O sucesso a longo prazo dos implantes tem como fatores críticos a incidência e a transferência de estresses mecânicos sobre a prótese, intermediários, implantes e destes para o tecido ósseo adjacente, devendo cada parte deste sistema ser submetido somente a forças às quais estão aptos a receber. A proposta deste trabalho foi avaliar a deformação gerada nos intermediários e na região óssea peri-implantar diante da aplicação de cargas funcionais e parafuncionais em prótese parcial fixa de três elementos parafusadas sobre dois implantes. Para este trabalho, foi utilizado um modelo experimental homogêneo à base de poliuretano, simulando o tecido ósseo, com dois implantes do tipo hexágono externo paralelos que receberam intermediários do tipo multi-unit. Na superfície de cada intermediário foram instalados três sensores (strain gauges), capazes de medir a microdeformação dispostos de maneira eqüidistante entre si. Na região óssea simulada, foram instalados quatro sensores para cada implante, posicionados nas faces mesial, distal, vestibular e lingual. A aplicação da carga estática de 300N foi realizada em uma máquina de ensaios universais. As leituras foram realizadas em quatorze momentos para todos os corpos de prova, variando o direcionamento da carga (axial e inclinada à 30 graus) e simulando ainda sete diferentes pontos de aplicação de carga (1- pilar mesial, 2 - pôntico, 3- pilar distal, 4- simultaneamente no pilar mesial, pontico e pilar distal, 5- no pilar mesial e distal, sem contato no pôntico, 6- no pilar mesial e no pôntico, 7- no pilar distal e no pôntico). Os resultados mostraram que a direção da carga interferiu na magnitude e distribuição da microdeformação, de forma que, no osso simulado, os valores encontrados na carga axial se encontraram dentro da tolerância fisiológica independente do local de aplicação de carga. Observou-se uma distribuição mais uniforme quando a carga foi aplicada simultaneamente nos pilres mesial, pôntico e pilar distal. Por outro lado, valores de microdeformação acima do limite de tolerância foram observados para a carga inclinada e nesta situação o local de aplicação teve influência na microdeformação, com valores extremamente elevados e sem uniformidade na distribuição, devendo o carregamento oblíquo ser evitado. / Long-term success with implants has some critical factors such as incidence and transmission of mechanical stress to the prosthesis, abutments, and implants to the adjacent bone tissue. Each part of the system should be subjected to loads under its strength limit. The purpose of the present study was to evaluate abutment and peri-implant bone tissue strains during functional and parafunctional loads application in a three-unit screw-retained fixed prosthesis supported by two implants. In order to simulate the bone tissue, an experimental model made of homogeneous polyurethane was used wherein two external hexagon implants were placed parallel to each other, provided with multi-unit abutments. On the surface of each abutment three sensors (strain gauges) were positioned equidistant to each other to measure microstrains. The simulated bone around each implant received four strain gauges, positioned on the mesial, distal, buccal and lingual aspects. The tests were performed applying a 300N static load on a universal testing machine. The readings were made at fourteen moments for each specimen, changing load direction (axial and 30 degrees oblique) and also simulating seven different points of load application (1- mesial abutment, 2- pontic, 3- distal abutment, 4- simultaneously on the mesial abutment, pontic and distal abutment, 5- mesial and distal abutment (no pontic contact), 6- mesial abumtent and pontic, 7- distal abutment and pontic. The results showed that the load direction significantly influenced the magnitude and distribution of microstrains, so that for the simulated bone, the values found during axial load were within the physiological threshold independent of the point of load application; however, a more uniform distribution was observed when force was applied simultaneously on the mesial abutment, pontic and distal abutment. Furthermore, microstrain values above the tolerance limits were observed during oblique load, and for this condition, the point of load application significantly influenced the microstrains, with extremely high values and non-uniform distribution for all load conditions tested. Therefore, oblique loading must be avoided.

