This retrospective clinical study aimed: (1) to establish and validate a reproducible geometrical measurement strategy in quantifying peri-implant alveolar bone changes based on CBCT images taken before and one year after implantation; (2) to quantify and compare the bone changes of Type 1 and Type 4 implant placement in the patient cohort that requested implant placement at premolar and molar sites; (3) to analyse the bone changes in relation to the two implant protocols in aspects of buccal and lingual, maxilla and mandible, within the cohort and combined cohorts. 3D imaging analysis in this study had used a software package - OnDemand3D. The evaluation of the measurement strategy was based on a simulation model which was made of human dry skull with and without a standard implant (Straumann Standard Plus, Ø3.3 mm diameter, L12 mm) to simulate before and after the implant placement. The recruited cases were 69 (44 Type 1 cases and 25 Type 4 cases); all data sets were provided by Shanghai 9th people's hospital, China. Each case had two CBCT data sets at before and one year after implant placement. With 69 cases, bone grafting was applied to all Type 1 cases, and the flap surgery was applied to Type 1 cases when buccal bone recession greater than 3 mm. The measurements were made in bone height (HL) and bone thickness (L0O0, L1O1, L2O2, L3O) at lingual side, while the same at buccal side (HB, B0O0, B1O1, B2O2, B3O3). The four sections of bone thickness were at 0, 1 mm, 4 mm and 7 mm from the top of the implant. Additionally, six special cases were reported, as they provided extra information. They were two spilt-mouth control cases, three 2-year follow-up cases and one 3-year follow-up case. The evaluation of the measurement strategy showed the error of the measurement strategy was -0.06 mm and the measurement uncertainty was ±0.05 mm. The main measurement outcomes from the clinical cases were as follows: (1) at buccal side, the mean value of bone changes in height was a positive value of +0.18±1.64 mm for Type 1, which was significantly more than +0.01±0.86 mm for Type 4 (p < 0.05). However the standard deviation over the 44 and 25 patient cohorts were as large as 1.64 mm and 0.86 mm; (2) at buccal side, the bone changes in thickness showed significantly more loss at B0O0 (p < 0.01) and B1O1 (p < 0.05) sections in Type 1 (-0.38±1.49 mm and -0.25±1.15 mm) compared with Type 4 (-0.19±0.34 mm and -0.16±0.76 mm); (3) in Type 1 cases, the bone thickness at buccal side showed significantly more absorption at L1O1B1 (p < 0.05), L2O2B2 (p < 0.01), L3O3B3 (p < 0.01) section (-0.25±1.15 mm, -0.19±0.99 mm, -0.12±0.57 mm) compared to lingual side (-0.13±0.85 mm, -0.16±0.28 mm, -0.05±0.28 mm); and the bone height (+0.18±1.64 mm) increased significantly more at buccal side than lingual side (-0.25±0.79 mm) with bone augmentation procedure (p < 0.01). However, within Type 4 cases, no significant difference in bone changes between buccal and lingual sides could be found. In conclusion, the measurement strategy established in this study was reproducible and provided valid quantifiable data of bone changes in relation to implant placement based on 3D CBCT images. The data analysis from these two patient cohorts suggested that Type 1 implant placement protocol could re-build the bone height at buccal side better than Type 4.

La solution la plus favorable cliniquement au remplacement des dents absentes est aujourd’hui la mise en place d’implants dentaires. Cette technique nécessite la maîtrise de plusieurs problématiques qui s’articulent autour des interfaces du système. Celles-ci sont au nombre de trois soit : l’interface os-implant, l’interface implant-pilier prothétique et l’interface pilier prothétique-prothèse. Dans cette étude, nous analysons les matériaux mis en présence au sein des interfaces et ce, par le biais de l’analyse mécanique afin d’apporter une contribution objective au choix clinique des matériaux par les praticiens. Les substituts osseux sont ainsi étudiés sous le prisme de leur stabilité mécanique, servant de trame à la reconstruction osseuse au contact de l’implant. Plusieurs systèmes implantaires (ensemble implant-pilier prothétique) sont ensuite étudiés pour en évaluer également la stabilité, gage de solidité du système et d’absence de dévissage. Enfin, plusieurs polymères dentaires sont évalués et comparés afin d’établir leur apport dans la solidité du complexe implanto-prothétique. / Today, the most favorable clinical solution for replacing absent teeth are dental implants. Several problems has to be addressed to master this technique, in particular those concerning the design of the many interfaces of this system. The three main interfaces are : the bone-implant junction, the implant-prosthetic pillar contact and prosthetic pillar-prosthesis assembly. In this study, the mechanical behavior of the constitutive materials of the system is evaluated to supply unbiased criteria to the practitioners for selecting the right materials in clinical conditions. Thus, bones substitutes are studied to evaluate their mechanical stability which is necessary condition to ensure bone reconstruction in contact with the implant surface. Then, several implant systems (implant + prosthetic pillar) are tested to estimate their stability, which guaranty solid system and prevent from any unscrewing failure. Finally, several dental polymers are evaluated and compared to establish their contribution in the implanto-prosthetic system robustness.

