scholarly journals Fabrication and Analysis of a Ti6Al4V Implant for Cranial Restoration

2019 ◽  
Vol 9 (12) ◽  
pp. 2513 ◽  
Author(s):  
Khaja Moiduddin ◽  
Syed Hammad Mian ◽  
Usama Umer ◽  
Hisham Alkhalefah
Keyword(s):  
3D Reconstruction ◽  
Mechanical Stability ◽  
Stress Shielding ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Implant Design ◽  
Reconstruction Technique ◽  
Element Analysis ◽  
Custom Made ◽  
Cranial Implant

A custom made implant is critical in cranioplasty to cushion and restore intracranial anatomy, as well as to recover the appearance and attain cognitive stability in the patient. The utilization of customized titanium alloy implants using three-dimensional (3D) reconstruction technique and fabricated using Electron Beam Melting (EBM) has gained significant recognition in recent years, owing to their convenience and effectiveness. Besides, the conventional technique or the extant practice of transforming the standard plates is unreliable, arduous and tedious. As a result, this work aims to produce a customized cranial implant using 3D reconstruction that is reliable in terms of fitting accuracy, appearance, mechanical strength, and consistent material composition. A well-defined methodology initiating from EBM fabrication to final validation has been outlined in this work. The custom design of the implant was carried out by mirror reconstruction of the skull’s defective region, acquired through computer tomography. The design of the customized implant was then analyzed for mechanical stresses by applying finite element analysis. Consequently, the 3D model of the implant was fabricated from Ti6Al4V ELI powder with a thickness of ≃1.76–2 mm. Different tests were employed to evaluate the bio-mechanical stability and strength of the fabricated customized implant design. A 3D comparison study was performed to ensure there was anatomical accuracy, as well as to maintain gratifying aesthetics. The bio-mechanical analysis results revealed that the maximum Von Mises stress (2.5 MPa), strain distribution (1.49 × 10−4) and deformation (3.26 × 10−6 mm) were significantly low in magnitude, thus proving the implant load resistance ability. The average yield and tensile strengths for the fabricated Ti6Al4V ELI EBM specimen were found to be 825 MPa and 880 MPa, respectively, which were well over the prescribed strength for Ti6Al4V ELI implant material. The hardness study also resulted in an acceptable outcome within the acceptable range of 30–35 HRC. Certainly, the chemical composition of the fabricated EBM specimen was intact as established in EDX analysis. The weight of the cranial implant (128 grams) was also in agreement with substituted defected bone portion, ruling out any stress shielding effect. With the proposed approach, the anatomy of the cranium deformities can be retrieved effectively and efficiently. The implementation of 3D reconstruction techniques can conveniently reduce tedious alterations in the implant design and subsequent errors. It can be a valuable and reliable approach to enhance implant fitting, stability, and strength.

Optimization of custom cementless stem using finite element analysis and elastic modulus distribution for reducing stress-shielding effect

2017 ◽  
Vol 231 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Gurunathan Saravana Kumar ◽  
Subin Philip George
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Elastic Modulus ◽  
Stress Shielding ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Implant Design ◽  
Element Analysis ◽  
Von Mises ◽  
Reducing Stress

This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress–strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.

Effect of material and dimensions on the mechanical behavior of a dental implant

2020 ◽  
Vol 62 (8) ◽  
pp. 775-782
Author(s):  
S. Hedia Hassan ◽  
Ismail M. R. Najjar ◽  
Noha Fouda ◽  
Fisal W. Al-Thobiani ◽  
Hattan A. Timraz
Keyword(s):  
Stainless Steel ◽  
Dental Implants ◽  
Dental Implant ◽  
Large Diameter ◽  
Stress Shielding ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Element Analysis ◽  
Maximum Increase ◽  
Von Mises

Abstract Metallic dental implants such as titanium and stainless steel have an elastic modulus 5-14 times greater than that of compact bone (15 GPa). These stiff implants do not adequately strain the bone, which can result in bone resorption through a phenomenon referred to as stress shielding. The implant length and diameter has a significant influence on the stress distribution within the surrounding jawbone. Therefore, the objective of this investigation is to optimize the material and the dimensions of a dental implant. A numerical solution of a 3D finite element analysis using ANSYS software was conducted to achieve this purpose. It was concluded that by using stainless steel, titanium or gold dental implants with a large diameter and short length the values of the maximum von Mises stress values in cortical bone were increased. The maximum increase in von Mises stress can be obtained by using a stainless steel implant. This dental implant will reduce the stress shielding effect as well as yield suitable values with respect to von Mises stress for both porcelain crowns and dental implants, thus increasing the service life of the implant.

