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Finite element analysis

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https://www.readbyqxmd.com/read/28092094/comparison-and-evaluation-of-stresses-generated-by-rapid-maxillary-expansion-and-the-implant-supported-rapid-maxillary-expansion-on-the-craniofacial-structures-using-finite-element-method-of-stress-analysis
#1
Varun Jain, Tarulatha R Shyagali, Prabhuraj Kambalyal, Yagnesh Rajpara, Jigar Doshi
BACKGROUND: The study aimed to evaluate and compare the stress distribution and 3-dimensional displacements along the craniofacial sutures in between the Rapid maxillary Expansion (RME) and Implant supported RME (I-RME). METHODS: Finite element model of the skull and the implants were created using ANSYS software. The finite element model thus built composed of 537692 elements and 115694 nodes in RME model & 543078 elements and 117948 nodes with implants model. The forces were applied on the palatal surface of the posterior teeth to cause 5mm of transverse displacement on either side of the palatal halves, making it a total of 10mm...
December 2017: Progress in Orthodontics
https://www.readbyqxmd.com/read/28091724/automatic-ct-based-finite-element-model-generation-for-temperature-based-death-time-estimation-feasibility-study-and-sensitivity-analysis
#2
Sebastian Schenkl, Holger Muggenthaler, Michael Hubig, Bodo Erdmann, Martin Weiser, Stefan Zachow, Andreas Heinrich, Felix Victor Güttler, Ulf Teichgräber, Gita Mall
Temperature-based death time estimation is based either on simple phenomenological models of corpse cooling or on detailed physical heat transfer models. The latter are much more complex but allow a higher accuracy of death time estimation, as in principle, all relevant cooling mechanisms can be taken into account.Here, a complete workflow for finite element-based cooling simulation is presented. The following steps are demonstrated on a CT phantom: Computer tomography (CT) scan Segmentation of the CT images for thermodynamically relevant features of individual geometries and compilation in a geometric computer-aided design (CAD) model Conversion of the segmentation result into a finite element (FE) simulation model Computation of the model cooling curve (MOD) Calculation of the cooling time (CTE) For the first time in FE-based cooling time estimation, the steps from the CT image over segmentation to FE model generation are performed semi-automatically...
January 14, 2017: International Journal of Legal Medicine
https://www.readbyqxmd.com/read/28090746/development-of-an-in-vivo-visual-robot-system-with-a-magnetic-anchoring-mechanism-and-a-lens-cleaning-mechanism-for-laparoendoscopic-single-site-surgery-less
#3
Haibo Feng, Dinghui Dong, Tengfei Ma, Jinlei Zhuang, Yili Fu, Yi Lv, Liyi Li
BACKGROUND: Surgical robot systems which can significantly improve surgical procedures have been widely used in laparoendoscopic single-site surgery (LESS). For a relative complex surgical procedure, the development of an in vivo visual robot system for LESS can effectively improve the visualization for surgical robot systems. METHODS: In this work, an in vivo visual robot system with a new mechanism for LESS was investigated. A finite element method (FEM) analysis was carried out to ensure the safety of the in vivo visual robot during the movement, which was the most important concern for surgical purposes...
January 16, 2017: International Journal of Medical Robotics + Computer Assisted Surgery: MRCAS
https://www.readbyqxmd.com/read/28090032/the-influence-of-elastic-moduli-of-core-materials-on-shear-stress-distributions-at-the-adhesive-interface-in-resin-built-up-teeth
#4
Ayaka Chiba, Takashi Hatayama, Kimisuke Kainose, Masatoshi Nakajima, David H Pashley, Noriyuki Wakabayashi, Junji Tagami
This study aimed to investigate shear stress distributions in resin built-up teeth using resin composites of varying elastic moduli (E), with or without fiber posts. Three-dimensional mathematical models of a root-filled mandibular premolar tooth were constructed. Resin post and cores were built-up with resin composites of three different E: 12,000, 18,000 and 24,000 MPa, with or without fiber posts. Finite element linear analysis was performed to calculate shear stress distributions at bonding interface between resin core and dentin...
