Numerical investigation of knee prosthesis stresses in daily activities: Insight into knee rehabilitation and Creation of a new optimal model.

Total knee arthroplasty (TKA) is a cornerstone in addressing knee joint disorders, significantly enhancing patients' quality of life. However, despite technological advancements, a comprehensive understanding of the dynamic stresses experienced by knee prostheses during daily activities, particularly under rehabilitation interventions, remains elusive. This study aims to bridge this gap by employing numerical simulations and finite element analysis to elucidate these dynamic stresses and their interaction with rehabilitation protocols. A real-life knee replacement prosthesis model was meticulously constructed through coordinate measuring and 3D scanning, facilitating detailed finite element analysis in ANSYS Workbench version 17.1. Two distinct boundary conditions and loading scenarios were applied, with comparisons made between linear and nonlinear material assumptions. The simulation results using these different boundary condition methods revealed minimal differences. Specifically, at a knee angle of 0°, the relative stress error rate between the two boundary condition types was approximately 1 % (1.11 MPa and 1.099 MPa, respectively). At 15° and 90°, the error rates were 1.9 % and 0.56 %, respectively (10.275 MPa and 10.078 MPa at 15°; 10.275 MPa and 10.078 MPa at 90°). Given these minimal differences, the first type of boundary condition was adopted for the subsequent scenarios to enhance convergence efficiency in the analysis. Moreover, comparative analyses between linear and nonlinear material behaviors demonstrated acceptable agreement, offering insights into potential efficiency gains in simulation methodologies. Building on this foundation, an optimized tibial model was proposed, incorporating geometric alterations to the tray. Quantitative assessments revealed significant reductions, with von Mises stress decreasing by 23.35 % and equivalent strain by 17 % at a knee angle of 140°. Further evaluations at varying angles, including 60°, consistently showed positive influences on stress and strain. These quantitative findings not only contribute valuable insights into the mechanical behavior of knee prostheses but also provide tangible evidence for the efficacy of linear material behavior assumptions. The proposed optimized model exhibits promising potential for enhancing the design and performance of knee prostheses, particularly under critical loading conditions. In conclusion, these results underscore the importance of a nuanced understanding of knee prosthesis behavior during rehabilitation, offering a quantitative foundation for refining existing designs and informing the development of next-generation prostheses.

Different estimation techniques and data analysis for constant-partially accelerated life tests for power half-logistic distribution.

Partial accelerated life tests (PALTs) are employed when the results of accelerated life testing cannot be extended to usage circumstances. This work discusses the challenge of different estimating strategies in constant PALT with complete data. The lifetime distribution of the test item is assumed to follow the power half-logistic distribution. Several classical and Bayesian estimation techniques are presented to estimate the distribution parameters and the acceleration factor of the power half-logistic distribution. These techniques include Anderson-Darling, maximum likelihood, Cramér von-Mises, ordinary least squares, weighted least squares, maximum product of spacing and Bayesian. Additionally, the Bayesian credible intervals and approximate confidence intervals are constructed. A simulation study is provided to compare the outcomes of various estimation methods that have been provided based on mean squared error, absolute average bias, length of intervals, and coverage probabilities. This study shows that the maximum product of spacing estimation is the most effective strategy among the options in most circumstances when adopting the minimum values for MSE and average bias. In the majority of situations, Bayesian method outperforms other methods when taking into account both MSE and average bias values. When comparing approximation confidence intervals to Bayesian credible intervals, the latter have a higher coverage probability and smaller average length. Two authentic data sets are examined for illustrative purposes. Examining the two real data sets shows that the value methods are workable and applicable to certain engineering-related problems.

Improving data interpretability with new differential sample variance gene set tests.