Problemática: De ocorrência clínica bastante comum, o afrouxamento dos parafusos que compõe uma prótese sobre implante é uma complicação que traz transtornos tanto para o profissional quanto para o paciente. Proposição: O objetivo deste estudo foi comparar o grau de rotação de parafusos de titânio (grau 5), durante testes de torque, re-torque e os valores de destorque (Ncm), sobre infra-estruturas fundidas em monobloco, a partir de abutments tipo UCLA totalmente calcináveis e com cinta usinada em Co-Cr. Material e métodos: Um dispositivo leitor da quantidade de graus foi especialmente desenvolvido para este estudo, juntamente com um software . Dois implantes Revolution - SIN de 3,75 mm de diâmetro e 13 mm de comprimento e hexágono externo foram montados na base de um dispositivo e diretamente sobre eles foram obtidos os padrões para fundição dos corpos de prova. Cada corpo de prova foi formado por dois abutments tipo UCLA, totalmente calcináveis ou com cinta em Co-Cr, interligados por uma barra acrílica. Foram obtidos 10 corpos de prova para cada grupo e 40 parafusos de titânio (Grau 5) foram usados para os testes. Obteve-se então a medição do ângulo criado durante o aperto e re-aperto dos parafusos, sendo o re-aperto realizado após 10 minutos do aperto inicial, ambos sob torque de 30Ncm. Após o procedimento de re-aperto, o valor de destoque era imediatamente aferido e anotado em Ncm, possibilitando avaliar a quantidade de torque retido pelo parafuso após o procedimento, sendo esta seqüência realizada 3 vezes para cada corpo de prova. Análises em MEV foram realizadas nas bases de assentamento dos abutments antes e após a realização dos testes, assim como na superfície dos parafusos, a fim de se encontrar eventuais danos na microestrutura dos mesmos. O teste ?t? de student foi aplicado para uma avaliação entre os grupos e o teste ANOVA a um critério foi utilizado para análise intra-grupo. Resultados: Os resultados revelaram que durante os procedimentos de torque (aperto), os parafusos empregados em infra-estruturas obtidas a partir de abutments totalmente calcináveis apresentaram um maior grau de rotação (ensaio1: 61,664°; ensaio 2: 47,718°; ensaio 3: 47,374°), quando comparados aos parafusos empregados em infra-estruturas obtidas de abutments com cinta usinada em Co-Cr (ensaio 1: 49,038°; ensaio 2: 41,636°; ensaio 3: 43,273°), sendo a diferença entre os grupos estatisticamente significante em todos os ensaios realizados; P<0,05. Além disso, em ambos os grupos, a maior rotação dos parafusos ocorreu no primeiro aperto dos mesmos tanto durante o procedimento de torque quanto no procedimento de re-torque. Durante o re-torque, o ângulo formado na cabeça dos parafusos também foi sempre maior para o grupo Acrílico Calcinável (ensaio 1: 14,591°; ensaio 2: 12,987°; ensaio 3: 13,095°), comparado ao grupo Co-Cr (ensaio 1: 11,481°; ensaio 2: 10,117°; ensaio 3: 12,213°), sendo que diferença estatisticamente significante foi encontrada entre os ensaio 1 e 2; P<0,05. Os valores médios de destorque (quantidade de torque retido durante o aperto dos parafusos) também foram sempre maiores para o grupo Acrílico Calcinável (ensaio 1: 27,325Ncm; ensaio 2: 27,050Ncm; ensaio 3: 26,975Ncm), quando comparado ao grupo Co-Cr (ensaio 1: 26,250Ncm; ensaio 2: 26,975Ncm; ensaio 3: 26,400Ncm), porém sem diferença estatisticamente significante. As Imagens obtidas das análises em MEV demonstraram que as superfícies das bases de assentamentos do abutments obtidos a partir de abutments totalmente calcináveis apresentaram grandes irregularidades superficiais, comparadas às obtidas a partir de bases usinadas em Co-Cr, as quais apresentaram um padrão mais liso e uniforme. Quanto à análise dos parafusos, foi encontrado que as maiores deformações dos mesmos ocorrem na base de assentamento de sua cabeça no interior do abutments assim como na região da sua primeira rosca (apical). Conclusões: Tanto para o momento de torque quanto para o momento de re-torque, infra-estruturas do grupo Acrílico Calcinável permitiram maior rotação dos parafusos dos abutments, quando comparados com o grupo Co-Cr. Na análise dos valores de destorque, estatisticamente os grupos foram considerados semelhantes. Imagens em MEV, antes da realização dos testes de torque, re-torque e destorque revelaram que a base de assentamento do grupo Acrílico Calcinável apresentou aspecto mais irregular da fundição quando comparado ao grupo Co-Cr. Em ambos os grupos, partículas de titânio foram encontradas incrustadas nestas bases de assentamento após a realização desses testes, segundo dados do EDS. As imagem em MEV revelaram ainda que os parafusos se deformam principalmente na base de sua cabeça que se assenta no interior dos abutments, assim como na região da sua primeira rosca(apical). / Problem: The abutment screw loosening is a common drawback which concerns both patients and practitioners. Purpose: The aim of this study is to compare the rotational angle degree of Grade V titanium screws during torque, retorque and detorque steps (Ncm) on one-piece cast metal frameworks obtained from UCLA burnout/Co-Cr machined collar abutments. Material and methods: Two external hexagonal implants with 3.75mm in diameter and 13mm in length (Revolution, SIN) were secured to a metallic base and the wax patterns directly fabricated over them. The UCLA burnout/ Co-Cr machined collar abutments were screwed to the implants and joined together with an acrylic resin bar. Ten samples for each abutment type were fabricated. Forty Grade V titanium screws were used in the test. The rotation angle degree was measured with the aid of an specially constructed device and a computer software, during torque and retorque procedures, being the retorque made 10 minutes after the initial torque, both under 30Ncm. After the retorque