Simulação em 3D da redução da fossa posterior no Chiari do tipo I

We proposed a 3D model to evaluate the role of platybasia and clivus length in the development of Chiari I (CI). Using a computer aided design software, two DICOM files of a normal CT scan and MR were used to simulate different clivus lengths (CL) and also different basal angles (BA). The final posterior fossa volume (PFV) was obtained for each variation and the percentage of the volumetric change was acquired with the same method. The initial normal values of CL and BA were 35.65 mm and 112.66 degrees respectively, with a total PFV of 209 ml. Ranging the CL from 34.65 to 29.65 - 24.65 - 19.65, there was a PFV decrease of 0.47% - 1.12% - 1.69%, respectively. Ranging the BA from 122.66 degrees to 127.66 degrees - 142.66 degrees, the PFV decreased 0.69% - 3.23%, respectively. Our model highlights the importance of the basal angle and clivus length to the development of CI.We proposed a 3D model to evaluate the role of platybasia and clivus length in the development of Chiari I (CI). Using a computer aided design software, two DICOM files of a normal CT scan and MR were used to simulate different clivus lengths (CL) and als745405408sem informaçãosem informaçãoNo presente estudo, propusemos a criação de um modelo computacional em 3D com elaboração de software onde dois arquivos em formato DICOM com uma TC e RNM de crânio foram usados para simular diferentes mensurações na extensão do clivus (EC) e no ângulo ba

Finite element analysis and fracture resistance testing of a new intraradicular post

OBJECTIVES: The objective of the present study was to evaluate a prefabricated intraradicular threaded pure titanium post, designed and developed at the São José dos Campos School of Dentistry - UNESP, Brazil. This new post was designed to minimize stresses observed with prefabricated post systems and to improve cost-benefits. MATERIAL AND METHODS: Fracture resistance testing of the post/core/root complex, fracture analysis by microscopy and stress analysis by the finite element method were used for post evaluation. The following four prefabricated metal post systems were analyzed: group 1, experimental post; group 2, modification of the experimental post; group 3, Flexi Post, and group 4, Para Post. For the analysis of fracture resistance, 40 bovine teeth were randomly assigned to the four groups (n=10) and used for the fabrication of test specimens simulating the situation in the mouth. The test specimens were subjected to compressive strength testing until fracture in an EMIC universal testing machine. After fracture of the test specimens, their roots were sectioned and analyzed by microscopy. For the finite element method, specimens of the fracture resistance test were simulated by computer modeling to determine the stress distribution pattern in the post systems studied. RESULTS: The fracture test presented the following averages and standard deviation: G1 (45.63±8.77), G2 (49.98±7.08), G3 (43.84±5.52), G4 (47.61±7.23). Stress was homogenously distributed along the body of the intraradicular post in group 1, whereas high stress concentrations in certain regions were observed in the other groups. These stress concentrations in the body of the post induced the same stress concentration in root dentin. CONCLUSIONS: The experimental post (original and modified versions) presented similar fracture resistance and better results in the stress analysis when compared with the commercial post systems tested (08/2008-PA/CEP)

Development of a methodology for bioengineering analysis of compact bones with surface remodeling using 3D boundary element method in transversely isotropic media

Orientador: Paulo SolleroTese (doutorado) - Universidade Estadual de Campinas. Faculdade de Engenharia MecanicaResumo: Este trabalho mostra o desenvolvimento de uma metodologia para análise de problemas de bioengenharia, aplicando modelagem numérica elastostática de tensões e deformações, baseada no método dos elementos de contorno com formulação 3D para meios transversalmente isotrópicos lineares, incluindo a capacidade de simulação do comportamento de remodelagem óssea superficial. A implementação do núcleo transversalmente isotrópico sobre a estrutura básica de análise por elementos de contorno 3D utilizou a solução fundamental proposta por Pan & Chou e revisada por Loloi, tendo exigido o cálculo adicional das soluções fundamentais de força de superfície a partir da derivação das soluções fundamentais de deslocamento. O modelo de remodelagem óssea superficial baseou-se na hipótese de estímulo biológico por campo de deformação, partindo de um modelo 2D, adaptado para o espaço 3D com o uso de deformações principais como grandezas de referência. As implementações foram testadas através de análises numéricas de problemas com solução analítica e validações com resultados de aplicações comerciais baseadas em elementos finitos, para problemas padrão de engenharia, bem como comparações com resultados da literatura para problemas de bioengenharia. A análise dos resultados mostrará que, tanto a metodologia quanto as implementações são funcionais, oferecendo uma base sólida para desenvolvimento e teste de novas soluções de bioengenhariaAbstract: This work shows the development of a methodology to analyse bioengineering problems using elastostatic stress-strain numerical modeling based on a 3D transversely isotropic linear boundary element formulation including surface bone remodeling simulation capabilities. The transversely isotropic kernel implementation on the basic 3D boundary element analysis program used the fundamental solution purposed by Pan & Chou and revised by Loloi, with additional fundamental solutions for traction calculation made with the displacement fundamental solution derivatives. The surface bone remodeling model was based on a 2D strain field biological stimulus, extended to the 3D space by using the principal strain as reference values. The implementations were tested through numerical analysis of problems with analytical solution and validation with commercial finite elements applications for standard engineering problems, as well as comparison with literature data for bioengineering problems. The analysis of results will show that both, the methodology and the implementations are fully functional, offering a solid start for development and test of new bioengineering solutionsDoutoradoMecanica dos Sólidos e Projeto MecanicoDoutor em Engenharia Mecânic