Creation and finite-element analysis of multi-lattice structure design in hip stem implant to reduce the stress-shielding effect

2021 ◽  
pp. 146442072110462
Author(s):  
Mustafa Guven Gok
Keyword(s):  
Lattice Structure ◽  
Stress Shielding ◽  
Proximal Part ◽  
Structure Design ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Face Centered Cubic ◽  
Element Analysis ◽  
Hip Implant ◽  
Hip Stems

The term stress-shielding is frequently used to mention the reduction in mechanical stimulus in the surrounding bone due to the presence of a biomaterial inert implant whose mechanical properties are superior to bone. As the natural consequence of this, mineral loss occurs in the bone over time and creating subsequent weakness. One of the methods to reduce stress-shielding problem is to develop hip-stem implant designs that will transfer the load more to the bone. Therefore, in this study, multi-lattice designs were developed to reduce the stress-shielding effect in hip implant applications. For this, the proximal part of the hip implant stems has been divided into three parts. Simple cubic, body centered cubic, and face centered cubic lattice structures were created on the upper parts. Inner vertical and inner vertical + inner horizontal beams were added to the lattice structure of the upper part for middle and lower parts, respectively. Due to the multi-lattice designs, the maximum von Mises stress values on the hip implant stem were reduced from 289 to 189 MPa, as well as a weight reduction of up to 25.89%. Stress-shielding signals were obtained by determining the change in strain energy per unit bone mass caused by the presence of the femoral hip implant stem and its ratio to intact bone. In the case of using hip-stems having multi-lattice designs, there is a significant increase (max. 150.47%) in stress-shielding signals from different zones of the femur.

EFFECTS OF DIFFERENT LATERAL FEMORAL WALL THICKNESSES IN INTERTROCHANTERIC HIP FRACTURE TREATED WITH DYNAMIC HIP SCREW

2019 ◽  
Vol 19 (02) ◽  
pp. 1940022
Author(s):  
CHENG-CHI WANG ◽  
CHENG-HUNG LEE ◽  
KUN-HUI CHEN ◽  
CHIEN-CHOU PAN ◽  
KUO-CHIH SU
Keyword(s):  
Hip Fractures ◽  
Stress Shielding ◽  
Simulation Models ◽  
Lateral Wall ◽  
Dynamic Hip Screw ◽  
Shielding Effect ◽  
Element Analysis ◽  
Lag Screw ◽  
Hip Screw ◽  
Biomechanical Effect

Dynamic hip screw (DHS) is commonly used for stable-type intertrochanteric hip fractures. The importance of lateral femoral wall has been mentioned while treating intertrochanteric hip fractures with DHS. The aim of this study was mainly to investigate the biomechanical effect of different thickness of lateral femoral wall using finite element analysis (FEA). This study constructed FEA simulation models for five different lateral femoral wall thicknesses, and demonstrated the stress distribution on the femoral bone, the cortical screws, the cancellous bone around the lag screw, and the lag screw. The main results showed that when the DHS is implanted, less stress will be distributed at the implantation site on the femur due to the stress-shielding effect. The stress on the cortical screws will be greater at the junction of the cortical screws and the cortical bone. Intertrochanteric hip fractures with a thinner lateral wall thickness may cause higher stress on the femur after DHS is implanted.

ACETABULAR LOAD-TRANSFER AND MECHANICAL STABILITY: A FINITE ELEMENT ANALYSIS COMPARING DIFFERENT CEMENTLESS SOCKETS

2014 ◽  
Vol 14 (05) ◽  
pp. 1450063 ◽  
Author(s):  
D. F. M. PAKVIS ◽  
D. JANSSEN ◽  
B. W. SCHREURS ◽  
N. VERDONSCHOT
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Load Transfer ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Stress Shielding ◽  
Physiological Strain ◽  
Element Analysis ◽  
Strain Pattern ◽  
Component Interface

