Made available in DSpace on 2014-06-11T19:28:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-17Bitstream added on 2014-06-13T18:34:49Z : No. of bitstreams: 1 chimendes_lh_me_guara.pdf: 1177725 bytes, checksum: d07ba490bc7382650c018bc1d64cd30d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Muitas das características do implante estão relacionadas com sua longevidade, e uma dessas é o perfil de rosca empregado no projeto de sua criação. Assim, este estudo teve como objetivo analisar a distribuição da tensão gerada por implantes com diferentes perfis de rosca, através do método dos elementos finitos, num modelo bidimensional. Foram realizados oito modelos matemáticos de implantes mantendo-se as mesmas dimensões e modelo do conjunto implante e tecido ósseo, houve alteração somente no desenho do perfil de rosca empregado. Através do programa Ansys, simulou-se um carregamento axial de 100 N para todos os modelos, e os resultados das tensões obtidos foram analisados à luz do critério de Von Mises. Desse modo, observaram-se, modificando o desenho da rosca, variações de tensão no implante de até 30%, no osso compacto de até 40%, e no osso esponjoso de até 70%. Levando-se em conta o que foi observado, percebe-se a grande importância no planejamento do desenho das roscas do implante. Dentre os perfis de rosca analisados, dois modelos propostos na inovação obtiveram melhores resultados na distribuição de tensão no tecido ósseo. / Many features of the implant are related to their longevity, and one of them is the profile of screw employed in the project of creation. Thus the present study aimed to analyze the distribution of stress generated by implants with different profiles threaded, through the finite element method in a two-dimensional model. Were up eight models of implants and has been the same size and model of the whole implant and bone tissue, there was only change in the design of screw profile employee. Through the program ANSYS, is a simulated axial loading of 100 N for all models, and the results of the tensions were analyzed in light of the criterion of Von Mises. Thus, there were, modifying the design of screw, variations of tension in the implantation of up to 30% in the compact bone of up to 40% and the spongy bone of up to 70%. Taking into account what has been observed, it is very important in planning the design of the threads of the implant. Among the scenarios analyzed threads, two proposed models in innovation obtained better results in the distribution of stress in bone tissue.