Background: Gene set analysis methods have played a major role in generating biological interpretations from omics data such as gene expression datasets. However, most methods focus on detecting homogenous pattern changes in mean expression and methods detecting pattern changes in variance remain poorly explored. While a few studies attempted to use gene-level variance analysis, such approach remains under-utilized. When comparing two phenotypes, gene sets with distinct changes in subgroups under one phenotype are overlooked by available methods although they reflect meaningful biological differences between two phenotypes. Multivariate sample-level variance analysis methods are needed to detect such pattern changes. Results: We use ranking schemes based on minimum spanning tree to generalize the Cramer-Von Mises and Anderson-Darling univariate statistics into multivariate gene set analysis methods to detect differential sample variance or mean. We characterize these methods in addition to two methods developed earlier using simulation results with different parameters. We apply the developed methods to microarray gene expression dataset of prednisolone-resistant and prednisolone-sensitive children diagnosed with B-lineage acute lymphoblastic leukemia and bulk RNA-sequencing gene expression dataset of benign hyperplastic polyps and potentially malignant sessile serrated adenoma/polyps. One or both of the two compared phenotypes in each of these datasets have distinct molecular subtypes that contribute to heterogeneous differences. Our results show that methods designed to detect differential sample variance are able to detect specific hallmark signaling pathways associated with the two compared phenotypes as documented in available literature. Conclusions: The results in this study demonstrate the usefulness of methods designed to detect differential sample variance in providing biological interpretations when biologically relevant but heterogeneous changes between two phenotypes are prevalent in specific signaling pathways. Software implementation of the developed methods is available with detailed documentation from Bioconductor package GSAR. The available methods are applicable to gene expression datasets in a normalized matrix form and could be used with other omics datasets in a normalized matrix form with available collection of feature sets.

Two versus three magnesium screws for osteosynthesis of mandibular condylar head fractures: a finite element analysis.

OBJECTIVES: Previous finite element analyses (FEA) have shown promising results for using two titanium screws in treating mandibular condylar head fractures but limited mechanical stability of a two-screw osteosynthesis with magnesium screws. Given the potential benefits of magnesium screws in terms of biocompatibility and resorption, this study aimed to compare two- and three-screw osteosynthesis solutions for a right condylar head fracture (AO CMF type p) with magnesium screws with a FEA. MATERIALS AND METHODS: A previously validated finite element model simulating a 350 N bite on the contralateral molars was used to analyze von Mises stress within the screws, fragment deformation, and fracture displacement. All screws were modeled with uniform geometric specifications mirroring the design of Medartis MODUS® Mandible Hexadrive cortical screws. RESULTS: The three-screw configuration demonstrated lower values for all three parameters compared to the two-screw scenario. There was a 30% reduction in maximum von Mises stress for the top screw and a 46% reduction for the bottom screw. CONCLUSIONS: Fracture treatment with three magnesium screws could be a valuable and sufficiently stable alternative to the established treatment with titanium screws. Further studies on screw geometry could help improve material stability under mechanical loading, enhancing the performance of magnesium screws in clinical applications. CLINICAL RELEVANCE: The use of magnesium screws for osteosynthesis of mandibular condylar head fractures offers the benefit of reducing the need for second surgery for hardware removal. Clinical data is needed to determine whether the advantages of resorbable screw materials outweigh potential drawbacks in condylar head fracture treatment.

Influence of Framework Material and Abutment Configuration on Fatigue Performance in Dental Implant Systems: A Finite Element Analysis.

Background and Objectives: This study uses finite element analysis to evaluate the impact of abutment angulation, types, and framework materials on the stress distribution and fatigue performance of dental implant systems. Materials and Methods: Three-dimensional models of maxillary three-unit fixed implant-supported prostheses were analyzed. Abutments with different angles and types were used. Two different framework materials were used. Conducted on implants, a force of 150 N was applied obliquely, directed from the palatal to the buccal aspect, at a specific angle of 30 degrees. The distribution of stress and fatigue performance were then assessed, considering the types of restoration frameworks used and the angles of the abutments in three distinct locations. The simulation aspect of the research was carried out utilizing Abaqus Software (ABAQUS 2020, Dassault Systems Simulation Corp., Johnston, RT, USA). Results: In all models, fatigue strengths in the premolar region were higher than in the molar region. Maximum stress levels were seen in models with angled implants. In almost all models with the zirconia framework, fatigue performance was slightly lower. Conclusions: According to the findings of this study, it was concluded that the use of metal-framework multi-unit restorations with minimum angulation has significant positive effects on the biomechanics and long-term success of implant treatments.

Finite Element Analysis of New Modified Three-dimensional Strut Miniplate versus Conventional Plating in Mandibular Symphysis and Angle Fractures - An In vitro Study.