procedures, the detorque values were measured. The overall sequence (torque, retorque, and detorque) was made three times for each sample. SEM analysis at the implant-abutment interfaces were made before and after the tests, as well as on the screw surfaces to detect possible microdamaging. The Student?s t test was used for between group analyses and the one-way ANOVA test for within group analyses. Results: The rotational angle degree was higher for screws used in the UCLA burnout (test 1: 61,664°; test 2: 47,718°; test 3: 47,374°) than in the Co-Cr machined collar abutments (test 1: 49,038°; test 2: 41,636°; test 3: 43,273°) (P<.05). The highest rotational degree values were observed on the first screwing during torque and retorque procedures. During retorque, the angle formed on the screw head was higher for the UCLA burnout (test 1: 14,591°; test 2: 12,987°; test 3: 13,095°) than the Co-Cr machined collar abutments (test 1: 11,481°; test 2: 10,117°; test 3: 12,213°), being these differences statistically significant between the first and second screwing (P<.05). The mean detorque values were higher in the UCLA burnout (test 1: 27,325Ncm; test 2: 27,050Ncm; test 3: 26,975Ncm) than in the Co-Cr machined collar screw abutments (test 1: 26,250Ncm; test 2: 26,975Ncm; test 3: 26,400Ncm), but not statistically significant. The SEM images demonstrated that the seating surface of the UCLA burnout abutments presented greater irregularities than the Co-Cr machined collar surfaces, which present a more smooth and flat pattern. Greater deformations were found at the seating abutment screw undersurfaces and in the first apical thread as well. Conclusions: The rotational degree was higher in the torque and retorque procedures for UCLA burnout than in the Co-Cr machined collar screw abutments. The detorque values were similar in both groups. The SEM images before torque, retorque and detorque procedures revealed more surface irregularities in the UCLA burnout abutments. In both groups, titanium debris were found in the seating abutment platforms after the tests by EDS images. The SEM images revealed that the abutment screws suffer deformation in the abutment head undersurface as well as in their first apical threads.

O tratamento cirúrgico do câncer bucal pode resultar em graves seqüelas das estruturas anatômicas envolvidas na fisiologia da cavidade bucal. A extensão e a localização da ressecção cirúrgica, assim como a condição dental, são determinantes do planejamento da prótese obturadora. Este trabalho emprega a Análise de Elementos Finitos para o estudo do comportamento biomecânico de uma prótese obturadora maxilar Classe IV de Aramany, em um modelo digital desenvolvido a partir de uma TC de um indivíduo adulto. O modelo tridimensional desenvolvido no programa Rhinoceros® versão 3.0 foi utilizado para a geração da malha de elementos finitos no programa FEMAP/NASTRAN®. Uma força de 120 N foi aplicada nas plataformas oclusal e incisal, correspondentes aos dentes posteriores e anteriores da prótese obturadora, para observação das forças de tensão geradas no tecido ósseo maxilar. Os resultados são apresentados sob a forma de análise qualitativa, indicada pela escala de Tensão Máxima Principal, e análise quantitativa, representada por valores em Mega Pascal (MPa). Observou-se que o carregamento posterior provoca tensão de tração e tensão de compressão, independentemente da região óssea avaliada, induz a uma maior tensão de tração em todas as regiões ósseas observadas e a uma maior tensão de compressão na região média anterior do palato. O carregamento anterior gera tensão de tração em todas as regiões ósseas consideradas e acarreta maior tensão de tração do que tensão de compressão, independentemente da região óssea avaliada. Concluiu-se que ocorre uma tendência de rotação da prótese em direção à área de ressecção cirúrgica, tanto para o carregamento posterior como para o carregamento anterior. O nível das tensões de tração e de compressão observado neste estudo indica que o comportamento biomecânico da prótese obturadora maxilar Classe IV de Aramany encontra-se dentro dos limites fisiológicos do tecido ósseo maxilar. / The surgical treatment of oral cancer may result in severe sequel of the anatomical structures involved in oral physiology. The extension and location of surgical resection, as well as the dental condition, enjoin the prosthetic planning of the obturator prostheses. This study employs the finite elements analysis to evaluate the biomechanical behavior of Aramany Class IV obturator prostheses, in a digital model developed from a computerized tomography of an adult individual. A tridimensional model was constructed applying the software Rhinoceros® version 3.0 and then it was used to develop the finite element mesh in the software FEMAP/NASTRAN®. A 120 N load was applied to the occlusal and incisal surfaces correspondent to the prosthetic teeth. The qualitative analysis was based on Principal Maximum Tension Scale and the quantitative analysis was expressed in Mega Pascal values. Results demonstrated that the posterior load generates tensile and compression stress and a higher tension stress regardless of the osseous region, as well as a higher compression stress on the anterior medial area of residual palate. Anterior load provokes tensile stress in each of the osseous regions evaluated, in addition to a higher tensile then compression stresses, despite of the osseous region. Therefore, it was concluded that the prostheses tends to rotate towards surgical resection areas during posterior and anterior loading. The amount of tensile and compression stresses observed herein indicates that the biomechanical behavior of Aramany Class IV obturator prostheses is within the physiological limits of the maxillary osseous tissue.

