scholarly journals The effect of cortical thickness and thread profile dimensions on stress and strain in bone-anchored implants for amputation prostheses

2021 ◽  
Author(s):  
Alexander Thesleff ◽  
Max Ortiz-Catalan ◽  
Rickard Brånemark
Keyword(s):  
Cortical Thickness ◽  
Load Transfer ◽  
Autologous Transplantation ◽  
Implant Design ◽  
Limb Amputation ◽  
Stress And Strain ◽  
Dimensional Changes ◽  
Structural Design Optimization ◽  
Thread Root ◽  
Implant System

<p>Skeletal attachment of limb prostheses ensures load transfer between the prosthetic leg and the skeleton. For individuals with lower limb amputation, these loads may be of substantial magnitude. To optimize the design of such systems, knowledge about the structural interplay between implant design features, dimensional changes, and material properties of the implant and the surrounding bone is needed. Here, we present the results from a parametric finite element investigation on a generic bone-anchored implant system of screw design, exposed to external loads corresponding to average and high ambulatory loading. Of the investigated parameters, cortical thickness had the largest effect on the stress and strain in the bone-anchored implant and in the cortical bone. 36 % – 44 % reductions in maximum longitudinal stress in the bone-anchored implant was observed as a result of increased cortical thickness from 2 mm to 5 mm. Changes in thread depth had larger effect on the maximum stresses in the fixture and the bone than changes in thread root radius within the evaluated parameter space. Stress reductions in the percutaneous abutment were obtained by autologous transplantation of bone tissue distal to the fixture. Results from this investigation may guide structural design optimization for bone-anchored implant systems for attachment of limb prostheses.</p>

scholarly journals The effect of cortical thickness and thread profile dimensions on stress and strain in bone-anchored implants for amputation prostheses

2021 ◽  
Author(s):  
Alexander Thesleff ◽  
Max Ortiz-Catalan ◽  
Rickard Brånemark
Keyword(s):  
Cortical Thickness ◽  
Load Transfer ◽  
Autologous Transplantation ◽  
Implant Design ◽  
Limb Amputation ◽  
Stress And Strain ◽  
Dimensional Changes ◽  
Structural Design Optimization ◽  
Thread Root ◽  
Implant System

<p>Skeletal attachment of limb prostheses ensures load transfer between the prosthetic leg and the skeleton. For individuals with lower limb amputation, these loads may be of substantial magnitude. To optimize the design of such systems, knowledge about the structural interplay between implant design features, dimensional changes, and material properties of the implant and the surrounding bone is needed. Here, we present the results from a parametric finite element investigation on a generic bone-anchored implant system of screw design, exposed to external loads corresponding to average and high ambulatory loading. Of the investigated parameters, cortical thickness had the largest effect on the stress and strain in the bone-anchored implant and in the cortical bone. 36 % – 44 % reductions in maximum longitudinal stress in the bone-anchored implant was observed as a result of increased cortical thickness from 2 mm to 5 mm. Changes in thread depth had larger effect on the maximum stresses in the fixture and the bone than changes in thread root radius within the evaluated parameter space. Stress reductions in the percutaneous abutment were obtained by autologous transplantation of bone tissue distal to the fixture. Results from this investigation may guide structural design optimization for bone-anchored implant systems for attachment of limb prostheses.</p>

scholarly journals Analysis on Force Transmission Characteristics of Two-Legged Shield Support under Impact Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Qing-liang Zeng ◽  
Zhao-sheng Meng ◽  
Li-rong Wan ◽  
Cheng-long Wang
Keyword(s):  
Structural Design ◽  
Load Transfer ◽  
Impact Load ◽  
Force Transmission ◽  
Full Account ◽  
Flexible Bodies ◽  
Powered Support ◽  
Structural Design Optimization ◽  
Hinge Points ◽  
The Impact

