Numerous applications in neuroscience research and neural prosthetics, such as retinal prostheses, spinal-cord surface stimulation for prosthetics, electrocorticogram (ECoG) recording for epilepsy detection, etc., involve electrical interaction with soft excitable tissues using a surface stimulation and/or recording approach. These applications require an interface that is able to set up electrical communications with a high throughput between electronics and the excitable tissue and that can dynamically conform to the shape of the soft tissue. Being a compliant and biocompatible material with mechanical impedance close to that of soft tissues, polydimethylsiloxane (PDMS) offers excellent potential as the substrate material for such neural interfaces. However, fabrication of electrical functionalities on PDMS has long been very challenging. This thesis work has successfully overcome many challenges associated with PDMS-based microfabrication and achieved an integrated technology platform for PDMS-based stretchable microelectrode arrays (sMEAs). This platform features a set of technological advances: (1) we have fabricated uniform current density profile microelectrodes as small as 10 microns in diameter; (2) we have patterned high-resolution (feature as small as 10 microns), high-density (pitch as small as 20 microns) thin-film gold interconnects on PDMS substrate; (3) we have developed a multilayer wiring interconnect technology within the PDMS substrate to further boost the achievable integration density of such sMEA; and (4) we have invented a bonding technology---via-bonding---to facilitate high-resolution, high-density integration of the sMEA with integrated circuits (ICs) to form a compact implant. Taken together, this platform provides a high-resolution, high-density integrated system solution for neural and muscular surface interfacing. sMEAs of example designs are evaluated through in vitro and in vivo experimentations on their biocompatibility, surface conformability, and surface recording/stimulation capabilities, with a focus on epimysial (i.e. on the surface of muscle) applications. Finally, as an example medical application, we investigate a prosthesis for unilateral vocal cord paralysis (UVCP) based on simultaneous multichannel epimysial recording and stimulation.

Abdominal aortic aneurysms are a leading cause of death in the U.S. where 14,000 people die from aneurysm rupture and 178,000 are diagnosed each year. A novel alternative treatment for abdominal aortic aneurysms has been proposed, where a biodegradable polymer scaffold is photopolymerized in situ around the exterior of the aneurysm. This scaffold will mechanically constrain the aneurysm from further expansion, and will deliver a drug, doxycycline, to treat the underlying biological cause of the disease. In order for device development, a suitable polymer must be designed with appropriate mechanical properties, degradation rate, polymerization, and elution rate. Poly(β-amino ester) networks have been proposed as the material of choice; however, many of their structure-property relationships have yet to be determined. Therefore, the overall goal of this work is to determine the structure-property relationships of the poly(β-amino ester) networks in order to advance the design of the treatment, and has been divided into three objectives: (1) understand the structure-property relationships of poly(β-amino ester) networks, specifically the polymerization, degradation rate, and thermo-mechanical properties, (2) determine the impact of doxycycline incorporation on degradation rate and mechanical properties, (3) evaluate the effect of simulated physiological conditions on degradation rate and mechanical properties. In the initial chapters, the fundamental structure-property relationships are established between reactant chemical structure, step-growth polymerization, photopolymerization, thermo-mechanical properties, and degradation rate using a systematic approach of two homologous series of reactants. Further tailoring of degradation rate, water content, and modulus in vitro was performed by using a copolymer network. Doxycycline inhibited photopolymerization due to overlapping absorbance spectra with the photoinitiator, but full network formation occurred by increasing the photoinitiator concentration. Networks displayed varying controlled release rates, and the underlying release mechanism was determined for each network using established methods. In order to increase mechanical properties, a co-monomer, methyl methacrylate, was added to the network to increase the glass transition temperature, toughness, and deformation capacity. These co-networks displayed temporal-control of mechanical properties in simulated physiological conditions, since degradation caused a shift in the glass transition temperature, which changed the mechanical behavior of the network. The temporal-control of mechanical properties was further investigated under degradation conditions in vitro and in vivo. Due to the mechanically active loading environment in vivo, networks displayed a decrease in toughness, yet maintained mechanical properties similar to native biological tissues. These networks establish a multifunctional biomaterials platform with materials that can be easily synthesized, photopolymerized into various geometries, and sustain mechanical properties while undergoing degradation and therapeutic agent release.