January 13, 2017: Dental Materials Journal
https://www.readbyqxmd.com/read/28089389/three-dimensional-finite-element-model-to-predict-patterns-of-pterygomaxillary-dysjunction-during-le-fort-i-osteotomy
#5
H Fujii, N Kuroyanagi, T Kanazawa, S Yamamoto, H Miyachi, K Shimozato
The aim of this study was to determine whether non-linear three-dimensional finite element analysis (3D-FEA) can be applied to simulate pterygomaxillary dysjunction during Le Fort I osteotomy (LFI) not involving a curved osteotome (LFI-non-COSep), and to predict potential changes in the fracture pattern associated with extending the cutting line. Computed tomography (CT) image data (100 snapshots) after LFI were converted to 3D-CT images. 3D-FEA models were built using preoperative CT matrix data and used to simulate pterygomaxillary dysjunction...
January 12, 2017: International Journal of Oral and Maxillofacial Surgery
https://www.readbyqxmd.com/read/28089330/finite-element-analysis-of-implant-assisted-removable-partial-dentures-framework-design-considerations
#6
Reza Shahmiri, Raj Das
STATEMENT OF PROBLEM: Connecting an acrylic resin base to both a metal framework and a rigidly fixed implant may affect the rotational displacement of the prosthesis during loading. PURPOSE: The purpose of this finite element analysis study was to analyze the effect of connecting a denture base metal framework to an implant with the aim of decreasing the rotational movement of an implant-assisted removable partial denture. MATERIAL AND METHODS: A mesial occlusal rest direct retainer and a distal occlusal rest direct retainer were modeled and adapted to incorporate a modified denture base metal framework in the connection area for each model...
January 12, 2017: Journal of Prosthetic Dentistry
https://www.readbyqxmd.com/read/28088646/bone-microarchitecture-in-adolescent-boys-with-autism-spectrum-disorder
#7
Ann M Neumeyer, Natalia Cano Sokoloff, Erin McDonnell, Eric A Macklin, Christopher J McDougle, Madhusmita Misra
BACKGROUND: Boys with autism spectrum disorder (ASD) have lower areal bone mineral density (aBMD) than typically developing controls (TDC). Studies of volumetric BMD (vBMD) and bone microarchitecture provide information about fracture risk beyond that provided by aBMD but are currently lacking in ASD. OBJECTIVES: To assess ultradistal radius and distal tibia vBMD, bone microarchitecture and strength estimates in adolescent boys with ASD compared to TDC. DESIGN/METHODS: Cross-sectional study of 34 boys (16 ASD, 18 TDC) that assessed (i) aBMD at the whole body (WB), WB less head (WBLH), hip and spine using dual X-ray absorptiometry (DXA), (ii) vBMD and bone microarchitecture at the ultradistal radius and distal tibia using high-resolution peripheral quantitative CT (HRpQCT), and (iii) bone strength estimates (stiffness and failure load) using micro-finite element analysis (FEA)...
January 11, 2017: Bone
https://www.readbyqxmd.com/read/28087415/estimation-of-the-young-s-modulus-of-the-human-pars-tensa-using-in-situ-pressurization-and-inverse-finite-element-analysis
#8
S Alireza Rohani, Soroush Ghomashchi, Sumit K Agrawal, Hanif M Ladak
Finite-element models of the tympanic membrane are sensitive to the Young's modulus of the pars tensa. The aim of this work is to estimate the Young's modulus under a different experimental paradigm than currently used on the human tympanic membrane. These additional values could potentially be used by the auditory biomechanics community for building consensus. The Young's modulus of the human pars tensa was estimated through inverse finite-element modelling of an in-situ pressurization experiment. The experiments were performed on three specimens with a custom-built pressurization unit at a quasi-static pressure of 500 Pa...
January 10, 2017: Hearing Research
https://www.readbyqxmd.com/read/28081009/influence-of-wall-thickness-and-diameter-on-arterial-shear-wave-elastography-a-phantom-and-finite-element-study
#9
Elira Maksuti, Fabiano Bini, Stefano Fiorentini, Giulia Blasi, Matthew Urban, Franco Marinozzi, Matilda Larsson
Quantitative, non-invasive and local measurements of arterial mechanical properties could be highly beneficial for early diagnosis of cardiovascular disease and follow up of treatment. Arterial Shear Wave Elastography (SWE) and wave velocity dispersion analysis have previously been applied to measure arterial stiffness. Arterial wall thickness (h) and inner diameter (D) vary with age and pathology and may influence the shear wave propagation. Nevertheless, the effect of arterial geometry in SWE has not yet been systematically investigated...
