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Finite element modeling

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https://www.readbyqxmd.com/read/27932407/torque-differences-according-to-tooth-morphology-and-bracket-placement-a-finite-element-study
#1
Spyridon N Papageorgiou, Iosif Sifakakis, Ludger Keilig, Raphael Patcas, Stefan Affolter, Theodore Eliades, Christoph Bourauel
INTRODUCTION: Torque of the maxillary incisors is essential in esthetics and proper occlusion, while torque expression is influenced by many factors. The aim of this finite element study was to assess the relative effect of tooth morphology, bracket prescription, and bracket positioning on tooth displacement and developed stresses/strains after torque application. METHODS: A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modelled...
December 8, 2016: European Journal of Orthodontics
https://www.readbyqxmd.com/read/27930791/computational-biomechanical-analysis-of-asymmetric-ectasia-risk-in-unilateral-post-lasik-ectasia
#2
Ali Vahdati, Ibrahim Seven, Naveen Mysore, J Bradley Randleman, William J Dupps
PURPOSE: To develop a computational approach to corneal biomechanical risk analysis in refractive surgery and to investigate its utility in an enigmatic case of unilateral ectasia after bilateral LASIK. METHODS: Preoperative corneal elevation datasets from both eyes of a patient who developed unilateral post-LASIK ectasia were used to construct geometrically patient-specific, microstructurally motivated finite element models. Models were assessed before and after implementation of case-specific treatment parameters for interocular differences in corneal geometry and strain behavior under physiological loading conditions...
December 1, 2016: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/27927513/biomechanical-assessment-of-providence-nighttime-brace-for-the-treatment-of-adolescent-idiopathic-scoliosis
#3
Amjad Sattout, Julien Clin, Nikita Cobetto, Hubert Labelle, Carl-Eric Aubin
STUDY DESIGN: Biomechanical study of the Providence brace for the treatment of adolescent idiopathic scoliosis (AIS). OBJECTIVES: To model and assess the effectiveness of Providence nighttime brace. SUMMARY OF BACKGROUND DATA: Providence nighttime brace is an alternative to traditional daytime thoracolumbosacral orthosis for the treatment of moderate scoliotic deformities. It applies three-point pressure to reduce scoliotic curves. The biomechanics of the supine position and Providence brace is still poorly understood...
July 2016: Spine Deformity
https://www.readbyqxmd.com/read/27925636/on-the-2d-simplification-of-3d-bone-implant-systems-application-to-a-femoral-cementless-hip-stem
#4
Fernando J Quevedo González, Michael Reimeringer, Natalia Nuño
Three-dimensional (3D) finite element (FE) models are commonly used to analyze the mechanical behavior of the bone under different conditions (i.e. before and after arthroplasty). They can provide detailed information but they are numerically expensive and this limits their use in cases where large or numerous simulations are required. On the other hand, 2D models show less computational cost but the precision of results depends on the approach used for the simplification. Two main questions arise: are the 3D results adequately represented in a 2D section of the model? Which approach should be used to build a 2D model that provides reliable results compared to the 3D model? In this paper, we first evaluate if the plane used for generating the 2D models of bone-implant systems adequately represents the results of the full 3D model...
December 7, 2016: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/27925634/influence-of-implant-surface-texture-design-on-peri-acetabular-bone-ingrowth-a-mechanobiology-based-finite-element-analysis
#5
Kaushik Mukherjee, Sanjay Gupta
The fixation of uncemented acetabular components largely depends on the amount of bone ingrowth, which is influenced by the design of the implant surface texture. The objective of this numerical study is to evaluate the effect of these implant texture design factors on bone ingrowth around an acetabular component. The novelty of this study lies in comparative Finite Element analysis of 3D microscale models of the implant-bone interface, considering patient-specific mechanical environment, host bone material property and implant-bone relative displacement, in combination with sequential mechanoregulatory algorithm and design of experiment based statistical framework...