The development of small diameter tissue engineered blood vessels (TEBVs) with low thrombogenicity, low immunogenicity, suitable mechanical properties, and a capacity to remodel to their environment could significantly advance the treatment of coronary and peripheral artery disease. Despite significant advances in the field of tissue engineering, autologous vessels are still primarily utilized as grafts during bypass surgeries. However, undamaged autologous tissue may not always be available due to disease or prior surgery. TEBVs lack long-term efficacy due to a variety of types of failures including aneurysmal dilations, thrombosis, and rupture; the mechanisms of these failures are not well understood. In vitro mechanical testing may help the understanding of these failure mechanisms. The typical mechanical tests lack standardized methodologies; thus, results vary widely. The overall goal of this study is to develop novel experimental and mathematical models to study the mechanical properties and failure mechanisms of TEBVs. Our results suggest that burst pressure tests, the current standard, are not sufficient to assess a TEBVs’ suitability as a coronary substitute; creep and/or cyclic loading tests are also required. Results from this model can help identify the most insightful experiments and quantities to be measured – ultimately reducing the overall number of experimental iterations. Improving the testing and characterization of TEBVs is critically important in decreasing the time necessary to validate the mechanical and functional responses of TEBVs over time, thus quickly moving TEBVs from the benchtop to the patient.

Les mesures de contrôle de la contamination croisée sont principalement concentrées dans la salle opératoire dentaire alors que les articles transférés entre la clinique et le laboratoire dentaire et les instruments de laboratoire ont reçu peu d’attention. Cette étude vise à documenter l’application des mesures d’asepsie sur ces articles par les professionnels du domaine dentaire ainsi que leurs perceptions entourant ces mesures. Un questionnaire autoadministré et anonyme a été envoyé à un échantillon aléatoire des dentistes, denturologistes et directeurs de laboratoire dentaire qui étaient inscrits aux listes des ordres professionnels en juin 2008 dans la province de Québec. Des 1100 questionnaires envoyés, 376 ont été retournés remplis. Presque trois quarts (72,1 %) des répondants affirment faire l’asepsie des instruments de laboratoire et 74,9 %, la désinfection des articles transférés mais avec des pourcentages variables selon le groupe d’articles (empreintes, prothèses, etc.). Seulement 9,1 % de professionnels identifient de façon générale les articles désinfectés avant l’envoi. Plus de la moitié des professionnels (51,4 %) trouvent qu’ils n’ont pas assez d’information sur l’asepsie des articles transférés et 62,4 %, qu’elle est difficile à appliquer. Cette étude est la première réalisée auprès des trois groupes de professionnels et la première à étudier leurs perceptions entourant l’asepsie des articles transférés et de l’instrumentation de laboratoire. Nous avons démontré que l’application des mesures d’asepsie à ces articles par les professionnels du domaine dentaire n’est pas toujours conforme aux normes proposées et qu’il existe un besoin de renforcer leur application, surtout en ce qui a trait aux articles transférés. / Infection control practices have been mainly concentrated in the dental operatory whereas the articles transferred between the dental clinic and the dental laboratory as well as laboratory instruments have received less attention. This study attempts to document the practices of dental care professional implicated in the fabrication of dental prosthesis as to the asepsis of these items as well as their perceptions towards it. In June 2008 an auto-administrated and anonymous questionnaire was sent to a random sample of dentists, denturologists and dental laboratory directors licensed to practice in the province of Quebec (Canada). From the 1,100 questionnaires sent, 376 were returned filled-in. Almost two thirds of responders (72.1%) claim to disinfect or sterilize laboratory instruments and 74.9% to disinfect transferred articles, with percentages varying according to the group of articles (impressions, prosthesis, etc.). However, only 9.1% regularly identify disinfected work. More than half of the responders (51.4%) think it is difficult to apply a form of asepsis on transferred articles and 62.4% believe there is a lack of information towards it. This study is the first to have been addressed simultaneously to the three groups of professionals and the first to question them on their perceptions. It demonstrated that the application of asepsis measures to transferred articles and laboratory instruments by dental care professionals is not always complying with existing recommendations. There is a need to reinforce their application, especially of asepsis measures on transferred articles.