Orientador: Guilherme Elias Pessanha Henriques / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-19T17:02:54Z (GMT). No. of bitstreams: 1 Tramontino-Mesquita_VanessaSilva_D.pdf: 1263598 bytes, checksum: 21599a6e0153542032add63750d48770 (MD5) Previous issue date: 2012 / Resumo: O objetivo neste estudo foi avaliar a distribuição das tensões geradas aos implantes modificados, por meio de análise extensométrica e força de destorque dos parafusos de retenção protética, de acordo com o tipo de metal da infraestrutura (Titânio comercialmente puro - Ti c.p ou Cobalto-Cromo - Co-Cr) e presença ou ausência de desajuste vertical padronizado. Um modelo metálico foi confeccionado, simulando uma mandíbula edêntula. Cinco análogos de pilares multi-unit foram fixados ao modelo metálico, posicionados de forma a reter uma prótese fixa total sobre implantes. Dez infraestruturas em titânio c.p. e 10 infraestruturas em Co-Cr foram obtidas através de fundição em monobloco. Cada infraestrutura originou dois modelos para mensuração, um adaptado e outro desadaptado em relação aos análogos. Para a obtenção dos modelos desadaptados, anéis metálicos de espessuras conhecidas (100, 200 e 300 ?m) foram posicionados entre a infraestrutura e seus análogos correspondentes. As infraestruturas foram distribuídas entre os grupos de tratamento (n=10): G1: Titânio adaptada; G2: Titânio desadaptada; G3: Co-Cr adaptada; G4: Co-Cr desadaptada. Em todos os casos, as infraestruturas foram fixadas aos análogos com torque de 10 N.cm com torquímetro digital. A força de destorque foi avaliada com torquímetro digital e o desajuste vertical, avaliado por meio de microscópio óptico (aumento de 120x), pelo teste do parafuso único. Extensometria foi utilizada para determinar as tensões geradas às fixações. As médias e desvio padrão de desajuste (?m) foram G1: 36,63 (15,84), G2: 174,45 (33,64), G3: 43,25 (14,06) e G4: 173,18 (24,45) (ANOVA e Tukey; alfa=5%), havendo diferença entre adaptados e desajuste, porém sem diferença entre Ti e Co-Cr. Não houve diferença entre os metais para tensão induzida aos implantes, mas maiores valores de desajuste promoveram maior tensão (ANOVA e Tukey; alfa=5%). Houve forte correlação positiva entre desajuste e tensão (Coeficiente de Correlação de Pearson, r=0,7475 e p<0,0001) e moderada correlação positiva entre desajuste e destorque (Coeficiente de Correlação de Pearson, r=0,3357 e p=0,0341). Para tensão e destorque, houve fraca correlação positiva (Coeficiente de Correlação de Pearson, r=0,2146 e p=0,1834). Pode-se concluir que próteses desadaptadas, independentemente do tipo de liga, promovem aumento nos valores de tensão aos implantes, mas não influenciam na força de destorque de parafusos protéticos / Abstract: This study evaluated stress induced on the implants using strain gauges analysis, and detorque loads of titanium prosthetic screws according to the type of the framework metal (c.p. Titanium or Cobalt-Chromium) and to the presence or absence of misfit. A metallic master model was fabricated, simulating an edentulous patient mandible. Five multi-unit abutment analogues were fixed on the master model, placed as though they would support a total fixed prosthesis. Ten c.p. titanium and 10 cobalt-chromium frameworks were obtained by 1-piece casting. Each framework created 2 measurement models, one passive fitted and the other misfitted to the analogues. To obtain the misfitted measurement models, metallic rings with known thickness (100, 200 and 300 ?m) were positioned between the framework and its analogues. Frameworks were distributed to treatment groups (n=10): G1: Titanium Passive Fit; G2: Titanium Misfit; G3: Cobalt-Chromium Passive Fit; and G4: Cobalt-Chromium Misfit. All infrastructures were screwed to their analogues using a digital torquimeter, with a torque of 10 N.cm. Detorque was assessed with a digital torquimeter, and misfit was evaluated by an optical microscope (120 X) according to the one-screw test. Strain gauges were used to determine stress generated on the fixations. Misfit mean values (?m) were G1: 36.63 (15.84), G2: 174.45 (33.64), G3: 43.25 (14.06) e G4: 173.18 (24.45), presenting difference between passive fit and misfit however no difference was found between the metals (ANOVA and Tukey; alfa=5%). There was no difference between materials for stress induced upon implants, but a higher level of misfit promoted higher values of stress (ANOVA and Tukey; alfa=5%). There was a strong positive correlation between fit and stress (Pearson's Correlation Coefficient, r=0.7475 and p<0.0001), and a moderate correlation between fit and detorque (Pearson's Correlation Coefficient, r=0.3357 and p=0.0341). For stress and detorque, there was a weak positive correlation (Pearson's Correlation Coefficient, r=0.2146 and p=0.1834). Misfitted prostheses, regardless of the metal type, promote high rates of stress to the implants, but do not influence the detorque of prosthetic screws / Doutorado / Protese Dental / Doutor em Clínica Odontológica