December 7, 2016: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/27925236/stresses-and-strains-analysis-using-different-palatal-expander-appliances-in-upper-jaw-and-midpalatal-suture
#6
Larissa Carvalho Trojan, Libardo Andrés González-Torres, Ana Claudia Moreira Melo, Estevam Barbosa de Las Casas
Rapid maxillary expansion (RME) is the technique of increasing the transverse dimension of the upper jaw using lateral forces applied by palatal expander. Usually, this palatal appliance is anchored on posterior teeth. The purposes of this computer simulation study were to analyze the stress and strain distribution generated in the maxilla, mainly in midpalatal suture (MPS), during RME by tooth-borne and bone-borne expanders and to study the correlation between mechanical strain and Wolff's Law. The analysis was performed with finite element models developed based on Cone Beam computed tomography (CT)...
December 7, 2016: Artificial Organs
https://www.readbyqxmd.com/read/27924499/pedicle-screw-fixation-with-kyphoplasty-decreases-the-fracture-risk-of-the-treated-and-adjacent-non-treated-vertebral-bodies-a-finite-element-analysis
#7
Pan Yang, Ying Zhang, Huan-Wen Ding, Jian Liu, Lin-Qiang Ye, Jin Xiao, Qiang Tu, Tao Yang, Fei Wang, Guo-Gang Sun
Adjacent vertebral fractures are common in patients with osteoporotic vertebral compression fractures (OVCFs) after kyphoplasty. This finite element study was to examine whether short segment pedicle screw fixation (PSF) with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae after kyphoplasty for OVCFs. By simulating cement augmentation with or without short segment pedicle screw fixation (PSF), two tridimensional, anatomically detailed finite element models of the T10-L2 functional spinal junction were developed...
December 2016: Journal of Huazhong University of Science and Technology. Medical Sciences
https://www.readbyqxmd.com/read/27923602/patient-specific-chondrolabral-contact-mechanics-in-patients-with-acetabular-dysplasia-following-treatment-with-peri-acetabular-osteotomy
#8
Christine L Abraham, Spencer J Knight, Christopher L Peters, Jeffrey A Weiss, Andrew E Anderson
OBJECTIVE: Using a validated, patient-specific finite element (FE) modeling protocol, we evaluated cartilage and labrum (i.e. chondrolabral) mechanics before and after peri-acetabular osteotomy (PAO) to provide insight into the ability of this procedure to improve mechanics in dysplastic hips. DESIGN: Five patients with acetabular dysplasia were recruited in this case-controlled, prospective study. Models, which included anatomy for bone, cartilage, and labrum, were generated from computed tomography arthrography scans acquired before and after PAO...
December 3, 2016: Osteoarthritis and Cartilage
https://www.readbyqxmd.com/read/27920938/comparison-of-effectiveness-between-cork-screw-and-peg-screw-electrodes-for-transcranial-motor-evoked-potential-monitoring-using-the-finite-element-method
#9
Ryosuke Tomio, Takenori Akiyama, Takayuki Ohira, Kazunari Yoshida
BACKGROUND: Intraoperative monitoring of motor evoked potentials by transcranial electric stimulation is popular in neurosurgery for monitoring motor function preservation. Some authors have reported that the peg-screw electrodes screwed into the skull can more effectively conduct current to the brain compared to subdermal cork-screw electrodes screwed into the skin. The aim of this study was to investigate the influence of electrode design on transcranial motor evoked potential monitoring...
2016: Surgical Neurology International
https://www.readbyqxmd.com/read/27918892/the-effects-of-muscle-weakness-on-degenerative-spondylolisthesis-a-finite-element-study
#10
Rui Zhu, Wen-Xin Niu, Zhi-Li Zeng, Jian-Hua Tong, Zhi-Wei Zhen, Shuang Zhou, Yan Yu, Li-Ming Cheng
BACKGROUND: Whether muscle weakness is a cause, or result, of degenerative spondylolisthesis is not currently well understood. Little biomechanical evidence is available to offer an explanation for the mechanism behind exercise therapy. Therefore, the aim of this study is to investigate the effects of back muscle weakness on degenerative spondylolisthesis and to tease out the biomechanical mechanism of exercise therapy. METHODS: A nonlinear 3-D finite element model of L3-L5 was constructed...
