Browsing by Author "Kaymaz, Irfan"

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An Analysis of Mandibular Symphyseal Graft Sufficiency for Alveolar Cleft Bone Grafting
(Lippincott Williams & Wilkins, 2017) Kilinc, Adnan; Saruhan, Nesrin; Ertas, Umit; Korkmaz, Ismail Hakki; Kaymaz, Irfan
The purpose of this study was to evaluate the sufficiency of the mandibular symphysis as a donor site for unilateral and bilateral alveolar grafting, measuring both the alveolar cleft volume and maximum bone graft volume that can be harvested from the mandibular symphysis using 3-dimensional computed tomography (CT) and software in children and adults. Computed tomography data obtained from 20 unilateral and bilateral cleft lip palates patients in the preoperative period were used in this study. The patients were divided into 2 groups: children (female, n = 5; male, n = 5) and adults (female, n = 5; male, n = 5). The required bone graft volume for grafting and the maximum bone graft volume that can be harvested from the mandibular symphysis were measured based on cone beam CT data and software. The average required bone graft volume (cleft volume) for unilateral alveolar grafting was 963.51 +/- 172.31 mm(3) in the children and 1001.21 +/- 268.16 mm(3) in the adults. The average required bone graft volume for bilateral alveolar grafting was 1457.82 +/- 148.18 mm(3) in the children and 2189.59 +/- 600.97 mm(3) in the adults. The average the mandibular symphysis bone graft volume was 819.29 +/- 330.85 mm(3) in the children and 2164.9 +/- 1095.86 mm(3) in the adults. The results demonstrated that the mandibular symphysis region provided an adequate bone volume for alveolar grafting in adults with unilateral alveolar clefts. However, it is difficult to standardize these results, due to cleft volume and graft volume that could be harvested from the mandibular symphysis are highly variable among individuals.
An Application of Finite Element Method in Material Selection for Dental Implant Crowns
(Walter de Gruyter GmbH, 2021) Sensoy, Abdullah T.; Colak, Murat; Kaymaz, Irfan; Findik, Fehim
Materials used for dental crowns show a wide range of variety, and a dentist's choice can depend on several factors such as patient desires, esthetics, tooth factors, etc. One of the most important issues for implant surgery is the primary stability and it should be provided to minimize the risks of screw loosening, failed osseointegration, or nonunion. The current study aims to present the Finite Element Analysis (FEA)-based material selection strategy for a dental crown in terms of reducing the aforementioned risks of dental implants. A virtual surgery mandible model obtained using MIMICS software was transferred to the ANSYS and material candidates determined using CES software were compared using FEA. The results indicated that ZrO2+Y2O3 (zirconia) has shown a 12.79% worse performance compared to Au83-88/Pt4-12/Pd4.5-6 alloy in terms of abutment loosening. On the other hand, zirconia is the most promising material for dental crowns in terms of the stability of the bone-implant complex. Therefore, it may show the best overall performance for clinical use. Moreover, as suggested in this study, a better outcome and more accurate predictions can be achieved using a patient-specific FEA approach for the material selection process.
CF-PEEK vs. Titanium Dental Implants: Stress Distribution and Fatigue Performance in Variable Bone Qualities
(MDPI, 2025) Polat Sagsoz, Nurdan; Murat, Fahri; Gul, Sema Nur Sevinc; Sensoy, Abdullah Tahir; Kaymaz, Irfan
This study aims to evaluate the biomechanical behavior of titanium and carbon fiber-reinforced polyetheretherketone (CF-PEEK) dental implants under varying bone densities and loading conditions using finite element analysis (FEA). A single-tooth mandibular molar implant system was modeled, comprising titanium or CF-PEEK abutment and fixture, and surrounding bone structures with four configurations: (I) fully cortical bone, (II) 2 mm cortical layer with trabecular bone, (III) 1 mm cortical with high-density trabecular bone, and (IV) 1 mm cortical with low-density trabecular bone. Vertical and oblique static loads of 100 N were applied to simulate masticatory forces. FEA results revealed that titanium implants exhibited higher von Mises stress values in the implant and abutment under oblique loading, exceeding 400 MPa, while CF-PEEK components showed reduced stress but significantly higher strain levels. Cortical and trabecular bone surrounding CF-PEEK implants received more uniform stress distribution, potentially minimizing stress shielding effects. However, fatigue life analyses indicated that CF-PEEK abutment and screw components were more susceptible to mechanical failure under oblique loads, particularly in low-density bone models. In conclusion, CF-PEEK implants offer a more physiological load transfer to bone and reduced stress shielding compared to titanium. However, their structural reliability under complex loading, especially in low-quality bone conditions, requires careful consideration. These findings support the potential use of CF-PEEK in select clinical scenarios but highlight the need for further material and design optimization.