Over one million hip prostheses are implanted in patients worldwide each year and the need is increasing as the patient group of younger and more active patients is increasing. Many parameters affect the longevity of the implant, where aseptic loosening caused by wear debris is the most common reason for revision. To be able to monitor wear in vivo and also to predict the longevity of new materials for hip prostheses are therefore important issues in this interdisciplinary research area. This thesis comprise a true non-invasive 3D method for determination of acetabular cup wear using Computed Tomography (CT) intended for clinical routine use in order to plan for a revision. It also comprises investigations of the influence of surface roughness and sterilization method in wear testing of materials for hip prostheses. Mainly wear of ultra high molecular weight polyethylene (UHMWPE) was investigated since it is the most common soft bearing in hip prostheses. The 3D-CT method was found to be easy to use and showed an accuracy and repeatability at a clinical relevant level for acetabular cup wear. It should lend itself well to semi-automation. The influence of surface roughness was investigated with both a multidirectional pin-on-disk machine and with a hip simulator. A new low friction coating, Micronite, was also evaluated with the pin-on-disk machine. This coating showed potential for use in artificial joints, but further investigations are needed. In the hip simulator test, it was found that not only a rougher counter surface increased wear, but also sterilization by γ-irradiation increased wear of UHMWPE cups. / QC 20101117

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007. / This thesis is concerned with the simulation of the in vivo biomechanical performance of a cervical disc replacement. A representative (averaged) maximum range of motion (ROM), determined by measurement of 10 student participants (5 male, 5 female), was used as head motion input to a simulation model of the cervical spine containing a disc implant at the C5/C6 intervertebral level. Intradiscal pressure, relative applied force on the C5 vertebrae, bending moments and vertebral rotations were recorded. The force and motion components of the results obtained were critically evaluated against the ISO and ASTM experimental protocol standards, probing the representativeness of these standards to the actual in vivo behaviour of the cervical functional spinal unit. Further, the wear resulting from a lifetime (10 million cycles) of the ISO prescribed -and simulation determined input cycles was simulated using a linear wear model with a triangulation technique for volume lost due to wear, and compared to in vitro results in the literature. The inputs used for the wear model were determined from a validated non-linear static contact finite element method (FEM) model. The simulation “chain” shows great potential as a comparative tool for the preexperimental testing of spinal implant designs and may be used with relative success as an alternative to expensive prototype testing.

Habilitacijos procedūrai teikiamoje mokslo darbų apžvalgoje apibendrinama Vilniaus universiteto Širdies ir kraujagyslių ligų klinikos Širdies chirurgijos centro patirtis, pakartotinai operuojant ligonius po širdies vožtuvų protezavimo. Įvertintas mažai trombogeniškų protezų efektyvumas. Nustatyta, kad labai sunkių ligonių su infekuotais protezais mirštamumas nemažėja, nors pastaraisiais metais daugiau operuojame III funkcinės klasės ligonių ir jų operacijų rezultatai puikūs. Dėl pasiūlyto radikalesnio triburio vožtuvo nesandarumo gydymo pirminių operacijų metu, efektyviai mažėja pakartotinių šio vožtuvo operacijų. Įteisinta planinė seno rutulinio protezo pakeitimo operacija. Įdiegti nauji širdies pjūviai, įdiegtos krūtinės ląstos pjūvių atlikimo metodikos, farmakologiniai ir nefarmakologiniai perioperacinio kraujavimo stabdymo būdai efektyviai sumažina kraujavimo pavojų. Pasiūlytas originalus kairio skilvelio drenavimo būdas per atskira torakotominį pjūvį padeda sumažinti pooperacinį širdies nepakankamumą. Šiame darbe remiuosi kartu su bendradarbiais atliktų operacijų rezultatais. Šiuo metu kaip skyriaus, kuriame gydomi ligoniai su vožtuvų patologija, vadovas atlieku daugiau kaip pusę pakartotinių operacijų. Moksliniai pranešimai apie pakartotinių operacijų rezultatus buvo daryti Lietuvos, Pasaulio ir Europos kongresuose ir suvažiavimuose. / The review of scientific work presented for habilitation procedure summarizes the experience of redo operations of patients after replacement of heart valves accumulated at the Heart Surgery Centre of Vilnius University Clinic of Angiology and Cardiology. The efficacy of low thrombogenicity valve prostheses was evaluated. It was found out that the mortality rate of very severely ill patients with infected did not decrease; however the larger number of patients in functional class III were being operated during the period of recent years and the results of these operations were excellent. The rate of redo tricuspid valve operations had decreased effectively because of more radical surgery treatment of this valve during the primary operation. The operation of replacement of old ball prosthesis has been validated. The new incisions of the heart were introduced as well as new methods of performance of chest box incisions and pharmacologic and non-pharmacologic methods of perioperative hemostasis; the methods mentioned above effectively reduced the risk of bleeding. The original method of the left ventricle venting via separate thoracotomy incision enabled to reduce postoperative heart failure. This work is based on the results of operations performed in cooperation with co-workers. As a chief of the department where the patients with pathology of heart valves are treated, I am performing more than a half of redo operations. The scientific presentations concerning the results of... [to full text]

