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Finite elements analysis

Young Woong Jang, DoHyung Lim, Hansol Seo, Myung Chul Lee, O-Sung Lee, Yong Seuk Lee
INTRODUCTION: Open-wedge high tibial osteotomy (OWHTO) is a well-established surgical option for medial compartment osteoarthritis of the varus knee. The initial strength of the fixation plate is critical for successful correction maintenance and healing of the osteotomy site. This study was conducted to verify if a newly designed anatomical plate (LCfit) improves the stability of both the medial implant and lateral hinge area, as well as to evaluate how the metal block contributes to both medial and lateral stability...
March 15, 2018: Archives of Orthopaedic and Trauma Surgery
Daisuke Nakashima, Tsukasa Kanchiku, Norihiro Nishida, Saki Ito, Junji Ohgi, Hidenori Suzuki, Yasuaki Imajo, Masahiro Funaba, Xian Chen, Toshihiko Taguchi
Vertebral fractures commonly occur at the thoracolumbar junction. These fractures can be treated with mild residual deformity in many cases, but are reportedly associated with increased risk of secondary vertebral fractures. In the present study, a three-dimensional (3D) whole spine model was constructed using the finite element method to explore the mechanism of development of compression fractures. The 3D model of the whole spine, from the cervical spine to the pelvis, was constructed from computed tomography (CT) images of an adult male...
April 2018: Experimental and Therapeutic Medicine
Alejandra Nieto, Holger Roehl
There has been a growing interest in recent years in the assessment of suitable vial/stopper combinations for storage and shipment of frozen drug products. Considering that the glass transition temperature (Tg) of butyl rubber stoppers used in Container Closure Systems (CCS) is between -55°C to -65°C, a storage or shipment temperature of a frozen product below the Tg of the rubber stopper, may require special attention, since below the Tg the rubber becomes more plastic-like and loses its elastic (sealing) characteristics...
March 15, 2018: PDA Journal of Pharmaceutical Science and Technology
Franz X Bauer, Veronika Heinrich, Florian D Grill, Felix Wölfle, Dennis M Hedderich, Andrea Rau, Klaus-Dietrich Wolff, Lucas M Ritschl, Denys J Loeffelbein
Nasoalveolar Molding (NAM) is associated with ambivalent acceptance regarding effectiveness and unknown long-term results. Our purpose was to analyze the stress distribution patterns within the viscero- and neurocranium of neonates during the first phase of NAM therapy. A finite element (FE) model of a healthy four-week-old neonate was generated, derived from a computed tomography scan allowing the implementation of a bone-density-dependent material model. The influence of dental germs with variable material properties, the cleft width and area of expected force application were analyzed in a worst-case scenario...
February 2, 2018: Journal of Cranio-maxillo-facial Surgery
Francesco Nappi, Antonio Nenna, Domenico Larobina, Angelo Rosario Carotenuto, Mohamed Jarraya, Cristiano Spadaccio, Massimiliano Fraldi, Massimo Chello, Christophe Acar, Thierry Carrel
OBJECTIVES: Reinforcements for the pulmonary autograft (PA) in the Ross operation have been introduced to avoid the drawback of conduit expansion and failure. With the aid of an in silico simulation, the biomechanical boundaries applied to a healthy PA during the operation were studied to tailor the best implant technique to prevent reoperation. METHODS: Follow-up echocardiograms of 66 Ross procedures were reviewed. Changes in the dimensions and geometry of reinforced and non-reinforced PAs were evaluated...
March 12, 2018: Interactive Cardiovascular and Thoracic Surgery
Royston K Y Tan, Xiaofei Wang, Shamira A Perera, Michaël J A Girard
PURPOSE: (1) To use finite element (FE) modelling to estimate local iris stresses (i.e. internal forces) as a result of mechanical pupil expansion; and to (2) compare such stresses as generated from several commercially available expanders (Iris hooks, APX dilator and Malyugin ring) to determine which design and deployment method are most likely to cause iris damage. METHODS: We used a biofidelic 3-part iris FE model that consisted of the stroma, sphincter and dilator muscles...