Introduction: Bien que l'importance de transférer les données de la recherche à la pratique a été largement démontrée, ce processus est toujours lent et fait face à plusieurs défis tels que la conceptualisation des évidences, la validité interne et externe de la recherche scientifique et les coûts élevés de la collecte de grandes quantités de données axées sur le patient. Les dossiers dentaires des patients contiennent des renseignements valables qui donneraient aux chercheurs cliniques une opportunité d'utiliser un large éventail d'informations quantitatives ou qualitatives. La standardisation du dossier clinique permettrait d’échanger et de réutiliser des données dans différents domaines de recherche. Objectifs: Le but de cette étude était de concevoir un dossier patient axé sur la recherche dans le domaine de la prosthodontie amovible à la clinique de premier cycle de l’Université de Montréal. Méthodes: Cette étude a utilisé des méthodes de recherche-action avec 4 étapes séquentielles : l'identification des problèmes, la collecte et l'interprétation des données, la planification et l’évaluation de l'action. Les participants de l'étude (n=14) incluaient des professeurs, des chercheurs cliniques et des instructeurs cliniques dans le domaine de la prosthodontie amovible. La collecte des données a été menée à l’aide d’une revue de littérature ciblée et complète sur les résultats en prosthodontie ainsi que par le biais de discussions de groupes et d’entrevues. Les données qualitatives ont été analysées en utilisant QDA Miner 3.2.3. Résultats: Les participants de l'étude ont soulevé plusieurs points absents au formulaire actuel de prosthodontie à la clinique de premier cycle. Ils ont partagé leurs idées pour la conception d'un nouveau dossier-patient basé sur 3 objectifs principaux: les objectifs cliniques, éducatifs et de recherche. Les principaux sujets d’intérêt en prosthodontie amovibles, les instruments appropriés ainsi que les paramètres cliniques ont été sélectionnés par le groupe de recherche. Ces résultats ont été intégrés dans un nouveau formulaire basé sur cette consultation. La pertinence du nouveau formulaire a été évaluée par le même groupe d'experts et les modifications requises ont été effectuées. Les participants de l'étude ont convenu que le cycle de recherche-action doit être poursuivi afin d'évaluer la faisabilité d’implémentation de ce dossier modifié dans un cadre universitaire. Conclusion: Cette étude est une première étape pour développer une base de données dans le domaine de la prothodontie amovible. La recherche-action est une méthode de recherche utile dans ce processus, et les éducateurs académiques sont bien placés pour mener ce type de recherche. / Introduction: Although the importance of research translating into practice has been widely recognized, this process is still slow and faces several barriers such as conceptualizations of evidence, internal and external validity of the evidence and high costs of providing large amounts of patient-based outcome data. Patient’s dental records contain valuable information that would give clinical researchers an opportunity to use a wide range of quantitative or qualitative information. Standardization of clinical record would allow the interoperability and reusability of data in different research fields. Objectives: The aim of this study was to design a research-based patient record in the field of removable prosthodontics in the undergraduate clinic of the “Université de Montréal.” Methods: This study used action research methods with 4 sequential steps: problem identification, gathering and interpreting data, action planning, and action evaluation. Study participants included professors, clinical researchers, and clinical instructors in the field of removable prosthodontics. Data collection consisted of a comprehensive literature review on prosthodontic outcomes as well as focus-group discussions and interviews. The qualitative data were analysed using QDA Miner 3.2.3. Results: The study participants raised several concerns about the deficiencies of the existing patients’ prosthodontic record in the undergraduate clinic. They shared their ideas for designing a new patient record based on 3 key objectives: clinical, educational, and research objectives. The prosthodontic outcomes of interest and appropriate instruments as well as the clinical parameters were selected by the research group and were integrated into a new research-based record. The appropriateness of the new record has been evaluated by the same panel of experts and the necessary modifications have been carried out. The study participants agreed that the action research cycle should be continued to evaluate the feasibility of the implementation of this redesigned record in the university-based setting. Conclusion: This study is a beginning effort to develop a database in the field of removable prosthodontics. Action research is a useful research method in this process, and academic educators are well placed to conduct such research.