Comparative Biomechanical Evaluation of Spinal Cages Made from Pcl, Peek, and Ti6al4v Via Support-Free Additive Manufacturing
(Wiley-V C H Verlag GmbH, 2025) Murat, Fahri; Kaymaz, Irfan
This study introduces a novel biodegradable spinal cage design optimized for additive manufacturing (AM) through topology optimization with overhang constraints, enabling the fabrication of designs without the need for support structures. The biomechanical performance of nonbiodegradable materials (Ti6Al4V and PEEK) and a biodegradable polymer (PCL) was evaluated using finite element analysis (FEA) and mechanical testing. A multilevel spinal model (T10-S1) simulates realistic biomechanics, focusing on the L4-L5 segment with a gyroid porous structure. Results demonstrate that Ti6Al4V exhibits the highest stiffness (78000 N mm-1) but raises stress-shielding concerns due to von Mises stress peaks (112.3 MPa). In contrast, PEEK and PCL demonstrate lower stress values (9.40 MPa and 7.59 MPa, respectively) and better biomechanical compatibility with spinal discs. This study highlights the potential of AM-filtered designs combined with biodegradable materials, such as PEEK and PCL, to advance patient-specific spinal cage applications while addressing challenges in AM fabrication. By eliminating support structures, this approach reduces material waste, manufacturing time, and postprocessing requirements, making spinal cage production more efficient and sustainable.
Designing a Novel Porous Fixation Plate with a Gyroid Lattice Structure for Humerus Fractures Using a Probabilistic Approach
(Wiley-V C H Verlag GmbH, 2024) Kaymaz, Irfan; Yavuz, Osman; Murat, Fahri; Korkmaz, Ismail Hakki
Conventional fixation plates permanently attached to the body can lead to complications, such as stress shielding and aseptic loosening, due to their contact with the bone, resulting in bone loss. The contact between these solid fixation plates and the bone surface inhibits blood flow, potentially leading to necrosis at the interface. To overcome this challenge, a porous implant featuring a gyroid lattice structure for humerus bone fixation is proposed. However, designing such an implant typically involves deterministic approaches, which do not account for uncertainties in design parameters, loadings on the plate, and additive manufacturing process parameters. Consequently, the actual conditions experienced by the plate may not be accurately modeled. Herein, both deterministic and probabilistic analyses of a porous implant with a gyroid lattice structure positioned on the humeral bone is conducted. The findings are compared to the failure probabilities of both the conventional fixation plate and the optimal plate derived from a previous study. The study reveals that uncertainties in design parameters significantly influence the plate's failure probability compared to deterministic analysis, emphasizing the importance of probability-based analyses for a reliable plate design. A porous implant featuring a gyroid lattice structure for humerus bone fixation is studied. Designing such an implant typically involves deterministic approaches, which do not account for uncertainties in design parameters, loadings on the plate, and additive manufacturing process parameters. However, this study applies both deterministic and probabilistic approaches to design a porous implant for humerus bone fractures.image (c) 2023 WILEY-VCH GmbH
Designing and In Vitro Testing of a Novel Patient-Specific Total Knee Prosthesis Using the Probabilistic Approach
(Walter de Gruyter GmbH, 2022) Korkmaz, Ismail H.; Kaymaz, Irfan; Yildirim, Omer S.; Murat, Fahri; Kovaci, Halim
In order to prevent failure as well as ensure comfort, patient-specific modelling for prostheses has been gaining interest. However, deterministic analyses have been widely used in the design process without considering any variation/uncertainties related to the design parameters of such prostheses. Therefore, this study aims to compare the performance of patient-specific anatomic Total Knee Arthroplasty (TKA) with off-the-shelf TKA. In the patient-specific model, the femoral condyle curves were considered in the femoral component's inner and outer surface design. The tibial component was designed to completely cover the tibia cutting surface. In vitro experiments were conducted to compare these two models in terms of loosening of the components. A probabilistic approach based on the finite element method was also used to compute the probability of failure of both models. According to the deterministic analysis results, 103.10 and 21.67 MPa von Mises stress values were obtained for the femoral component and cement in the anatomical model, while these values were 175.86 and 25.76 MPa, respectively, for the conventional model. In order to predict loosening damage due to local osteolysis or stress shield, it was determined that the deformation values in the examined cement structures were 15% lower in the anatomical model. According to probabilistic analysis results, it was observed that the probability of encountering an extreme value for the anatomical model is far less than that of the conventional model. This indicates that the anatomical model is safer than the conventional model, considering the failure scenarios in this study.