This thesis describes the fabrication and characterization of an inorganic catalyst based glucose Biofuel cell using nanoporous (mesoporous) silica thin-film as a functional membrane. The desired use of nanoporous silica based biofuel cell is for a blood vessel implantable device. Blood vessel implantable Biofuel Cells (iBFCs) are subjected to higher glucose concentrations and blood flow rates. However, reduction in the implant thickness is critical for the intra-vascular implantable Biofuel cells. Platinum thin-film (thickness: 25 nm) deposited on Silicon substrate (500 [mu]m) served as the anode while Graphene pressed on Stainless steel mesh (175 [mu]m) was used as the cathode. Control experiments involved the use of surfactant-coated polypropylene membrane (50 [mu]m) and Activated Carbon (198 [mu]m) electrodes. Preliminary results show that nanoporous silica thin film (270 nm) is capable of replacing the conventional polymer based membranes with an increased power density output of as high as 10 [mu]W/cm2 under physiological conditions. in-vitro (5 [mu]W/cm2) and in-vivo (10 [mu]W/cm2) experiments demonstrate the potential of ultra-thin iBFCs towards powering future medical implants. / text

This research investigates the effects of the human body on the mechanical, chemical, and morphological properties of the surface of internal fixation devices. Stainless steel and titanium devices that had failed were provided from the Shandong Provincial Hospital in China, along with controls: implants that had never been used. Comparative study was conducted by evaluating properties of these implants before and after implanting. The first part of the research was simulation, and a model of the human femur was analyzed in Solidworks. The stress analysis software simulated the stress distribution, the strain distribution, and the deformation pattern. Two cases were simulated: walking and car accident. The simulations showed the points of highest stress and led to the analysis of the implants that were used in those regions. The next part of the research was to experimentally examine the properties and behavior of materials. Test samples fell into one of three categories: stainless steel femur implant, stainless steel tibia implant, and titanium femur implant. Material properties were characterized and effects of the human body on each of these groups were studied. Hardness was measured using Vickers hardness indentation. Surface roughness was analyzed using light interferometric technique. Potentiodynamic polarization analysis was performed to evaluate corrosive behavior before and after implanting. Scratch tests were conducted to evaluate wear resistance and the microstructure was analyzed to further understand the morphological changes that occurred of implanted samples. Results showed that the human body generally degraded the material properties of the stainless steel femur implant. There were no measurable effects of the same on stainless steel tibia and on titanium alloy.

Pulse Pressure Metal-Organic Chemical Vapour Deposition (PP-MOCVD) is a technique for creating thin coatings. It is less dependent on the volatility of precursors than other Chemical Vapour Deposition (CVD) processes as the precursors are introduced into the reaction chamber as an aerosol; therefore sublimation of the precursor is not necessary. This allows solutions of multiple compounds to be created with a known concentration and ratio of precursors. We explored the formation of hydroxyapatite (HAp) coatings for use on bone implants, using a methanolic solution of calcium lactate and trimethyl phosphate (TMP) as a PP-MOCVD precursor solution. The thermal decomposition of the precursors and the reaction between them were investigated using Thermogravimetric Analysis (TGA). Several variables on the PP-MOCVD apparatus were varied to test their effect on the formed coating: deposition temperatures, ratio of precursors, number of pulses, precursor concentration, the use of ambient temperatures and annealing the coatings after formation. All the coatings were analysed using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infra-Red spectroscopy (FTIR). These coatings were not uniformly smooth in appearance at the micro level. However, using higher deposition temperatures, an excess ratio of TMP to calcium lactate and annealing the coatings for short periods of time and low temperatures improved the uniformity of the coating. When vigorous annealing was performed it resulted in surface oxidation and the production of titanium dioxide (TiO2 ). The EDS results showed that both calcium and phosphorus were present in the coatings. The use of high deposition temperatures, excess TMP or gentle annealing resulted in calcium to phosphorous ratios similar to the stoichiometry of HAp. These same conditions gave improved coating uniformity.

