scholarly journals DENSITOMETRY-BASED FEM SIMULATIONS OF NOVEL POROUS IMPLANTS AND CORRESPONDING STRESS DISTRIBUTION AT THE PERI-IMPLANT AREA

2020 ◽  
Vol 26 ◽  
pp. 76-80
Author(s):  
Luboš Řehounek ◽  
Aleš Jíra
Keyword(s):  
Stress Distribution ◽  
Stress Shielding ◽  
Real Patient ◽  
Fem Model ◽  
Stl File ◽  
Young’S Moduli ◽  
Minimum Principal Stress ◽  
3D Geometry ◽  
Ct Data ◽  
Reducing Stress

The presented work focuses on determining the stress distribution at the peri-implant area around dental implants. A numerical analysis simulating the conditions of chewing food has been performed on a FEM model. This model has been created using anonymized real patient CT data and a dental implant model developed at CTU. The CT data served as a 3D geometry and also as a way to construct the global matrix of stiffness of the bone material. Bone density was used as the defining parameter in determining the values of Young’s moduli of individual finite elements by the computational program (Mechanical Finder). The implant was introduced as a user-created STL file, which was imported to the computational software and situated inside the geometry of the human mandible. The results show that, as predicted, porous implants achieve higher values of minimum principal stress in the bone as opposed to homogeneous implants (13.4 MPa vs. 7.0 MPa), thus reducing stress shielding.

Research of the Connecting Form about the Spherical Shell and the Nozzle

2011 ◽  
Vol 413 ◽  
pp. 520-523
Author(s):  
Cai Xia Luo
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Finite Element Model ◽  
Spherical Shell ◽  
Maximum Stress ◽  
Peak Stress ◽  
Element Model ◽  
Small Opening ◽  
Large Opening ◽  
Reducing Stress

The Stress Distribution in the Connection of the Spherical Shell and the Opening Nozzle Is Very Complex. Sharp-Angled Transition and Round Transition Are Used Respectively in the Connection in the Light of the Spherical Shell with the Small Opening and the Large One. the Influence of the Two Connecting Forms on Stress Distribution Is Analyzed by Establishing Finite Element Model and Solving it. the Result Shows there Is Obvious Stress Concentration in the Connection. Round Transition Can Reduce the Maximum Stress in Comparison with Sharp-Angled Transition in both Cases of the Small Opening and the Large Opening, Mainly Reducing the Bending Stress and the Peak Stress, but Not the Membrane Stress. the Effect of Round Transition on Reducing Stress Was Not Significant. so Sharp-Angled Transition Should Be Adopted in the Connection when a Finite Element Model Is Built for Simplification in the Future.

EFFECTS OF GEOMETRY OF THE INTRAMEDULLARY STEM OF THE ULNA COMPONENT OF HINGED ELBOW JOINT PROSTHESES ON THE BONE AND IMPLANT BENDING STRESSES

2011 ◽  
Vol 11 (05) ◽  
pp. 1271-1293 ◽  
Author(s):  
R. S. AMARASINGHE ◽  
R. A. M. RUPASINGHE ◽  
P. ANURATHAN ◽  
S. R. HERATH
Keyword(s):  
Stress Distribution ◽  
Elastic Foundation ◽  
Cross Section ◽  
Elbow Joint ◽  
Stress Shielding ◽  
Transfer Model ◽  
Bending Stress ◽  
Foundation Model ◽  
Beams On Elastic Foundation ◽  
Joint Prostheses