Determining the Optimum Process Parameters of Selective Laser Melting Via Particle Swarm Optimization Based on the Response Surface Method
(Korean Inst Metals Materials, 2023) Murat, Fahri; Kaymaz, Irfan; Sensoy, Abdullah Tahir; Korkmaz, Ismail H.
Manufacturing high-quality and desired products from additive manufacturing necessitate careful adjustment of the process parameters. Various methods can be utilised to determine optimum process parameters, such as the Taguchi method, Design of Experiments (DoE). Rather than evaluating limited information obtained from statistical analysis of the experiments, optimisation methods can help find the best possible combination for the process parameters. Therefore, an optimisation approach based on Particle Swarm Optimization (PSO) was utilised to find the optimum process parameters. The most important process parameters of Selective Laser Melting (SLM) such as laser power, layer thickness, scan speed, and build orientation were selected as input parameters, and their effects on the tensile properties of the manufactured part were investigated to find out the optimal operating conditions for the SLM process. Since there is not any explicit mathematical expression relating these process parameters to the tensile strength, the Response Surface Method (RSM) was used to obtain a meta-model so that it can be used as an objective function in the optimisation formulation. This approach enabled us to predict the optimum process parameters to maximise the tensile strength without conducting an excessive number of experiments. Moreover, the mathematical model can also predict tensile strength corresponding to the parameter values that are not tested according to the DoE chosen for such studies. Furthermore, it was also shown that the PSO outperforms the Genetic Algorithm (GA), which is widely employed to find out the optimum process parameters, in terms of less number of iteration.
Determining the Patient-Specific Optimum Osteotomy Line for Severe Mandibular Retrognathia Patients
(Lippincott Williams & Wilkins, 2018) Sensoy, Abdullah Tahir; Kaymaz, Irfan; Ertas, Umit; Kiki, Ali
Purpose: The purpose of this study is to suggest a patient-specific osteotomy line to optimize the distractor position and thus to minimize the disadvantages of conventional mandibular distraction osteogenesis (MDO) protocols. In addition, this study also aims to compare the conventional MDO protocols with the new MDO protocol proposed in this study in terms of both orthodontic outcomes and mechanical effects of osteotomy level on callus stabilization by means of the finite element method. Methods: A preoperative patient-specific 3-dimensional bone model was created and segmented by using computed tomography images of an individual patient. Virtual orthodontic set-up was applied to the segmented model prior to the virtual surgery. In order to compare the proposed osteotomy line with the conventional lines used in clinical applications, virtual surgery simulations were performed and callus tissues were modelled for each scenario. The comparison of the success of each osteotomy line was carried out based on the occlusion of the teeth. Results: The osteotomy line determined using the method proposed in this study has resulted in far less malocclusion than the conventional method. Namely, any angular deviation from the optimum osteotomy line determined in this study might result in deep-bite or open-bite. On the other hand, the finite element analysis results have indicated that this deviation also negatively affects the callus stability. Conclusion: In order to achieve a better MDO treatment in terms of occlusion of the teeth and the callus stability, the location of the osteotomy line and the distractor position can be computationally determined. The results suggest that MDO protocol developed in this study might be used in clinic to achieve a better outcome from the MDO treatment.