Introduction: Mandibular fractures are common injuries during maxillofacial trauma, and currently, open reduction and internal fixation are considered gold-standard treatments. There is a wide discussion about which plates give the best outcomes. Hence, we are conducting a biomechanical comparison of two plates for mandibular symphysis and angle fracture with finite element analysis (FEA). The aim of this study was to do a comparative study of FEA between the conventional and our new modified three-dimensional (3D) strut miniplate in mandibular fractures at symphysis and angle regions. Materials and Methods: Finite element models of symphyseal and angle fractures of the mandible were developed. Each fracture model was then realigned and fixed by the conventional method 2.0 mm system, and our modified 3D strut plating method 2.0 mm system followed by the analysis of various stresses developed in plates and mandibular fracture area after application of load was observed in the study. Results: The modified 3D strut plating system with 2.0 mm miniplates is significantly better in preventing displacement of fracture segments by better distribution of forces compared to the conventional plating system. Rest of the parameters were within the permitted limits. Discussion: Modified 3D strut plating method was reasonably effective and superior in managing force-displacement compared to the conventional method of fixation for comminuted and unfavourable mandibular symphyseal fracture and angle fracture.

From Wald to Schnorr: von Mises' definition of randomness in the aftermath of Ville's Theorem.

The first formal definition of randomness, seen as a property of sequences of events or experimental outcomes, dates back to Richard von Mises' work in the foundations of probability and statistics. The randomness notion introduced by von Mises is nowadays widely regarded as being too weak. This is, to a large extent, due to the work of Jean Ville, which is often described as having dealt the death blow to von Mises' approach, and which was integral to the development of algorithmic randomness-the now-standard theory of randomness for elements of a probability space. The main goal of this article is to trace the history and provide an in-depth appraisal of two lesser-known, yet historically and methodologically notable proposals for how to modify von Mises' definition so as to avoid Ville's objection. The first proposal is due to Abraham Wald, while the second one is due to Claus-Peter Schnorr. We show that, once made precise in a natural way using computability theory, Wald's proposal constitutes a much more radical departure from von Mises' framework than intended. Schnorr's proposal, on the other hand, does provide a partial vindication of von Mises' approach: it demonstrates that it is possible to obtain a satisfactory randomness notion-indeed, a canonical algorithmic randomness notion-by characterizing randomness in terms of the invariance of limiting relative frequencies. More generally, we argue that Schnorr's proposal, together with a number of little-known related results, reveals that there is more continuity than typically acknowledged between von Mises' approach and algorithmic randomness. Even though von Mises' exclusive focus on limiting relative frequencies did not survive the passage to the theory of algorithmic randomness, another crucial aspect of his conception of randomness did endure; namely, the idea that randomness amounts to a certain type of stability or invariance under an appropriate class of transformations.

Three-dimensional finite element analysis of the biomechanical behaviour of different dental implants under immediate loading during three masticatory cycles.

The study aimed to evaluate the impact of varying modulus of elasticity (MOE) values of dental implants on the deformation and von Mises stress distribution in implant systems and peri-implant bone tissues under dynamic cyclic loading. The implant-bone interface was characterised as frictional contact, and the initial stress was induced using the interference fit method to effectively develop a finite element model for an immediately loaded implant-supported denture. Using the Ansys Workbench 2021 R2 software, an analysis was conducted to examine the deformation and von Mises stress experienced by the implant-supported dentures, peri-implant bone tissue, and implants under dynamic loading across three simulated masticatory cycles. These findings were subsequently evaluated through a comparative analysis. The suprastructures showed varying degrees of maximum deformation across zirconia (Zr), titanium (Ti), low-MOE-Ti, and polyetheretherketone (PEEK) implant systems, registering values of 103.1 µm, 125.68 µm, 169.52 µm, and 844.06 µm, respectively. The Zr implant system demonstrated the lowest values for both maximum deformation and von Mises stress (14.96 µm, 86.71 MPa) in cortical bone. As the MOE increased, the maximum deformation in cancellous bone decreased. The PEEK implant system exhibited the highest maximum von Mises stress (59.12 MPa), whereas the Ti implant system exhibited the lowest stress (22.48 MPa). Elevating the MOE resulted in reductions in both maximum deformation and maximum von Mises stress experienced by the implant. Based on this research, adjusting the MOE of the implant emerged as a viable approach to effectively modify the biomechanical characteristics of the implant system. The Zr implant system demonstrated the least maximum von Mises stress and deformation, presenting a more favourable quality for preserving the stability of the implant-bone interface under immediate loading.