To study the load transfer characteristics of a two-legged shield powered support, a numerical simulation model of the support was established using the multibody dynamics software ADAMS. The model took full account of the hydraulic-elastic deformation characteristics of the support, as a series spring-damper system was used to replace the leg and the equilibrium jack. The canopy, goaf shield, lemniscate bars, and equilibrium jack are equivalent to flexible bodies. The setting force of the leg was provided by the preload of the equivalent spring, the static roof load was simulated using a slope signal, and the impact load was simulated using a step signal. Using the model, the impact and excitation effects of each hinge joint of the support were analyzed under different impact load conditions across the canopy. The results show that the location of the impact load affects the force transmissions of all hinge points of the support. Both the impact effect and the excitation effect are at a minimum when the impact force is located near the leg action line. These results are useful for the adaptive control and structural design optimization of the support.

Irregular Implant Design Decreases Periimplant Stress and Strain Under Oblique Loading

2017 ◽  
Vol 26 (5) ◽  
pp. 744-750 ◽  
Author(s):  
Ling He ◽  
Jiwu Zhang ◽  
Xiucheng Li ◽  
Hongcheng Hu ◽  
Songhe Lu ◽  
...  
Keyword(s):  
Implant Design ◽  
Stress And Strain ◽  
Oblique Loading

Comparison of the Compressive Strength of 3 Different Implant Design Systems

2007 ◽  
Vol 33 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jose E. Pedroza ◽  
Ysidora Torrealba ◽  
Augusto Elias ◽  
Walter Psoter
Keyword(s):  
Compressive Strength ◽  
Failure Mode ◽  
Mechanical Stability ◽  
Testing Machine ◽  
Implant Design ◽  
Static Compression ◽  
Implant Abutment ◽  
Holding Device ◽  
Design Systems ◽  
Implant System

Abstract The aims of this study were twofold: to compare the static compressive strength at the implant-abutment interface of 3 design systems and to describe the implant abutment connection failure mode. A stainless steel holding device was designed to align the implants at 30° with respect to the y-axis. Sixty-nine specimens were used, 23 for each system. A computer-controlled universal testing machine (MTS 810) applied static compression loading by a unidirectional vertical piston until failure. Specimens were evaluated macroscopically for longitudinal displacement, abutment looseness, and screw and implant fracture. Data were analyzed by analysis of variance (ANOVA). The mean compressive strength for the Unipost system was 392.5 psi (SD ± 40.9), for the Spline system 342.8 psi (SD ± 25.8), and for the Screw-Vent system 269.1 psi (SD ± 30.7). The Unipost implant-abutment connection demonstrated a statistically significant superior mechanical stability (P ≤ .009) compared with the Spline implant system. The Spline implant system showed a statistically significant higher compressive strength than the Screw-Vent implant system (P ≤ .009). Regarding failure mode, the Unipost system consistently broke at the same site, while the other systems failed at different points of the connection. The Unipost system demonstrated excellent fracture resistance to compressive forces; this resistance may be attributed primarily to the diameter of the abutment screw and the 2.5-mm counter bore, representing the same and a unique piece of the implant. The Unipost implant system demonstrated a statistically significant superior compressive strength value compared with the Spline and Screw-Vent systems, at a 30° angulation.

Comparison of Stress Distribution in Surrounding Bone during Insertion of Dental Implants on Four Implant Threads under the Effect of an Impact: A Finite Element Study

2022 ◽  
Vol 54 ◽  
pp. 89-101
Author(s):  
Noureddine Djebbar ◽  
Abdessamed Bachiri ◽  
Benali Boutabout
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Load Transfer ◽  
Three Dimensional ◽  
Primary Stability ◽  
Implant Design ◽  
Element Analysis ◽  
Three Dimensional Finite Element ◽  
The Impact ◽  
Surrounding Bone

The design of an implant thread plays a fundamental role in the osseointegration process, particularly in low-density bone. It has been postulated that design features that maximize the surface area available for contact may improve mechanical anchorage and stability in cancellous bone. The primary stability of a dental implant is determined by the mechanical engagement between the implant and bone at the time of implant insertion. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. Numerous factors influence load transfer at the bone-implant interface, for example, the type of loading, surface structure, amount of surrounding bone, material properties of the implant and implant design. The purpose of this study was to investigate the effects of the impact two different projectile of implant threads on stress distribution in the jawbone using three-dimensional finite element analysis.