Acetabular stress shielding may be a failure mechanism of acetabular constructs promoting osteolysis, aseptic loosening and failure. We used three-dimensional finite element analysis (FEA) to evaluate the effect of flexible sockets on acetabular stress shielding. The sockets were made of (1) full polyethylene (PE), (2) PE with a metal bearing and (3) a PE insert with a metal backing was used as a traditional stiff implant. We compared the strain energy density and interfacial micro-motions between bone and cementless sockets during walking. In our FEA model, the most elastic socket (case 1) showed the highest levels of micro-motion during walking (400 μm). The most rigid socket (case 3) showed smaller areas of high micro-motions. Assuming a threshold for ingrowth of 50 microns, the flexible cup showed an ingrowth area of almost 40%, whereas the other two cases showed stable areas covering 60% of the total bone–component interface. Furthermore, we found that the introduction of an implant generates a very different strain pattern directly around the implant as compared with the intact case, which has a horse-shoe shaped cartilage layer in the acetabulum. This difference was not affected much by the stiffness of the implant; a more flexible implant resulted in only slightly higher strain levels. Bone strains over 1.5 mm from the cup showed physiological values and were not affected by the stiffness of the implant. Hence, this study shows that the physiological strain patterns are not obtained in the direct periprosthetic bone, regardless of the stiffness of the material.

scholarly journals Influence of PEEK Coating on Hip Implant Stress Shielding: A Finite Element Analysis

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Jesica Anguiano-Sanchez ◽  
Oscar Martinez-Romero ◽  
Hector R. Siller ◽  
Jose A. Diaz-Elizondo ◽  
Eduardo Flores-Villalba ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cancellous Bone ◽  
Stress Shielding ◽  
Design Concept ◽  
Von Mises Stress ◽  
Hip Implants ◽  
Element Analysis ◽  
Stress Transmission ◽  
Von Mises

Stress shielding is a well-known failure factor in hip implants. This work proposes a design concept for hip implants, using a combination of metallic stem with a polymer coating (polyether ether ketone (PEEK)). The proposed design concept is simulated using titanium alloy stems and PEEK coatings with thicknesses varying from 100 to 400 μm. The Finite Element analysis of the cancellous bone surrounding the implant shows promising results. The effective von Mises stress increases between 81 and 92% for the complete volume of cancellous bone. When focusing on the proximal zone of the implant, the increased stress transmission to the cancellous bone reaches between 47 and 60%. This increment in load transferred to the bone can influence mineral bone loss due to stress shielding, minimizing such effect, and thus prolonging implant lifespan.

scholarly journals Finite Element Analysis of Porous Ti-6Al-4V Alloy Structures for Biomedical Applications

2021 ◽  
Vol 2070 (1) ◽  
pp. 012224
Author(s):  
N Ganesh ◽  
S Rambabu
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Cortical Bone ◽  
Bone Ingrowth ◽  
Stress Shielding ◽  
Shielding Effect ◽  
Element Analysis ◽  
Human Cortical Bone ◽  
Porous Ti ◽  
Manufacturing Technologies

Abstract In this article, design and finite element simulation of porous Ti-6Al-4V alloy structures was presented. Typically, titanium and titanium alloy implants can be manufactured with required pore size and porosity volume by using powder bed fusion techniques due to advancement in additive manufacturing technologies. However, the mismatch of elastic modulus between human cortical bone and the dense Ti-6Al-4V alloy implant resulted in stress shielding which accelerate the implant failure. The porous implant structures help in reduce the mismatch of elastic modulus between the cortical bone and implant structure and also improve the bone ingrowth. Hence, the present work focuses on design of Ti-6Al-4V alloy porous structures with various porosities ranging from 10% to 70% and simulated to determine the elastic modulus suitable for human cortical bone. The sample with 45% porosity is found to be best suited for replacement of cortical bone with elastic modulus of 74Gpa, preventing stress shielding effect and enhanced chances of bone ingrowth.

