Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: A methodology to facilitate analysis of dynamic subject-specific patellofemoral function is presented. An enhanced understanding of patellofemoral biomechanics will enable orthopaedic surgeons to identify the mechanisms responsible for imbalances in the joint stabilisers, while also providing objective information on which to base treatment methods. Dynamic patellofemoral function of three volunteers was simulated with a musculoskeletal computational model. The individuals underwent scans from which three-dimensional models of their patellofemoral joints were constructed. Skeletal muscles and soft tissue stabilisers were added to the skeletal models, after which subject-specific motion was simulated. After trochlear engagement, the patellae of the volunteers followed a lateral path, whereas patella tilt was subject-specific. Comparison of the predicted tilt and mediolateral position values at 30 degrees knee flexion to in-vivo MRI values showed a mean accuracy of 62.1 % and 96.9 % respectively. The patellofemoral contact load . quadriceps tendon load ratio varied between 0.7 and 1.3, whereas the mediolateral load component . resultant load ratio ranged between 0 and 0.4. Both parameters. values were similar to previous findings. The medial patellofemoral ligament tension decreased with knee flexion, while the patellar tendon-quadriceps tendon ratio followed a similar trend to that of previous findings (varied between 0.4 and 1.2). After induction of a tubercle osteotomy in the coronal plane, Volunteer One.s patella engaged the trochlear groove at an earlier knee flexion angle, while the patella of Volunteer Two only underwent a small medial displacement. Finite element analyses were employed to investigate the influence of the osteotomy on the patellofemoral pressure distribution. The mean pressure in Volunteer One.s patellofemoral joint was alleviated (17 % smaller) at all angles of flexion with the exception of 60 degrees (12 % greater). Pressure in Volunteer Two.s joint was alleviated at 30 and 45 degrees knee flexion (6 % smaller), while it was elevated (9.1 % greater) at other angles of flexion. Two commercial patellofemoral prostheses were tested on the three Volunteers. joints in the virtual environment. Prosthesis Two delivered patella shift and tilt patterns similar to the baseline values. Patellar tendon tension was slightly greater after resurfacing, with the tensions elevated most with Prosthesis Two. Medial patellofemoral ligament tension was reduced most with Prosthesis Two, while lateral retinaculum tension was increased slightly. Prosthesis Two was the best candidate to reproduce patella kinematics, while the patellofemoral kinetics was largely independent from the type of prosthesis used. The prostheses performed worse for Volunteer Three, supporting the need for the development of patient-specific prostheses. Three validated subject-specific musculoskeletal models facilitated the analysis of the individuals. patellofemoral biomechanics. The technique can potentially be employed by orthopaedic surgeons to visualise the change that an osteotomy or patellofemoral arthroplasty might induce on an individual.s patellofemoral joint. This technique might aid in the development of a tool to assist biomedical engineers in the development of new patellofemoral prostheses. Most importantly, the outcome of surgical intervention may be predicted beforehand, and a treatment procedure may be tailored to optimally fit the patellofemoral biomechanics of that individual. / AFRIKAANSE OPSOMMING: 'n Ondersoekmetode van die dinamiese gedrag van pasiënt-spesifieke patellofemorale gewrigte word beskryf. Indien die patellofemorale biomeganika beter verstaan word, kan ortopediese chirurge die meganismes wat verantwoordelik is vir oneffektiewe stabiliseerders identifiseer en behandeling op objektiewe bevindinge baseer. Die dinamiese patellofemorale funksie van drie vrywilligers is gesimuleer m.b.v. `n spier-skelet rekenaarmodel. Drie-dimensionele modelle van die individue se patellofemorale gewrig is gekonstrueer m.b.v. skanderings. Die skeletspiere en sagte ondersteuningsweefsel is tot die model toegevoeg, voordat vrywilliger-spesifieke beweging gesimuleer is. Die knieskywe van die vrywilligers het `n laterale pad gevolg nadat dit die groef binnegetree het, met die tiltwaardes uniek vir elke vrywilliger. Vergelyking van die beraamde knieskyf mediolaterale tilt en posisies by 30 grade fleksie met in-vivo magnetiese resonansieskandering waardes het `n akkuraatheid van 62.1 % en 96.9 % respektiewelik getoon. Die patellofemorale kontaklas-kwadriseps seningspanning verhouding het gewissel tussen 0.7 en 1.3; asook die mediale komponent – resultante komponent patellofemorale kontaklas wat gewissel het tussen 0 en 0.4. Beide parameters se waardes was soortgelyk aan voorheen-gepubliseerde data. Die mediale patellofemorale ligamentspanning het