Human Thoracolumbar Spine Tolerance to Injury and Mechanisms From Caudo-Cephalad Impacts

2020 ◽  
Author(s):  
Narayan Yoganandan ◽  
Prashant Khandelwal ◽  
Vaibhav Porwal ◽  
John Humm
Keyword(s):  
Load Transfer ◽  
Thoracolumbar Spine ◽  
Spinal Column ◽  
The Body ◽  
Von Mises Stress ◽  
Whole Body ◽  
Stress And Strain ◽  
Male And Female ◽  
Vertical Loading ◽  
Flexion Extension

Abstract The human thoracolumbar spinal column sustains axial loading under physiological and traumatic loading situations. Clinical studies have focused on the former scenario, and the investigation of low back pain issues and spinal stabilization using artificial devices such as arthroplasty are examples. Investigative studies have largely used quasi-static and vibration loading on the spine segment(s) and spinal columns. The traumatic loading scenario is relatively less researched, and it is a dynamic event. Injuries under this scenario occur in sports, automotive, and combat environments. Impact vectors include flexion-extension modes in automotive crash events. Vertical or caudal to cephalad oriented impacts have been identified in both automotive and military scenarios. Frontal impacts to restrained occupants in the automotive and underbody blast impacts from improvised explosive device in combat situations are examples of the vertical loading vector. Although some studies have been conducted using whole body human cadavers and isolated spinal columns, determinations have not been made of the injury risks and stress and strain responses for a variety of accelerative pulses. The aims of the present investigation were to delineate the internal biomechanics of the spinal column under this impact vector and assess the probability of injury. Male and female whole-body human finite element models were used in the study. The occupants were restrained and positioned on the seat, and caudo-cephalad impacts were applied to the base. Different acceleration-time profiles (pulse durations ranging from 50 to 200 ms and peak accelerations varying from 11 g to 46 g) were used as inputs in both male and female models. The resulting stress-strain profiles in the cortical and cancellous bones were evaluated at different vertebral levels. Using the peak transmitted forces at the thoracolumbar disc level as the response variable, the probability of injury for the male spine was obtained from experimental risk curves for the various accelerative pulses. Results showed that the shorter pulse durations and rise times impart greater loading on the thoracolumbar spine. The analysis of von Mises stress and strain distributions showed that the compression-related fractures of vertebrae are multifaceted with contributions from both the cortical and cancellous bony components of the body. Profiles are provided in the body of the paper for different spinal levels. The intervertebral disc may be involved in the fracture mechanism, because it acts as a medium of load transfer between adjacent vertebrae. Injury risks for the shortest pulse was sixty-three percent, and for the widest pulse it was close to zero, and injury probabilities for other pulses are given. The present computational modeling study provides insights into the mechanisms of the internal load transfer and describe the injury risk levels from caudal to cephalad impacts.

scholarly journals Finite Element Analysis of the Stress Field in Peri-Implant Bone: A Parametric Study of Influencing Parameters and Their Interactions for Multi-Objective Optimization

2020 ◽  
Vol 10 (17) ◽  
pp. 5973
Author(s):  
Paul Didier ◽  
Boris Piotrowski ◽  
Gael Le Coz ◽  
David Joseph ◽  
Pierre Bravetti ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Young’S Modulus ◽  
Load Transfer ◽  
Young's Modulus ◽  
Element Model ◽  
Implant Design ◽  
Main Effects ◽  
Full Factorial ◽  
Surrounding Bone

