0,6503 e p = 0,0019; MP, r =0,7338 e p = 0,0002);torque de afrouxamento x tensão para UCLA ( r = 0,5373 e p = 0,0145); desajuste e tensão (r = 0,5678 e p = 0,0001). Pode-se concluir que os parafusos protéticos apresentam maior afrouxamento em próteses não passivas. Infraestruturas protéticas desadaptadas induzem maiores níveis de tensão e desajuste vertical quando comparadas com infraestruturas passivas. Pilares UCLAs mostraram os melhores resultados próteses não passivas.Tensão, desajuste vertical e torque de afrouxamento foram fatores correlacionados / Abstract: The passive fit of prosthetic frameworks is considered essential to the longevity of rehabilitation treatment on dental implants.The aim of this study was to analyze vertical misfit of overdentures bars casted in Ti cp; measure the strain, vertical misfit and loosening torque of prosthetic screws, in passive and non-passive frameworks. Twenty bars were casted with Ti cp, retained by two implants, using two types of abutments (UCLA and MA), on which they were evaluated using an optical microscope comparison, the marginal misfit inherent of casting. The misfit quantification followed the protocol of single-screw test (32 Ncm and 10 Ncm). Twenty index were manufactured (10 for each abutment). The misfit were standardized by interposing a metal ring of 200 µm between pilar A abutment and prosthetic cylinder. In the index were evaluated the misfit level, following the same protocol used for measure after casting, and the loosening torque. The measurements of strain were made by strain gauges fixed in the replicas, after retorque of prosthetic screws. The loosening torque of prosthetic screws was evaluated using a digital torque meter with 0.1 Ncm of precision. The results were statistically analyzed (ANOVA, test t, Pearson correlation). Statistical difference was found between passive and non-passive groups: for vertical misfit (p< 0.0001 for both abutments); percentage of loosening torque (UCLA, p = 0.0087; MA, p = <0.0001); mean strain (MA, p = 0.0192) independently of passivity and between the bars desadapted (p = 0.0001) regardless the abutment used. Pearson's correlation (? = 0.05) indicated a positive correlation between: misfit x loosening torque (UCLA, r = 0.6503 e p = 0.0019; MA, r =0.7338 e p = 0.0002); loosening torque x strain for UCLA ( r = 0.5373 e p = 0.0145); misfit x strain (r = 0.5678 e p = 0.0001). It can be concluded: the prosthetic screws have a higher tendency for loosening in ill-fitting prostheses; non-passive frameworks induce higher levels of strain and vertical misfit compared with passive frameworks; UCLA abutments showed the better results in non-passive prostheses; strain, vertical misfit and loosening torque were correlated factors / Mestrado / Protese Dental / Mestre em Clínica Odontológica

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Phase transformations have been studied in titanium-rich binary alloys with iron and nickel. Particular attention has been given to the formation and decomposition of metastable phases in powder specimens. All alloys were prepared by a levitation melting technique and precautions were taken throughout the experimental work to minimize contamination. In the Ti=Fe system martensitic α'is produced when powder specimens containing up to 12% iron are quenched-from 1000⁰C. The hardness of hypoeutectoid specimens increases with iron content to a maximum at 12% Fe The eutectoid temperature for the system has been reassessed at 625 ± 10⁰C. During tempering the decomposition rates of retained β phase are slow but the appearance of FeTi is accompanied by an increase in slope of the β /log time curve. The hardness of tempered alloys increases as the FeTi content increases. Contrary to the results of other Investigators Ti₂Fe has been found to exist in sensibly oxygen-free -alloys. This phase forms at 1000⁰C in crushed powder specimens but decomposes below the euteetoid temperature. In the Ti-Ni system the .constitution of quenched alloys is found to depend on both composition and cooling rate from the β range. An 'inverse stabilization' of the β phase has been observed and the 100% β phase exhibits two types of substructures which have been attributed to polygonization and stacking faults. The hardness of quenched alloys is higher for higher nickel contents and for faster cooling rates. Orientation relationships were observed between β and α¹ and a shear mechanism suggested by Burgers for Zr is proposed for this system. Decomposition studies have shown that α¹ breaks down by a growth-controlled process similar to that described by Johnson and Mehl. An activation energy of 84000 cal/mole has been determined and a model has been proposed which involves planar interfaces of Ti₂Ni advancing into α regions to produce a Widmanstatten-type microstructure. The self-diffusion of titanium is believed to be the growth -controlling factor. Hardness values decrease with longer tempering times and higher tempering temperature. Retained β decomposes on tempering by a two stage process: β →α" →α + Ti₂Ni X-ray diffraction data indicate that α" has the same crystal structure as α'. The β-α" reaction appears to be a diffusion process although reaction curves are similar to those observed for isothermal martensite formation in steels. During the first stage of the reaction (β-α") the hardnesses and x-ray diffraction line breadths initially show a sharp increase, probably due to coherence between β and α¹¹ The reaction α" →α + Ti₂Ni proceeds In a similar way to the decomposition of α ; but with a shorter induction period for Ti2Ni formation. Further, the. activation energy for the α" →α + Ti₂Ni growth process (71000 cal/mole) is lower than that for α' decomposition. These observations suggest that Ni-rich regions exist in the α" phase and accelerate the nucleation and growth processes. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Zinc-titanium alloys (0.07-0.6 wt.