Development of Particle Swarm and Topology Optimization-Based Modeling for Mandibular Distractor Plates
(Elsevier, 2020) Sensoy, Abdullah Tahir; Kaymaz, Irfan; Ertas, Umit
Mandibular Distraction Osteogenesis (MDO) is a common clinical procedure to correct mandibular retrognathia. However, since there is not a gold standard for determining the screw positions for current MDO operations, deviation of distraction direction and malocclusion increases. This case results in need of additional operations that affect the callus stability. In these cases, relapse risk increases and remodelling period gets longer. On the other hand, large volume of the distractor plates results in more invasive treatment and negatively affects the patients' comfort. To overcome these problems, this study offers a new method including; virtual surgery simulation, determining the optimum screw configuration using particle swarm optimization loop linked between MATLAB-PYTHON-ANSYS programs and the design of distractor plate geometry with topology optimization. In order to test the proposed method, two different Finite Element (FE) models, CM and OM, were established based on conventional and optimum method, respectively. FEA results of the current study reveals that OM has 33.56% less displacement compared to CM, and the most critical screw in terms of screw loosening for OM has 35.29% less strain value than CM. These outcomes show OM shows superior callus stability in comparison with CM. On the other hand, redesign of the distractor plates using topology optimization according to the best screw positions provides 43.32% reduction in the total implant volume which means reduced cost and a less invasive MDO operation. Therefore, the clinical use of this protocol is expected to increase the success of the operation by shortening the recovery period.
Effect of Uncertain Quantities on the Stability Analysis of a Miniscrew Anchorage System
(Taylor & Francis Ltd, 2023) Kaymaz, Irfan; Alibeyoglu, Fatih; Dagsuyu, Ilhan Metin
PurposeTo determine how the uncertainties related to both the material properties and failure threshold value affect the failure prediction of a miniscrew using the FE analysis.Materials and MethodsThree-dimensional surface models for molar, and premolar, segments of the mandibular bone surrounding these two teeth were generated using patient-specific CT data. The 3D model was exported to a finite element Ansys/Workbench to conduct a static analysis with the traction load of 2 N exerted on the miniscrew. The probabilistic analysis was carried out to determine the failure of the miniscrew, in which Kriging was selected as the metamodeling method.ResultsThe uncertainties related to material properties significantly affect the failure probability of the miniscrew, especially for the values with a higher percentage of variability. The analyses in which a constant threshold value is considered indicate no failure, whereas the probabilistic analysis in which the random effect of the threshold value is considered yields a failure probability for the miniscrew.ConclusionTo accurately evaluate the stability of a miniscrew from an FE analysis, the computation of the failure probability of the miniscrew should take into account the uncertainty regarding the threshold value.