Cemented intramedullary stems are commonly used in total elbow arthroplasty and a considerable amount of time and money are spent for the design of such devices. In the endeavor of reducing production cost of implants, it is of particular interest as to how the geometry of the intramedullary stem can be altered in order to reduce the amount of raw material used in the manufacture of these components. The main aim of this study was to establish a simple mechanics model in preliminary designing of an elbow joint, so that the effects of the geometry of the intramedullary stem of the ulna component of hinged elbow joint prostheses on the bending stress distribution in the ulna bone and the prosthesis stem during static loading after cemented fixation of the implant can be readily estimated. Two mathematical models, namely (i) linear load transfer model and (ii) beams on elastic foundation model were used. The material considered is biocompatible stainless steel (316L). The locations of maximum bending stress occurrence were identified. Special attention was given toward identifying the locations of stress concentrations as well as the degree of stress shielding expected with various stem geometries. The results were compared to that obtained using well-established finite element analysis techniques and the beams on elastic foundation model were chosen to interpret the stresses. It was found that reducing the length of the intramedullary stem or alternatively tapering the distal end of the stem results in a considerable reduction of stress shielding and renders the bending stress distribution in the bone to be more natural. The use of a tapered stem of rectangular cross section showed a 50% reduction in material usage and a reduction of stress shielding compared to that for a stem of uniform circular cross section. Tapered rectangular sections gave the best results in terms of functionality and cost effectiveness. This observation agrees very well with the rationale of implant design that is practiced over the years. The stresses found using this study can be used for preliminary checks against yield and fracture of the stem material and bone material.

The Effect of Fillet Geometry on Stress in Weld-Bonded Joints

2010 ◽  
Vol 97-101 ◽  
pp. 767-770 ◽  
Author(s):  
Jia Ling Yan ◽  
Min You ◽  
Xiao Ling Zheng ◽  
Ding Feng Zhu ◽  
Mei Rong Zhao
Keyword(s):  
Finite Element Method ◽  
Stress Distribution ◽  
Adhesive Layer ◽  
Bonded Joints ◽  
Lap Joint ◽  
Load Bearing Capacity ◽  
Single Lap Joint ◽  
Reducing Stress ◽  
Peak Value ◽  
Alloy Weld

The influence of fillets with different geometry shape on the stress distribution in aluminum alloy weld-bonded single lap joint was investigated using elasto-plastic finite element method (FEM). The results show that it is advantageous of reducing stress concentration in adhesive layer near the ends of the lap zone in single lap weld-bonded aluminum joints and part of the stress transferring from adhesive layer to the nugget when the joints with a couple of right triangle fillets over other shapes. The load-bearing capacity of the whole weld-bonded joints may be improved. The full-triangular fillet is recommended that it be more advantageous of decreasing the stress peak value and making the stress distribution in overlap zone more uniform.

scholarly journals Is Anterior Guidance a Key Factor on Planning Implant Treatment for Free-End Missing in the Posterior Mandible?

2019 ◽  
Vol 45 (2) ◽  
pp. 100-105 ◽  
Author(s):  
Mitsuharu Nagao ◽  
Chihiro Masaki ◽  
Mihoko Nakao ◽  
Yoshinori Ito ◽  
Shintaro Tsuka ◽  
...  
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Lateral Force ◽  
Von Mises Stress ◽  
Vertical Force ◽  
Experimental Conditions ◽  
Element Analysis ◽  
Implant Placement ◽  
Ct Data ◽  
Implant Treatment

To perform safe implant treatment, the anatomical structure and bone quality at implant placement sites are evaluated based on a patient's computerized tomography (CT) data, but there is no definite method to determine placement sites and the appropriate number of implants. The objective of this study was to investigate the influence of the number and arrangement of implants on the stress distribution in 3-unit posterior fixed partial dentures for the posterior mandible by mechanical analysis using the finite element method. Three-dimensional finite element analysis models were constructed from the CT data of a patient with missing mandibular teeth (Nos. 35, 36, 37). Implant placement was simulated under various conditions. Superstructures were connected and fixed with a titanium frame. As the loading conditions, 400 N vertical and lateral loads (45° on the lingual side and 45° on the buccal side) were applied to the upper areas of Nos. 35, 36, and 37, and the stress distribution and frame displacement were evaluated. When a vertical force was applied, no difference of the von Mises stress was noted among the 5 experimental conditions. When lateral force was applied from the lingual and buccal sides at 45°, the stress was higher than that induced by vertical force under all conditions, and it was especially high under mesial and distal cantilever conditions. When displacement of the titanium frame was measured, the displacement caused by lateral force was greater than that due to vertical force. In addition, comparison between long and short distal cantilever bridges revealed that displacement of the titanium frame tended to be smaller when the short cantilever was used. These findings suggested that the stress on peri-implant tissues and displacement of the titanium frame vary depending on the configuration and number of implants, with greater stress and more marked displacement of the titanium frame being induced by lateral force when the number of implants is reduced and a cantilever bridge is selected.