afgeneem met fleksie. Die patella sening-kwadriseps seningspanning verhouding was soortgelyk aan vorige gepubliseerde waardes en het gewissel tussen 0.4 en 1.2. Nadat 'n tuberkel-osteotomie in die koronale vlak aangebring is, het Vrywilliger Een se patella die femorale groef vroeër binnegetree. Vrywilliger Twee se patella het slegs `n mediale verskuiwing ondergaan. Eindige element analises is ingespan om die effek van die osteotomie op die spanningsverspreiding in die patellofemorale gewrig te ondersoek. Die gemiddelde spanning in Vrywilliger Een se gewrig was minder by alle hoeke van fleksie (17 % minder), met uitsondering van die spanning by 60 grade (12 % meer). Die spanning in Vrywilliger Twee se gewrig was minder by 30 en 45 grade (6 % minder), maar hoër by ander hoeke (9.1 % meer). Twee kommersiële patellofemorale prosteses is getoets op die drie Vrywilligers d.m.v. die model. Prostese Twee het die knieskyf-kinematika die beste nageboots. Die patella-seningspanning was effens groter na die vervanging. Prostese Twee het gesorg vir die grootste toename. Die mediale patellofemorale ligamentspanning was die kleinste toe Prostese Twee gebruik is, maar dit het gesorg vir effense hoër laterale retinakulumlaste. Die analises het getoon dat Prostese Twee die beste kandidaat is om die korrekte kinematika te herbewerkstellig. Die kinetika daarteenoor was onafhanklik van die tipe prostese wat gebruik is. Geeneen van die twee prosteses was geskik vir Vrywilliger Drie nie, wat as motivering vir die ontwikkeling van pasiënt-spesifieke prosteses dien. Drie bekragtigde vrywilliger-spesifieke spier-skelet modelle het die analise van patellofemorale biomeganika bewerkstellig. Die tegniek het die potensiaal om ortopediste in staat te stel om die effek van `n osteotomie of patellofemorale vervanging te visualiseer. Die tegniek kan verder gebruik word deur biomediese ingenieurs in die vervaardiging van nuwe patellofemorale prosteses. Meer belangrik is die feit dat die resultaat van chirurgiese ingryping voorspel kan word en optimale behandelingsprosedures beplan kan word vir die patellofemorale biomeganika van `n individu.

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Background: Cambodia has one of the highest percentages of persons living with disability in the world. Disabled people often encounter stigma in the community, and they do not have the same access to a range of services as the rest of the population. A prosthetic device can enable a disabled person and help them to become more active and participating.   Aim: The aim of this study was to investigate the perception of individuals who have received lower limb prosthesis from Exceed regarding factors that affect their level of activity and participation.  Method: The study is based on recorded qualitative interviews with semi-structured questions. 10 participants between the age of 22-68 who had a prosthesis were included in the study. An inductive content analysis was performed on the data.   Results:The study yielded two main categories which affected the participants activity and participation; Prosthetic limb and a Psychosocial environment. Conclusion: This study gives a deeper understanding of facilitators and barriers affecting activity and participation for individuals with a prosthesis. The results of this study highlight the complexity of the issue and the importance of both the prosthetic device and psychosocial environment. The study gives an insight into factor contributing to different levels of activity and participation and it can help to improve the outcome for prosthetic users. / Bakgrund: Kambodja är ett av de länder i världen med störst andel personer med funktionshinder. De stöter ofta påstigma och har inte samma tillgång till en del av de tjänster som resten av befolkningen. En protes kan göra det möjligt för en person med funktionsnedsättning att övervinna svårigheter och att bli mer aktiv och deltagande. Syfte: Syftet med denna studie var att undersöka hur protesanvändare som mottagit sin protes från Exceed uppfattar sin aktivitet och delaktighet och vilka faktorer de anser påverkar detta.    Metod: Inspelade kvalitativa intervjuer med semi-strukturerade frågor användes i studien. 10 deltagare i åldrarna 22–68 deltog i studien. En induktiv content-analys användes för att bearbeta den insamlade datan.    Resultat:Studien resulterade i två huvudkategorier; Protes och Psykosocial miljö, som enligt deltagarna påverkade deras aktivitet och delaktighet Slutsats: Denna studie ger en djupare förståelse för vad som underlättar och hindrar protesanvändare att vara aktiva och delaktiga i vardagen. Studien lyfter också fram ämnets komplexitet där protesen spelar en viktig roll men där även den psykosociala miljön har stor betydelse. Resultatet av denna studie kan hjälpa till att förstå de bakomliggande orsakerna till olika nivåer av aktivitet och deltagande och hjälpa till att förbättra situationen för protesanvändare.