November 26, 2016: Clinical Biomechanics
https://www.readbyqxmd.com/read/27918708/patient-specific-hip-fracture-strength-assessment-with-microstructural-mr-imaging-based-finite-element-modeling
#11
Chamith S Rajapakse, Alexandra Hotca, Benjamin T Newman, Austin Ramme, Shaleen Vira, Elizabeth A Kobe, Rhiannon Miller, Stephen Honig, Gregory Chang
Purpose To describe a nonlinear finite element analysis method by using magnetic resonance (MR) images for the assessment of the mechanical competence of the hip and to demonstrate the reproducibility of the tool. Materials and Methods This prospective study received institutional review board approval and fully complied with HIPAA regulations for patient data. Written informed consent was obtained from all subjects. A nonlinear finite element analysis method was developed to estimate mechanical parameters that relate to hip fracture resistance by using MR images...
December 2, 2016: Radiology
https://www.readbyqxmd.com/read/27917580/a-combined-registration-and-finite-element-analysis-method-for-fast-estimation-of-intraoperative-brain-shift-phantom-and-animal-model-study
#12
Amrollah Mohammadi, Alireza Ahmadian, Shahram Rabbani, Ehsan Fattahi, Shapour Shirani
BACKGROUND: Finite element models for estimation of intraoperative brain shift suffer from huge computational cost. In these models, image registration and finite element analysis are two time-consuming processes. METHODS: The proposed method is an improved version of our previously developed Finite Element Drift (FED) registration algorithm. In this work the registration process is combined with the finite element analysis. In the Combined FED (CFED), the deformation of whole brain mesh is iteratively calculated by geometrical extension of a local load vector which is computed by FED...
December 4, 2016: International Journal of Medical Robotics + Computer Assisted Surgery: MRCAS
https://www.readbyqxmd.com/read/27916382/neochord-placement-versus-triangular-resection-in-mitral-valve-repair-a-finite-element-model
#13
Ashley E Morgan, Joe L Pantoja, Eugene A Grossi, Liang Ge, Jonathan W Weinsaft, Mark B Ratcliffe
BACKGROUND: Recurrent mitral regurgitation after mitral valve repair is common, occurring in nearly 50% of patients within 10 years of surgery. Durability of repair is partly related to stress distribution over the mitral leaflets. We hypothesized that repair with neochords (NCs) results in lower stress than leaflet resection (LR). MATERIALS AND METHODS: Magnetic resonance imaging and 3D echocardiography were performed before surgical repair of P2 prolapse in a single patient...
November 2016: Journal of Surgical Research
https://www.readbyqxmd.com/read/27915026/effects-of-model-definitions-and-parameter-values-in-finite-element-modeling-of-human-middle-ear-mechanics
#14
Daniel De Greef, Felipe Pires, Joris J J Dirckx
BACKGROUND: Despite continuing advances in finite element software, the realistic simulation of middle ear response under acoustic stimulation continues to be challenging. One reason for this is the wide range of possible choices that can be made during the definition of a model. Therefore, an explorative study of the relative influences of some of these choices is potentially very helpful. METHOD: Three finite element models of the human middle ear were constructed, based on high-resolution micro-computed tomography scans from three different human temporal bones...
November 30, 2016: Hearing Research
https://www.readbyqxmd.com/read/27914668/three-dimensional-finite-element-analysis-of-implant-assisted-removable-partial-dentures
#15
Ju-Won Eom, Young-Jun Lim, Myung-Joo Kim, Ho-Beom Kwon
STATEMENT OF PROBLEM: Whether the implant abutment in implant-assisted removable partial dentures (IARPDs) functions as a natural removable partial denture (RPD) tooth abutment is unknown. PURPOSE: The purpose of this 3-dimensional finite element study was to analyze the biomechanical behavior of implant crown, bone, RPD, and IARPD. MATERIAL AND METHODS: Finite element models of the partial maxilla, teeth, and prostheses were generated on the basis of a patient's computed tomographic data...