Effects of Process Parameters on Selective Laser Melting of Ti6Al4V-Eli Alloy and Parameter Optimization via Response Surface Method
(Elsevier Science Sa, 2023) Kaya, Gurkan; Yildiz, Fatih; Korkmaz, Ismail Hakki; Kaymaz, Irfan; Yetim, Ali Fatih; Ergueder, Tevfik Oguzhan; Sen, Cagdas
Selective laser melting (SLM) allows for manufacturing intricate and accurate component designs that are challenging, expensive, or impossible to achieve using traditional methods. To achieve a high-quality final product with SLM, it is necessary to optimize the process parameters carefully. This optimization helps to minimize internal structural defects and control the microstructure. In this study, the optimum production parameters of Ti6Al4V alloy were determined using the Response Surface Method (RSM). The micro-CT analysis was utilized to calculate the relative densities of the samples fabricated using different production parameters. Furthermore, the influence of heat treatment, conducted below and above the & beta; transformation temperature, on the mechanical properties was examined. The results were analyzed by considering the microstructure images obtained from Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis. The optimum production parameters for the SLM method were found to be 80W laser power, 1125 mm/s scanning speed, 25 & mu;m layer thickness, and 45 & mu;m hatch distance. Samples created with these optimized parameters achieved 99.919% relative density, 1050 MPa ultimate tensile stress, and 13.8% elongation, surpassing the minimum standards outlined in ASTM F3001-14. Additionally, the systematic parameter reduction approach used in the study led to savings in both powder consumption and time in SLM, a method that could be applied to various metallic materials.
Eklemeli Üretim ile Elde Edilen Fonksiyonel Kademelendirilmiş Gözenekli İmplantlar
(2019) Murat, Fahri; Şensoy, Abdullah Tahir; Korkmaz, İsmail Hakkı; Kaymaz, Irfan
Gözenekli yapılar, vücutta kullanılan implant ve protezler için doku oluşumunun desteklenmesi, gerilme kalkanı ve aseptik gevşeme problemlerinin giderilmesi gibi üstünlüklerinden dolayı biyomedikal endüstrisinde giderek artan bir kullanım oranına sahiptir. Homojen yoğunluğa sahip gözenekli yapıların biyolojik süreçlere olumlu katkıları olsa da, bu yapılar mekanik açıdan istenen özellikleri sergilemede yetersiz kalmışlardır. Bu durumda kullanılacak olan implantın biyolojik ve mekanik olarak optimum tasarımı sunması gerekmektedir. Bahsedilen problemin çözümü için yük taşıyan ortopedik implant üzerinde doku rejenerasyonu ve mekanik davranışın birbirleriyle uyumunu sağlayan fonksiyonel kademelendirilmiş yapılar sunulmuştur. Gözenekliliğin, implantın yük taşıyan kesitlerinde çok yoğun, doku ile temas eden bölgelerinde ise az yoğun olduğu tasarımlar, eklemeli üretim yöntemleri ile uygulanabilir hale gelmiştir. Yapılan bu çalışmada gözenekli implantlar, fonksiyonel kademelendirilmiş gözenekli yapılar ve bu yapıların eklemeli üretim uygulamalarının bulunduğu literatürdeki son gelişmeler derlenmiştir. Sonuç olarak eklemeli üretim uygulamalarında biyolojik iyileşme süreçlerini hızlandırarak mekanik özellikleri geliştirmek için kullanılacak olan gözenekli implant tasarımları hakkında bir yol haritası sunulmuştur.
Fatigue Performance of Additively Manufactured Gyroid and Diamond Lattice Structures with Varying Porosities
(Springer London Ltd, 2025) Kaya, Gurkan; Yildiz, Fatih; Korkmaz, Ismail Hakki; Yetim, Ali Fatih; Kaymaz, Irfan
This study investigates the fatigue performance of gyroid and diamond lattice structures fabricated by laser powder bed fusion (L-PBF) at porosity levels of 60%, 70%, And 80%. The lattice structures were fabricated from Ti6Al4V alloy And subjected to comprehensive fatigue testing to evaluate their behavior under cyclic loading. High-cycle fatigue tests were performed under compression-compression loading conditions, And the fatigue lives of the samples were determined based on a 90% stiffness degradation criterion. Fatigue strength significantly declined with increasing porosity in both gyroid and diamond lattices. Gyroid lattices outperformed diamond lattices at the same porosity levels, likely due to their surface-based geometry that enables more uniform stress distribution. In contrast, diamond lattices experienced localized stress concentrations, leading to premature failure. The fracture surfaces of the fatigued samples were analyzed via scanning electron microscopy (SEM) to investigate crack initiation and propagation mechanisms, revealing that surface defects and unmelted powder particles played a critical role in the fatigue failure of both lattice types. This research provides valuable insights into the fatigue behavior of gyroid and diamond lattice structures, particularly for lightweight applications requiring long-term durability, such as in biomedical implants and aerospace components. These findings highlight the critical role of lattice design and porosity in optimizing fatigue performance.