Speech perception outcomes for people with a prelingual hearing loss, implanted with a cochlear implant in adolescence or adulthood, are characterized by a large degree of variability. Research findings indicate that some recipients do very well and gain significant open set speech perception skills, whilst a large percentage show little or no change in open set speech results, post implant. In studies to-date, mean speech perception scores were typically substantially poorer than those recorded for implant recipients with a postlingual hearing loss. Despite this, the majority of recipients with a prelingual hearing loss implanted with a cochlear implant in adolescence or adulthood reported satisfaction with their implant and used it regularly. Although there have been a number of studies in the area, none has taken a holistic approach and investigated both objective and subjective outcomes for a large group of participants. In addition, no study has employed a multiple regression analysis to investigate which characteristics were associated with speech perception outcomes in people with a prelingual hearing loss implanted with a cochlear implant in adolescence or adulthood. The objectives of the study were to examine speech perception and other outcomes in people with a bilateral prelingual or perilingual hearing loss, implanted with a cochlear implant as an adolescent or adult, and to investigate prognostic factors associated with positive outcomes. The design consisted of a retrospective review of both speech perception outcomes and other outcomes for 38 recipients, diagnosed with a bilateral hearing loss before age 3, and implanted with a cochlear implant at 14 years or older. There were 24 females and 14 males and the average age at initial stimulation was 33 years. All participants were implanted with a Nucleus device at a private audiology clinic (Attune). Four questionnaires were completed by approximately half of the participants – Glasgow Benefit Inventory (GBI); International Outcome Inventory (IOI-CI); Study Questionnaire; and the Hearing Abilities and Quality of Life Scale. The Study Questionnaire was developed specifically for this project and investigated satisfaction, benefit and advantages/disadvantages of the implant. The Hearing Abilities and Quality of Life Scale was developed by Attune and was completed by recipients pre and post implant. It evaluated the ability to understand conversation in different situations, environmental awareness, safety concerns, involvement in social activities and impact of the hearing loss on relationships. Approximately one third of participants scored between 30 and 90% on the CID/ CUNY test administered via CD post implant and approximately one fifth scored over 90%. The mean score on the CID/CUNY test administered via CD was 8% pre implant and 48% post implant. Over 80% of recipients used their device more than 8 hours a day and all recipients reported being satisfied with it. Three factors accounted for 65% of the variance on the open set sentence test score, post implant. These were stable versus progressive loss, mode of communication in childhood and time without a hearing aid on the implant ear. For the purposes of this research, a ‘stable’ loss was defined as a bilateral severe to profound hearing loss at diagnosis and a ‘progressive’ loss was one that deteriorated to this degree at some point after diagnosis. The findings from this study reveal that a cochlear implant is a viable option for adults and adolescents with a prelingual hearing loss. The majority of participants gained benefit from the device and were satisfied with it. In addition, a substantial number gained good open set speech perception ability, post implant. Consistent with previous studies, there was large intersubject variability in speech scores. The recipients who had a progressive loss, used oral communication in childhood and wore a hearing aid on the implant ear up to the time of surgery were more likely to obtain better speech perception outcomes.

Pulse Pressure Metal-Organic Chemical Vapour Deposition (PP-MOCVD) is a technique for creating thin coatings. It is less dependent on the volatility of precursors than other Chemical Vapour Deposition (CVD) processes as the precursors are introduced into the reaction chamber as an aerosol; therefore sublimation of the precursor is not necessary. This allows solutions of multiple compounds to be created with a known concentration and ratio of precursors. We explored the formation of hydroxyapatite (HAp) coatings for use on bone implants, using a methanolic solution of calcium lactate and trimethyl phosphate (TMP) as a PP-MOCVD precursor solution. The thermal decomposition of the precursors and the reaction between them were investigated using Thermogravimetric Analysis (TGA). Several variables on the PP-MOCVD apparatus were varied to test their effect on the formed coating: deposition temperatures, ratio of precursors, number of pulses, precursor concentration, the use of ambient temperatures and annealing the coatings after formation. All the coatings were analysed using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infra-Red spectroscopy (FTIR). These coatings were not uniformly smooth in appearance at the micro level. However, using higher deposition temperatures, an excess ratio of TMP to calcium lactate and annealing the coatings for short periods of time and low temperatures improved the uniformity of the coating. When vigorous annealing was performed it resulted in surface oxidation and the production of titanium dioxide (TiO2 ). The EDS results showed that both calcium and phosphorus were present in the coatings. The use of high deposition temperatures, excess TMP or gentle annealing resulted in calcium to phosphorous ratios similar to the stoichiometry of HAp. These same conditions gave improved coating uniformity.

No description available.