O objetivo deste estudo foi avaliar clínica e radiograficamente implantes curtos com 5 e 6 mm de comprimento (Titamax WS Neodent/ Curitiba-Brasil) unitários instalados em região posterior de mandíbula e maxila com pouca altura óssea. Foram instalados 10 implantes em 8 pacientes devidamente selecionados a partir de critérios de inclusão pré-determinados. Os mesmos receberam carregamento protético somente após o tempo convencional de espera para a osseointegração. Seis implantes foram instalados em mandíbula e 4 implantes em maxila. Tomadas radiográficas foram realizadas para avaliação das perdas ósseas verticais e horizontais nos tempos T0 (Instalação cirúrgica), T1 (Reabertura), T2 (Instalação protética) e T3 (Acompanhamento de 6 meses). Foram avaliados parâmetros biológicos como, sangramento gengival, índice de mucosa ceratinizada, índice de placa e índice de inflamação gengival. Também foram avaliados parâmetros protéticos como proporção coroa-implante e distância mesiodistal. Apenas um implante (Titamax WS Cortical 5.0x6.0) foi perdido ainda no período de osseointegração portanto o índice de sucesso foi de 90% no período avaliado. A alteração do nível ósseo foi analisada em três períodos diferentes, da instalação cirúrgica à cirurgia de reabertura (período 1), da reabertura à instalação protética (Período 2) e da instalação protética ao controle de seis meses (Período 3). Avaliando-se a perda óssea vertical nos três períodos separadamente foram encontrados valores muito semelhantes, inclusive iguais estatisticamente (ANOVA, p<0,05). O valor de perda óssea no período 1 foi de 0,32mm; no período 2 foi de 0,22mm e no período 3 foi de 0,29mm. Isso significa que os procedimentos cirúrgicos foram igualmente causadores de perda óssea marginal mesmo tomando-se alguns cuidados na execução destas etapas. A média de perda óssea vertical e horizontal no período total de acompanhamento foi de 0,87 ±0,46 e 0,24± 0,34 respectivamente. Estes valores foram considerados dentro do intervalo de perda óssea esperado. A boa condição de saúde gengival e higiene oral descartaram a possibilidade de associação entre os índices periodontais e a perda óssea periimplantar. O teste estatístico de Regressão Linear (p<0,05) mostrou não haver relação de causa/efeito entre perda óssea e os parâmetros protéticos, apesar de elevada proporção coroa/implantes (média 1,88). Com base nos resultados encontrados neste trabalho, concluiu-se que os implantes curtos, mesmo os de comprimento 5 e 6mm, devem ser considerados como uma importante alternativa de tratamento para casos unitários. Sugere-se porém, um maior tempo clínico de acompanhamento para que seja possível traçar um perfil do comportamento destes implantes a longo prazo. / The aim of this study was to evaluate clinically and radiographically short unit implants with 5 and 6 mm in length (Titamax WS - Neodent / Curitiba, Brazil) installed in the posterior mandible and maxilla with little bone height. Ten implants were installed in eight carefully selected patients from inclusion criteria pre-determined. They received prosthetic loading only after the conventional time waiting for the osseointegration. Six implants were placed in the mandible and four implants in the maxilla. Radiographs were performed to evaluate the vertical and horizontal bone loss in T0 (surgery installation), T1 (uncovering), T2 (prosthetic installation) and T3 (follow-up of 6 months). Biological parameters were evaluated such as gingival bleeding index, keratinized mucosa amount, plaque index and gingival inflammation index. Prosthetic parameters were also evaluated as crown-implant ratio and mesiodistal distance. Only one implant (Titamax WS Cortical 5.0x6.0) was lost, it occurred during the healing fase. Therefore the success rate was 90% in the period. Bone level change was analyzed in three different periods, from surgical installation to uncovering surgery (1st period), from uncovering to prosthetic installation (2nd Period) and from prosthetic installation prosthetic to six months control (3rd Period ). Vertical bone loss values were very similar when evaluated in the three periods separately, even the same statistically (ANOVA, p <0.05). The amount of bone loss in 1st period was 0.32 mm in the 2nd period was 0.22 mm and in the 3rd period was 0.29 mm. This means that surgical procedures were also cause marginal bone loss even taking some care in implementing these steps. The average vertical and horizontal bone loss in the total period of observation was 0.87 ± 0.46 and 0.24 ± 0.34 respectively. These values were considered within the range of bone loss expected. The gingival good condition of health and oral hygiene ruled out the possibility of an association between periodontal indices and bone loss. Statistical analysis of linear regression (p <0.05) showed no cause and effect relationship between bone loss and prosthetic parameters, despite the high crown / implant ratio (average 1.88). Based on the findings of this study, it was concluded that short implants, even the 5 and 6 mm in length, should be considered as an important alternative treatment for single crows. It is suggested a longer clinical follow-up to make it possible to trace a pattern of behavior of these implants over the long term.

