1,720,975 research outputs found
A review of carbon fiber-reinforced polymer composite used to solve stress shielding in total hip replacement
Full text linkArthroplasty is generally used to treat advanced osteoarthritis or other degenerative joint diseases. However, it can also be considered in younger patients with severe joint damage that seriously limits their function and quality of life. Young patients are at risk of aseptic mobilization and bone resorption due to the uneven distribution of stress on the contact surface between the prosthesis and the femur that generates the stress-shielding phenomenon. To overcome this occurrence, it is necessary to use biocompatible materials with a stiffness that is similar to bone. Composite hip prostheses, consisting of continuous fiber-reinforced polymers, play a progressively key role in the development of prosthetic devices. Composite materials can be designed more carefully than monolithic stems (single-phase materials such as metals), allowing for the development of more effective tissue substitutes. Our purpose of this review was to analyze the state of the art in the use of carbon femoral prostheses. In particular, the major mechanical properties of reinforcement (fiber) and matrix were outlined with their applications in the prosthetic fiel
Evaluation of Rotational Stability and Stress Shielding of a Stem Optimized for Hip Replacements—A Finite Element Study
No full textThe natural distribution of stress in the femur is altered when total hip arthroplasty (THA) is performed. In fact, when a stem is inserted inside the femur, there is a variation in stress due to the difference in rigidity between the material with which the stem is made and the femur. This generates the phenomenon of stress shielding. The aim of this study is to design an optimized prosthesis that guarantees an excellent rotational stability and a reduced stress shielding. Methods: Through the finite element method (FEM), the mechanical behavior of the stem subjected to the loads described by ISO 7206-4:2010 is studied. Results: Through topological optimization, there is a reduction in stress shielding in the proximal zone of 31.46%. The addition of ridges on the dorsal side of the stem also improves rotational stability by 27.82%. Conclusions: The decrease in stiffness that is recorded with the optimized stem guarantees a greater distribution of stress on the bone. The presence of dorsal ridges also favors the corticalization of the bone as it loads the bone near the dorsal, ensuring further stability. The perforated prosthesis presented in this study shows an increase in primary stability and an improvement in rotational stability as there is also a bone regrowth inside the prosthesis
A Finite Element Study of Simulated Fusion in an L4-L5 Model: Influence of the Combination of Materials in the Screw-and-Rod Fixation System on Reproducing Natural Bone Behavior
Full text linkThe mechanical properties of materials for spinal fixation can significantly affect spinal surgical outcomes. Traditional materials such as titanium exhibit high stiffness, which can lead to stress shielding and adjacent segment degeneration. This study investigates the biomechanical performance of titanium and PEEK (polyetheretherketone) in spinal fixation using finite element analysis, through the evaluation of the Shielding Strength Factor (SSF). Methods: A three-dimensional finite element analysis (FEA) model of an L4/L5 functional spinal unit was developed to simulate the mechanical behavior of three fixation systems: titanium screws and rods (model A), titanium screws with PEEK rods (model B), and PEEK screws and rods (model C). The analysis evaluated stress distribution and load transfer under physiological conditions, in comparison with the intact spine (baseline model). Results: The analysis showed that titanium fixation systems resulted in higher stress shielding effects, with a significant difference in stress distribution compared to PEEK. The maximum stress recorded in the neutral position was 24.145 MPa for PEEK, indicating better biomechanical compatibility. Conclusions: The results suggest that PEEK may be an attractive alternative to titanium for spinal fixation, promoting more healthy load transfer and minimizing the risk of stress shielding complications
Reduction of Ceramic Wear by Concave Dimples on the Bearing Surface in CoC Hip Implants: A Finite Element Analysis
No full textThe wear of hip prostheses represents a significant challenge for the longevity and functionality of joint implants. Recent studies have explored surface texturing of prostheses as a strategy to enhance tribological performance. This study aims to evaluate the impact of textured ceramic surfaces with dimples on wear and friction reduction in ceramic-on-ceramic (CoC) prostheses. Materials and Methods: Three-dimensional models of ceramic surfaces with and without dimples were created. Contact pressure was analyzed and wear volume was estimated using Archard’s law. Simulations were conducted using finite element methods (FEM) under various loading conditions. Results: Numerical simulations demonstrated that the wear rate for the dimpled femoral head was 0.2369 mm3/year, compared to 0.286 mm3/year for the smooth counterpart, highlighting a wear reduction of 17.2%. Conclusions: The integration of textured surfaces with dimples in ceramic prostheses can substantially improve their functionality and durability, representing a promising approach to addressing the issues associated with hip prosthesis wear
FEA Comparison of the Mechanical Behavior of Three Dental Crown Materials: Enamel, Ceramic, and Zirconia