De traditionella armproteser som tillverkas i utvecklingsländer står inför stora problem i att leverera patienter med lämpliga hjälpmedel. Processen är inte bara tidskrävande eftersom varje enhet måste anpassas för varje enskild användare men vissa komponenter kan inte produceras lokalt vilket driver upp priset ytterligare. Syftet med detta examensarbete var att utveckla en armprotes för utvecklingsländerna med hjälp av additiv tillverkning (3D Printing) för klienten 3D Life Prints som baseras i Nairobi, Kenya. En protes är ett hjälpmedel som används för att underlätta en amputerad människa i dagliga aktiviteter och med hjälp av additiv tillverkning kan även en lokal tillverkningsprocess utvecklas och förbättras vilket skulle kunna minska tiden för tillverkning och distribution av proteser. Den initiala protesen, som låg till grund för designarbetet, var en underarmsprotes som fortfarande var i utvecklingsstadiet hos klienten. Protesen tillverkades med hjälp av tillverkningsmetoden Fused Deposit Modelling (FDM), som har den fördelen att den använder sig av relativt billiga 3D skrivare. För att sammanfatta syftet med projektet utvecklades följande frågeställningar 1. Hur tillverkas, distribueras och används konventionella proteser i jämförelse med additivt tillverkade proteser i Nairobi, Kenya? 2. Vem är den primära användaren av proteser i utvecklingsländer, vilka problem upplevs hos dagens lösningar och vilka faktorer anses vara den viktigaste hos användaren? Och varför?  3. Hur ska additivt tillverkade proteser utformas för optimal användning i utvecklingsländer?  Förutom att besvara frågeställningarna var målet att utvecklingen av systemet skulle leda till förbättrad funktionalitet för användaren och underlätta tillverkningen för organisationen.  För att få en allmän översikt över det vetenskapliga området av additivt tillverkade proteser studerades kontexten för utvecklingsländer, användarcentrerad design (eftersom syftet var att förbättra en produkt för en specifik användare), armproteser och additiv tillverkning. Resultatet, från de olika stadier av designprocessen, var den slutgiltiga designen av "3D Life Arm". Det slutliga systemet bestod av fyra huvudkomponenter, Kroppsselen, Inlägget, Proteshanden och Hylsan. Komponenterna använde sig utav additiv tillverkning i både styvt material (Kroppsselen, Hylsan och Inlägget) och flexibelt material (Proteshanden). Lokalt tillgängliga komponenter användes där additiv tillverkning inte var möjligt till exempel fisketråd och skruvar. En slutsats drogs att de två faktorer som ansågs viktigast för användaren var att produkten skulle vara estetiskt tilltalande och billig. Även sociala stigman spelar en stor roll och enligt användare och experter i Nairobi, måste protesen efterlikna den saknade armen så mycket som möjligt för att kunna smälta in. Författarna konstaterade att kostnaden var den viktigaste faktorn när man utformar proteser för utvecklingsländerna, eftersom användaren i dagsläget inte har råd med de proteser som tillverkas i Nairobi. Sammanfattningsvis utfördes en kostnads- och tidsanalys för att kontrollera tillverkningskostnaderna för hela systemet. Med tre skrivare kunde alla delar tillverkas för 282 kronor och skulle ta cirka 15 timmar och 15 minuter att skriva ut som är betydligt lägre än de funktionella proteser som tillverkades i Nairobi. Ytterligare utvärderingar krävs för att fastställa att protesen kommer att klara av påfrestningarna från dagliga aktiviteter hos användaren och en fungerande strategi för passning måste utvärderas ytterligare. Författarna tror dock att med hjälp av en fullt utbildad protestillverkare finns det en framtid för additiv tillverkning av armproteser. / The traditional prosthetic arms that are being fitted in developing countries are facing major issues in suppling patients with proper assistive aids. Not only is the process time consuming with every single unit having to be customized for the user but some parts can’t be locally produced which drives up price even further. The objective of this master thesis was to develop a prosthetic arm for developing countries with the help of additive manufacturing (3D printing) for the client 3D Life Prints which are based in Nairobi, Kenya. A prosthesis is used to aid an amputee in daily living activities. With additive manufacturing the intention is that a local manufacturing process could be developed and improved which would reduce the time of fitting and distributing a prosthesis. The initial prosthesis, that was the origin of the design, was a below elbow prosthetic arm that was being developed by the client. The prosthesis was fabricated with the additive manufacturing process fused deposition modelling (FDM) which has the advantage of providing the cheapest printers. To summarize the aim of the project the research questions that was established was as followed 1. How are conventional prosthetic arms generally being manufactured, distributed and used compared to additive manufactured prostheses in Nairobi, Kenya?  2. Who is the primary user of prosthetic arms in developing countries, what problems are they facing with current solutions and what factors are considered as the most important? And why? 3. How should additive manufactured prostheses be designed for optimal usage in developing countries? In addition to answer the research questions the aim was that the development of the system would lead to enhanced functionality for the user and to facilitate manufacturing for the organization. To get a general overview of additive manufacturing prostheses the fields theories that was studied included context of developing countries, user centred design (since the aim was to approve on a product which needed to suit a specific user), upper limb prostheses and additive manufacturing. As a result, from different stages of the design process a final design was reached called the “3D Life Arm”.  