2018: PloS One
Valessa F Carvalho, Priscilla Bf Soares, Crisnicaw Verissimo, Roberto S Pessoa, Antheunis Versluis, Carlos J Soares
PURPOSE: The purpose of this study was to evaluate mouthguard shock absorption ability, strain, and stress generation during impact on dental implants placed in the anterior maxilla. The mouthguard material was also characterized. MATERIALS AND METHODS: Sixty experimental models were created and divided into six groups (n = 10): implant type, external hexagon (EH) and Morse taper (MT); without and with two mouthguards (MTG), EVA custom-fitted (Ct-MTG) and standard self-adapted (St-MTG)...
March 2018: International Journal of Oral & Maxillofacial Implants
Sung-Yong Cho, Yun-Hyuk Huh, Chan-Jin Park, Lee-Ra Cho
PURPOSE: To investigate the stress distribution in an implant-abutment complex with a preloaded abutment screw by comparing implant-abutment engagement features using three-dimensional finite element analysis (FEA). MATERIALS AND METHODS: For FEA modeling, two implants-one with a single (S) engagement system and the other with a double (D) engagement system-were placed in the human mandibular molar region. Two types of abutments (hexagonal, conical) were connected to the implants...
March 2018: International Journal of Oral & Maxillofacial Implants
Hamed A Hamed, Hamdy A Marzook, Nahed E Ghoneem, Mohamed I El-Anwar
AIM: This study aimed to evaluate the effect of different implant angulations in posterior maxilla on stress distribution by finite element analysis and verify its results experimentally. METHODS: Two simplified models were prepared for an implant placed vertically and tilted 25° piercing the maxillary sinus. Geometric models' components were prepared by Autodesk Inventor then assembled in ANSYS for finite element analysis. The results of finite element analysis were verified against experimental trials results which were statistically analysed using student t-test (level of significance p < 0...
February 15, 2018: Open Access Macedonian Journal of Medical Sciences
Miguel Arocena, Jorge M Pérez Zerpa, Andrés Di Paolo, Pedro A Aguilera, José Sotelo-Silveira
Cell migration involves the precise coordination between extension at the front of the cell and retraction at the rear. This coordination is particularly evident in fast moving cells such as fish keratocytes, where it leads to highly stable gliding motion, propelled at the front by broad, 0.1-0-2 μm thick lamellipodia. Transient uncoupling between extension and retraction can occur if the rear is temporarily stuck, which might eventually lead to cell shape instabilities. We have frequently observed in fish keratocytes the presence of lamellipodial radial wrinkles, detected by confocal, scanning electron and side-view microscopy as folds in the lamellipodium up to 2 μm in height...
March 9, 2018: Biochemical and Biophysical Research Communications
Oleksandr Zelyak, B Gino Fallone, Joel St-Aubin
Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field, material density, energy, and anisotropy expansion...
March 12, 2018: Physics in Medicine and Biology
Shuman Yang, Yunhua Luo, Lang Yang, Enrico Dall'Ara, Richard Eastell, Andrew L Goertzen, Eugene V McCloskey, William D Leslie, Lisa M Lix
BACKGROUND: Dual-energy X-ray absorptiometry (DXA)-based finite element analysis (FEA) has been studied for assessment of hip fracture risk. Femoral strength (FS) is the maximum force that the femur can sustain before its weakest region reaches the yielding limit. Fracture risk index (FRI), which also considers subject-specific impact force, is defined as the ratio of von Mises stress induced by a sideways fall to the bone yield stress over the proximal femur. We compared risk stratification for prior hip fracture using FS and FRI derived from DXA-based FEA...
March 8, 2018: Bone
Zainab Altai, Marco Viceconti, Amaka C Offiah, Xinshan Li
Fractures of bone account 25% of all paediatric injuries (Cooper et al. in J Bone Miner Res 19:1976-1981, 2004. ). These can be broadly categorised into accidental or inflicted injuries. The current clinical approach to distinguish between these two is based on the clinician's judgment, which can be subjective. Furthermore, there is a lack of studies on paediatric bone to provide evidence-based information on bone strength, mainly due to the difficulties of obtaining paediatric bone samples...
