PhD Dissertations

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Browsing by Author "Al Saeedi, Riaid Hadi Salih"

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    Evaluation of bioimplants surface nano-micro design by chemical mechanical polishing against alternative methods
    (2019-01-11) Al Saeedi, Riaid Hadi Salih; Ertunç, Özgür; Ertunç, Özgür; Mengüç, Mustafa Pınar; Bundur, Zeynep Başaran; Çakır, M. C.; Budaklı, M.; Department of Mechanical Engineering; Al Saeedi, Riaid Hadi Salih
    Biomaterials comprise a representative fraction of the products used in the health area. Biomedical devices (such as biosensors, blood circulation tubes, hemodialysis systems) can be cited as examples. Biomaterials can be of internal or external placement which must be pharmacologically inert and designed to be implanted or incorporated into the living system (such as sutures, plaques, bone substitutes, tendons, screens or meshes, heart valves, lenses, teeth), devices for the release of medications (in the form of films, subdermal implants and particles), artificial organs kidney, liver, pancreas, lungs, skin) and dressings. The term biomaterial has been defined in different ways by different authors over the last years. In the scope of this review, biomaterials are defined as devices that come in contact with biological systems (including biological fluids), with diagnostic, vaccine, surgical or therapeutic applications, and may consist of compounds of synthetic or natural origin, as well as chemically natural materials both in the form of solids and gels, pastes or even liquids, not necessarily manufactured, such as pig heart valves and human skin flaps treated for use as implants. The most biocompatible material in this field is titanium and its alloys have been widely used as biomaterials, especially in prostheses, devices for cardiovascular use and for fixation of fractures, due to their high biocompatibility, low density, low modulus of elasticity and superior corrosion resistance compared to stainless steel. Titanium has the additional advantage of a greater tendency for osseointegration, an important characteristic for long-term implants. The reduced or non-existent reaction of the titanium with the tissues surrounding the implant is due to the passivation formed by the titanium dioxide film (TiO2), usually of nanometric thickness, on the surface of the metal. Surface processing techniques for the implant materials also affect its properties and may lead to contaminated surface which can affect on the biocompatibility which may cause infection in implantation. The surface roughness and chemistry are the most important factors that can affect the long-term successful of the implant. Forming a protective surface oxide layer have been introduced through different methods in the literature to increase the biocompatibility and to assure the mechanical anchoring and hence the primary stability as a result the success and survival of the bio-implant. the method of choice in recent manufacturing processes is sand blasting correlated with chemical etching are commonly used for engineering the titanium surfaces to give a desired surface roughness to be accepted in the host. The sand blasting method consist of jetting specific particles to induce a micro roughness to the surface being treated, these particles may adhere to the implant surface which can cause surface contamination. However, the other alternative surface structuring methods such as high temperature plasma coating and laser peening are costly. In this dissertation, Three-Dimensional Chemical Mechanical Polishing (3-D CMP) process is established as an alternative technique to process non-flat bioimplant surfaces such as dental implant cylindrical-threaded surfaces in addition to the existing methods in the literature to alter the implant surface properties. Originally CMP process is one of the methods used in the semiconductor manufacturing industry to assure surface planarization through simultaneous mechanical cutting and chemical actions associated with the presence of the abrasive particles in the polishing slurries which provides the mechanical cutting effect through the process enabling the surface cleaning through the nanometer level erosion process. The unified set of variables including the chemical components of the slurry stabilizers, pH adjusters and oxidizers are combined to stimulate the formation process of the passive oxide film that can cover the surface and enhance the biocompatibility. Generally, the CMP is used to polish the surfaces and induce smoothness, but here it has been shown that changing the process variables includes the slurry particles concentration, the pad material properties, pad-sample velocity oxidizer type and concentration gives the possibility to engineer and control the surface roughness on the treated surfaces. The main purpose of the CMP treatment is to produce a uniform protective film. The application of 3-D CMP is believed to reduce the organic and inorganic contamination on the surface of the bio-implants which is in contact with the human body environment and limiting the periimplantitis and infection risk by reducing the reject reactions in-vivo due to ion release processes. The application of CMP on titanium alloys has been shown in the literature the ability of producing TiO2 films and creating a smooth surface. However, its native oxide is a self-forming process, but it is a slow process and the CMP treatment is accelerating this process. Titanium oxide film is known to promote the biocompatibility, cell adhesion, osteo-formation and bacteria growth prevention. Yet, the oxide films produced in similar treatments such anodization method resulted in thick-porous films structures which have the advantage of using these cavities as drug releasing spots. In the other hand this porosity can affect the corrosion prevention process. Therefore, in this study, the 3-D CMP process has been implemented to the Ti-based implants to eliminate the organic and inorganic contaminations on the implant surface and provide the desired roughness on the implant surfaces. Furthermore, biocompatibility of the CMP treated surfaces have been evaluated through surface wettability and corrosion resistance through electrochemical analyses and optimal surface parameters through biomechanical evaluations as a result determine the desired surface roughness according to the surface responses.