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1992 | Buch | 2. Auflage

Introduction to Biomaterials Kapitel lesen Erstes Kapitel lesen

Biomaterials

An Introduction

verfasst von: Joon B. Park, Roderic S. Lakes

Verlag: Springer US

Enthalten in: Professional Book Archive

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Über dieses Buch

This book is intended as a general introduction to the uses of artificial materials in the human body for the purposes of aiding healing, correcting deformities, and restoring lost function. It is an outgrowth of an undergraduate course for senior students in biomedical engineering, and it is offered as a text to be used in such courses. Topics include biocompatibility, techniques to minimize cor­ rosion or other degradation of implant materials, principles of materials science as it relates to the use of materials in the body, and specific uses of materials in various tissues and organs. It is expected that the student will have successively completed elementary courses in the mechanics of deformable bodies and in anatomy and physiology, and preferably also an introductory course in materials science prior to undertaking a course in biomaterials. Many quantitative examples are included as exercises for the engineering student. We recognize that many of these involve unrealistic simplifications and are limited to simple mechanical or chemical aspects of the implant problem. We offer as an apology the fact that biomaterials engineering is still to a great extent an empirical discipline that is complicated by many unknowns associated with the human body. In recognition of that fact, we have endeavored to describe both the successes and the failures in the use of materials in the human body. Also included are many photographs and illustrations of implants and devices as an aid to visualization.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction to Biomaterials
Abstract
In the treatment of disease or injury it has been found that a variety of nonliving materials are of use. Commonplace examples include sutures and tooth fillings. A biomaterial is a synthetic material used to replace part of a living system or to function in intimate contact with living tissue. The Clemson University Advisory Board for Biomaterials has formally defined a biomaterial to be “a systemically and pharmacologically inert substance designed for implantation within or incorporation with living systems.” By contrast, a biological material is a material such as bone matrix or tooth enamel, produced by a biological system. Artificial materials that simply are in contact with the skin, such as hearing aids and wearable artificial limbs are not biomaterials since the skin acts as a barrier with the external world. The uses of biomaterials, as indicated in Table 1-1, include replacement of a body part that has lost function due to disease or trauma, to assist in healing, to improve function, and to correct abnormalities. The role of biomaterials has been influenced considerably by advances in many areas of medicine. For example, with the advent of antibiotics, infectious disease is less of a threat than in former times, so that degenerative disease assumes a greater importance. Moreover, advances in surgical technique have permitted materials to be used in ways that were not possible previously.
Joon B. Park, Roderic S. Lakes
Chapter 2. The Structure of Solids
Abstract
The properties of a material are determined by its structure and chemical composition. Since chemical behavior depends ultimately upon the internal structural arrangement of the atoms, all material properties may be attributed to structure. Structure occurs on many levels of scale. These scales may be somewhat arbitrarily defined as the atomic or molecular (0.1–1 nm), nanoscale or ultrastructural (1 nm–1 µm), microstructural (1 µm–1 mm), and macrostructural (>1 mm). In pure elements, alloys, ceramics, and in polymers, the major structural features are on the atomic/molecular scale. Polycrystalline materials such as cast metals consist of grains, which may be quite large; however, the boundaries between the grains are atomic-scale features.
Joon B. Park, Roderic S. Lakes
Chapter 3. Characterization of Materials I
Abstract
The characterization of materials is an important step to be taken before utilizing the materials for any purpose. Depending on the purpose, one can subject the material to mechanical, thermal, chemical, optical, electrical, and other characterizations to make sure that the material under consideration can function without failure for the life of the final product. We will consider only mechanical, thermal, and surface properties in this chapter while in the next chapter we will study electrical, optical, and diffusional properties.
Joon B. Park, Roderic S. Lakes
Chapter 4. Characterization of Materials II
Abstract
In addition to the mechanical and thermal properties of materials, other physical properties could be important in particular applications of biomaterials. Properties considered in this chapter include electrical, optical, absorption of X rays, density, porosity, acoustic, ultrasonic, and diffusion.
Joon B. Park, Roderic S. Lakes
Chapter 5. Metallic Implant Materials
Abstract
Metals have been used in various forms as implants. The first metal developed specifically for human use was the “Sherman Vanadium Steel,” which was used to manufacture bone fracture plates and screws. Most metals such as Fe, Cr, Co, Ni, Ti, Ta, Mo, and W used for manufacturing implants can be tolerated by the body in minute amounts. Sometimes those metallic elements, in naturally occurring forms, are essential in cell functions (Fe) or synthesis of a vitamin B12 (Co), but cannot be tolerated in large amounts in the body. The biocompatibility of the implant metals is of considerable concern because they can corrode in the hostile body environment. The consequence of corrosion is loss of material, which will weaken the implant, and probably more important, the corrosion products escape into the tissue resulting in undesirable effects. In this chapter we study the composition-structure-property relationship of metals and alloys used for implant fabrications.