January 12, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28079810/risk-of-vertebral-compression-fractures-in-multiple-myeloma-patients-a-finite-element-study
#10
D Anitha, Baum Thomas, Kirschke S Jan, Karupppasamy Subburaj
The purpose of this study was to develop and validate a finite element (FE) model to predict vertebral bone strength in vitro using multidetector computed tomography (MDCT) images in multiple myeloma (MM) patients, to serve as a complementing tool to assess fracture risk. In addition, it also aims to differentiate MM patients with and without vertebral compression fractures (VCFs) by performing FE analysis on vertebra segments (T1-L5) obtained from in vivo routine MDCT imaging scans. MDCT-based FE models were developed from the in vitro vertebrae samples and were then applied to the in vivo vertebrae segments of MM patients (n = 4) after validation...
January 2017: Medicine (Baltimore)
https://www.readbyqxmd.com/read/28079471/pre-implant-modeling-of-depth-lead-placement-in-white-matter-for-maximizing-the-extent-of-cortical-activation-during-direct-neurostimulation-therapy
#11
Leopoldo Cendejas Zaragoza, Richard W Byrne, Marvin A Rossi
INTRODUCTION: The objective of this work was to predict preoperatively the maximum extent to which direct stimulation therapy can propagate through an epileptic circuit for stabilizing refractory focal-onset epilepsy. A pre-surgical workflow is presented which comprises a computationally intensive process for calculating the volume of cortical activation (VOCA) surrounding cylindrical depth contacts virtually placed in white matter. The process employs an activation function (AF) derived from cable modeling of an axon...
January 12, 2017: Neurological Research
https://www.readbyqxmd.com/read/28077396/the-effects-of-kinematically-aligned-total-knee-arthroplasty-on-stress-at-the-medial-tibia-a-case-study-for-varus-knee
#12
S Nakamura, Y Tian, Y Tanaka, S Kuriyama, H Ito, M Furu, S Matsuda
OBJECTIVES: Little biomechanical information is available about kinematically aligned (KA) total knee arthroplasty (TKA). The purpose of this study was to simulate the kinematics and kinetics after KA TKA and mechanically aligned (MA) TKA with four different limb alignments. MATERIALS AND METHODS: Bone models were constructed from one volunteer (normal) and three patients with three different knee deformities (slight, moderate and severe varus). A dynamic musculoskeletal modelling system was used to analyse the kinematics and the tibiofemoral contact force...
January 2017: Bone & Joint Research
https://www.readbyqxmd.com/read/28077378/peripheral-skeleton-bone-strength-is-positively-correlated-with-total-and-dairy-protein-intakes-in-healthy-postmenopausal-women
#13
Claire Durosier-Izart, Emmanuel Biver, Fanny Merminod, Bert van Rietbergen, Thierry Chevalley, François R Herrmann, Serge L Ferrari, René Rizzoli
BACKGROUND: Bone mineral content (BMC) and bone mineral density (BMD) are positively correlated with dietary protein intakes, which account for 1-8% of BMC and BMD variances. However, the relation between bone strength and microstructure, which are variables that are not captured by areal bone mineral density (aBMD), and dietary protein intakes, particularly from specific dietary sources, has not been clearly established. OBJECTIVE: We investigated the association between the peripheral skeleton-predicted failure load and stiffness, bone microstructure, and dietary protein intakes from various origins (animal, divided into dairy and nondairy, and vegetable origins) in healthy postmenopausal women...
January 11, 2017: American Journal of Clinical Nutrition
https://www.readbyqxmd.com/read/28074250/cortical-porosity-exhibits-accelerated-rate-of-change-in-peri-compared-with-post-menopausal-women
#14
L A Burt, J L Bhatla, D A Hanley, S K Boyd
: The rate of change in bone density was not different between peri- and post-menopausal women. Differences in rate of change were observed in bone microarchitecture, specifically cortical porosity (Ct.Po), where peri-menopausal women increased +9% per year compared with the +6% per year for post-menopausal women. INTRODUCTION: The purpose of this study was to compare changes in bone density and microarchitecture in peri- and post-menopausal women over 6 years...
January 10, 2017: Osteoporosis International
https://www.readbyqxmd.com/read/28073093/subject-specific-finite-element-analysis-of-the-carpal-tunnel-cross-sectional-to-examine-tunnel-area-changes-in-response-to-carpal-arch-loading
#15
Piyush Walia, Ahmet Erdemir, Zong-Ming Li
BACKGROUND: Manipulating the carpal arch width (i.e. distance between hamate and trapezium bones) has been suggested as a means to increase carpal tunnel cross-sectional area and alleviate median nerve compression. The purpose of this study was to develop a finite element model of the carpal tunnel and to determine an optimal force direction to maximize area. METHODS: A planar geometric model of carpal bones at hamate level was reconstructed from MRI with inter-carpal joint spaces filled with a linear elastic surrogate tissue...
