Papers by Keyword: Implant

Abstract: This paper describes a development of Electrical Discharge Machining (EDM) system for biomedical application. In general, the mechanism of EDM comprises of mechanical structure and electronic control system. This laboratory scale of the EDM system has a capability to accommodate the machining of hip implant which employs low power generator. The holder for the workpiece is created to accurately position the hip implant, ensuring that the machining angle of the implant directs the micro-pits precisely toward the workpiece. A traditional linear x-y-z axis setup (Cartesian coordinate system) is utilized, along with two types of spherical coordinates (swing-swing and swing-rotate configurations). By the results of performance test, the Swing Motor behaves differently to the common servo motor. The Swing Motor is affected by unbalanced load and gravity in which the Ziegler-Nichols PID optimization method has been altered from the conventional model. The average of absolute error is 0.2308 degrees. However, optimized PI controller by Ziegler-Nichols method is able to eliminate the effect in term of final achieved position (steady state condition) and fulfil the objectives.

Abstract: Due to its low density, high strength to weight ratio, and been unreactive to the human body, titanium is commonly used in human bone implants. Titanium in bone implants can be used in its porous form because the porosity reduces the elastic modulus of the implant, near to that of human cortical or trabecular bone, which prevents the effects of stress-shielding. To date, majority of the published studies using the space holder (SH) method to produce porous titanium, utilized-45 μm titanium hydride dehydride (Ti-HDH) powder, or similar titanium powder. However, there is limited research conducted on the use of coarse titanium powder particles, such as-150 μm Ti-HDH powder to produce porous titanium. Fine Ti-HDH powders are known to have higher oxygen content than coarse Ti-HDH powders, thus the specimens produced from fine powders are harder, require higher compaction pressures and are expected to have lower impact resistance. The following study thus investigated the use of-150 μm Ti-HDH powder to produce porous titanium specimens, by the SH method. The porous specimens of 45 mm diameter were produced by uniaxially compacting mixtures of sodium chloride (NaCl) powder and Ti-HDH powder at 500 MPa. The NaCl powder utilized was hand sieved to a range of-500 μm. The specimens were sintered at 1150 for 4 hours in a high-vacuum tube furnace. Three porosity levels were investigated i.e. 40%, 50% and 60%. The sintered compacts were assessed for density, porosity and elastic moduli. It was found that the sintered porosity of the specimens ranged from 42.7-59.1%, and the sintered density ranged from 1.84-2.58 g/cm³. The elastic moduli of the specimens were found to reduce as the porosity increased, and ranged from 0.59-1.3 GPa, which is similar to the elastic moduli of human trabecular bone. The use of-150 μm Ti-HDH powder is thus potentially a lower cost alternative, than the use of-45 μm Ti-HDH powder, to produce porous titanium for human bone implants.

Abstract: This article focused on investigating the influence of current density on the morphology and structure of silver nanoparticles (n-Ag) electrodeposited on anodized titanium substrates (denoted as TiO₂/Ti) on the surface. The TiO₂/Ti substrate served as the cathodic electrode placed in an electrolyte solution containing ionic [Ag(NH₃)₂]⁺ complex solution. The n-Ag/TiO₂/Ti samples were synthesized at current densities ranging from 0.2 A/dm² to 0.5 A/dm² for 20 seconds at room temperature. The study performed morphological and surface composition analysis of n-Ag/TiO₂/Ti using Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD) techniques. Additionally, the study assessed the electrochemical properties using the AutoLab system with Nova 2.1 software, based on Tafel curve measurements to compare the corrosion resistance of the samples before and after modification.

Abstract: Today, the ability to form porous structures and coatings from titanium powder on implants parts of specified porosity, size and morphology of pores into which newly formed bone tissues and, thus, they contribute to the osseointegration and high and long-term stability of the implant functioning in the body is widely used. The ability to obtain work pieces of complex geometry by powder metallurgy methods with a minimum of mechanical rework by cutting, it also promotes the diffusion of this technology in the implants manufacturing as the titanium alloys are classified as difficult to process. The future progress in the development of new materials and types of implants is directly related to powder metallurgy - there is information about the creation of a highly solid biocompatible composite based on the intermetallic system β-Ti3Au, from which rib replacement implants are made

Abstract: The surface has a vital function in the tissue's response to the presence of foreign material in the field of body implants. Surface modification with coatings can be adjusted to provide the highest service performance at the lowest cost. Coatings can increase corrosion resistance by reducing metal ion and corrosion product migration in the body. We fabricated polymer based bio-composite coatings by blending chitosan (Chi), alginate (Alg) and nanoparticles ((TiO₂, Nb₂O₅) by dip coating onto a 316L stainless steel substrate. The coatings’ surface morphology and phases were studied using FESEM and FTIR analysis. The wettability behavior of the coated samples was also studied by investigating their contact wetting attributes. The antibacterial activity of the functionalized coatings was determined too. The FTIR results showed that the blending of Chi-Alg and nanoparticles was excellent, and no obvious differences in the spectra or any changes in the structures of the polymer matrices were observed. The SEM results demonstrated that the coating layers were uniform, homogeneous, and crack-free on the 316L Stianless steel substrate when using TiO₂-Nb₂O₅ nano particles. The contact angle results showed the highly hydrophilic properties of the pure chitosan-alginate blend. As well, coatings containing nano particles showed the same antibacterial effect of chitosan-alginate blend coating.