La surdité est un problème de santé publique. Le vieillissement de la population explique ainsi une grande partie des causes de surdités, par la fréquence de la presbyacousie. Le principal moyen de la réhabilitation auditive est représenté par les prothèses auditives conventionnelles. Les aides auditives ont considérablement progressé ces dernières années, principalement en termes d’amélioration du traitement du signal. Ceci étant dit, outre le problème économique, certains facteurs limitent encore les bénéfices que les patients peuvent ressentir (occlusion du conduit auditif, effet larsen, absence d’amplification en ambiance sonore,…). Les implants d’oreille moyenne sont destinés à amplifier le signal sonore en le transmettant à l’oreille moyenne pour compenser une perte auditive. Ils sont indiqués en cas d’échec ou de contre-indication de l’appareillage conventionnel. Cependant, les implants d’oreille moyenne présentent certaines limites comme l’insuffisance de performance. Des données récentes montrent que les performances des techniques de réparation de la chaîne ossiculaire sont dépendantes du couplage des prothèses ossiculaires à la chaîne des osselets. Par ailleurs, des avancées dans la compréhension de la biomécanique de la chaîne ossiculaire confirment l’importance du placement et du couplage des procédés de restauration chirurgicaux. Nous avons formulé l’hypothèse selon laquelle ces données pouvaient être appliquées aux implants d’oreille moyenne pour en améliorer les performances. Nous avons voulu analyser expérimentalement les effets sur les performances de variables telles que : placement d’un transducteur, le couplage à la chaîne des osselets, la taille de l’effecteur, l’effet de stimulations alternatives. Nous avons utilisé un transducteur électromagnétique de dernière génération (Otologics MET-V Gen 2) et une technique d’analyse de la vibration des structures de l’oreille moyenne par vélocimétrie laser. Les résultats ont montré une nette amélioration des performances en fonction des modifications de placement et de couplage à la chaîne des osselets ou à la fenêtre ronde. / Hearing loss is a public health issue. Ageing is the most frequent cause of deafness. The main option for the rehabilitation of hearing loss is the use of conventional hearing aids. These aids have dramatically improved their performance for the past 20 years, mostly with regards to signal processing. However, in addition to economic reasons, some limitations remain (occlusion, feedback, hearing in noise…) and limit the satisfaction of patients. Active middle ear implants (AMEI) have been developed to overcome some of these problems and are indicated n conventional hearing failed to improve patients’ quality of hearing. However, AMEI suffer from limitations, as insufficient performances for severe hearing losses. Recent experimental and clinical data have highlighted the importance of coupling and placement of ossicular reconstruction passive prosthesis use. Other reported new findings regarding the biomechanism of the ossicular chain, especially for high frequency hearing, which is, unfortunately, where most people have their hearing loss. We hypothesized that these findings could be applied to AMEI use. We have analysed experimentally the effects on AMEI performance of variables such as: placement, coupling, size of tranduscer vibrating tip, alternative stimulation options. We used a electromagnetic tranducer from Otologics LLC to drive the middle ear or round window membrane, and a laser Doppler vibrometer to assess for the induced middle transfer function. Results have shown that we could provide great improvement in performance when varying the coupling method and the placement to the ossicular chain or the round window membrane.

Magister Chirurgiae Dentium - MChD / Aim: To determine the prevalence of peri-implant mucositis and the association between systemic and local risk factors

No description available.

Total hip replacements are being used to relieve pain and restore the hip function of unhealthy hip joints. The various sizes and geometries of the modular femoral neck implants allow the surgeon to optimize the range of motion and patient’s leg length. However, some in vivo modular femoral neck retrievals have shown early fatigue and advanced wear-corrosion at the neck-stem taper interface, which can lead to adverse tissue reactions and failure of the implant. The overall objective of this study was to simulate in vivo fatigue fracture, wear, and corrosion of modular necks at the neck-stem taper interface in a laboratory setting (in vitro) to better predict the failure mechanisms and implant limitations. More specifically, after optimizing the laboratory setup and the testing conditions, this study aimed to compare the effects of the modular neck material (Ti6Al4V and CoCrMo) and the implant assembly technique (hand and impact assembly) on fatigue life, wear-corrosion resistance, and distraction force. The PROFEMUR® Modular Neck System with CoCrMo femoral heads and Ti6Al4V stems was used in this study. The in vitro simulation was divided into two types of tests: fatigue tests (high compression load for a short cyclic loading duration) and corrosion tests (low compression load for a long cyclic loading duration). The neck-stem interface was submersed in a phosphate buffered saline solution, which was maintained at a temperature of 80 ºC to accelerate the corrosion reaction. The simulation results showed that the Ti6Al4V necks were more vulnerable to fatigue fracture than CoCrMo necks. In addition, impact assembly of the components resulted in an increased implant fatigue life compared to hand assembly, but also increased the distraction force. The observed wear-corrosion damage was higher in fatigue tests than corrosion tests, suggesting that the level of mechanical load was a major factor influencing implant surface damage and fatigue fracture. On the other hand, corrosion tests showed that longer exposure resulted in more fluid accumulation in the stem pocket. This may lead to the formation of a corrosion cell with strongly acidic conditions in the stem pocket, as well as the potential for larger metal ion release. Overall, the in vitro simulation was successful in reproducing femoral modular neck fracture and wear-corrosion damage similar to retrieved in vivo specimens. Results may play a major role in the future development of total hip replacements and international standards for implant testing.

