Biomaterials Epd Subjected To Surface Treatment Coats Biology Essay


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Replacing body parts goes at least 2500 years, when the Etruscans learned to substitute missing teeth with bridges made from artificial teeth carved from the bones of oxen. However The development of biomaterials, as a science, is about fifty years old. A biomaterial is any matter, surface, or construct that interacts with biological systems. Biomaterials engineering is concerned with the application of biomaterials science in the design and engineering aspects of medical devices' fabrication. Traditionally the study of biomaterials focuses on issues such as biocompatibility, host-tissue reaction to implants, cytotoxicity, and basic structure-property relationships. There is an increasing demand for biomedical implants due to the increase in ageing population worldwide.

A wide range of materials is routinely used (Table 1). A biomedical material (also known as a biomaterial) is a polymer, metal, ceramic, or natural material that provides structure and/or function to an implantable medical device.

Biomaterials must have special properties that can be tailored to (use in human body ) meet the

needs of a particular application this is an important concept to bear in mind. For example, a biomaterial must be biocompatible, non-carcinogenic, corrosion-resistant, and has low toxicity and wear [ 1,2]. However, depending on the application, differing requirements may arise. A number of different materials, such as 316L stainless steel, titanium alloy , cobalt-chromium alloys, magnesium alloys, etc., have been used to replace many different parts of the human body. One of the most commonly performed orthopaedic procedures worldwide using these materials are total hip replacement as well as dental implants.

(newfolder : Biomaterials Science)

Generally, the requirements of biomaterials can be grouped into four broad categories:

1. Biocompatibility: The material must not disturb or induce un-welcoming response from the host, but rather promote harmony and good tissue-implant integration.

2. Sterilizability: The material must be able to undergo sterilization. Sterilization techniques include gamma, gas (ethylene oxide (ETO)) and steam autoclaving.

3. Functionability: The functionability of a medical device depends on

the ability of the material to be shaped to suit a particular function.

4. Manufacturability: It is often said that there are many candidate materials that are biocompatible. However it is often the last step, the manufacturability of the material, that hinders the actual production of the medical device. It is in this last step that engineers can contribute significantly.

Metals and their alloys have a long history as orthopedic implants and bone graft substitutes for their well-known strength (elastic modulus larger than 100 GPa), especially in load-bearing areas [5].The advantages of metallic alloys include a light-weight nature, high strength and biocompatibility. Their use is however also associated with several limitations, which include permanence, cracking, low volumetric porosity, relatively high modulus of elasticity and the potential of releasing metallic ions and introducing corrosion products into the body from these materials [7-12]. Most metals cannot be used to produce a complete tissue replacement for bone defects because they are not biodegradable.

On the other hands we can classified biodegradable material into 2 general groups : degradable and nondegradable???????

Corrosion is a great concern, particularly, when a metallic implant is placed in hostile electrolytic environments such as in human body because the corrosion products have been implicated in causing infections, local pain, swelling, and loosening. It can, therefore, severely limit the fatigue life and ultimate strength of the material, leading to the in vivo failure of implants. The human body shows natural reaction against prosthetic devices causing the osteolysis and has the tendency to isolate from the surrounding live tissues.

In order to improve corrosion resistance, biodegradation and bioactive properties, bioceramic coatings on metallic substrates have been widely used in bone substitutes because of their biocompatibility, bioactivity, and osteoconductivity. Surface engineering processes can be used successfully to either modify existing surfaces or to apply coatings. Coatings can be applied for a diversity of reasons. As the corrosion of a metal surface is an electrochemical reaction between the metal and external agents (for example, oxygen and/or water) a coating can act as a barrier, preventing this reaction.

The biocompatibility of most metallic biomaterials is based on a passive oxide layer which is always present on the metal surface and which will be restored quickly (milliseconds) after damage. These oxide layers, similar to alumina, show an inert behaviour towards the surrounding tissue. Therefore, the chemical bonding of a metallic implant with the tissue, which is observed between bioactive ceramics like hydroxyapatite and bone, seems to be improbable, and the adhesion strength between the bone and the metal will have a primarily mechanical character.