The final system was comprised of four main components, the Harness system, the Insert, the Cover and the Socket. These components used additive manufacturing in both rigid material (Harness parts, Socket and Insert) and flexible material (the Cover). Locally available components were used for parts not feasible to additive manufacture e.g. fishing wire and screws. The two factors that were concluded to be the most important for the user were the aesthetic appeal and cost. With social stigmas playing a major part according to users and experts in Nairobi, the prosthesis needs to resemble the missing limb as much as possible. It was concluded that cost was the major factor when designing prostheses for developing countries since user just wasn’t able to afford the prostheses that was being manufactured in Nairobi. In the end a cost and time analysis was conducted to verify what price the complete system would need to be manufactured. With three printers all parts could be printed for the price of 282 SEK and would take approximately 15 hours and 15 minutes to print which is considerably lower than that of the functional prosthesis being distributed in Nairobi. Further evaluations need to be done to establish that the prosthesis will manage the strains and stresses of daily living activities of the user and a complete fitting strategy needs to be evaluated further. It’s the authors belief however, that with the help of fully educated prosthetist there is a future for additive manufacturing of upper limb amputees.

Total hip joint prostheses made of CoCrMo heads versus ultra high molecular weight polyethylene (UHMWPE) cups have a limited lifetime, mainly due to the wear of the UHMWPE cups as a result of high friction between the articulating surfaces leading to osteolysis and implant loosening with revision surgery becoming inevitable in more active patients. Tribology plays an important role in developing the design, minimizing wear and reducing friction of hip joint prostheses in order to improve their long-term performance, with good lubricating properties. Metal-on-metal hip resurfacing prostheses have shown significantly lower wear rates compared with conventional metal-on-polyethylene implants and thus osteolysis is potentially reduced leading to increased lifetime of the prosthesis. Nevertheless, excessive wear of metal-on-metal joints leads to metal ion release, causing pseudo-tumours and osteolysis. An alternative approach to such bearings is the use of newly developed carbon fiber-reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups articulating against ceramic femoral heads due to their better wear resistance compared to UHMWPE. In this study, therefore, friction and lubrication properties of large diameter, as cast, Co-Cr-Mo metal-on-metal hip resurfacing implants with various diameters and clearances have been investigated and compared to those of the newly developed zirconia toughened alumina (ZTA) ceramic femoral heads articulating against carbon fiber reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups with different diameters and clearances. Friction hip simulator was used to measure frictional torque and then friction factors were calculated along with Sommerfeld numbers leading to Stribeck analysis and hence the lubricating mode was also investigated. This involved using lubricants based on pure bovine serum (BS) and diluted bovine serum (25 vol. %BS+75 vol. %distilled water) with and without carboxymethyl cellulose (CMC) (as gelling agent). Standard Rheometer was used to measure lubricant viscosity ranged from 0.0014 to 0.236 Pas at a shear rate of 3000 . Pure bovine serum, diluted bovine serum without CMC and with CMC (25BS+75DW+0.5gCMC and +1gCMC) showed pseudoplastic flow behaviour up to shear rate of ~139 s⁻¹ above which a Newtonian flow with significant increase in shear stress was observed. The viscosity flow curves for the 25BS+75DW+2gCMC, +3.5gCMC and +5gCMC showed only shear thinning up to a shear rate of 3000 . The shear rate application modified the flow behaviour of bovine serum from a pseudoplastic to a Newtonian flow depending on its purity and CMC content. This will cause a different frictional behaviour depending on joint diameter and clearance, as seen in this work. The experimental data were compared with theoretical iv predictions of the lubricating regimes by calculating theoretical film thickness and lambda ratio. The metal-on-metal Biomet ReCaps showed similar trends of Stribeck curves, i.e. friction factors decreased from ~0.12 to ~0.05 as Sommerfeld numbers increased in the range of viscosities ~0.001-0.04Pas indicating mixed lubrication regimes above which the friction factor increased to ~0.13 at a viscosity of 0.236Pas. The Stribeck analyses suggested mixed lubrication as the dominant mode with the lowest friction factor in the range ~0.09 - ~0.05 at the physiological viscosities of ~0.01 to ~0.04 Pas and that such joints can be used for more active patients as compared to the conventional total hip replacement joints with 28mm diameter. The Stribeck curves for all ZTA ceramic-on-CFR PEEK components illustrated a similar trend with BS fluids showing higher friction factors (in the range 0.22-0.13) than the diluted