Experimental and Theoretical Investigation of Structural and Mechanical Properties of Bulk/Cage Systems Produced from Ti6Al4V Alloy Using Selective Laser Melting (SLM) Method with Variable Production Parameters.



218M425: Evaluation of Factors Related to Patient-Specific Implant Selection and Probability-Based Finite Element Method. 

Project Coordinator: İrfan KAYMAZ,

Researchers: İsmail Hakkı Korkmaz, Fahri Murat , Osman Yavuz

Project Finish Date: 01.09.2021


Implants that are used to facilitate healing or to artificially complete any lost part or non-functioning part of a body are one of the indispensable treatments. Materials such as 316L, titanium alloys etc. are widely used in the manufacturing process of the implants due to having both biocompatible properties and high mechanical strength.  However, implants can undertake most of the loads that are necessary for bone regeneration since metallic materials have young’s modulus that is almost 6 times greater than that of hard tissues. This causes the formation of bone resorption, and might lead to implant dislocation and aseptic loosening. Therefore, one of the main aims of an implant design is to develop such designs that have high resistance to loads but to have rigidity as close as possible to tissue concerned. On the other hand, to use optimization techniques is necessary to meet conflicting requirements in designing implants, such as low young’s modulus but higher strength.  Although the optimization techniques have been recently leap forward, analyses that do not take into account uncertainties also entail risks not to reach the reliability level required.


The aim of this project is to develop a new method which eliminates the difficulties that arise in topology optimization of porous implant design for which rigidity is aimed to be as close as possible to the bone. In the proposed method, it is aimed to obtain a reliable implant design by adding the uncertainty into the formulation of the topology optimization by a new response surface method. Besides, for the first time in the literature, the uncertainties related to the manufacturing parameters will be considered in the formulation of the reliability-based topology optimization.


There are very few study on the application of the reliability-based topology optimization to an implant design. However, the contour of the implant was determined by the solution of the optimization problem and the interior of the implant was designed as bulk material. It is aimed to design a porous fixation plate for humerus diaphysis fractures, using the reliability-based topology optimization.  Therefore, for the first time in the literature, the reliability-based topology optimization will be utilized both obtaining the contour of the fixation plate and having an implant with porous structure. 


The fixation plate will be manufactured using additive manufacturing, and the method will be verified by comparing the results obtained from finite element simulation and three-point bending tests. It is aimed to gain necessary knowledge to fill the gap of our country in designing and manufacturing of unique implants. The team proposing this project has been actively studying in the area of implant design, analysis and manufacturing, and graduate studies will be also carried out within the context of this project.


117M870: Development of Optimum Surgical Technique in Mandibular Distraction Osteogenesis. 

Project Coordinator: Abdullah Tahir ŞENSOY

Researchers: İsmail Hakkı KORKMAZ, Ümit ERTAŞ, İrfan KAYMAZ

Project Finish Date: 01.10.2018


Mandibular Distraction Osteogenesis (MDO) is a common clinical procedure to correct mandibular retrognathia cases. In spite of consolidated clinical use, lots of questions still remain to be answered concerning distraction osteogenesis. The two most important questions among them are to localise the optimum MDO osteotomy line and to obtain the best screw configuration providing bone-remodelling in a healthy way due to the stabilization of callus. Therefore, to answer to those two questions in this project, artificial mandibles were modeled as cortical and trabecular segments using Computed Tomography (CT) images. In the following step, MDO osteotomy line providing minimal malocclusion was determined due to the virtual surgery simulation and patient-specific surgical guide modeled was fabricated in order to easily transfer the preoperatively planned line into the real surgical operation. By using this guide, it was aimed to eliminate the pathologies encountered during intraoperative and postoperative period that may result from the variation of osteotomy line angulation and reducing the length of the total treatment period.

Since the bone-remodelling period could be shortened by increasing stabilization of the callus structure, it is clinically important to determine the best screw configuration and Optimum Osteotomy Line (OOL) providing the maximum callus stability. Within the scope of this project, 3 different Finite Element (FE) models have been set up. The first model, M1, which was created according to the Conventional Osteotomy Line (COL) and Conventional Screw Configuration (CSC); the second model, M2, was created according to the OOL and CSC and the last model, M3, was created according to the OOL and Optimum Screw Configuration (OSC). For M3 model, optimum locations of the screws were determined by means of the optimization loop set up between MATLAB, PYTHON programming languages and ANSYS using an algorithm based on PSO. On the other hand, optimum plate geometry was determined using the Topology Optimization method. At the experimental stage, replicas of the FE models were prepared and tested by using an experimental system simulating the same boundary conditions of the FEA. Both the experimental and FEA results showed that the effects of the osteotomy line and screw configuration on callus stabilization were highly significant.

As a result, experimental and numerical studies have both shown that the new MDO protocol developed in this project provides much more stability for callus tissues and the use of this protocol for clinical cases is expected to increase the success of the operation by shortening the recovery period.


114M899: Design of Anatomical Total Knee Prosthesis and Experimental Examination of Its Performance. 