The master’s thesis deals with issues belonging to the field of dental biomechanics, specifically the mechanical interaction of dental implants with the bone tissue of the mandible. The thesis focuses on the stress-strain analysis of the mandible with the implant inserted in different positions, with a different angle relative to the occlusal plane. The solution is performed by computational modeling using the finite element method. The geometry model of mandible was created based on CT images. The aim of the master’s thesis was also to compare the influence of the choice of the material model of cancellous bone tissue on the resulting stress-strain states of the mandible with the dental implant. Three material models of cancellous bone tissue were created - two homogeneous material model and a heterogeneous material model, which was based on CT image data. The work also investigates the effect of rotation (+5° or -5°) of implants in basic positions on the resulting stress-strain states. The stress-strain analysis showed that position and rotation has a greater effect on the stress and strain of bone tissue and implant than the chosen material model of cancellous bone tissue.

Introduction: The prevalence of implant treatment has increased tremendously over the past few decades. In the process of either treating peri-implantitis or during the implant maintenance phase, it has been noted that certain implant decontamination methods may generate particles from implant surfaces. This may result in potential for disease exacerbation and irreversible damage to the implant surface. Although the Er: YAG (erbium-doped yttrium aluminum garnet) laser has been considered to have the best properties for the decontamination of the implant surface, there is limited data on the amount of titanium and zirconia particles that can be generated and released in the process. Purpose: The aim of this in vitro study was to investigate the possible generation of titanium and zirconia particles when the Er:YAG laser is used as a tool for implant decontamination and to assess for any possible surface alterations that may have resulted from the use of the Er:YAG laser. Materials and Methods: Six (N=6) Ti-Zirconium alloy (Roxolid®; Straumann® USA) and six (N=6) yttra-stabilized tetragonal zirconia (PURE® Ceramic; Straumann® USA) machined material discs, as well as two (N=2) expired Ti sandblasted acid-treated implants (Ti SLA® Implant; Straumann USA) and two (N=2) expired acid-etched zirconium-dioxide ceramic implants (PURE® Ceramic ZLA® Implant; Straumann® USA) were irradiated with the Er:YAG laser (LiteTouchTM) using the gentle treatment mode for implant decontamination for 30 and 60 seconds. The coolant water generated during laser irradiation was collected and filtered through polycarbonate track etch (PCTE) hydrophilic membrane filters using a vacuum filtration assembly unit. The PCTE membranes were then analyzed for presence of titanium and zirconia particles using a Field Emission Gun Scanning Electron Microscope (FEG-SEM). The elemental composition of the particles was compared with that of the implants and discs using Energy-dispersive X-ray spectroscopy (EDS). The surfaces of the discs and implants were also inspected for morphological alterations. The average surface roughness (Ra, Ry, Rz) of the discs before and after laser application were measured using a 2-dimensional surface profilometer. A paired sample t-test was used for statistical analysis to compare the surface roughness values before and after laser application. Results: No titanium or zirconia particles were collected after laser irradiation of the material discs after laser irradiation. Titanium and zirconia particles were detected after laser irradiation on the implants. There were no surface topographical alterations evident at higher magnification for the titanium and zirconia material discs, and implants after laser irradiation. There was a statistically significant decrease in all surface roughness parameters measured (Ra, Ry, Rz) after 60 seconds of laser irradiation for the zirconia discs. Conclusions: Within the limitations of this study, the Er:YAG laser used in gentle treatment mode for implant decontamination resulted in no visible damages to the titanium and zirconia implant surfaces. There were some titanium and zirconia particles produced during the laser irradiation on implants but no produced over discs. Additional in-vitro and clinical studies will have to be conducted to assess the clinical significance of these particles. / Oral Biology