Student Number : 8701355N - MDent research report - School of Oral Health Sciences - Faculty of Health Sciences / Purpose: The aim of this research project was to determine the fracture resistance to linear vertical compressive forces of acrylic and metal-reinforced acrylic fixed implant supported prosthesis cantilever arms. Methods: Ten non-reinforced and 10 reinforced acrylic superstructures were secured on five evenly distributed implants and subjected to linear axial compressive forces utilising an Instron® materials testing machine. The reinforcement consisted of commercially available preformed titanium metal strengthener bars. Force was applied to the cantilever arms 15mm distal to the distal most implant and two tests were conducted on each sample. The first drop in load recorded was noted as a fracture of the sample. Results: Fracture of the acrylic was noted at the distal most implant in both non-reinforced and the reinforced samples. The mean fracture value for the non-reinforced samples was 679N and for the reinforced samples, 628N. Conclusion: No significant difference between the fracture resistance of the two designs was noted.

Coroas cerâmicas têm sido amplamente utilizadas, entretanto, problemas relacionados com a fratura destes materiais persistem principalmente nos sistemas ceramocerâmicos na região de molar. As hipóteses nulas testadas foram que o desenho da infraestrutura e o tipo de material não terão efeito significante na resistência à fadiga. Coroas metalocerâmicas e ceramocerâmicas foram fabricadas sobre o preparo de um molar superior, o qual reproduzia a complexa morfologia dos preparos dentários. Quatro grupos foram estabelecidos (n=10 por grupo) baseados no desenho das infraestruturas (padrão ou alterada) das coroas metalocerâmicas (MC) e das ceramocerâmicas (CC), denominadas de MCSA e CCSA para as I.E. com desenho padrão e MCCA e CCCA para as com alteração no seu desenho. As infraestruturas com desenho padrão apresentaram espessura de 0,5mm em todas as suas paredes e as com alteração no desenho apresentaram a cinta lingual com 2,0mm de altura e postes proximais com 3,5mm de altura e as demais áreas com 0,5mm de espessura. As coroas ceramocerâmicas consistiam do sistema à base de alumina (In-Ceram Alumina slip cast) e as infraestruturas das coroas metalocerâmicas foram fabricadas com metal não nobre (Ni-Cr). Todas as coroas foram cimentadas com cimento resinoso Rely X ARC sobre uma réplica do preparo de resina composta, a qual teve a proposta de simular o módulo de elasticidade encontrado na dentina. Estas coroas foram submetidas ao teste de resistência à fadiga, ciclagem dinâmica, por 106 ciclos ou até que qualquer tipo de fratura fosse observada, com carga variando entre 30-300N. A força foi aplicada axialmente entre as vertentes palatina e vestibular, com endentador metálico esférico. Em intervalos de 125.000 as coroas eram verificadas à procura de danos com auxílio de estereomicroscopia. As coroas que não sofreram fraturas foram polidas sequencialmente e cada corpo de prova recebeu escores de acordo com o tipo de falha apresentada. O teste Kruskal Wallis foi utilizado para verificar se houve diferença estatisticamente significante entre os materiais e o teste de Student-Newman-Keusl foi utilizado para as comparações múltiplas. Diferenças estatisticamente significante foi encontrada entre materiais e desenhos, entretanto, os grupos com I.E. metálica (MCCA e MCSA) não apresentaram diferença estatisticamente significante. O grupo CCCA mostrou diferença estatisticamente significante em relação ao grupo CCSA. A presença do metal na infraestrutura foi preponderante na resistência à fadiga. A alteração no desenho da infraestrutura cerâmica provou ser superior em relação ao desenho sem alteração. / Ceramic crowns have been widely used, however, problems related to brittle fracture of these materials persist, especially in the posterior area. The present study tested the null hypothesis that there were no differences in fatigue resistance related to the framework design as well as to the materials used. One maxillary molar was prepared, reproducing the complex morphology of a dental preparation, to receive metal-ceramic and all-ceramic crowns. Four groups (n=10) were established based on framework designs (standard and modified) for metal-ceramic (MC) and all-ceramic (CC) crowns, named as MCSA and CCSA for standard framework designs and MCCA and CCCA for the proposed framework design modifications. On the standard design, frameworks presented 0.5mm thick walls and those with design modification a 0.5mm thick framework with a vertical increase of 2.0mm lingual and 3.5mm proximal walls. All-ceramic frameworks were made with In-Ceram Alumina slip cast and the metal-ceramic frameworks were made with nickel-chromium alloy. All crowns were cemented with resin cement (Rely X ARC) on resin composite replicas, witch have an elastic modulus similar to dentin. They were subjected to dynamic cycling fatigue test (106 cycles or until fracture), at ranging load of 30-300N. Load was located between the buccal and lingual cuspals of the crowns. At 125.000 cycles intervals, crowns were analysed under a stereomicroscopy to search for damages. Crowns without fracture were polished sequentially and received scores according to the failure mode. Kruskal Wallis test was used to check if there were a significant differences between the framework design and materials (metal and ceramic) and the Student-Newman-Keuls was used for multiple comparisons. Significant differences were found between materials and designs, however, both metal frameworks (MCCA e MCSA) were similar. CCCA group showed higher survival than CCSA group. The metal presence in the framework seemed to improve the resistance to fatigue test. However, the design modification in ceramics achieved better results than the standard design.

O tratamento cirúrgico do câncer bucal pode resultar em graves sequelas 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 próteses obturadoras maxilares Classe I, II e 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 4.0 foi utilizado para a geração da malha de elementos finitos no programa Ansys Workbench 14.0®. Uma força de 120 N foi aplicada nas plataformas oclusal e incisal, correspondentes aos dentes posteriores e anteriores das próteses obturadoras, para observação das tensões geradas sobre as próteses obturadoras. Os resultados são apresentados sob a forma de análise qualitativa, indicada pelo estudo de Tensão Máxima Principal para as estruturas acrílicas da prótese e estudo de Von Mises para as estruturas metálicas da prótese, e análise quantitativa, representada por valores em Mega Pascal (MPa). Tanto nos carregamentos posteriores como nos carregamentos anteriores, foram observadas dissipações de cargas significativas localizadas na placa palatina próxima a ressecção e na junção do metal com o acrílico, sendo os maiores valores alcançados na placa de retenção metálica para retenção do acrílico localizada posteriormente na condição de carregamento posterior em ordem crescente na Classe II de Aramany com 149,17 MPa, Classe I de Aramany com 344,08 MPa e Classe IV de Aramany alcançando valor de 390,25 MPa. No acrílico da prótese obturadora, no caso de Classe I de Aramany em carregamento posterior, foi observada uma concentração de tensão principal na região correspondente ao limite lateral e anterior da junção da placa de retenção e do acrílico no valor de 19,796 MPa de tração. Na Classe IV de Aramany em carregamento posterior, foi observada uma concentração de tensão na região posterior da junção da placa de retenção e do acrílico no valor de 18,33 MPa. Na Classe II de Aramany, em carregamento posterior foi observada uma concentração de tensão na região anterior próxima ao limite da ressecção anterior no valor de 25,45 MPa de tração. Concluiu-se que os valores quantitativos alcançados neste estudo parecem não apresentar riscos de fratura sobre a armação metálica de liga de CrCo, porem podem apresentar riscos de falha na retenção metal/acrílico da prótese obturadora maxilar. A configuração de placa de recobrimento palatino proporciona uma melhor distribuição das tensões ao longo de sua superfície. / 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, determine the prosthetic planning of the obturator prostheses. This study employs the finite elements analysis to evaluate the biomechanical behavior of Aramany Class I,II andIV 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 4.0 and then it was used to develop the finite element mesh in the software Ansys Workbench 14.0 ®. 