Investigating the Optimum Model Parameters for Casting Process of A356 Alloy: A Cross-Validation Using Response Surface Method and Particle Swarm Optimization
(Springer Heidelberg, 2020) Sensoy, Abdullah Tahir; Colak, Murat; Kaymaz, Irfan; Dispinar, Derya
This study aimed to determine the optimal casting parameters for the maximum fluidity of A356 alloy. Gravity die cast method was used. For this purpose, central composite design (CCD) was performed. The input parameters and their limits for the trial design were selected as pre-heating temperature (100-400 degrees C), casting temperature (680-760 degrees C), and cross-sectional thickness (1-10 mm). Using the CCD-based simulation results of the feed distance, a highly correlated full-quadratic regression equation was obtained with the highestR(2)(0.99), which then was used as the objective function for the particle swarm optimization (PSO) process. The highest value of the response parameter, flow distance, reached up to 491.19 mm when the input parameters were selected as 400 degrees C, 760 degrees C and 10 mm, respectively. The sensitivity analysis has shown that the most effective parameter on the fluidity is the cross-sectional thickness. The response surface method (RSM)-based optimization results have been also validated using the PSO method. Although the higher temperatures have been found to result in better fluidity, there may be some drawbacks to working at higher temperatures such as energy cost and mould life. To determine the optimum input parameters, the RSM model suggested in this study can be modified for any type of casting process. Moreover, especially for a complex-shaped part, the manufacturer can be advised regarding operating conditions such as pre-heating and casting temperatures.
Investigation of Subcrestally Placed Dental Implants with and without Apical Cortical Bone Anchorage Under Conventional or Immediate Loading
(Elsevier - Division Reed Elsevier India Pvt Ltd, 2023) Aydin, Tugba; Korkmaz, Ismail Hakki; Sahin, Ahmet Bedreddin; Kaymaz, Irfan
There is no firm evidence regarding the effect of apical cortical bone anchorage of subcrestally placed dental implants in terms of the stress and strain distribution in the peri-implant bone, implant and pros-thetic components and in terms of the micromotion of the implant. The purpose of this study was to form an estimate of the effect of different apical bone anchorages of subcrestally placed implants on the stress and strain values of peri-implant bone, implant and prosthetic components and micromotion of the implants by making use of three-dimensional (3D) finite element analysis (FEA). Six 3D FEA models with different apical bone anchorages and different implant loading protocols were created. Both the von Mises stress values for implant and prosthetic components and the maximum (tensile) principal stresses (TPS) and minimum (compressive) principal stresses (CPS) and principal elastic strain (PES) values in peri-implant bone were obtained. Additionally, micromotion values in the implants were analyzed. In subcrestally placed implants, it is observed that providing apical cortical anchorage diminishes the aver-age values of TPS and CPS in the trabecular bone (TPS oblique M2A-0.63 MPa, TPS oblique M3A-0.58 MPa; CPS oblique M2A-0.82 MPa, CPS oblique M3A-0.65 MPa; TPS axial M2A-0.37 MPa, TPS axial M3A-0.14 MPa; CPS axial M2A-0.78 MPa, CPS axial M3A-0.30 MPa). Similarly, it is seen that the apical cortical anchorage diminishes the maximum and minimum PES values in the trabecular bone in subcrestally placed implants (min PES oblique M2A-15542 ge, min PES oblique M3A-14334 ge; max PES oblique M2A-9607 ge, max PES oblique M3A-8850 ge; min PES axial M2A-5156 ge, min PES axial M3A-2206 ge; max PES axial M2A-4487 ge, max PES axial M3A-3096 ge). It was also found that apical cortical bone anchorage is advantageous in terms of micromotion in the subcrestally placed implant (trabecular bone -implant (4th) micromotion values: oblique M2A-3.23 gm, oblique M3A-2.36 gm; axial M2A-0.96 gm, axial M3A-0.49 gm; trabecular bone-implant (6th) micromotion values: oblique M2A-3.45 gm, oblique M3A-2.72 gm; axial M2A-1.32 gm, axial M3A-0.59 gm). The present study demonstrated that apical cor-tical bone anchorage in subcrestally placed implants provided more favorable values of stress and strain in the peri-implant bone and reduced the micromotion of the implant.(c) 2023 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