Biomechanical Evaluation of Zygomatic Implant Versus Pterygoid Implant in Atrophic Maxilla: An In vitro Finite Element Study.

Background and Purpose: Dental implants are considered to be one of several treatment options that can be used to replace missing teeth. The objective of the study is to examine and compare the biomechanics of zygomatic and pterygoid implants planned on the atrophic maxilla with three different bone types. Materials and Methods: An in vitro finite element study was conducted on a three-dimensional model of zygomatic and pterygoid implants. In a total of 24 implants, two bilateral zygomatic and pterygoid implants with two anterior dental implants were inserted in models. 150 N vertical occlusal and 300 N load on masseter and medial pterygoid were simulated on the modeled prosthesis. The data were processed with ANSYS software. The stress on and deformations of the bones and implants were observed and compared. Results: When comparing the D4, D3, and D2 bones in subgroup I with zygomatic implants, the D2 bone was subjected to less stress compared to D3 and D4. The smallest displacement (0.125784 mm) was seen in D4 followed by the largest displacement (0.74073 mm) in D2. Similarly, when comparing the D2, D3, and D4 bone in subgroup II with pterygoid implants, the D2 bone in the atrophic maxilla received the least amount of stress from the pterygoid implants compared to D3 and D4. Furthermore, the smallest displacement (0.030934 mm) was seen in D2, and the largest (0.046319 mm) in D4. Conclusion: Results suggest firstly, that the overall stress was better distributed in D2 bone and secondly, the pterygoid implant showed higher stress concentration than the zygomatic implant.

Effect of margin designs and loading conditions on the stress distribution of endocrowns: a finite element analysis.

BACKGROUND: Margin designs and loading conditions can impact the mechanical characteristics and survival of endocrowns. Analyzing the stress distribution of endocrowns with various margin designs and loading conditions can provide evidence for their clinical application. METHODS: Three finite element analysis models were established based on the margin designs: endocrown with a butt-joint type margin (E0), endocrown with a 90° shoulder (E90), and endocrown with a 135° shoulder (E135). The E0 group involved lowering the occlusal surface and preparing the pulp chamber. The E90 group created a 90° shoulder on the margin of model E0, measuring 1.5 mm high and 1 mm wide. The E135 group featured a 135° shoulder. The solids of the models were in fixed contact with each other, and the materials of tooth tissue and restoration were uniform, continuous, isotropic linear elasticity. Nine static loads were applied, with a total load of 225 N, and the maximum von Mises stresses and stress distribution were calculated for teeth and endocrowns with different margin designs. RESULTS: Compared the stresses of different models under the same loading condition. In endocrowns, when the loading points were concentrated on the buccal side, the maximum von Mises stresses were E0 = E90 = E135, and when there was a lingual loading, they were E0 < E90 = E135. In enamel, the maximum von Mises stresses under all loading conditions were E0 > E90 > E135. In dentin, the maximum von Mises stresses of the three models were basically similar except for load2, load5 and load9. Compare the stresses of the same model under different loading conditions. In endocrowns, stresses were higher when lingual loading was present. In enamel and dentin, stresses were higher when loaded obliquely or unevenly. The stresses in the endocrowns were concentrated in the loading area. In enamel, stress concentration occurred at the cementoenamel junction. In particular, E90 and E135 also experienced stress concentration at the shoulder. In dentin, the stresses were mainly concentrated in the upper section of the tooth root. CONCLUSION: Stress distribution is similar among the three margin designs of endocrowns, but the shoulder-type designs, especially the 135° shoulder, exhibit reduced stress concentration.

Experimental and Numerical Investigation of the Fracture Behavior of Extruded Wood-Plastic Composites under Bending.

The ability of wood-plastic composites (WPCs) to withstand various loads and resist plastic failure is attracting more and more interest due to the global increase in demand for WPCs by over 6 million tons per year. Among the most important and innovative research methods are those based on fracture mechanics-their results enable material designers to optimize the structures of these hybrid polymer composites at the nano, micro and macro levels, and they allow engineers to more accurately evaluate and select functional, sustainable, long-lasting and safe product designs. In this study, standard single-edge notched bending (SENB) tests were used to analyze the fracture toughness of two different extruded WPCs along the longitudinal (L) and transverse (T) directions of extrusion. In addition to their resistance to crack propagation, critical fracture criteria, initial contact stiffness, fracture parameters and fracture surfaces, the mechanical properties of these composites were also investigated. The results showed that WPC-A coded composites withstood higher loads until failure in both directions compared to WPC-B. Despite the larger data spread, both types of composites were more resistant to crack propagation in the T direction. Mode II of crack propagation was clearly visible, while mode III was not as pronounced. The experimental results and the numerical finite element (FE) model developed up to 58% of the maximum load correlated well, and the obtained deformation curves were best approximated using cubic equations (R2 > 0.99). The shear stress zone and its location, as well as the distribution of the equivalent stresses, had a major influence on crack propagation in the fracture process zone (FZP).