With life expectancy on the rise, age-related ailments are a significant strain on the welfare of individuals and the economy. Progress is being made towards combating the leading cause of unavoidable blindness, age-related macular degeneration (AMD). AMD affects ten million Americans and costs the world economy $343 billion annually. Retinal implants promise to restore sight by replacing the eye's damaged photoreceptors with electronic photodiodes. Clinical trials succeed at restoring some vision, but are limited by the stimulating electrodes. We study the electrode-neuron interface with a focus on the geometrical dependence of the electrode. The functionality of neurons is intimately connected to their branching and curving shape, described by fractal geometry. We examine the morphology of neurons using fractal analysis. The results inform our electrode designs, which are fabricated using top-down lithographic and bottom-up self-assembly techniques. A novel technique for fabricating a fractal electrode is presented. Heating and cooling a film of poly(methyl methacrylate) on a SiO2 substrate causes fractal structures to form on the surface. The geometry of the structures is temperature dependent, producing crystalline branches at lower temperatures and diffusion-limited aggregates at higher temperatures. Subsequent deposition of antimony nanoclusters shows preferred diffusion to the fractal surface features. The dependence of a photodiode's performance on its top contact geometry is explored using modified nodal analysis. The results reinforce the need to balance a low mean semiconductor-metal separation distance with an adequate contact width for low resistance, all while maximizing light input. Future designs will benefit from the spatial voltage maps produced by the simulation. The electric field emanating from an electrode is also dependent on the geometry of the electrode. The Faraday cage effect is exploited to achieve similar electric field responses to traditional electrode shapes. A preliminary study of neural adhesion to SU-8 fractal electrodes is promising. The neuron grows along the electrode even at 90° turns. The role the fractal geometry plays in neuron and electrode functionality is shown to be significant. Continued study of, and experimentation with, new electrode designs is sure to produce exciting possibilities in the future. This dissertation includes previously unpublished co-authored material.

Made available in DSpace on 2014-06-11T19:34:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-30Bitstream added on 2014-06-13T21:06:52Z : No. of bitstreams: 1 oliveira_ur_dr_guara.pdf: 4040810 bytes, checksum: a055438a4cb6be924bf399878920deb9 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Observam-se, nos dias atuais, nas indústrias brasileiras, a ocorrência de inúmeros problemas que afetam direta e indiretamente seus processos produtivos e que, na maioria das vezes, são desenvolvidas ações corretivas ao invés de ações preventivas. Apesar da Gestão de Riscos utilizar ferramentas, técnicas e abordagens para identificação, análise e avaliação de riscos, para que muitos dos riscos mapeados não se tornem problema, constatou-se na literatura específica, a quase completa ausência de abordagens que tratem dos riscos quando esses se concretizam na manufatura, tornando-se, portanto, problemas. Assim, para se atuar na mitigação dos riscos, recomenda-se a inserção da flexibilidade de manufatura como a última etapa do Gerenciamento de Riscos na manufatura. Entretanto, a característica multidimensional da flexibilidade de manufatura dificulta essa tarefa, no sentido de adequar o grau de flexibilidade frente às variáveis existentes. Assim, o problema está na escolha correta das diferentes dimensões de flexibilidade, ou seja, quanto se investir para ser flexível, uma vez que existem inúmeros tipos de flexibilidade. Por meio de uma investigação empírica na manufatura de oito indústrias, utilizando-se o método hipotético dedutivo, aqui se desenvolveu uma ferramenta, chamada de Matriz de Decisão sobre Flexibilidades, para auxílio à tomada de decisão sobre qual tipo de flexibilidade de manufatura deve-se escolher para a solução de diferentes tipos de problemas que ocorrem na manufatura, em distintos segmentos industriais. Como resultados adicionais, a pesquisa empírica em oito empresas forneceu informações sobre quais são os problemas críticos para cinco segmentos industriais pesquisados; sugeriu novos usos de alguns tipos de flexibilidade de manufatura, e ofereceu informações úteis para a disseminação de conhecimento sobre flexibilidade. / It is observed, nowadays, in the Brazilian industries, the occurrence of several problems that affect directly and indirectly their productive processes and that, most of the time, are only developed corrective actions instead of preventive ones. Although Risks Management to use tools, techniques and approaches for identification, analysis and evaluation of risks, in order to many of these mapped risks do not become problems, was evidenced in specific consulted literature, the absence of approaches that deal with the risks just when they appear, becoming, therefore, problems. Thus, to mitigate risks, insertion of the manufacturing flexibility as the last stage of Risks Management it is recommended. However, the multidimensional characteristic of the manufacture flexibility makes difficult the task to adjust the degree of flexibility in function of existing variable. Thus, the great problem is to do the correct choice from the flexibility dimensions set, usually presenting several options, that is, to choice how much to invest to be flexible. Here was developed a tool, named Flexibility Decision Matrix, for decision-making about which kind of manufacture flexibility must be chosen for the solution of manufacturing problems, in distinct industrial branches. As additional results, an empirical research in eight companies gave information on which are the worse problems for five industrial segments; suggested new utilization of some types of manufacture flexibility, and offered highlights to collaborate to flexibility knowledge dissemination.