A New Design for the Humerus Fixation Plate Using a Novel Reliability-Based Topology Optimization Approach to Mitigate the Stress Shielding Effect
(Elsevier Sci Ltd, 2022) Kaymaz, Irfan; Murat, Fahri; Korkmaz, Ismail H.; Yavuz, Osman
Background: Due to high stiffness, metal fixation plates are prone to stress shielding of the peri-prosthetic bones, leading to bone loss. Therefore, it has become important to design implants with reduced rigidity but increased load-carrying capacity. Considering the uncertainties in the parameters affecting the implant-bone structure is critical in making more reliable implant designs. In this study, a Response Surface Method based Reliabilitybased Topology Optimization approach was proposed to design a fixation plate for humerus fracture having less stiffness than the conventional plate. Methods: The design of the fixation plate was described as an Reliability-based Topology Optimization problem in which the probabilistic constraint was replaced with a meta-model generated using the Kriging method. The artificial humerus bone model was scanned, and the 3D simulation model was used in the finite element analysis required in the solution. The optimum plate was manufactured using Selective Laser Melting. Both designs were experimentally compared in terms of rigidity.Findings: The volume of the conventional plate was reduced from 2512.5 mm3 to 1667.3 mm3; nevertheless, the optimum plate had almost one-third less rigidity than the conventional plate. The probability of failure of the conventional plate was computed as 0.994. However, this value was almost half for the optimum fixation plate.Interpretation The studies showed that the new fixation plate design was less rigid but more reliable than the conventional one. The computation time required to have the optimum plate was reduced by one-tenth by applying the Response Surface Method for the Reliability-based Topology Optimization problem.
A New Porous Fixation Plate Design Using the Topology Optimization
(Elsevier Sci Ltd, 2021) Murat, Fahri; Kaymaz, Irfan; Korkmaz, Ismail Hakki
Fixation plates are used to accelerate the biological healing process in the damaged area by providing mechanical stabilization for fractured bones. However, they may cause mechanical and biological complications such as aseptic loosening, stress shielding effect and necrosis during the treatment process. The aim of this study, therefore, was to reduce mechanical and biological complications observed in conventional plate models. For this purpose, an optimum plate geometry was obtained using the finite element based topology optimization approach. An optimum and functionally graded porous model were obtained for the plates used for transverse fractures of diaphysis in long bones. This model was combined with a functional graded porous cage structure, and thus a new generation porous implant model was proposed for fixation plates. In order to determine the performance of the optimum plate model, it was produced by additive manufacturing. Three models; i.e. conventional, optimum and porous fixation plates were statically tested, and they were compared experimentally and numerically using the finite element analysis (FEA). The porous model can be considered as the most suitable option since it requires less invasive inputs, and might lead minimum necrosis formation due to having lesser contact surface with the bone. (c) 2021 IPEM. Published by Elsevier Ltd. All rights reserved.