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 stress and the quantitative analysis was expressed in Mega Pascal values. Results demonstrated that in the posterior loadings as in the anterior loadings were observed charge dissipation plate located in significant palate resection and near the junction of the metal with the acrylic and the highest values obtained in the metal retaining plate for retaining acrylic located further provided that subsequently loaded in ascending order in Class II Aramany with 149.17 MPa, Aramany with Class I and Class IV 344.08 MPa Aramany reaching value of 390.25 MPa. In acrylic prosthesis obturator in the case of Class I Aramany in subsequent loading, was observed a stress concentration in the region corresponding to the limit lateral and anterior junction of the retaining plate and the value of acrylic 19.796 MPa. Class IV for loading Aramany later, it was observed a stress concentration in the posterior region of the junction of the retaining plate of acrylic and the value of 18.336 MPa. In Class II Aramany in load was later observed a stress concentration in the anterior region near the boundary of the anterior resection worth 25.455 MPa. It was concluded that the quantitative values obtained in this study do not appear to present a risk of fracture of the metal frame CrCo alloy, but may present risks of failure in the metal retention / acrylic obturator prostesis . The configuration of palatal plate coating provides a better stress distribution along its surface.

Introdução: O objetivo desta pesquisa é analisar, pelo método fotoelástico, o comportamento das tensões que ocorrem nas estruturas periimplantares, em suportes de prótese fixa, segundo o protocolo de Brånemark, parafusada sobre cinco implantes, de diferentes comprimentos (10mm; 13mm e 15mm), quando submetidas às cargas oclusais. Métodos: Foram construídos três modelos fotoelásticos de mandíbulas: MD10; MD13 e MD15, com cinco implantes cada um, de 3,75mm de diâmetro, hexágono interno e posicionados paralelamente na região interforaminal. Sobre os implantes, em cada modelo, foram instalados pilares do tipo micro unit com cinta de 1mm e, sobre eles, uma única prótese, com uma infraestrutura metálica em cobalto/cromo, com cantilever de 15mm, revestida em resina acrílica. Foram aplicadas pressões de 1,0 e 3,0 bars e as imagens foram fotografadas e avaliadas. Resultados: Os resultados mostraram que as maiores tensões ocorreram nos implantes com 10mm de comprimento e o padrão de tensões se manteve nos vários comprimentos de implantes, mudando apenas a magnitude das tensões ao longo do corpo do implante. O incremento do comprimento foi relevante quanto à diminuição dos níveis de tensão na região analisada no modelo. Conclusões: Conclui-se que: 1) Os implantes de maior comprimento distribuíram melhor as tensões ao longo do corpo do implante; 2) As tensões se localizaram mais apicalmente, tanto por mesial como distal, nos implantes de maior comprimento, 3) Os implantes que sofreram maiores tensões foram os mais próximos do cantilever e o implante central. / The purpose of this study was to analyze, using the photoelasticity method, the behavior of stresses occurring in peri-implant structures and fixed prosthesis supports following Brånemark protocol that are screwed on five implants of different lengths, 10mm; 13mm and 15mm, when submitted to occlusal loads. Three mandible photoelastic models were built: MD10; MD13 and MD15, with five implants each, 3.75mm of internal diameter and located in parallel with each other in the interforaminal region. Microunit pillars were installed on each implant model with a 1mm-belt, and a single prosthesis was installed over them with a cobalt/chrome metallic infrastructure covered with thermoplastic acrylic resin. Loads of 1.0 and 3.0 bars were applied and images were photographed and evaluated. Results showed that highest tensions occurred in 10mm-length implants; the patterns of stresses was the same in implants of different lengths and only the magnitude of stresses changed along implant body. The greater the length the lower the stress in the analyzed region of the model. We concluded that: 1) The implants of greater length tension better distributed along the body of the implant. 2) Tensions were located more apically by both mesial and distal implants of greater length. 3) The implants have suffered greater tensions were the closest to the cantilever and implant center.