Abstract: Titanium and its alloys are potential candidates widely used to manufacture medical implants. In spite of possessing excellent properties suitable for a biomaterial, Ti suffers from lack of ability to bond with the local tissue termed as “bioactivity”. Several strategies have been adopted to increase the bioactivity of titanium for bone implant applications. Micro arc oxidation (MAO) is one of such promising surface treatments which produces an oxide layer on the surface of Ti which promote better tissue interactions at the surface Ti. Hence, in the present work, commercial pure Ti (CP-Ti) has been treated with MAO process and the produced surface was characterized to study the oxide layer developed on the Ti surface. X-Ray diffraction studies demonstrated the formation of TiO₂ layer on the surface of CP-Ti. Scanning electron microscope images and EDS analysis confirms the porosity in the produced oxide layer which is favorable towards better cell interactions. The presence of considerable amount of phosphorous in the oxide layer which is form the electrolyte used during MAO process was also observed. The preliminary findings demonstrate the simple and effective way to produce porous oxide layer on Ti for biomedical applications.

Abstract: The article presents a scientific review of the literature on the known methods of producing polyetheretherketane and composites based on it used in the medical manufacture practice of implants. The main substances used in the synthesis of PEEK, as well as modifiers included in the PEEK-based composite material, are generalized.

Abstract: The research data on the specific features of the formation of oxide films on the Ti6Al4V alloy in the ethylene glycol-water electrolytes have been given. The kinetic dependences obtained for the alloy allowed us to establish that the specific features of the formation of oxide films during the electrochemical oxidation of the alloy surface depend on the solution composition and the current density. For the water-to-alcohol ratio of 50:50 the kinetic dependences show the sections that correspond to the formation of the barrier oxide layer and also to the formation of the pores due to the desorption of fluoride ions and the growth of the porous portion of oxide. As the water-to- alcohol ratio is decreased the indicated peculiarities of kinetic dependences are met not so often and do not obey any regularity. The obtained data are explained by the fact that an increase in the portion of the organic component of the solution results in a decreased etching capacity of the electrolyte due to the controlled activity of fluoride ions. The anode current density value has a similar effect on the variation of kinetic dependences. Its effect is explained by that an increase in the alloy oxidation rate results in the fast formation of the surface oxide and the specific features of kinetic curves are concealed. The linear relationship between the formation time of oxide of a minimum thickness for given conditions and the current density is unavailable and it is conditioned by the chemical interaction of the oxide film with electrolyte components. The obtained research data can be used for the formation of the individual bioinert and bioactive coatings for the implants of a medical purpose or for the formation of the matrix used for the production of composite coatings.

Abstract: Investment casting of an orthopedic implant plate based on stainless steel 316L was considered an economical process. Nevertheless, the mechanical properties of the investment casting product were found to be inferior as compared to the implant plate fabricated with other methods such as forging due to their differences in the microstructure. Investment casting mostly produced coarser grain as compared to those with forging or rolled process. In order to improve their mechanical properties, cold-rolling followed by a repetitive thermal cycling process is proposed. The goal is to generate finer grain size through recrystallization process leading to nucleation of new grain during the thermal cycling process thus increasing their strength. Stainless steel 316L was cold-rolled to 52% reduction in thickness and this process generate stored strain energy in the form of dislocation density in the material. The thermal cycling treatment performed within several cycles after cold rolling enabling gradual disperse of stored strain energy that facilitates the recrystallization process that initiates new grain formation. The short holding time within several cycles limits the grain growth that normally occurs during annealing. It was found that thermal cycling treatment at a temperature of 950 °C for 35 seconds within four cycles led to the formation of finer grain size of 22 µm on average as compared to the initial investment casting average grain size of 290 µm. The hardness also increases to 253 HV_0.3 in this condition as compared to 155 HV_0.3 of investment casting products. Lower thermal cycling temperature than 950 °C during the test did not result in grain refinement thus indicating that strain energy relieves were not enough to aid the recrystallization process.

Abstract: Hydroxyapatite (HA) is potentially used as a coating material for titanium alloys to improve their bioactivity and then enhancing the osseointegration characteristic of metal implants for orthopedic application. Electrophoretic Deposition (EPD), one of the coating methods that is widely applied for coating metal because of its simplicity and relatively low cost, is chosen for coating metal implants. HA coating layer quality can be controlled by adjusting applied voltages and coating time of the EPD process. However, the optimum voltage and exposing time has not yet been known for new type titanium implant such as Ti-12Cr and TNTZ. This work is, therefore, focusing on the effect of applied voltage and coating time on the mass growth, HA coating thickness, and surface coverage that can be produced on the surfaces of both alloys, and also on the conventional titanium alloy, Ti6Al4V, for comparison. The result of this work showed that there is a significant influence of the titanium alloy type on the HA layer performances. However, it is necessary to choose a suitable voltage and to expose time for producing a sufficient coating layer that meets the standard of orthopedic implants.