Browsing by Author "Murat, Fahri"

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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.
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.
Evaluation of Biomechanical Effects of Mandible Arch Types in All-On and All-On Dental Implant Design: A 3D Finite Element Analysis
(MDPI, 2025) Gul, Sema Nur Sevinc; Murat, Fahri; Sensoy, Abdullah Tahir
This study evaluates the biomechanical effects of different implant configurations in various mandibular arch types using finite element analysis (FEA). Stress distribution and deformation patterns were analyzed under different loading conditions in square, U-shaped, and V-shaped arches. The results indicate that increasing the number of implants generally reduces cortical bone stress, particularly in U and V arches, while implant-level stress tends to increase. Under molar loading, cortical bone stress in the square arch decreased by 16.9% (from 90.61 MPa to 75.27 MPa) with the All-on-5 system, while implant stress in the V arch dropped by 46.26% (from 142.35 MPa to 76.5 MPa). Additionally, the cantilever effect in All-on-4 configurations resulted in higher stress on the prosthesis and implants, particularly in V arches. While the All-on-5 system provided better load distribution, the study highlights the importance of optimizing implant positioning based on mandibular anatomy. Despite limitations such as the use of static forces and standardized arch types, these findings offer valuable insights into the biomechanical performance of full-arch implant rehabilitations, supporting future clinical applications and research.
İmplant Tasarımında Eklemeli Üretim Kriterlerini Dikkate Alan Bir Topoloji Optimizasyon Yaklaşımının Geliştirilmesi
(2024) Murat, Fahri; Kaymaz, İrfan
Topoloji optimizasyonu, belirli kısıtlar ve hedefler altında bir yapının malzeme dağılımını optimize ederek, minimum malzeme kullanımı ile maksimum performans elde etmeyi amaçlayan bir mühendislik yaklaşımıdır. Malzeme kullanımı optimize edilirken destek yapılarını en aza indirmek, üretim maliyetlerini ve çevresel etkileri önemli düzeyde azaltmaktadır. Bu çalışmada, topoloji optimizasyonu ile tasarlanan titanyum alaşımı, polietereterketon (PEEK) ve polikaprolakton (PCL) malzemelerinden eklemeli imalat yöntemleri ile üretilen gözenekli spinal implantların, mekanik performansları ve biyolojik davranışları kapsamlı bir şekilde incelenmiştir. İmplant tasarımında kullanılan topoloji optimizasyonu için, eklemeli imalatta üretim yönü kısıtlamasını dikkate alarak destek yapılarını ortadan kaldıran bir algoritma geliştirilmiştir. Elde edilen tasarımlar, sonlu elemanlar analizi ile sayısal olarak değerlendirilmiş ve mekanik testlerle deneysel olarak doğrulanmıştır. Eklemeli üretim parametrelerinin optimizasyonu için yanıt yüzeyi metodolojisi kullanılarak, lazer üretim parametrelerinin ürün performansı üzerindeki etkileri detaylı bir şekilde analiz edilmiştir. Çalışma sonucunda, çekme dayanımı için optimum parametre dağılımı belirlenerek optimize edilen titanyum implant tasarımları bu doğrultuda üretilmiştir. Mekanik testler ile implant yüzeylerinde ortaya çıkan deformasyon ölçümleri, iki boyutlu dijital görüntü korelasyon tekniği ile değerlendirilmiştir. Biyolojik testler sonucunda optimize edilmiş spinal implantların biyouyumluluk ve biyobozunurluk kapasitesi değerlendirilmiştir. Sonuçta, eklemeli üretim filtresi ile %19 oranında üretim süresi ve %22 oranında malzeme kazancı sağlanmıştır. Ayrıca polikaprolakton malzemede 90. gün sonunda PCL malzemesinde %1,26 oranında biyobozunma izlenmiştir.
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.
Predictive Mathematical Modeling of Biomechanical Behavior in All-On Implants Design: Effects of Distal Implant and Occlusal Load Angulation Using RSM Based on FEA
(Frontiers Media Sa, 2025) Murat, Fahri; Sevinc Gul, Sema Nur; Sensoy, Abdullah Tahir
This study presents a predictive biomechanical modeling approach for optimizing distal implant placement in the All-on-4 treatment concept, with a focus on implant angulation and occlusal load direction. Finite Element Analysis (FEA) was integrated with Response Surface Methodology (RSM) to develop 15 simulation models based on a Central Composite Design, incorporating distal implant angulations of 15 degrees, 30 degrees, and 45 degrees, and occlusal load directions in both sagittal and frontal planes (45 degrees, 67.5 degrees, and 90 degrees). The maximum von Mises stress in cortical bone was selected as the response variable. Regression analysis revealed that the frontal load angle had the most significant effect on stress distribution, followed by implant angulation. The resulting second-order predictive model demonstrated a strong statistical fit (R2 = 93.39%, adjusted R2 = 81.49%). The lowest cortical stress (95.75 MPa) occurred at 15 degrees implant angulation with 45 degrees occlusal loading in both planes, whereas the highest stress (265.72 MPa) was recorded at 45 degrees angulation with 90 degrees frontal loading. Although reducing implant tilt generally decreases peri-implant stress, no universally optimal angle can be defined due to variability in biomechanical responses under different occlusal loading conditions. Clinically, optimizing cusp inclination and load direction in conjunction with implant positioning may enhance the biomechanical performance and long-term success of full-arch implant-supported prostheses.
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.
Sonlu Elemanlar Esaslı Topolojik Optimizasyon ile Rijitliği Azaltılmış Gözenekli Sabitleme Plağının Tasarlanması
(2019) Murat, Fahri; Kaymaz, İrfan
Sabitleme plakları kırık kemik dokusunun mekanik açıdan stabilizasyonunu sağlayarak hasarlı bölgede biyolojik iyileşme sürecini hızlandırmak için kullanılmaktadır. Bu implantlar tedavi sürecinde aseptik gevşeme, gerilme kalkanı etkisi ve nekroz oluşumu gibi mekanik ve biyolojik komplikasyonlara sebep olmaktadır. Bu çalışmada geleneksel plak modellerinde görülen mekanik ve biyolojik komplikasyonların azaltılması/ortadan kaldırılması amaçlanmıştır. Bu amaçla sonlu elemanlar esaslı topoloji optimizasyon yaklaşımı kullanılarak optimum plak geometrisi elde edilmiştir. Elde edilen optimum plak modeli fonksiyonel kademelendirilmiş gözenekli kafes yapısı ile birleştirilerek yeni nesil gözenekli implant modeli sabitleme plakları için uygulanmıştır. Bu çalışmada, uzun boylu kemiklerde diyafiz bölgesi transvers kırıklar için kullanılan plakların optimum geometrisi, sonlu elemanlar esaslı topoloji optimizasyon yöntemi kullanılarak fonksiyonel kademelendirilmiş gözenekli plak modeli olarak elde edilmiştir. Gözenekli plak modeli, eklemeli üretim ile üretilerek statik olarak test edilmiştir. Testler sonucunda geleneksel, optimum ve gözenekli model, sonlu elemanlar yöntemi ile rijitlik açısından karşılaştırılmıştır.