Desenvolvimento de um programa base em elementos de contorno para aplicações a analises mecanicas tridimensionais em bioengenharia

Orientador: Paulo SolleroDissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia MecanicaResumo: Este trabalho apresenta o desenvolvimento de um programa base, em elementos de contorno, aplicado à. análise tridimensional de tensões, para utilização como ferramenta de investigação do comportamento estrutural de ossos. A análise de tensões em estruturas ósseas é uma aplicação de grande interesse dentro da biomecânica, principalmente na área ligada à ortopedia. Esse tipo de aplicação exige que o programa possibilite a modelagem de geometrias complexas, típicas de estruturas ósseas, além de dispor de uma via aberta para a implementação de novas formulações, mais adequadas aos fenômenos naturais de materiais ósseos. Para realizar a análise tridimensional de tensões foi desenvolvido o programa E-Con3D, que utiliza elementos de contorno do tipo contínuo, quadrilateral de oito nós, quadrático e isoparamétrico. A solução fundamental implementada é a isotrópica linear homogênea. Embora o modelo de material isotrópico seja simples em comparação com o comportamento observado para o material ósseo, este consiste num primeiro passo para o desenvolvimento futuro de modelos mais adequados. Além disso, a utilização do modelo isotrópico é suficiente para o estabelecimento da funcionalidade do programa frente a aplicações envolvendo geometrias reais de estruturas ósseas. O programa foi implementado em linguagem MatLab. O programa MatLab é apresentado como uma ferramenta poderosa no desenvolvimento de programas para análise numérica, pois contém funções pré-programadas que possibilitam a implementação do método numérico em uma programação de alto nível assim como a visualização e análise dos resultados obtidos, como são apresentadas no trabalhoAbstract: This work presents a development of a boundary elements program applied to the tridimensional stress analysis and its use in the investigation of the structural behavior of a femur bone. The stress analysis' in bone structures is an application of great interest in biomechanics, mainly at the area of orthopedic applications. This kind of application requires a program which enables the modeling of complex geometries, typical of bone structures, and presents an expansion capability for implementation of new formulations more fitting to the natural phenomena that occurs in the bone material. Considering the tridimensional stress analysis a program called E-Con3D was developed. This program uses continuous, quadrilateral, eight nodes, and quadratic isoparametric boundary elements. The fundamental solution implemented is the isotropic linear homogeneous. Although the material isotropic model is quite simple when compared with the behavior observed on the bone material, this model consists in a first step to the future development of more fitting formulations. Beyond this, the use of an isotropic model is sufficient to the functionality verification of the program when applied to real geometries of bone structures. The program was implemented in MatLab® language. The MatLab® program is presented, in this work, as a powerful tool for the development of numerical analysis programs, once contains pre-programmed functions that makes possible the numerical method implementation using a high level programming language. The same may be used to the results visualization, making possible an efficient results interpretationMestradoMecanica ComputacionalMestre em Engenharia Mecânic