November 30, 2016: Journal of Prosthetic Dentistry
https://www.readbyqxmd.com/read/27914393/influence-of-vocal-tract-geometry-simplifications-on-the-numerical-simulation-of-vowel-sounds
#16
Marc Arnela, Saeed Dabbaghchian, Rémi Blandin, Oriol Guasch, Olov Engwall, Annemie Van Hirtum, Xavier Pelorson
For many years, the vocal tract shape has been approximated by one-dimensional (1D) area functions to study the production of voice. More recently, 3D approaches allow one to deal with the complex 3D vocal tract, although area-based 3D geometries of circular cross-section are still in use. However, little is known about the influence of performing such a simplification, and some alternatives may exist between these two extreme options. To this aim, several vocal tract geometry simplifications for vowels [ɑ], [i], and [u] are investigated in this work...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914390/a-substructuring-approach-for-modeling-the-acoustic-scattering-from-stiffened-submerged-shells-coupled-to-non-axisymmetric-internal-structures
#17
Valentin Meyer, Laurent Maxit, Christian Audoly
The scattered pressure from a stiffened axisymmetric submerged shell impinged by acoustic plane waves has been investigated experimentally, analytically and through numerical models. In the case where the shell is periodically stiffened, it is shown that helical, Bragg, and Bloch-Floquet waves can propagate. The influence of non-axisymmetric internal frames on these scattering phenomena is nevertheless not well known, as it can considerably increase the computational cost. To overcome this issue, the condensed transfer function (CTF) method, which has been developed to couple subsystems along linear junctions in the case of a mechanical excitation, is extended to acoustical excitations...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914383/the-development-of-a-whole-head-human-finite-element-model-for-simulation-of-the-transmission-of-bone-conducted-sound
#18
You Chang, Namkeun Kim, Stefan Stenfelt
A whole head finite element model for simulation of bone conducted (BC) sound transmission was developed. The geometry and structures were identified from cryosectional images of a female human head and eight different components were included in the model: cerebrospinal fluid, brain, three layers of bone, soft tissue, eye, and cartilage. The skull bone was modeled as a sandwich structure with an inner and outer layer of cortical bone and soft spongy bone (diploë) in between. The behavior of the finite element model was validated against experimental data of mechanical point impedance, vibration of the cochlear promontories, and transcranial BC sound transmission...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914306/a-contactless-ultrasonic-surface-wave-approach-to-characterize-distributed-cracking-damage-in-concrete
#19
Suyun Ham, Homin Song, Michael L Oelze, John S Popovics
We describe an approach that utilizes ultrasonic surface wave backscatter measurements to characterize the volume content of relatively small distributed defects (microcrack networks) in concrete. A simplified weak scattering model is used to demonstrate that the scattered wave field projected in the direction of the surface wave propagation is relatively insensitive to scatterers that are smaller than the propagating wavelength, while the scattered field projected in the opposite direction is more sensitive to sub-wavelength scatterers...
November 9, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27913901/3d-active-passive-response-of-human-knee-joint-in-gait-is-markedly-altered-when-simulated-as-a-planar-2d-joint
#20
H Marouane, A Shirazi-Adl, M Adouni
Musculoskeletal models of the lower extremity make a number of important assumptions when attempting to estimate muscle forces and tibiofemoral compartmental loads in activities such as gait. The knee is commonly idealized as a planar 2D joint in the sagittal plane with no consideration of motions and equilibrium in remaining planes. With muscle forces predicted, the static equilibrium in the frontal plane is then used to estimate compartmental loads neglecting also joint passive resistance and assuming condylar contact centers...
December 2, 2016: Biomechanics and Modeling in Mechanobiology
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