scholarly journals Individualized Ophthalmic Exoplants by Means of Reverse Engineering and 3D Printing Technologies for Treating High Myopia Complications with Macular Buckles

Biomimetics ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 54
Author(s):  
George Pappas ◽  
Nectarios Vidakis ◽  
Markos Petousis ◽  
Athena Maniadi
Keyword(s):  
High Myopia ◽  
Surgical Intervention ◽  
Polymer Materials ◽  
Eye Disease ◽  
Pattern Recognition Techniques ◽  
Surgical Methods ◽  
3D Geometry ◽  
Myopic Traction Maculopathy ◽  
3D Printed ◽  
Ct Data

Myopic macular foveoschisis maculopathy is an eye disease that is treated, in most cases, with surgical intervention, in which a macular buckle is applied to restore eye anatomy and functionality. A macular buckle is a type of exoplant that comes in various designs and sizes. Often, they are difficult to apply or they do not fit properly in the eye geometry since they have a generic form. In this work, the effort to develop the most suitable tailor-made macular buckle for each individual patient for treating myopic traction maculopathy is studied. Pattern recognition techniques are applied to the patient’s Computed Tomography (CT) data to develop the exact 3D geometry of the eye. Using this 3D geometry, the trajectory of the buckle is fitted and the buckle is formed, which is then 3D-printed with biocompatible polymer materials. It is expected that the power of technology will be used to activate the most precise approach for each individual patient. Considering the possible complications and technical difficulties of other surgical methods, the customized macular buckle is an appropriate, easy-to-use, and most precise piece of medical equipment for the treatment of myopic traction maculopathy.

A Study on the External and Internal Morphology of the Mandibular First Premolar Using a Micro-CT

2006 ◽  
Vol 321-323 ◽  
pp. 1139-1144
Author(s):  
Keyoung Jin Chun ◽  
Ho Jung Li
Keyword(s):  
Stress Distribution ◽  
Stress Analysis ◽  
Boundary Surface ◽  
Outer Part ◽  
Morphological Data ◽  
Micro Ct ◽  
Internal Morphology ◽  
Mandibular First Premolar ◽  
Males And Females ◽  
Ct Data

Mandibular first premolars in superlative state were scanned by a Micro-CT. Data were obtained from the scanned 2-D images, and reconstructed into 3-D models for FEA, at which point stress distribution of the inner and outer part of the tooth were shown. It was found that when compared with the teeth data used as a standard by G. V. Black, the aspect of the external morphology of the teeth is comparatively small regardless of gender. Also, differences exist between the Micro-CT data and G. V. Black’s data. This study also presents the internal morphological data that was not shown in G. V. Black’s data. The dentin size is larger than the enamel size in both males and females in the case of the internal morphological data. It is found that the stress was concentrated on the cervical line, and the stress varied around the boundary between dentin and enamel within the teeth. It is also revealed that the stress varied at the boundary surface between dentin and pulp. The results using a Micro-CT and stress analysis may reveal the cause of the abfraction, and bring up a guideline for endodontic treatment.

Evaluation of Stress Shielding for Three Types of Implanted Femurs Based on Stress Distribution

2013 ◽  
Vol 459 ◽  
pp. 524-529
Author(s):  
Koki Ouchi ◽  
Gang Deng ◽  
Go Yamako ◽  
Etsuo Chosa ◽  
Tsutomu Nakanishi
Keyword(s):  
Total Hip Arthroplasty ◽  
Stress Distribution ◽  
Hip Arthroplasty ◽  
Stress Shielding ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Gruen Zone ◽  
Total Hip ◽  
Method Analysis ◽  
Thrust Plate Prosthesis

This research investigates the stress distribution of the three types of implanted femurs using the finite element method analysis. The comparisons of the stress distribution between the implanted femursand the healthy femur were performed and the characteristics in the stress shielding of each casewere clarified. Since the load is transferred on the contact surface between the implant and the inner surface of the femur in the case of the total hip arthroplasty, the stress in the intertrochanteric zone (Gruen zone 7) become very small, and the phenomenon of the stress shielding is confirmed obviously. The stress distributions of the femurs afterthe resurfacing hiparthroplasty and the thrust plate prosthesis are about the same with that of the healthy femur, so, the possibility of the stress shielding is considered lower compared with the femur after the total hip arthroplasty. However, considering the stress concentration thatwill increase the risk of femoral fracture caused by the screws for the fixation of the implant in the thrust plate prosthesis, the resurfacing hiparthroplastymay beconcluded as the best method among these three types of implants to avoid stress shielding.