Optimal Material Selection for Total Hip Implant: A Finite Element Case Study
(Springer Heidelberg, 2019) Sensoy, Abdullah Tahir; Colak, Murat; Kaymaz, Irfan; Findik, Fehim
The selection of most proper materials in engineering design is known as an important stage of the design process. In order to successfully complete this stage, it is necessary to have sufficient knowledge about the structure of materials, density, melting point, thermal expansion coefficient, tensile and yield strength, elongation, modulus of elasticity, hardness and many other properties. There are several selection systems that help the design engineer to choose most suitable material that meet the required properties. In the field of bioengineering, the selection of materials and the development of new materials for the clinical needs are increasingly important. In this study, the cases of optimal implant stabilization were investigated, material alternatives for hip prosthesis were evaluated, and optimal materials were determined. Using computerized tomography data with MIMICS software, virtual surgery was applied the hip bone and the implant was attached to bone. Boundary conditions and material properties have been defined, and finite element model has been created. FEA investigation of the mechanical behavior of the hip implant for various material alternatives determined by the CES software showed that the best material candidate is austenitic, annealed and biodurable stainless steel in terms of the micromotions at the implant-bone cement interface regarding osseointegration. This candidate showed 20.69% less strain value than the most commercially used hip implant material, Ti6Al4V. Therefore, the findings of this study suggest that the use of some specific stainless steel materials for implants may reduce the operation cost and increase the operation success for the total hip arthroplasty.
Reliability-Based Topology Optimization Considering Overhang Constraints for Additive Manufacturing Design
(MDPI, 2025) Murat, Fahri; Kaymaz, Irfan; Sensoy, Abdullah Tahir
This study examines the combination of overhang constraints and Reliability-Based Topology Optimization (RBTO) in additive manufacturing (AM). AM offers intricate component production but faces challenges due to support structures. Incorporating overhang constraints in topology optimization enables self-supporting structures. RBTO addresses uncertainties in design variables to enhance reliability. This research investigates build direction parameter solutions using deterministic and RBTO algorithms. Topological properties, compliance, sensitivity, and density filters are assessed, alongside optimization techniques like Method of Moving Asymptotes (MMA) criterion and Optimality Criteria (OC). In numerical experiments on the MBB beam, the AM-RBTO algorithm reduced 3D printing time by approximately 18.3% and improved structural performance by lowering the objective function value by 1.85% compared to conventional RBTO. Results contribute to merging overhang constraints and RBTO in AM topology optimization, improving design by considering uncertainties. The study enhances computational efficiency and stability in optimizing build direction parameters, offering valuable insights for future AM applications.
Triad of Foot Deformities and Its Conservative Treatment: with a 3D Customized Insole
(Sage Publications Ltd, 2021) Yildiz, Kadri; Medetalibeyoglu, Fatih; Kaymaz, Irfan; Ulusoy, Gokhan Ragip
The coexisting of three deformities as hallux valgus, flatfoot, and the calcaneal spur is an undefined medical condition, and it may be called triad of foot deformities (TFD) as a definition for a new disease entity. A customized 3D insole prototype was created by postprocessing of MRI data, and printed by 3D printer technology for the purpose of providing effective and innovative treatment for TFD. A 42 years-old female was clinically examined for TFD findings. All radiological measurements were made on the weightbearing anteroposterior and lateral X-rays. The patient underwent the pedogram (RSscan International, footscan (c)). MRI images were taken for the purpose of 3D scanning that was used for producing the 3D splint for TFD. AOFAS (American Orthopedic Foot and Ankle Society scores) and FHSQ (Foot Health Status Questionnaire) were used for clinical follow-up. MRI images of the patient were imported to Mimics software in order to create a 3D model using image processing. Thus, Patient-Specific 3D customized silicone orthotic insole that was based on 3D printing technology was produced. The one-simple test was used to compare the results of AOFAS and FHSQ scores. The measurements of radiological measurements were given. On the clinical follow-up, AOFAS was FHSQ scores were obtained. There was a significant difference in terms of AOFAS and FHSQ scores (p <= 0.05). As a result of our study; our 3D customized insole was produced at the price of approximately 1/3 of the total cost of three standard medical products. The coexisting of these three deformities may be called triad of foot deformities (TFD). The 3D printer technology enables us to access a customized, personalized conservative treatment option for TFD. The conservative treatment of TFD is possible by a single orthotic insole.