January 4, 2017: Clinical Biomechanics
https://www.readbyqxmd.com/read/28070866/finite-element-analysis-of-patient-specific-mitral-valve-with-mitral-regurgitation
#16
Thuy Pham, Fanwei Kong, Caitlin Martin, Qian Wang, Charles Primiano, Raymond McKay, John Elefteriades, Wei Sun
Functional mitral regurgitation (FMR) is a significant complication of left ventricular dysfunction and strongly associated with a poor prognosis. In this study, we developed a patient-specific finite element (FE) model of the mitral apparatus in a FMR patient which included: both leaflets with thickness, annulus, chordae tendineae, and chordae insertions on the leaflets and origins on the papillary muscles. The FE model incorporated human age- and gender-matched anisotropic hyperelastic material properties, and MV closure at systole was simulated...
January 9, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28070611/dual-mobility-cups-provide-biomechanical-advantages-in-situations-at-risk-for-dislocation-a-finite-element-analysis
#17
Alexandre Terrier, Adeliya Latypova, Maika Guillemin, Valérie Parvex, Olivier Guyen
PURPOSE: Constrained devices, standard implants with large heads, and dual mobility systems have become popular options to manage instability after total hip arthroplasty (THA). Clinical results with these options have shown variable success rates and significant higher rates of aseptic loosening and mechanical failures with constrained implants. Literature suggests potential advantages of dual mobility, however little is known about its biomechanics. We present a comparative biomechanical study of a standard implant, a constrained implant, and a dual mobility system...
January 9, 2017: International Orthopaedics
https://www.readbyqxmd.com/read/28069517/fast-estimation-of-colles-fracture-load-of-the-distal-section-of-the-radius-by-homogenized-finite-element-analysis-based-on-hr-pqct
#18
Hadi S Hosseini, Andreas Dünki, Jonas Fabech, Martin Stauber, Nicolas Vilayphiou, Dieter Pahr, Michael Pretterklieber, Jasmin Wandel, Bert van Rietbergen, Philippe K Zysset
Fractures of the distal section of the radius (Colles' fractures) occur earlier in life than other osteoporotic fractures. Therefore, they can be interpreted as a warning signal for later, more deleterious fractures of vertebral bodies or the femoral neck. In the past decade, the advent of HR-pQCT allowed a detailed architectural analysis of the distal radius and an automated but time-consuming estimation of its strength with linear micro-finite element (μFE) analysis. Recently, a second generation of HR-pQCT scanner (XtremeCT II, SCANCO Medical, Switzerland) with a resolution beyond 61 μm became available for even more refined biomechanical investigations in vivo...
January 7, 2017: Bone
https://www.readbyqxmd.com/read/28064363/morphometric-and-mechanical-characteristics-of-equisetum-hyemale-stem-enhance-its-vibration
#19
Urszula Zajączkowska, Stanisław Kucharski, Zdzisław Nowak, Kamila Grabowska
The order of the internodes, and their geometry and mechanical characteristics influence the capability of the Equisetum stem to vibrate, potentially stimulating spore liberation at the optimum stress setting along the stem. Equisetum hyemale L. plants represent a special example of cellular solid construction with mechanical stability achieved by a high second moment of area and relatively high resistance against local buckling. We proposed the hypothesis that the order of E. hyemale L. stem internodes, their geometry and mechanical characteristics influence the capability of the stem to vibrate, stimulating spore liberation at the minimum stress setting value along the stem...
January 7, 2017: Planta
https://www.readbyqxmd.com/read/28064103/why-do-some-titanium-alloy-total-hip-arthroplasty-modular-necks-fail
#20
Samo K Fokter, Andrej Moličnik, Rajko Kavalar, Primož Pelicon, Rebeka Rudolf, Nenad Gubeljak
BACKGROUND: Increased modularity in total hip arthroplasty (THA) through extra junction between the neck and the femoral stem is gaining popularity among orthopaedic community. However, the advantage of the additional junction is shadowed by an increased risk of mechanical failure. The aim of this study was to describe the exact mechanism of fracture of the modular femoral neck in an uncemented stem. METHODS: Clinical, metallurgical, and mechanical analysis including finite-element modelling and elemental-sensitive tissue analysis with the micro-PIXE method was performed on two patients treated with fully modular primary THA made from Titanium alloy of the same oval taper-cone design...
December 27, 2016: Journal of the Mechanical Behavior of Biomedical Materials
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