Project Coordinator: İsmail Hakkı KORKMAZ

Researchers: İrfan KAYMAZ, Ömer Selim YILDIRIM, Halim KOVACI

Project Finish Date: 01.12.2015


This project involves the design of a total knee prosthesis (TKP), for which the number of the applications have been significantly increased day by day, especially for patients above 60 years-old, and studies its performance by both the finite element analysis and the experiments. The average life of a TKP that is used in the total knee arthroplasty (TKA) known as replacement of degenerated knee joints by main metal components and polyethylene based intermediate components is approximately between 15 and 20 years. The fact that the age of patients who undergo TKP gradually drops causes insufficiency of the life of the prosthesis, and ultimately the need for a revision operation. Since the success rate of revision operations is significantly lower than that of the first TKAs, a critical period for the patient might start for his/her life left.

In recent years, patient-specific design has been used to eliminate failures occurred at the TKP as well as increasing the usage life. This kind of designs has been started to be used in overseas. The fact that the design/production of a patient-specific TKP has not yet been initiated in our country indicates the importance of knowledge to be generated from this project.

In the studies carried out in this project, 3D bone models along with the TKP components that were designed as full-compatible to the anatomical bone model were assembled in a computer program with the help of an orthopaedist. The full model including all the bones and components were studied by deterministic and probabilistic analysis based on the finite element method, and the patient-specific components of the prosthesis that was designed in this project were manufactured using the laser melting method, after the results from the analyses were verified. The orthopaedist concerned assembled the artificial bone models with the prosthesis designed, and the strain behaviour under static loading was investigated. The finite element model was verified by comparing the results from the experiments and the finite element analysis, thus a base model was obtained for further studies in this field.


110M055:Evaluation of Factors Related to Patient-Specific Implant Selection and Probability-Based Finite Element Method 

Project Coordinator: İrfan KAYMAZ

Researchers: Fatih MEDETALİBEYOĞLU, İlhan Metin DAĞSUYU, Ömer Selim YILDIRIM

Project Finish Date: 01.11.2012


Selection of proper implants, which are planted into tissue in order to heal or artificially to complete any part of a body incurring losses, is depending on experiences and predictions made using the knowledge gained from these experiences. Considering previous cases, this approach is utilized on the mean values of parameters. In addition, uneven stress distributions on both the implant and surrounding bones may not only make the patient suffer from the pain but also causes physiological anomalies due to bone remodelling. Owing to these problems, it may be necessary to pull out the implant from the body. In recent years, "patient-specific implant" approaches have been come into use in order to eliminate these disadvantageous.

In this project, a realistic patient-specific computer model was obtained from the patient-specific computerized tomography, in which dispersion of cortical and trabecular bone was modelled according to the real structure, contrary to the model in the literature in which the interface between cortical and trabecular bone is smoothly modelled. In addition, the behaviour of the bone and implant subjected to loading was determined using a finite element software. Thus, the behaviour of the implant after the operation was predicted before the operation. The parameters such as the properties of the implants used in the body, the forces acting on the implants and bone properties do not take a single value, rather they are random variables having a statistical distribution. Therefore, within the scope of this project, the results such as stresses and displacements that indicate the performance of the implant were obtained as random variables by considering the variations of the bone material properties as well as the load acting on the implant.

The use of a patient-specific data as proposed in this project has become one of the pioneering works when the studies carried out on biomechanics field in our country are considered. Generating background information necessary for the multidisciplinary work that is essential for designing patient-specific implant is one of the most important added value, which reached at the end of the project. Thus, it is very important for the contribution to the national economic benefit to share the experiences and knowledge gained from this project with the firms manufacturing implants in our country since the use of patient specific implant during the implant selection process will widely spread.


108S085: Finite Element Analysis of the Effects of New Treatment Approaches on Craniofacial Structures in Maxillary Expansion 

Project Coordinator: İlhan Metin DAĞSUYU,

Researchers: İrfan KAYMAZ, Mustafa Cemil BÜYÜKKURT

Project Finish Date: 15.05.2010


The treatment of extreme transverse maxillary deficiency and posterior crossbites by means of rapid maxillary extension (RME) is a major orthodontic therapy procedure with an over 100-year history.

Many clinical researches have been made to determine the effects of rapid maxillary expansion on cranio-facial structures. In recent years, however, experimental simulation researches, including the method of finite elements analysis have started to be used because clinical researches have had some inadequacies in showing skeletal effects. The classical treatment procedure that is applying a support of maxillary posterior teeth with an interrupted force module, due to excess use of force, side effects like root resorption in teeth, losses in surrounding bone structures and unwanted tooth movements might come out and to obtain more skeletal effect, recently, new treatment approaches that include implant-bone anchored treatment and different force modules were proposed.

However, these applications are quite new so comprehensive clinical and experimental researches on the subject do not exist yet. This project, with the data obtained and transferred to computer medium from a real patient who had transverse maxillary deficiency, aims to evaluate, compare and interpret experimentally the effects of interrupted and continuous forces, which are produced by tooth-anchored and implant-bone anchored treatment procedures, on the cranio- facial structures using the method of finite elements analysis.

In this project, a new finite element model has been proposed for rapid maxillary extension, and the effects of four different treatments on the same patient have been evaluated as the first time in the literature. From the results of this project, implant- bone anchored -continuous force treatment is proposed for the treatment of rapid maxillary extension since it has more skeletal effect, but less potential side effects.