HAp, Ca10(PO4)6(OH)2, is composed primarily of calcium and phosphorous with hydroxide ions that are eliminated at elevated temperatures. HAp and other related calcium phosphate minerals have been utilised extensively as implant materials for many years due to its excellent biocompatibility and bone bonding ability and also due to its structural and compositional similarity to that of the mineral phase of hard tissue in human bones. HAp coatings have good potential as they can exploit the biocompatible and bone bonding properties of the ceramic, while utilising the mechanical properties of substrates such as Ti6-Al4-V and other biocompatible alloys. While the metallic materials have the required mechanical properties, they benefit from the HAp which provides an osteoconductive surface for new bone growth, anchoring the implant and transferring load to the skeleton, helping to combat bone atrophy have been extensively used for the purpose of bone graft substitute and bone tissue engineering [63, 64]. Because of their similarity to bone mineral, CaP based materials are biocompatible, osteoconductive and bone-bonding.

In orthopaedic field, hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ) coated metal implants have been studied extensively due to their outstanding biological responses in the physiological environment.

Several coating methods have been introduced for coating of HA on the metallic substrates: plasma spraying, sol-gel, RF magnetron sputter, ion beam dynamic mixing, pulse laser deposition, biomimetic coating, electrophoretic deposition, and electrolytic deposition. Among the various fabrication methods, electrophoretic deposition (EPD) is a promising technique, with advantages including short formation time, simplicity in instrumentation, and capability of coating complex-shaped implants.

Electrophoretic deposition is a colloidal processing technique that allows not only shaping free standing objects but also allows depositing thin films and coatings on substrates.

EPD is known to be one of the most effective and efficient techniques to assemble fine particles. This technique has received significant attention due to its simplicity in setup, low equipment cost, and capability to form complex shapes and patterns [8-9].

Electrophoretic deposition is also a potentially attractive process for obtaining bioceramic coatings from aqueous and non-aqueous solutions of nanoparticles on metallic surfaces. The application of EPD in the biomaterials area, in particular for obtaining HA and bioactive glass coatings on metallic implants, has been demonstrated.

Electrophoresis was used in the current work as the

coating technique due to its efficiency, flexibility, and

economy [16]. In general, a short deposition time is

required for electrophoretic forming or coating (a few

seconds to a few minutes). The deposition rate of elec-

trophoresis can be as high as 1 mm/min. Uniform coat-

ings of complex shapes can be easily formed by us-

ing appropriately shaped electrodes, such as wire, coil

or plate. A high degree of control of coating deposit

morphology can be obtained by adjusting the deposi-

tion conditions and the ceramic powder size and shape.

With increasing deposition time and voltage, the thick-

ness of the coating increases [17].

The aims of this study are investigation for design and produce a nano- hydroxyapatite coating on several metallic substrates by EPD coating, and also surface treatment metals before coating.

Metallic materials are often used as biomaterials to replace structural components of the human body. This is because, when compared to polymeric and ceramic materials, they possess more superior tensile strength, fatigue strength, and fracture toughness the very key properties required of structural materials. As such, metallic biomaterials are used in medical devices such as artificial joints, bone plates, screws, spinal fixations, spinal spacers, artificial heart valves, stunts, and dental implants. Stainless steel is one of the metallic biomaterials which are widely used as orthopaedic and dental implants due to its low cost and good mechanical properties [6,7].

Problem statement of the project

Corrosion the biomaterials during life time is a significant issue, these days many methods suggested for enhance the effectiveness of medical and dental applications such as implants and amalgams. Surface film and coating layer use for increasing corrosion resistance.

Moreover having enough Biocompatibility, based on the applications and properties, tends to test many metals as substrate. Like stainless steel, titanium, magnesium, cobalt chrome.







Objectives of the project

Comparing several substrate and

Establish the characteristics of biomaterial subjected to surface treatment and EPD coating



The primary aim of this research is to understand the fundamentals of

electrohydrodynamic processing to utilise this route to prepare hydroxyapatite (HA)

depositions with desirable chemical, topographical and biological characteristics for

bone implants.??????


Scope of the project

The scope of this project is:

1: surface treatment of six materials; stainless steel 316 and nickel free, TiAlV, CoCr Mo, Mg 1%Ca as cast and forged

2: using EPD for applying Hap coating layer

3: testing and analysis contain Corrosion test (Immersion test (ASTM G31 - 72) and Electrochemical test (ASTM G5)), Mechanical properties(Hardness test)



Introductions to biomaterials

Biomaterials are materials intended to use in the human body to replace, augment or interact with the living tissue or function of the body. Vast numbers of different material types, such as metals, ceramics and polymers are used as biomaterials. Metals are commonly used in weight bearing applications, i.e. as bone implants.

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