The plantar plate is a fibrocartilaginous tissue beneath the metatarsophalangeal joint (MTPJ). Plantar plate function centers around maintaining the static stability of the MTPJ, and its integrity facilitates the dynamic stabilizing functions of surrounding soft tissue structures. Injury to the plantar plate can cause significant forefoot discomfort focused around the MTPJ, swelling, and altered forefoot biomechanics from toe instability. Significant injury like either partial or complete tear of the plantar plate commonly requires surgical intervention to repair the tissue. As fibrocartilage, the plantar plate lacks an intrinsic capacity for robust healing, thus requiring a surgical repair aiming to restore proper function. Existing plantar plate repair techniques afford different perspectives for restoring plantar plate biomechanical function, though room for improvement exists for an enhanced repair. Our senior design team developed a novel approach for plantar plate repair using a two-piece snap fitting permanent implant. This novel technique was reduced to practice and required further experimental analysis of its functional capacity to inform future development. Two methodologies were used to evaluate the novel implant device designed for plantar plate repair. An implant isolated mechanical testing protocol was developed to evaluate the implant and suture construct of the repair in anatomically relevant orientations. A human cadaver tissue model protocol was employed to evaluate the integrity of the native plantar plate tissue, a simulated conventional repair, and our novel implant fixation repair. These methodologies used uniaxial tensile testing with custom test configurations to evaluate the structural integrity and properties of the implant-suture construct and simulated tissue only or tissue-repair constructs, respectively. Our results provided encouraging support for the use of mechanical testing and the continued development of this novel implant device for plantar plate repair. Additionally, qualitative outcomes from this testing revealed additional avenues to improve the novel implant device in support of further advancing the product for future use in the field of podiatric medicine. / Master of Science / The plantar plate is a soft, biological tissue that lies beneath the metatarsophalangeal joint (MTPJ), which comprises the ball of the foot. When injured, the plantar plate lacks capacity to fully heal the tissue, as its structural properties more closely resemble that of cartilage and ligaments, which also commonly fail to fully heal after injury. Due to the difficulties in facilitating healing and restoring its function, a plantar plate tear or rupture is commonly repaired surgically. Current methods for repairing a plantar plate tear vary, though room to enhance the overall surgical repair technique exists. Our senior design team developed a novel implant device for use in a modified surgical repair of the plantar plate, which aimed to improve upon the existing methods. This work focused on developing experimental methods to analyze and evaluate the function of this novel implant device that is relevant to the clinical application of plantar plate repairs. Two experimental setups were developed and used to analyze the function of our novel implant device. A simulated repair setup, relevant to the natural function of the plantar plate, was employed to evaluate the function of the implant and suture used in the repair. A human cadaver model experimental setup aimed to evaluate the plantar plate naturally, a conventional or existing repair, and our novel repair of a simulated torn plantar plate. The outcomes from these experiments encourage further exploration of implant product development as well as continued testing of this device in the future. Ultimately, this work has provided a foundation for the continued development of our novel implant device for plantar plate repair with the aim to bring this product to market and enhance the field of podiatric medicine.

4H-SiC n-channel power MESFETs with nitrogen-doped epitaxially grown channel and nitrogen n+-implanted source/drain ohmic contact regions, with and without p-buffer layer fabricated on semi-insulating substrates exhibited hysteresis in the drain I-V characteristics of both types of devices at 300 K and 480 K due to traps. However, thermal spectroscopic measurements could detect the traps only in the devices without p-buffer. In this study the two-dimensional device simulator, MediciTM, and optical admittance spectroscopy (OAS) measurements are used to help resolve the discrepancy in the initial experimental characterization results and interpret the results. Device simulations also showed hysteresis in the drain I-V curves of both types of devices at 300 K and 480 K. Simulations suggest that, in addition to the SI substrate traps, which are known to be major cause of hysteresis in MESFET drain I-V characteristics, acceptor traps due to source/drain residual implant lattice damage could also contribute to the hysteresis observed in the drain I-V characteristics of the experimental MESFETs. Although surface traps are known to cause hysteresis in the I-V curves of MESFETs, their presence was not observed in the experimental devices. The results of the OAS measurements showed several peaks in the spectra of the devices without p-buffer, while in the spectra of the devices with p-buffer the peaks were generally non-existent or reduced. This demonstrates that the peaks observed in the OAS spectra are largely due to substrate traps and that the p-buffer layer is effective in isolating the channel from the substrate. A peak centered around 1.51 eV below the conduction band, which has also been observed in the literature after He+-implantation, is consistently observed in the spectra of both types of devices although it appears reduced in the spectra of the devices with buffer. In this dissertation it is shown that it is likely the traps responsible for this peak could contribute to the hysteresis observed at 300 K and could be solely responsible for the hysteresis observed at high temperatures such as 480 K, since simulations suggest that hysteresis due to semi-insulating substrate traps disappear at high temperatures such as 480 K.