Background: Some patients with chronic middle ear disease and multiple failed revisions, who also need a hearing aid, may benefit from an active middle ear implant. An advantage of an active middle ear implant is that the ear canal is unoccluded. Methods: Following extensive experimental development in temporal bones and investigations of various locations and attachments of a Vibrant Soundbridge transducer, a new titanium clip holder for the vibrant floating mass transducer was developed. This assembly is a total ossicular replacement prosthesis (TORP) that is placed on the stapes footplate. Six patients were implanted with this device. Results: Acoustic results demonstrate significantly improved gain, especially in the high frequencies, which is typically unobtainable by conventional hearing aids. Conclusion: The simple procedure of placing an active TORP assembly on the stapes footplate, similar to the implantation of a passive TORP prosthesis during tympanoplasty, offers promising treatment for cases of incurable middle ear disease. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

After nearly a decade of development, human-implantable sensors for detection of muscle activity have recently been demonstrated in the literature. The implantable sensors are powered and communicate wirelessly through the skin using coupled inductor coils. The focus of the present work has been the development of a new approach to modeling the inductively coupled link by using the finite element method (FEM) to simulate a three-dimensional representation of the coils and surrounding magnetic field. The validity of the simulation is tested by comparison to analytically-developed formulas for self-inductance, ac resistance and mutual inductance of the coils. Determination of these parameters is necessary for calculation of the coupling coefficient between the coils, and to fully define the lumped circuit model of the link. This 3D FEM approach is novel and attractive because it is able to encompass physical geometric parameters and material properties that have been traditionally been a challenge to determine. In particular the contribution of a ferrite-core, and the case of non-symmetrical relative coil positioning can be evaluated. / Graduate

Compliance mismatch is a significant hurdle to long-term patency in small-diameter arterial bypass grafts. Vascular tissue engineering has the potential to produce compliant, non-thrombogenic small-diameter grafts. However, current engineered grafts are relatively non-compliant, resulting in intimal hyperplasia and graft occlusion when subjected to arterial pressures. This research investigates the mechanical and biological properties of engineered constructs based on a biodegradable synthetic elastomer, poly(glycerol sebacate) (PGS). Several methods for fabricating porous PGS scaffolds in a tubular geometry were developed and compared. Adult baboon vascular cells were cultured in the scaffolds under various in vitro experimental conditions, including variations in initial cell seeding density, the type of scaffold used for culture, culture time, scaffold material, and hydrostatic pressure, and properties of the resultant constructs were compared. Scaffold fabrication using heat-shrinkable mandrels and glass tubes coated with hyaluronic acid significantly decreased tolerances of wall thickness and mechanical properties, improved handling, and decreased culture time required to reach luminal cellular confluence compared to scaffolds made with other fabrication techniques. Altering scaffold material from PGS to poly(lactide-co-glycolide) (PLGA), a benchmark biomaterial, did not affect scaffold yield, porosity, or luminal cellular confluence. Extracellular matrix (ECM) deposition increased with SMC-only culture time, and ECM deposition and remodeling during culture influenced construct compliance. Compared to PLGA scaffolds, PGS scaffolds promoted elastin crosslinking by SMCs and elastic tissue properties but attenuated collagen deposition. Hydrostatic pressure promoted ECM synthesis and deposition by SMCs and decreased construct compliance. Collagen and crosslinked elastin content in constructs correlated positively with construct burst pressure, and a negative correlation dependent on scaffold type was found between collagen content and construct compliance at low pressures. The systematic investigation of culture conditions in this research provides insights into the control of engineered blood vessel properties. The central hypothesis of this work, that grafts engineered from PGS scaffolds and adult vascular cells under biomimetic in vitro culture conditions can possess compliance comparable to autologous vessels, is true at pressures below 60 mmHg and demonstrates potential for PGS-based vascular tissue engineering. Overall, this work provides tools for engineering tubular soft tissues based on porous PGS scaffolds.

Electrical stimulation of the retina affected by photoreceptor loss (e.g., cases of retinitis pigmentosa) elicits the perception of luminous spots (so-called phosphenes) in the visual field. This phenomenon, attributed to the relatively high survival rates of neurons comprising the retina's inner layer, serves as the cornerstone of efforts to provide a microelectronic retinal prosthesis -- a device analogous to the cochlear implant. This thesis concerns phosphenes -- their elicitation and modulation, and, in turn, image analysis for use in a prosthesis. This thesis begins with a comparative review of visual modelling of electrical epiretinal stimulation and analogous acoustic modelling of electrical cochlear stimulation. The latter models involve coloured noise played to normal listeners so as to investigate speech processing and electrode design for use in cochlear implants. Subsequently, four experiments (three psychophysical and one numerical), and two statistical analyses, are presented. Intrinsic signal optical imaging in cerebral cortex is canvassed appendically. The