Full text linkThe restoration of endodontically treated teeth is one of the main challenges of restorative dentistry. The structure of the tooth is a complex assembly in which the materials that make it up, enamel and dentin, have very different mechanical behaviors. Therefore, finding alternative replacement materials for dental crowns in the area of restorative care isa highly significant challenge, since materials such as ceramic and zirconia have very different stress load resistance values. The aim of this study is to assess which material, either ceramic or zirconia, optimizes the behavior of a restored tooth under various typical clinical conditions and the masticatory load. A finite element analysis (FEA) framework is developed for this purpose. The 3D model of the restored tooth is input into the FEA software (Ansys Workbench R23)and meshed into tetrahedral elements. The presence of masticatory forces is considered: in particular, vertical, 45° inclined, and horizontal resultant forces of 280 N are applied on five contact points of the occlusal surface. The numerical results show that the maximum stress developed in the restored tooth including a ceramic crown and subject to axial load is about 39.381 MPa, which is rather close to the 62.32 MPa stress computed for the natural tooth; stresses of about 18 MPa are localized at the roots of both crown materials. In the case of the zirconia crown, the stresses are much higher than those in the ceramic crown, except for the 45° load direction, while, for the horizontal loads, the stress peak in the zirconia crown is almost three times as large as its counterpart in the ceramic crown (i.e., 163.24 MPa vs. 56.114 MPa, respectively). Therefore, the zirconia crown exhibits higher stresses than enamel and ceramic that could increase in the case of parafunctions, such as bruxism. The clinician’s choice between the two materials should be evaluated based on the patient’s medical condition
Stress Analysis of Tibial Bone Using Three Different Materials for Bone Fixation Plates
Full text linkStress shielding is a problem for traditional metal bone fixation plates made of magnesium and titanium alloys. This problem can be solved by using composite materials with a low elastic modulus. This study analyzed the effect of carbon fiber reinforced PEEK (CFRP) composites on stress shielding under static loading using finite element simulations. Callus formation times relative to the healing period were gradually imposed according to the elapsed time, considering 1% and 75% as healing stages. The Inventor© 3D CAD 2024 software was used for modeling, and the ANSYS© FEA R2023 software was used for analysis. The results showed that metal fixation plates made of titanium and magnesium alloys transferred less stress to the bone than the CFRP fixation plate. In particular, the use of the CFRP fixation plate resulted in a higher peak stress and a more uniform stress field in the bone, especially in the bone-plate contact area, where the risk of stress shielding is higher in the 1% and 75% healing phases
Finite Element Analysis of a 3D-Printed Acetabular Prosthesis for an Acetabular Defect According to the Paprosky Classification
No full textThe treatment of Paprosky Type III acetabular defects is a significant challenge in orthopedic surgery, as standard components often do not fit properly. This study aims to evaluate the biomechanical efficacy of a custom 3D-printed PEEK acetabular prosthesis compared to a conventional titanium implant. A 3D model of the pelvis was created using a computed tomography scanner and a custom-made acetabular implant was designed. Finite element analysis (FEA) was performed using Ansys Workbench to evaluate the stress and strain distribution of two materials on the pelvic bone. The results showed that the titanium prosthesis model had less strain transmitted to the bone, while the PEEK model had better stress transmission and bone stimulation. The use of custom implants reduced the risk of stress shielding, potentially improving long-term bone health. Three-dimensional-printed acetabular prostheses therefore offer significant advantages over traditional implants, suggesting improved implant stability and reduced failure rates
Finite element analysis of primary healing implants with different transmucosal designs
Full text linkPurpose: This study aimed to assess the response of peri-implant tissues, both hard and soft, to mechanical stress when using a primary healing implant (PHI) with two different transmucosal profiles: concave (Model A) and divergent (Model B). The investigation also sought to observe bone modeling under post-extraction conditions. Materials and methods: The methodology involved the creation of a three-dimensional bone model of the first molar region, derived from a computed tomography scan. Subsequently, two implants were inserted into the bone site and subjected to a loading force of 100 N at a 45° angle. Results: The results of stress analysis, using the von Mises criterion, indicated that Model A exhibited a more uniform stress distribution within the soft tissues, registering a maximum value of 75 MPa, in contrast to 126 MPa observed in Model B. Concerning implant stress, the peak value was recorded at the conometric connection zone between the implant and the abutment, measuring 138 MPa for Model B and 125 MPa for Model A. The study specifically analyzed cortical bone stress, which revealed levels of 72 MPa for Model B and 64 MPa for Model A. Additionally, stress distribution in immature bone ranged from 1.3 to 9 MPa for Model A and from 1.5 to 12 MPa for Model B. Conclusions: The finite element method represents a valuable tool for the design and optimization of implant shapes, taking into account occlusal loads and specific anatomical locations. This approach aims to enhance the stimulation of both soft and hard tissues, thereby mitigating the risk of implant failure
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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