The present work proposes a parametric finite element model of the general case of a single loaded dental implant. The objective is to estimate and quantify the main effects of several parameters on stress distribution and load transfer between a loaded dental implant and its surrounding bone. The interactions between them are particularly investigated. Seven parameters (implant design and material) were considered as input variables to build the parametric finite element model: the implant diameter, length, taper and angle of inclination, Young’s modulus, the thickness of the cortical bone and Young’s modulus of the cancellous bone. All parameter combinations were tested with a full factorial design for a total of 512 models. Two biomechanical responses were identified to highlight the main effects of the full factorial design and first-order interaction between parameters: peri-implant bone stress and load transfer between bones and implants. The description of the two responses using the identified coefficients then makes it possible to optimize the implant configuration in a case study with type IV. The influence of the seven considered parameters was quantified, and objective information was given to support surgeon choices for implant design and placement. The implant diameter and Young’s modulus and the cortical thickness were the most influential parameters on the two responses. The importance of a low Young’s modulus alloy was highlighted to reduce the stress shielding between implants and the surrounding bone. This method allows obtaining optimized configurations for several case studies with a custom-made design implant.

Stress and Strain Distribution in the Bone Surrounding a New Design of Dental Implant: A Comparison with a Threaded Branemark Type Implant

1993 ◽  
Vol 207 (3) ◽  
pp. 133-138 ◽  
Author(s):  
S E Clift ◽  
J Fisher ◽  
C J Watson
Keyword(s):  
Stress Concentration ◽  
Dental Implant ◽  
Load Transfer ◽  
Bone Ingrowth ◽  
High Stress ◽  
Neck Region ◽  
Lateral Loading ◽  
Porous Coating ◽  
Stress And Strain ◽  
Bonded Interface

The stress and strain distributions in the bone surrounding a new dental implant, designed specifically for use with a bioactive porous coating and thus having a fully bonded interface to the bone, have been analysed. The new implant geometry was slightly tapered, with deep concentric grooves to allow bone ingrowth and load transfer, and had a parallel cylindrical section at the neck. The results have been compared with stress and strain predictions in the bone surrounding a ‘Branemark type’ threaded implant with a fully bonded interface. Under axial loading both implant types produced similar stress and strain distributions with a higher level of stress in the cortical bone surrounding the neck of the implant. Under lateral loading a high stress concentration was found in the neck region of both implants, but this was lower around the neck of the new design compared with the threaded implant. When the new implant was surrounded by cancellous bone, the reduction in the stress concentration was up to 50 per cent. This reduction should help to reduce fatigue failure and bone resorption in this area under lateral loading.

Numerical Simulations of the Global Behaviour of Implant Supported or Retained Dental Prostheses

2010 ◽  
Vol 638-642 ◽  
pp. 518-523
Author(s):  
Anne Sophie Bonnet ◽  
Marwan Daas ◽  
Michel Postaire ◽  
Paul Lipiński
Keyword(s):  
Load Transfer ◽  
World Health ◽  
Stress And Strain ◽  
Industrialized Countries ◽  
Global Behaviour ◽  
Dental Prostheses ◽  
Solution Type ◽  
Removable Denture ◽  
Dental Diseases ◽  
The Difference

In spite of the recent efforts concerning prevention and treatment of dental diseases, total edentulism remains an important world health problem, even in industrialized countries. Different solutions to mandibular total edentulism are available from the classical removable denture to the implant supported prostheses. The aim of the present work is to compare, through finite element simulations, two distinct types of prosthetic solutions. The first one is an implant-supported prosthesis (ISP) using a “All-On-Four” base and the second one is a mandibular implant-retained overdenture (IRO) using two implants. A foodstuff situated on molar is modelled to simulate the mastication force. An orthotropic behaviour is assumed inside the symphyseal area. The results of the simulations show a strong influence of the prosthetic solution type on the stress and strain repartition in the implant and peri-implant bone. This can be explained by the difference of load transfer to bone between those two configurations. Indeed, in the implant-supported prosthesis, the totality of the mastication force is directly transmitted to peri-implant bone whereas the implant-retained solution benefits from a large participation of mucosa to the global load transfer from overdenture to bone.

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