Simulation of stress in a blood vessel due to plaque sediments in coronary artery disease.

Atherosclerosis is a cardiovascular disease mainly caused by plaque deposition in blood vessels. Plaque comprises components such as thrombosis, fibrin, collagen, and lipid core. It plays an essential role in inducing rupture in a blood vessel. Generally, Plaque could be described as three kinds of elastic models: cellular Plaque, hypocellular Plaque, and calcified Plaque. The present study aimed to investigate the behavior of atherosclerotic plaque rupture according to different lipid cores using Fluid-Structure Interaction (FSI). The blood vessel was also varied with different thicknesses (0.05, 0.25, and 0.5 mm). In this study, FSI simulation with a cellular plaque model with various thicknesses was investigated to obtain information on plaque rupture. Results revealed that the blood vessel with Plaque having a lipid core represents higher stresses than those without a lipid core. Blood vessels' thin thickness, like a thin cap, results in more considerable than Von Mises stress. The result also suggests that even at low fracture stress, the risk of rupture due to platelet decomposition at the gap was more significant for cellular plaques.

Biomechanical behavior of implant retained prostheses in the posterior maxilla using different materials: a finite element study.

BACKGROUND: The aim of this study is to evaluate the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials using finite element analysis (FEA). METHODS: Three dimensional (3D) finite element models with three implant configurations and prosthetic designs (fixed-fixed, mesial cantilever, and distal cantilever) were designed and modelled depending upon cone beam computed tomography (CBCT) images of an intact maxilla of an anonymous patient. Implant prostheses with two materials; Monolithic zirconia (Zr) and polyetherketoneketone (PEKK) were also modeled .The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). Then, individual models were subjected to separate axial loads of 300 N. Von mises stress values were computed for the prostheses, implants, and bone under axial loading. RESULTS: The highest von Mises stresses in implant (111.6 MPa) and bone (100.0 MPa) were recorded in distal cantilever model with PEKK material, while the lowest values in implant (48.9 MPa) and bone (19.6 MPa) were displayed in fixed fixed model with zirconia material. The distal cantilever model with zirconia material yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), while the least stresses in prosthesis (35.4 MPa) were recorded in fixed fixed models with PEKK material. CONCLUSIONS: In the light of this study, the combination of fixed fixed implant prosthesis without cantilever using a rigid zirconia material exhibits better biomechanical behavior and stress distribution around bone and implants. As a prosthetic material, low elastic modulus PEKK transmitted more stress to implants and surrounding bone especially with distal cantilever.

Stress Distribution on Prepared Tooth With Shoulder and Radial Shoulder Margin to Receive Crowns of Three Different Materials: A Finite Element Analysis.

Aim and background This study aims to determine the stress distribution on the prepared tooth at the margins with shoulder and radial shoulder finish lines when an occlusal load of 300N was applied to ceramic, zirconia, and polyether ether ketone (PEEK) crowns. Materials and methods Six models of mandibular first molar teeth were fabricated. The tooth models were subdivided into two groups with shoulder and radial shoulder margins, respectively (n = 18). The teeth were restored with three different prosthetic crown materials (ceramic, zirconia, and PEEK). To simulate the typical forces experienced by a prosthetic crown material in a lower posterior tooth during chewing and biting, an occlusal load of 300N was applied to each of the samples, and the maximum principal stress (Pmax) and von Mises stress were calculated, respectively. These samples were then compared and evaluated to determine the material best suited as a prosthetic crown material of choice for a lower posterior tooth. Results Among the materials used, the maximum principal stress value was the least in PEEK crowns. The von Mises stress value was highest for the zirconia crown with shoulder margin and was least for the PEEK crown with a similar margin. Conclusion PEEK as a crown material was found to be a better choice for lower posterior teeth as there was the least maximum principal stress at the margin, irrespective of either shoulder or radial shoulder finish line used.

