Projects

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.

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.

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.