Influence of Dental Implant Design on Stress Distribution and Micromotion of Mandibular Bone

2020 ◽  
Vol 899 ◽  
pp. 81-93
Author(s):  
Nur Faiqa Ismail ◽  
M. Saiful Islam ◽  
Solehuddin Shuib ◽  
Rohana Ahmad ◽  
M. Amar Shahmin
Keyword(s):  
Shear Stress ◽  
Dental Implant ◽  
Cancellous Bone ◽  
3D Models ◽  
Von Mises Stress ◽  
Implant Design ◽  
Element Analysis ◽  
Reconstruction Process ◽  
Mandibular Bone ◽  
Von Mises

This research was conducted to provide a feasible method for reconstructing the 3D model of mandibular bone to undergo finite element analysis to investigate von Mises stress, deformation and shear stress located at the cortical bone, cancellous one and neck implant of the proposed dental implant design. Dental implant has become a significant remedial approach but although the success rate is high, the fixture failure may happen when there are insufficient host tissues to initiate and sustain the osseointegration. Computerised Tomography scan was conducted to generate head images for bone reconstruction process. MIMICS software and 3-matic software were used to develop the 3D mandibular model. The reconstructed mandibular model was then assembled with five different 3D models of dental implants. Feasible boundary conditions and material properties were assigned to the developed muscle areas and joints. The highest performance design with the best responses was the design B with the value for the von Mises stress for the neck implant, cortical and cancellous bone were 7.53 MPa, 16.91 MPa and 1.34 MPa respectively. The values for the maximum of micromotion for the neck implant, cortical and cancellous bone of design B were 20.60 μm, 21.17 μm and 5.83 μm respectively. Shear stress for neck implant, cortical and cancellous bone for this design were 0.15 MPa, 4.74 MPa and 1.54 MPa respectively. The design with a cone shaped hole which is design B was the proper design when compared with other designs in terms of von Misses stress, deformations and shear stress.

Evaluation of Biomechanical Health Degree of Peri-Implant Bone Through Finite Element Analysis: A First Approach

2018 ◽  
Vol 10 (09) ◽  
pp. 1850097 ◽  
Author(s):  
Junxiong Lin ◽  
Ge Zhang ◽  
Zhenyu Jiang ◽  
Liqun Tang ◽  
Keqian Lian
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Critical Role ◽  
Control Sample ◽  
Stress Shielding ◽  
Element Model ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Computer Tomography Scan ◽  
Von Mises

The biomechanical health degree of peri-implant bone plays a critical role during the service of implants. This paper presents a preliminary exploration of the quantitative evaluation of the biomechanical health degree for the bone tissues around dental implant through finite element method. The finite element model of a part of mandible with three molars is constructed based on computer tomography scan image as a control sample, which is supposed to represent a healthy state. The model of treated mandible is made by replacing the middle tooth in the healthy model with a commercial implant. A regional average strain energy density (RASED) is proposed as a more accurate index to describe the stress state of peri-implant bone tissues, compared with the widely used maximum equivalent von Mises stress. The simulation shows that the stress state in peri-implant bone, i.e., the distribution and level of stress, is highly dependent on the modulus of implant material. Among the implants made of materials with various moduli, including Ti, stainless steel, zirconia, porous Ti, dentin material and polyether-ether-ketone (PEEK), the ones with medium modulus (15–40[Formula: see text]GPa) are found to achieve relatively healthy stress states. This study provides an effective tool to assess the risk of overloading or stress shielding in peri-implant bone tissues. It demonstrates a great potential in the optimization of design, production and usage of implants.

scholarly journals Minimizing Stress Shielding and Cement Damage in Cemented Femoral Component of a Hip Prosthesis through Computational Design Optimization

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Abdellah Ait Moussa ◽  
Justin Fischer ◽  
Rohan Yadav ◽  
Morshed Khandaker
Keyword(s):  
Hip Prosthesis ◽  
Numerical Technique ◽  
Stress Shielding ◽  
Computational Design ◽  
Functionally Graded ◽  
Implant Design ◽  
Homogeneous Material ◽  
Element Analysis ◽  
Term Survival

The average life expectancy of many people undergoing total hip replacement (THR) exceeds twenty-five years and the demand for implants that increase the load-bearing capability of the bone without affecting the short- or long-term stability of the prosthesis is high. Mechanical failure owing to cement damage and stress shielding of the bone are the main factors affecting the long-term survival of cemented hip prostheses and implant design must realistically adjust to balance between these two conflicting effects. In the following analysis we introduce a novel methodology to achieve this objective, the numerical technique combines automatic and realistic modeling of the implant and embedding medium, and finite element analysis to assess the levels of stress shielding and cement damage and, finally, global optimization, using orthogonal arrays and probabilistic restarts, were used. Applications to implants, fabricated using a homogeneous material and a functionally graded material, were presented.

Sign in / Sign up

Export Citation Format

Share Document