%Ti.) in the form of compacted powder and chill castings have been extruded at temperatures between 150°C and 350°C. The mechanical properties of these alloys have been studied as a function of temperature, strain rate, grain size and intermetallic (Zn₁₅Ti) distribution. Due to a high value of "k" in the Hall-Petch relationship, maximum strengthening is obtained by a reduction in grain size. However because of an increasing amount of grain boundary shear, this potential is not realized. The operation of dynamic recovery mechanisms at 20°C and higher also results in limitations upon the development of high strength. The use of powder metallurgical techniques gives rise to the formation of intermetallic distributions which inhibit these processes and results in high strength (>60,000 p.s.i.) and low strain rate sensitivity (m ∼ 0.02). The mechanical properties are not a function of initial powder size. The properties obtained using chill castings do not reach these levels due to the difficulty associated with forming a fine second phase on solidification. Such a distribution is required to obtain a small stable grain size during subsequent extrusion. To satisfy compatibility requirements deformation modes other than the two supplied by basal slip must be invoked. High strengths are observed when grain boundary shear and migration are inhibited by the distribution of the second phase or by orientation effects. Under such conditions, non basal slip and basal slip are the operative deformation mechanisms. Significantly lower strengths result if grain boundary shear and basal slip satisfy the conditions necessary for ductile behaviour. The strain rate sensitivity parameter at 20°C lies in the range 0.02-0.07. Varying amounts of grain boundary shear occur, nevertheless deformation is slip controlled. Increased strain rate sensitivities are observed at high temperatures, but failure by cavitation limits ductility. The strain rate sensitivity is not a function of titanium concentration. Under constant fabrication conditions the strength generally increases with increased Zn₁₅Ti content. The thermal stability of the intermetallic distribution prescribes the fabrication conditions which must be used to develop high strength, and the temperature to which the mechanical properties can be retained. The high strength microstructures appear to be stable up to at least 150°C for short periods of time. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Plasma electrolytic oxidation is used to prepare corrosion- and wear-resistant coatings on light metals. The extensive literature reports on coatings formed under a wide range of different electrical regimes and in diverse electrolyte compositions. However, little work is available that investigates systematically PEO of titanium under a range of electrical variables in a particular electrolyte. In the present work, coatings are formed in a silicate electrolyte under a range of current densities, duty cycles and rates of positive to negative current density. The coatings were found to contain anatase, rutile and amorphous silicate-rich material, with comparatively minor influences of the PEO parameters. Further, coatings were limited in thickness to 40 μm due to a decrease in voltage and intensity of sparks at longer treatment times. The coatings were relatively soft with poor wear- and corrosion- resistances, and a high coefficient of friction although the last could be reduced by incorporation of PTFE particles into the coating. The study also investigates coatings formed in aluminate-phosphate based electrolytes, which generated wear-resistant and corrosion-resistant coatings of increased hardness. A focus was on the use of high-resolution electron microscopy, which has not been reported previously, to determine the details of the coating composition and structure. The findings revealed the distribution of coating species, showing an aluminum-rich outer layer and a titanium-rich inner layer, with phosphorus enriched in a band near the base of the coating. However, the coatings also revealed highly localized variations in composition within their noanocrystalline structures, due to the melting and rapid solidification of the coating material. The study also examined the role of electrolyte purity on the formation and properties of the coatings, which has not been examined elsewhere. Importantly chlorine species from the lower purity electrolyte were shown to enrich near the substrate, resulting in a cracked interfacial layer and reduced adhesion of the coating. Such observations may account for reports of poor coating adhesion in the literature. Further, a reduced purity of the electrolyte results in an erratic voltage response, due to cycles of mechanical breakdown and healing of the coating, with high levels of chloride resulting in a highly porous coating. The distributions of phosphorus and chlorine species within the coatings suggest that these species migrate inwards, with chlorine species migrating faster than phosphorus species.

The Li-Ti-S ternary system was investigated. The elements and/or compounds, such as lithium sulfide, titanium disulfide and titanium trisulfide, were combined at high temperature (typically 500-900°C). The synthesized compounds containing one or more phases were structurally characterized using x-ray powder diffraction. When Lix TiS₂, (0 ≤ x ≤ 1) was synthesized at elevated temperature, a new polytype, 3R-LixTiS₂, was found for some values of x. The regions of stability of the 3R polytype and the well known 1T polytype are presented. Lithium can be intercalated or de-intercalated from both polytypes at room temperature. Ambient temperature Li/3R-LixTiS₂ cells have higher average voltages than Li/1T-Li TiS₂, cells. The lithium spinel oxides are another class of materials receiving attention as cathode materials in lithium secondary batteries. LiTi₂0₄ is metallic, has the cubic spinel structure and reacts with one further lithium atom to form Li₂Ti₂0₄. The related spinel Li₄/₃Ti₅/₃⁰₄͵ which is electrically insulating, also reacts reversibly with one lithium atom. Both Li₂Ti₂0₄ and Li₄/₃Ti₅/₃⁰₄͵ cells cycle reversibly, but have subtle differences in their voltage profiles. The difference in cell behaviour was interpreted based on the band structure of Li₁˖xTi₂₋x⁰₄. The mixed spinels LiMnyTi₂₋y⁰₄ (0 ≤ y ≤ 2) were also investigated. These compounds were synthesized at high temperature but their performance as cathodes in lithium batteries was not encouraging. / Science, Faculty of / Physics and Astronomy, Department of / Graduate