Influences of Prosthesis Stem Lengths in Cementless Total Hip Arthroplasty

2011 ◽  
Vol 52-54 ◽  
pp. 2088-2093 ◽  
Author(s):  
Abdul Halim Abdullah ◽  
Emmi Farisa Jaafar ◽  
Nursalbiah Nasir ◽  
Eli Nadia Abdul Latip ◽  
Giha Tardan
Keyword(s):  
Stress Distribution ◽  
Hip Arthroplasty ◽  
Maximum Stress ◽  
Stress Shielding ◽  
Primary Stability ◽  
Middle Region ◽  
Cementless Total Hip Arthroplasty ◽  
Calculated Stress ◽  
Long Stem ◽  
Stability Issues

Stress shielding phenomenon is an important issues in considering the primary stability of the cementless hip arthroplasty. Stress shielding occurs when there is a mismatch in the elastic modulus of two materials perfectly bonded to each other, such as the prosthesis stem and the bone. In this study, influences of different prosthesis stem lengths on stress distribution in cementless THA are examined using finite element method. The calculated stress distribution is discussed with respect to stress shielding and primary stability issues in THA femur cases. Results show that similar pattern in stress distribution for intact and THA femur but differs in magnitudes. The stress level increases from the neck to the middle region and peaks at locations coinciding with the tip of the prosthesis. The maximum stress for intact femur is 55.5 MPa, THA with short stem is defined up to 112 MPa, while with medium and long stem are 204 MPa and 278 MPa, respectively.

Piston Pin Hole Design Improvement for Engines of Higher Rating

2005 ◽  
Author(s):  
B. Krishna Kumar ◽  
C. Jebaraj ◽  
S. Manivasagam ◽  
R. Mahadevan
Keyword(s):  
Stress Distribution ◽  
Internal Combustion Engines ◽  
Hoop Stress ◽  
Thermal Loading ◽  
Combined Loading ◽  
Base Line ◽  
Combustion Engines ◽  
Element Analysis ◽  
Design Modification ◽  
Reducing Stress

This paper studies the effect of design improvements generally prescribed for the piston pin hole on induced stresses with the help of finite element analysis techniques. This decade has seen a very significant increase in the load rating of internal combustion engines. The engines develop a pressure to the tune of 180 bar and more, which needs to be supported by the pin hole, which rests on the piston pin. Predictions of the effect of the increased load on the pin hole and design modifications to support the higher load have become very important activities during the course of piston development. Two design modification options are studied in this paper. The first modification is based on reducing stress concentration by suitably machining a taper profile for a pre-calculated distance at the inner boss zone. The second modification is carried out by having pin hole longitudinal relieves, popularly known as lube slots. Any modification carried out in the pin hole has an influence on the stress distribution at the bowl zone. Therefore, in addition to the pin hole stress, a thorough study on the stress distribution in the bowl zone is also carried out. The numerical results obtained for the modified designs are compared with the base line configuration and the effects of the modifications are discussed in detail. The modifications are found to have a significant effect in reducing the pin hole hoop stress, which is tensile in nature. But at the same time, it has been observed that the tensile hoop stress value in the bowl area increases. Therefore, it is concluded that the suggested pin hole improvements can be carried out if the induced hoop stress values do not exceed the prescribed values for the selected material. Further studies were made to analyze the influence of thermal loading on the stress induced and also to analyze the influence of combined (mechanical and thermal) loading on the induced stress. The thermal hoop stress were compressive in nature and hence its influence on the combined loading is significant. In this paper the results are normalized and shown as tables and figures.

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