A comparative evaluation of masticatory load distribution in different types of prosthesis with varying number of implants: A FEM analysis.

Aim: To identify the optimal number and position of implants to reduce stress concentration on the implant, denture, and attachment system for sustaining an overdenture prosthesis. Materials and methods: By incorporating one to eight indigenous implants with bar-type attachments, eight 3D finite element models of mandibular overdentures were created. All models received a 200 N vertical load, and the biomechanical characteristics of peri-implant bone were assessed. Result: The study observed that with a vertical load of 200 N, the maximum equivalent stress around peri-implant tissue in all models was within the physiological tolerance threshold of bone. The von Mises stress values ranged from 116.18 MPa to 536.7 MPa. Conclusion: The three-implant-supported overdenture model revealed superior peri-implant stress, stability, cost-effectiveness, and hygiene maintenance outcomes. Placing a third implant in the mid-symphysis region may offer a practical solution to reduce rotations in two-implant-supported overdentures.

Displacement and stress distribution pattern during complete mandibular arch distalization using buccal shelf bone screws - A three-dimensional finite element study.

BACKGROUND: To evaluate and compare the distribution of stress and displacement of teeth during mandibular arch distalization using buccal shelf screws. MATERIALS AND METHODS: Three three-dimensional finite element models of mandibular arch were constructed with third molars extracted. Models 1, 2, and 3 were constructed on the basis of the lever arm heights of 0 mm, 3 mm, and 6 mm, respectively, between the lateral incisor and canine. A buccal shelf screw was placed at the area in the second molar region with the initial point of insertion being inter-dental between the first and second molars and 2 mm below the mucogingival junction. MBT pre-adjusted brackets (slot size 0.022 × 0.028") were placed over the clinical crown's center with a 0.019 × 0.025" stainless-steel archwire on three models. A retraction force of 300 g was applied with buccal shelf screws and a lever arm bilaterally using nickel-titanium closed coil springs. The displacement of each tooth was calculated on X, Y, and Z axes, and the von Mises stress distribution was visualized using color-coded scales using ANSYS 12.1 software. RESULT: The maximum von Mises stress in the cortical and cancellous bones was observed in model 1. The maximum von Mises stress in the buccal shelf screw and the cortical bone decreased as the height of the lever arm increased. Applying orthodontic forces at the level of 6 mm lever arm height resulted in greater biomechanical bodily movement in distalization of the mandibular molars compared to when the orthodontic forces were applied at the level of 0 mm lever arm height. CONCLUSION: Displacement of the entire arch may be dictated by a direct relationship between the center of resistance of the whole arch and the line of action generated between the buccal shelf screw and force application points at the archwire, which makes the total arch movement highly predictable.

Patient-specific finite element analysis for assessing hip fracture risk in aging populations.

The femur is one of the most important bone in the human body, as it supports the body's weight and helps with movement. The aging global population presents a significant challenge, leading to an increasing demand for artificial joints, particularly in knee and hip replacements, which are among the most prevalent surgical procedures worldwide. This study focuses on hip fractures, a common consequence of osteoporotic fractures in the elderly population. To accurately predict individual bone properties and assess fracture risk, patient-specific finite element models (FEM) were developed using CT data from healthy male individuals. The study employed ANSYS 2023 R2 software to estimate fracture loads under simulated single stance loading conditions, considering strain-based failure criteria. The FEM bone models underwent meticulous reconstruction, incorporating geometrical and mechanical properties crucial for fracture risk assessment. Results revealed an underestimation of the ultimate bearing capacity of bones, indicating potential fractures even during routine activities. The study explored variations in bone density, failure loads, and density/load ratios among different specimens, emphasizing the complexity of bone strength determination. Discussion of findings highlighted discrepancies between simulation results and previous studies, suggesting the need for optimization in modelling approaches. The strain-based yield criterion proved accurate in predicting fracture initiation but required adjustments for better load predictions. The study underscores the importance of refining density-elasticity relationships, investigating boundary conditions, and optimizing models throughin vitrotesting for enhanced clinical applicability in assessing hip fracture risk. In conclusion, this research contributes valuable insights into developing patient-specific FEM bone models for clinical hip fracture risk assessment, emphasizing the need for further refinement and optimization for accurate predictions and enhanced clinical utility.