FINITE ELEMENT ANALYSIS OF MAXILLARY BONE STRESS CAUSED BY ARAMANY CLASS IV OBTURATOR PROSTHESES

Statement of problem. The retention of an Aramany Class IV removable partial dental prosthesis can be compromised by a lack of support. The biomechanics of this obturator prosthesis result in an unusual stress distribution on the residual maxillary bone. Purpose. This study evaluated the biomechanics of an Aramany Class IV obturator prosthesis with finite element analysis and a digital 3-dimensional (3-D) model developed from a computed tomography scan; bone stress was evaluated according to the load placed on the prosthesis. Material and methods. A 3-D model of an Aramany Class IV maxillary resection and prosthesis was constructed. This model was used to develop a finite element mesh. A 120 N load was applied to the occlusal and incisal platforms corresponding to the prosthetic teeth. Qualitative analysis was based on the scale of maximum principal stress; values obtained through quantitative analysis were expressed in MPa. Results. Under posterior load, tensile and compressive stresses were observed; the tensile stress was greater than the compressive stress, regardless of the bone region, and the greatest compressive stress was observed on the anterior palate near the midline. Under an anterior load, tensile stress was observed in all of the evaluated bone regions; the tensile stress was greater than the compressive stress, regardless of the bone region. Conclusions. The Aramany Class IV obturator prosthesis tended to rotate toward the surgical resection when subjected to posterior or anterior loads. The amount of tensile and compressive stress caused by the Aramany Class IV obturator prosthesis did not exceed the physiological limits of the maxillary bone tissue. (J Prosthet Dent 2012;107:336-342

Análise Biomecânica em implantes com diferentes tipos de conexão: estudo pelo MEF-3D

The aim of this study was to evaluate the biomechanical behavior of different implant connection types, by means of three-dimensional finite element analysis. 3 Three-dimensional models were created with a graphic modeling software: SolidWorks 2006 and Rhinoceros 4.0, and InVesalius (CTI, São Paulo, Brasil), the bone was obtained by computerized tomography of a sagittal section of the molar region. The model was composed by bone block with an implant (4 x 10 mm) (Conexão Sistemas de Prótese, São Paulo), with different implant connections: external hex, internal hex and Morse-taper with the corresponding prosthetic component Ucla or Morse-taper abutment. The Three-dimensional models were transferred to finite element software Femap 10.0 (Siemens PLM Software Inc., CA, USA), to generate a mesh, boundary conditions and loading. An axial (200N) and oblique load (100N) was applied on the occlusal surface of the crowns. Analyses were performed using the finite element software NEiNastran 9.0 (Noran Engineering, Inc., USA) and transferred to the Femap 10.0 to obtain the results; after the results were visualized using von Mises stress maps and Maximum stress principal. The results showed the stress distribution was similar between models, with a little superiority of Morse-taper connection. It was concluded that: the three connection types were biomechanical viable; The Morse-taper connection presented the better internal stress distribution; there was not significant biomechanical differences on the bone.O objetivo deste estudo foi analisar o comportamento biomecânico em implantes com diferentes tipos de conexão, pelo método dos elementos finitos tridimensionais. Foram confeccionados três modelos tridimensionais, com auxílio dos programas de modelagem gráfica SolidWorks 2006 e Rhinoceros 4.0, além do programa InVesalius (CTI, São Paulo, Brasil), utilizado para gerar o modelo ósseo a partir de uma tomografia computadorizada. Cada modelo foi composto por um bloco ósseo, com um implante de 4 x 10 mm (Conexão Sistemas de Prótese, São Paulo), variando-se o tipo de conexão: hexágono externo, interno e cone-morse; utilizando seu correspondente componente protético Ucla ou pilar cone-morse sobre o implante. Após geração de geometrias, os modelos foram importados para o programa de pré e pós-processamento de elementos finitos Femap 10.0 (Siemens PLM Software Inc., EUA), onde foram geradas malhas, condições de carregamento e contorno. A carga aplicada foi de 200 N axial e 100 N oblíqua, na superfície oclusal das coroas. Os modelos foram resolvidos pelo programa NeiNastran 9.0 (Noran Engineering, Inc., EUA) e novamente importados no Femap 10.0 para obtenção dos resultados, que foram visualizados por meio de mapas de tensão von Mises e tensão máxima principal. Os resultados mostraram que a distribuição de tensões é semelhante entre os modelos, com leve superioridade dos implantes de cone-morse, sob os dois tipos de tensão estudados. Nas condições do estudo, foi possível concluir que: os três tipos de conexão são biomecanicamente viáveis; o implante cone-morse apresentou tensões internas melhores distribuídas e não houve diferenças biomecânicas significativas no tecido ósseo