KATALIN BALAZSI and CSABA BALAZSI

ABSTRACT

Biomaterials used for implant should posses some important properties in order to long-term usage in the body without rejection. One of the most important property is biocompatibility. These materials are used in different parts of the human body as artificial valves in the heart, stensts in blood vessels, replacement implant in shoul­ders, knees, hips and orodental structures. Materials used as different biomaterials should be made with certain properties as excellent biocompatibility, superior cor­rosion resistance in body environment, excellent combination of high strength and low modulus, high ductility and be without toxicity.

The creation of nanocomposites of ceramic materials with particle size few ten nanometers can significantly improve the bioactivity of the implant and enhance the osteoblast adhesion. One of the most used biomaterial is hydroxyapatite. The major inorganic constituent of bones and teeth is calcium phosphate, whose composition is similar to that of synthetic hydroxyapatite (HAp; Ca10(PO4)6OH)2. This similarity provides HAp based materials excellent bioactivity like bone bonding capability, osteoconductivity, and biocompatibility.

On the other hand, titanium (Ti) is most commonly used as orthopedic implant materials or bone substitute materials. Ti has good biocompatibility and sufficient mechanical properties for medical applications. One negative property of Ti is a low abrasion resistance and minute Ti abrasion powders may cause inflammatory reac­tions. Biomaterials must be chemically inert, stable and mechanically strong enough to wish stand the repeated forces a lifetime. From this point of view, TiC is a very stable phase in comparison to pure Ti or Ti alloys. Titanium carbide (TiC) is useful material for biomedical instruments because has a range of desirable properties. In this work, the combination of excellent bioactive hydroxyapatite with very stable and mechanically strong TiC has been studied. The nanostructured hydroxyapatite has been prepared by high efficient milling starting from biogenic eggshells. TiC

thin films were deposited by dc magnetron sputtering in argon atmosphere at differ­ent deposition temperatures. Spin coating was applied to obtain HAp decorated TiC films. Structural, mechanical and biological properties of HAp, Polymer-HAp and TiC-HAp coatings are being presented in this study.

2.1 INTRODUCTION

Biomaterials used for implant should posses some important properties in order to long-term usage in the body without rejection. One of most important properties is the biocompatibility. The biomaterial is “any substance, synthetic or natural in ori­gin, which can be used for any period of time, as a whole a part of a system which treats, augments or replaces any tissue, organ or function of the body.”1 Biomaterials are used in different parts of the human body as artificial valves in the heart, stents in blood vessels, replacement implant in shoulders, knees, hips and orodental structures.24 Materials used as different biomaterials should be made with certain properties. The materials used for orthopedic in plants should possess excellent biocompatibility, superior corrosion resistance in body environment, excellent combination of high strength and low modulus, high ductility and be without toxicity 5.

The materials currently used for implants include hydroxyapatite, 316L stain­less steel, cobalt-chromium alloys and pure titanium or its alloys. Elements such as Ni, Cr and Co are found to be released from the stainless steel and cobalt chro­mium alloys due to the corrosion in the body environment 6. The toxic effects of metals, Ni, Co and Cr released from prosthetic implants have been reviewed by Wapner7. Skin related diseases such as dermatitis due to Ni toxicity have been reported and numerous animal studies have shown carcinogenicity due to the pres­ence of Co 8.

The success of a biomaterial or an implant is highly dependent on three major factors; (i) the mechanical, tribological and chemical properties of the biomaterial, (ii) biocompatibility of the implant and (iii) the health conditions of the recipient and competency of the surgeon 9.

The biomaterials are grouped according to use in body. The situation is similar in the case of tissue. The tissue is grouped into hard and soft tissues. Tooth or bone are examples of hard tissue. Cartilage and ligament sor skin are the examples of soft tissues. These two types of tissues have the different properties from the structural or mechanical view. Considering the structural or mechanical compatibility with tissues, metal sor ceramics are chosen for hard tissue applications and polymers for soft tissue applications. The different mechanical properties of both types of tissues are shown in Table. 2.1.10.

In this chapter, THA hydroxyapatite based biomaterials developed as hard and soft tissue replacement were studied. The structural, mechanical and biological properties of bioinerttic—bioactive hydroxyapatite, biogen hydroxyapatite prepared from eggshells and polymer—hydroxyapatite composites were characterized.