first experiment describes a visual tracking task administered to 20 normal observers afforded simulated prosthetic vision. Fixation, saccade, and smooth pursuit, and the effect of practice, were assessed. Further, an image analysis scheme is demonstrated that, compared to existing approaches, assisted fixation and pursuit (but not saccade) accuracy (35.8% and 6.8%, respectively), and required less phosphene array scanning. Subsequently, (numerical) information-theoretic reasoning is provided for the scheme's superiority. This reasoning was then employed to further optimise the scheme (resulting in a filter comprising overlapping Gaussian kernels), and may be readily extended to arbitrary arrangements of many phosphenes. A face recognition study, wherein stimuli comprised either size- or intensity-modulated phosphenes, is then presented. The study involved unpracticed observers (n=85), and showed no 'size' --versus--'intensity' effect. Overall, a 400-phosphene (100-phosphene) image afforded subjects 89.0% (64.0%) correct recognition (two-interval forced-choice paradigm) when five seconds' scanning was allowed. Performance fell (64.5%) when the 400-phosphene image was stabilised on the retina and presented briefly. Scanning was similar in 400- and 100-phosphene tasks. The final chapter presents the statistical effects of sampling and rendering jitter on the phosphene image. These results may generalise to low-resolution imaging systems involving loosely packed pixels.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Os sistemas de retenção utilizados em próteses totais sobre implante (sobredentaduras) tem sido discutidos ao longo das últimas décadas a fim de se obter uma padronização a respeito do tratamento clínico desses pacientes. Considerando o importante papel da estabilidade das próteses para a eficiência mastigatória, bem como para elaboração do plano de tratamento adequado, o objetivo deste estudo foi avaliar a estabilidade das próteses implantossuportadas e/ou implantorretidas, utilizando para isso um estudo in vitro que simulou a força de mordida. Materiais e Métodos: Foram testadas quatro tipo diferentes de próteses totais: 1) G1 Prótese Total Removível Convencional; 2) G2 - Próteses Total Removível sobre Implantes (Overdenture), retida pelo sistema ERA; 3) G3 Prótese Total Removível sobre Implantes (Overdenture), retida pelo sistema de Barra com clipes e Encaixes - ORCE; e 4) G4 - Prótese Total Fixa sobre Implantes, seguindo o protocolo Brånemark e utilizando o sistema de barras-distais da marca Neodent. Cada grupo foi submetido ao carregamento em pontos específicos, localizados sobre os elementos 16 (F=300N), 26 (F=300N) e na região anterior 11/21(F=100N). A aferição da estabilidade foi feita através da mensuração do deslocamento vertical da prótese durante o a aplicação da força e a distância do local do carregamento, sobre os elementos 16, 26 e na região anterior, nos elementos 11 e 21. Os dados passaram no teste de normalidade de Shapiro-Wilk e foram submetidos à análise de variância ANOVA e à comparação múltipla através do teste de Bonferroni (p<0.05) Resultados: O tipo de sistema utilizado influenciou na movimentação vertical da prótese na região posterior contralateral à aplicação de força, sendo a movimentação vertical G1 > G2 > G3 &#8805; G4. Na movimentação vertical da prótese nos dentes anteriores, quando a força foi aplicada nos dentes posteriores (rotação para posterior), a movimentação vertical foi de G1 > G2 > G3 &#8805; G4. Durante a rotação para posterior, quando a força foi aplicada nos dentes anteriores (rotação para anterior) e a movimentação medida nos dentes posteriores, o comportamento foi de G1 > G2 > G3 > G4. Conclusão: Em duas das três situações testadas não houve diferença estatística entre a movimentação vertical entre o G3 e o G4, sugerindo que a estabilidade da overdenture retida por barra com clipes e encaixes se comportou, em relação a estabilidade, semelhante a prótese fixa sobre implantes. / The retain systems used by the complete dentures have been discussed over the past decades in order to achieve a standardization regarding to the clinical treatment of the patients. Considering the important meaning of the stability of dentures for chewing efficiency and for planning appropriate treatment, the aim of this study was to evaluate the stability of the implant-supported and implant-retained prosthesis, using an in vitro study that simulated the bite force. Materials and Methods: Four different types of dentures were tested: 1) G1 - Conventional Denture; 2) G2 Overdenture retained by the ERA system ; 3) G3 - Overdenture retained by bar system using clipes and fittings; and 4) G4 - Total implant-supported Prosthesis, following the Brånemark protocol and using Neodent`s distal bar. Each group was subjected to loading at specific points, located on the elements 16, 26 (F = 300Ncm) and at the anterior region 11/21 (F = 100Ncm). The measurement of vertical displacement during the test was taken out-lying from the loading area and at the elements 16, 26 and in the anterior region, at the element 11/21. Results: The data was analyzed by Shapiro -Wilk normality Test and than by ANOVA and multiple comparisons using the Bonferroni test. Conclusions: The retention system have influenced the vertical movement of the prosthesis in the posterior region contralateral to force application point, with the vertical movement as G1 > G2 > G3 > G4. In the vertical movement of the prosthesis at anterior point, when the force was applied to the posterior teeth, the vertical movement was G1 > G2 > G3 > G4. When the load was applied to the anterior teeth and movement was measured ate the posterior teeth, the behavior was G1 > G2 > G3 > G4. In two of the three situations simulated, there was no statistical difference between the vertical movement between the G3 and G4, suggesting that the stability of overdentures retained by bar with clips and fittings performed like fixed prosthesis.