March 10, 2018: Biomechanics and Modeling in Mechanobiology
Anne Caroline Oenning, Alexandre Rodrigues Freire, Ana Cláudia Rossi, Felippe Bevilacqua Prado, Paulo Henrique Ferreira Caria, Lourenço Correr-Sobrinho, Francisco Haiter-Neto
OBJECTIVES: Previous studies have suggested a relationship between resorption in second molars and pressure from the eruptive force of the third molar. The aim of this study was to simulate functional forces in a mandible model by means of finite element analysis and then assess the biomechanical response produced by impacted third molars on the roots of the second molar. MATERIALS AND METHODS: A cone beam computed tomography scan presenting an impacted mandibular third molar was segmented (Mimics V17 software)...
March 10, 2018: Clinical Oral Investigations
H J A Meijer
Changes in the bone around permucosal endosseous implants can be caused by biomechanical factors. Computer models are used to calculate the location and magnitude of stresses in the bone. The finite element method is used for the construction and calculation of models. The ongoing development of software and hardware 25 years ago made it possible to construct more complex 3-dimensional models. The general aim of the dissertation was to develop a state-of-the-art computer model of an edentulous mandible with dental implants and then to calculate the influence of a number of parameters on the location and magnitude of stresses in the bone...
March 2018: Nederlands Tijdschrift Voor Tandheelkunde
Linchu Han, Chengzhi Liu, Cunbo Fan, Zhenwei Li, Jingxu Zhang, Xiaolin Yin
A warping harness is proposed to simply and efficiently correct low-order aberrations that occur during manufacturing and operation of a telescope. For the Thirty Meter Telescope (TMT) tertiary mirror, the issue to be solved by the warping harness is particularly challenging due to its complicated load conditions and limited mounting space. In this study, first, a new type of whiffletree-based warping harness configuration applied to a ¼-prototype TMT tertiary mirror is presented and optimized using finite element analysis (FEA) to improve the output precision of the moment actuator...
March 1, 2018: Applied Optics
Abdullah Tahir Şensoy, Irfan Kaymaz, Ümit Ertaş, Ali Kiki
PURPOSE: The purpose of this study is to suggest a patient-specific osteotomy line to optimize the distractor position and thus to minimize the disadvantages of conventional mandibular distraction osteogenesis (MDO) protocols. In addition, this study also aims to compare the conventional MDO protocols with the new MDO protocol proposed in this study in terms of both orthodontic outcomes and mechanical effects of osteotomy level on callus stabilization by means of the finite element method...
March 8, 2018: Journal of Craniofacial Surgery
Gustavo Assis de Paula, Guilherme Carvalho Silva, Ênio Lacerda Vilaça, Tulimar Machado Cornacchia, Cláudia Silami de Magalhães, Allyson Nogueira Moreira
PURPOSE: Biomechanical behavior of tooth-implant-supported prostheses (TISPs) with external and internal implants was compared. MATERIALS AND METHODS: Two 3-D models of TISP were designed by varying the implant: external (Model EH) and internal hexagons (Model IH). After loading, von Mises stresses were obtained in implants, abutments, and screws. Principal maximum (σmax) and minimum (σmin) stresses were analyzed in periodontal ligament (PL), alveolar bone, and periimplant bone...
March 7, 2018: Implant Dentistry
Massimiliano De Agostinis
This work deals with the structural analysis of screw clamps for external fixator devices. Screw clamps are widely used in external fixators as a means to connect the half-pins to the fixator body. The analysis is carried out by both numerical and experimental techniques, based on the case study of a clamp produced by Citieffe (Bologna, Italy). As a preliminary activity, the tribological parameters involved in the screw-clamp interaction have been characterized by means of a mixed finite element analysis and experimental procedure...
March 1, 2018: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
O Ustun, A N Ozturk
Background: Fractures in porcelain laminate veneers (PLVs) are a significant clinical problem. Preparation designs can affect stress distribution, which leads to fractures in PLVs. Therefore, identification of the most favorable preparation design in terms of stress distribution is required. Objective: The purpose of this study is to examine the functional stress patterns of PLVs with featheredge, incisal bevel, and overlapped preparation designs under 0°, 60°, and 120° functional loads using finite element analysis...
March 2018: Nigerian Journal of Clinical Practice
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