Evaluate the effect of bone density variation on stress distribution at the bone-implant interface using numerical analysis.

The current study aims to comprehend how different bone densities affect stress distribution at the bone-implant interface. This will help understand the behaviour and help predict success rates of the implant planted in different bone densities. The process of implantation involves the removal of bone from a small portion of the jawbone to replace either a lost tooth or an infected one and an implant is inserted in the cavity made as a result. Now the extent of fixation due to osseointegration is largely dependent on the condition of the bone in terms of the density. Generally, the density of the bone is classified into four categories namely D1, D2, D3, and D4; with D1 being purely cortical and D4 having higher percentage of cancellous bordered by cortical bone. A bone model with a form closely resembling the actual bone was made using 3D CAD software and was meshed using Hyper Mesh. The model was subjected to an oblique load of 120 N at 70° to the vertical to replicate occlusal loading. A finite element static analysis was done using Abaqus software. The stress distribution contours at the bone-implant contact zone were studied closely to understand the changes as a result of the varying density. It was revealed that as the quantity of the cancellous bone increased from D1 to D4 the cortical peak stress levels dropped. The bone density and the corresponding change in the material characteristics was also responsible for the variation in the peak stress and displacement values.

Partial femoral head replacement: a new innovative hip-preserving approach for treating osteonecrosis of the femoral head and its finite element analysis.

Purpose: Controversy remains regarding the optimal treatment for stage III Osteonecrosis of the femoral head (ONFH). This study presents, for the first time, the precise treatment of stage III ONFH using the "substitute the beam for a pillar" technique and performs a comparative finite element analysis with other hip-preserving procedures. Methods: A formalin-preserved femur of male cadavers was selected to obtain the CT scan data of femur. The proximal femur model was reconstructed and assembled using Mimics 20.0, Geomagic, and UG-NX 12.0 software with four different implant types: simple core decompression, fibula implantation, porous tantalum rod implantation, and partial replacement prosthesis. The finite element simulations were conducted to simulate the normal walking gait, and the stress distribution and displacement data of the femur and the implant model were obtained. Results: The peak von Mises stress of the femoral head and proximal femur in the partial replacement of the femoral head (PRFH) group were 22.8 MPa and 37.4 MPa, respectively, which were 3.1%-38.6% and 12.8%-37.4% lower than those of the other three surgical methods. Conclusion: The PRFH group exhibits better mechanical performance, reducing stress and displacement in the ONFH area, thus maintaining femoral head stability. Among the four hip-preserving approaches, from a biomechanical perspective, PRFH offers a new option for treating ONFH.

Scope of magnesium ceria nanocomposites for mandibular reconstruction: Degradation and biomechanical evaluation using a 3-dimensional finite element analysis approach.

Magnesium/Ceria nanocomposites (Mg/xCeO2 NCs (x = 0.5 %, 1 % and 1.5 %)) prepared by using powder metallurgy and microwave sintering method are assessed for their corrosion rate for a period of 28 days. As per the immersion tests results, the addition of ceria nanoparticles to pure Mg, brought about a noteworthy improvement to corrosion resistance. A corrosion rate of approximately 0.84 mm/year for Mg/0.5CeO2 and 0.99 mm/year for Mg/1.0CeO2 nanocomposites were observed. Another aspect of the study involves employing the simulation method i.e. finite element analysis (FEA) to compare the stress distribution in magnesium-ceria nanocomposite based screws and circular bars especially for Mg/0.5CeO2 and Mg/1.0CeO2. Further, the simulation also gives a perception of the impact of masticatory forces, the biting force and shear stress exerted on the Mg/0.5CeO2 and Mg/1.0CeO2 based screws. The simulations results show that the screws showed an acceptable level of stresses for a biting force up to 300 N. The circular bar as well kept its stresses at acceptable levels for the same load of 300N. The shear stress results indicated that a biting force up to 602 N can be safely absorbed by Mg/0.5CeO2 screw. The comprehensive approach allows for a better understanding of the corrosion behavior, stress distribution, and mechanical properties of the Mg/CeO2 nanocomposites, enabling the development of effective temporary implants for craniofacial trauma fixation that can withstand normal physiological forces during mastication. The study reported in this paper aims to target Mg/xCeO2 NCs for temporary implants for craniofacial trauma fixation.