Bioceramics and their Clinical Applications

Tadashi Kokubo

• Publisher: Woodhead Publishing
• Year: 2008
• eBook ISBN: 9781845694227
• Topic: Biological Sciences
• Subtopic: Biotechnology
• Index: Biological Sciences

Bioceramics have been used very successfully within the human body for many years. They are commonly used in orthopaedic surgery and dentistry but they are potentially suitable for a wide range of important applications within the medical device industry. This important book reviews the range of bioceramics, their properties and range of clinical uses.Chapters in the first section of the book discusses issues of significance to a range of bioceramics such as their structure, mechanical properties and biological interactions. The second part reviews the fabrication, microstructure and properties of specific bioceramics and glasses, concentrating on the most promising materials. These include alumina and zirconia ceramics, bioactive glasses and bioactive glass-ceramics, calcium sulphate, tricalcium phosphate-based ceramics, hydroxyapatite, tricalcium phosphate/hydroxyapatite biphasic ceramics, si-substrated hydroxyapatite, calcium phosphate cement, calcium phosphate coating, titania-based materials, ceramic-polymer composites, dental ceramics and dental glass-ceramics. The final group of chapters reviews the clinical applications of bioceramics in joint replacement, bone grafts, tissue engineering and dentistry.Bioceramics and their clinical applications is written by leading academics from around the world and it provides an authoritative review of this highly active area of research. This book is a useful resource for biomaterials scientists and engineers, as well as for clinicians and the academic community. - Provides an authoritative review of this highly active area of research - Discusses issues of significance of a range of bioceramics such as their structure, mechanical properties and biological interactions - Reviews the clinical applications of bioceramics in joint replacement, bone grafts, tissue engineering and dentistry

Part I

Fundamentals of bioceramics

Outline

Chapter 1: The structure and mechanical properties of bone

Chapter 2: Fabrication processes for bioceramics

Chapter 3: The microstructure of bioceramics and its analysis

Chapter 4: Mechanical properties of bioceramics

Chapter 5: The design of ceramics for joint replacement

Chapter 6: Cellular response to bioactive ceramics

Chapter 7: In vitro evaluation of bone bioactivity

Chapter 8: Osteoconduction and its evaluation

Chapter 9: Osteoinduction and its evaluation

1

The structure and mechanical properties of bone

J CURREY, University of York, UK

Publisher Summary

Bone is an extremely hierarchical composite. This is one of the things that make it extremely difficult to analyze properly. This chapter discusses bone’s mechanical properties in the context of its structure. This structure has been fashioned by millions of generations of natural selection. Any advantageous change that can be produced incrementally, and whose advantage appears immediately, will almost certainly have been incorporated into the structure of bone. There is one thing that has happened over the last century or so that is quite new and that is the existence of a large proportion of people who live so long after they have reproduced that natural selection is no longer interested in them. The orthopedic trials of old age, such as osteoporosis and osteoarthritis, essentially do not exist as far as natural selection is concerned. This is a problem for workers who design drugs and procedures for old people. They are always working against the grain, as it were.

1.1 Introduction

Bone is an extremely hierarchical composite. This is one of the things that makes it extremely difficult to analyse properly. This chapter attempts to make some sense of bone’s mechanical properties in the context of its structure. This structure has been fashioned by millions of generations of natural selection. Any advantageous change that can be produced incrementally, and whose advantage appears immediately, will almost certainly have been incorporated into the structure of bone. There is one thing that has happened over the last century or so that is quite new, and that is the existence of a large proportion of people who live so long after they have reproduced that natural selection is no longer interested in them. The orthopaedic trials of old age, such as osteoporosis and osteoarthritis, essentially do not exist as far as natural selection is concerned. This is a problem for workers who design drugs and procedures for old people. They are always working against the grain, as it were. I shall say virtually nothing about disease in this chapter, but it should always be kept in mind.

1.2 Structure

Bone is a composite of mineral, collagen, non-collagenous proteins, other organics and water. It is one of a set of vertebrate mineralised tissues that uses some version of calcium phosphate as their mineral. First there are the tissues that have as their principal organic component type I collagen. These are bone itself, dentine and enameloid. Enameloid is a structure covering the teeth of many fish, and seems (usually!) to be a very highly mineralised collagen-based tissue (Sasagawa et al., 2006), rather like the petrodentine of the lungfish Lepidosiren (Currey and Abeysekera, 2003). Next there is calcified cartilage. This occurs in two main places. One is a temporary calcification of type II collagen-based cartilage. This occurs in the metaphyses of growing long bones, and is soon eroded and replaced by bone. The other, which is much more interesting from the mechanical point of view, is in the permanent skeletal structures of well-mineralised type II collagen-based cartilage structures found almost entirely in the chondrichthyean fishes, the sharks, rays and so on (Summers, 2000). All these different types of mineralised collagens are an embarrassment to people who like neat classifications, but biology is like that (Donoghue et al., 2006). Lastly there is enamel. This is very highly mineralised, and its distinguishing feature is that the organic component, such as it is, is not collagen at all.

Bone’s organic material is about 90% by mass collagen type I. The other organics are various non-collagenous proteins and glycoproteins. The function of these other organics is the subject of intense research. Some of them have ‘biological’ functions; for instance, bone sialoprotein and bone morphogenetic protein have roles in the initiation and control of mineralisation and it has been suggested that a glycoprotein is necessary for the determination of apatite nucleation sites.

The bone mineral is the version of calcium phosphate called hydroxyapatite, whose unit cell contains Ca₁₀(PO₄)₆(OH)₂. The crystals are impure. In particular about 4–6% of carbonate replaces the phosphate, making the mineral more truly a carbonate apatite (dahllite). The shape of the crystal is to some extent in dispute, and partially this is because it is different in different tissues. It is certainly true that in one direction the crystals are small, of the order of 5 nm. They are about 40 nm wide, but sometimes they are hardly wider than 5 nm. What is less clear is the size of the crystals in their long direction (which is the c-axis of the crystal). They can be at least 50 nm long, and it is quite possible that they can join, or grow, until they are several hundreds of nanometres long (Ziv and Weiner, 1994). This small size in one direction may have, as we shall see, profound mechanical implications. ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• Contributor contact details
• Preface
• Part I: Fundamentals of bioceramics
• Part II: Types of bioceramics
• Part III: Clinical applications of bioceramics
• Index