BS+CMC fluids (in the range 0.24-0.05). The friction tests revealed boundary-mixed lubrication regimes for the ZTA ceramic-on-CFR-PEEK joints. The results, so far, are promising and suggest clearly that the newly developed ZTA ceramic femoral heads articulating against CFR PEEK cups have similar friction and lubrication behaviour at optimum clearances to those of currently used metal-onmetal hip resurfacing implants at the range of viscosities 0.00612 to 0.155Pas. These results clearly suggest that the ZTA ceramic-on-CFR-PEEK joints showed low friction at the physiological viscosities of ~0.01Pas in the range ~0.1-0.05, suggesting that these novel joints may be used as an alternative material choice for the reduction of osteolysis. The result of this investigation has suggested that the optimum clearance for the 52mm diameter MOM Biomet ReCaps could be ~170μm. However, 48 and 54mm joints showed lower friction due to clearances to be >200μm. For the 52mm ZTA ceramic-on-CFR-PEEK joints the optimum clearance seems to be ≥ 630μm radial clearance. These results suggested that increased clearance bearings have the potential to generate low friction and hence no risk of micro- or even macro-motion for the ceramic-on-CFR-PEEK joints. This study found no correlation between theoretical predictions and experimental data for all metal-onmetal and ZTA ceramic-on-CFR PEEK bearings at the physiological viscosity (0.0127Pas). However, at lubricant viscosity of 0.00157Pas, the theoretical prediction of lubrication regime correlated well with the experimental data, both illustrating boundary lubrication. As expected, a decrease in viscosity resulted decrease in the film thickness.

Apesar da confiabilidade e das altas taxas de sucesso relacionadas aos tratamentos com implantes, falhas das reabilitações protéticas ainda são persistentes, especialmente o afrouxamento dos parafusos de retenção dos pilares. A aplicação de um torque, que gere uma pré-carga no mesmo, tem sido o seu principal meio de prevenção, embora não tenha sido capaz de eliminá-lo completamente. A natureza do afrouxamento é complexa, e os mecanismos responsáveis pelas falhas mecânicas dos parafusos de conexão dos sistemas de implantes não estão totalmente elucidados. Modificações nos modelos das conexões protéticas e dos parafusos de retenção vêm sendo desenvolvidas com o intuito de resolver essa intercorrência. Porém, a literatura relativa à configuração ideal destas modificações biomecânicas e seus fatores determinantes envolvidos ainda é inconclusiva. Assim, o objetivo do presente do estudo foi avaliar por meio da análise tridimensional de elementos finitos, a distribuição de tensões em dois diferentes sistemas de implantes, hexágono externo (HE) e triângulo interno (TI), com parafusos de retenção de pilares planos convencionais e parafusos modificados tipo Cone Morse, estabelecendo-se qualitativamente os mapas de tensões e quantitativamente os valores de pré-carga diante do torque e de carregamentos axiais e oblíquos pré-estabelecidos. Os resultados evidenciaram que, para todos os modelos, os carregamentos externos não exerceram influência sobre os valores das tensões de von Mises e da pré-carga, e que as tensões mais elevadas concentraram-se especificamente na haste dos parafusos. A conexão TI apresentou-se biomecanicamente mais favorável do que a conexão HE, com distribuição mais homogênea de tensões ao longo do conjunto implante/pilar/parafuso. Adicionalmente, os parafusos planos convencionais apresentaram, significativamente, menores tensões e valores de pré-carga superiores aos parafusos modificados tipo Cone Morse, portanto estes últimos revelaram-se mais susceptíveis a falhas mecânicas como o afrouxamento e/ou fratura. / Despite the reliability and high success rates related to treatment with implants, prosthetic rehabilitation failures are still persistent, especially the loosening of the screws holding the abutments. Applying a torque, which generates a preload on the screw, has been its primary means of prevention, although not being able to eliminate it completely. The nature of loosening is complex, and the mechanisms responsible for mechanical failure of the screw connecting the implant systems are not fully elucidated. Changes in designs of connections and prosthetic retaining screws have been developed in order to solve this complication. However, the literature on the optimal configuration of these changes and their biomechanical factors involved is still inconclusive. The objective of this study was to evaluate through three-dimensional finite element analysis, the stress distribution in two different implant systems, external hexagon (EH) and internal triangle (IT), with conventional plan screws and modified Morse Taper screws, establishing up qualitatively the stress maps and quantitatively the values of preload in front of the torque and of pre-established axial and oblique loads. The results showed that, for all models, the external loads exerted no influence on the values of von Mises stress and preload, and that the higher stresses have focused specifically on the spindle of the screws. The IT connection appeared biomechanically more favorable than the EH, with more homogeneous distribution of stresses throughout the whole implant/abutment/screw. Additionally, conventional screws showed significantly lower stress values and higher preload than the modified Morse Taper screws, then, this latter proved to be more susceptible to mechanical failures as loosening and/or fracture.