Evaluation of Infection Resistance of Biological Implants through CMP based Micro-Patterning
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Evaluation of Infection Resistance of Biological Implants through CMP based MicroPatterning G. Bahar Basim, Zeynep Ozdemir, Ayse Karagoz Department of Mechanical Engineering, Ozyegin University, Istanbul, 34794, Turkey.
ABSTRACT Biomaterials are widely used for dental implants, orthopedic devices, cardiac pacemakers and catheters. One of the main concerns on using bio-implants is the risk of infection on the materials used. In this study, our aim is to quantify the effect of controlled surface roughness on the infection resistance of the titanium based bio-materials which are commonly used for orthopedic devices and dental implants. To modify the surface roughness of the surfaces in a controlled manner, Chemical Mechanical Polishing (CMP) technique, which is extensively used in semiconductor industry for the planarization of the interlayer dielectrics and metals, is utilized. To determine the infection resistance of the created films with varying surface roughness, bacteria growth response was studied on titanium plates after CMP. INTRODUCTION Biomaterials are widely used for dental prostheses, orthopedic devices, cardiac pacemakers and catheters [1]. Particularly titanium and its alloys are favored as bio implants due to their surface characteristics which promote biocompatibility [2]. However, the surface of titanium maybe contaminated during casting due to its highly reactive nature which in turn lessens the biocompatibility and the mechanical properties at the tissue/bio implant interface [3-4]. Patients with bioimplants face on the average of 4% infection that maybe caused by the contamination and this ratio goes up to 40% for ventular support implants. In the case of infection, both medical treatment and the time spent in a medical institution would result in considerably high expenses. Therefore, it is very critical to produce implant materials with the contaminated surface layers removed and with a protective oxide film formed on the surface to limit further contamination and minimize risk of infection at the interface where they are exposed to the live tissue. Metals tend to form native oxides when they are exposed to oxidizing environments. The formed oxide layers are at nanometric scale and may have a self-protective nature in some cases. One of the main processes where the protective metal oxide films are closely investigated is CMP for metals. CMP is used to planarize the interlayer metal connectors in microelectronics manufacturing. During the CMP process, the top film surface of the metal is exposed to chemically active slurry which is made of submicron size particles and corrosives. This interaction forms a chemically altered top film that is removed by the mechanical action of the slurry abrasive particles. The chemically altered top films have to be a protective oxide to enable planarization by stopping chemical corrosion on the recessed metal surfaces while the elevated structures are polished [5]. It has been shown by an earlier study that the application of CMP on Ti films has been very success
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