Joon B. Park, Roderic S. Lakes
Chapter 6. Ceramic Implant Materials
Abstract
Ceramics are refractory, polycrystalline compounds, usually inorganic, including silicates, metallic oxides, carbides, and various refractory hydrides, sulfides, and selenides. Oxides such as Al2O3, MgO, and SiO2 contain metallic and nonmetallic elements, whereas others such as NaCl, CsCl, and ZnS are ionic salts. Exceptions are diamond and carbonaceous structures like graphite and pyrolized carbons, which are covalently bonded. Important factors influencing the structure-property relationship of the ceramic materials are radius ratios (Section 2.2.2) and the relative electronegativity between the positive and negative ions.
Joon B. Park, Roderic S. Lakes
Chapter 7. Polymeric Implant Materials
Abstract
Polymers (poly = many, mer = unit) are made by linking small molecules (mers) through primary covalent bonding in the main chain backbone with C, N, O, Si, etc. One example is polyethylene, which is made from ethylene (CH2=CH2) where the carbon atoms share electrons with two other hydrogen and carbon atoms: -CH2-(CH2-CH2)n-CH2-, in which n indicates the number of repeating units. Also note the repeating unit is -CH2CH2-, not -CH2-.
Joon B. Park, Roderic S. Lakes
Chapter 8. Composites as Biomaterials
Abstract
Composite materials are those that contain two or more distinct constituent materials or phases, on a microscopic or macroscopic size scale. The term composite is usually reserved for those materials in which the distinct phases are separated on a scale larger than the atomic, and in which properties such as the elastic modulus are significantly altered in comparison with those of a homogeneous material. Accordingly, fiberglass and other reinforced plastics as well as bone are viewed as composite materials, but alloys such as brass, or metals such as steel with carbide particles are not. Natural biological materials tend to be composites; these are discussed in Chapter 9. Natural composites include bone, wood, dentin, cartilage, and skin. Natural foams include lung, cancellous bone, and wood. Natural composites often exhibit hierarchical structures in which particulate, porous, and fibrous structural features are seen on different microscales. In this chapter composite material fundamentals and applications in biomaterials are explored.
Joon B. Park, Roderic S. Lakes
Chapter 9. Structure-Property Relationships of Biological Materials
Abstract
The major difference between biological materials and biomaterials (implants) is viability. There are other equally important differences that distinguish living materials from artificial replacements. First, most biological materials are continuously bathed with body fluids. Exceptions are the specialized surface layers of skin, hair, nails, hooves, and the enamel of teeth. Second, most biological materials can be considered as composites.
Joon B. Park, Roderic S. Lakes
Chapter 10. Tissue Response to Implants
Abstract
In order to implant a material, the surgeon has to injure the tissue first. Also the injured or diseased tissues should be removed to some extent in the process of implantation. The success of the entire operation depends on the kind and degree of tissue response. This is an important aspect of biocompatibility. Biocompatibility entails mechanical, chemical, pharmacological, and surface compatibility as mentioned in Chapter 1. The tissue response toward injury may vary widely according to the site, species, contamination, etc. However, the inflammation and the cellular response to the wound for both intentional and accidental injuries are the same regardless of the sites.
Joon B. Park, Roderic S. Lakes
Chapter 11. Soft Tissue Replacement I: Sutures, Skin, and Maxillofacial Implants
Abstract
In soft tissue implants as in other applications that involve engineering, the performance of an implanted device depends on both the materials used and the design of the device or implant. The initial selection of material should be based on sound materials engineering practice. The final judgment on the suitability of the material depends on observation of the in vivo clinical performance of the implant. Such observations may require many years. This requirement of in vivo observation represents one of the major problems in the selection of appropriate materials for use in the human body. Another problem is that the performance of an implant may also depend on the design rather than the materials per se.
Joon B. Park, Roderic S. Lakes
Chapter 12. Soft Tissue Replacement II: Blood-Interfacing Implants
Abstract
Blood-interfacing materials can be divided into two categories: short-term extracorporeal devices such as membranes for artificial organs (kidney and heart/lung machine), tubes and catheters for the transport of blood, and long-term in situ implants such as vascular implants and implantable artificial organs. Although pacemakers for the heart are not interfaced with blood directly, they are considered here since they are devices that help to circulate blood throughout the body.
Joon B. Park, Roderic S. Lakes
Chapter 13. Hard Tissue Replacement I: Long Bone Repair
Abstract
The design principles, selection of materials, and manufacturing criteria for orthopedic implants are the same as for any other engineering products undergoing dynamic loading. Although it is tempting to duplicate the natural tissues with materials having the same strength and shape, this has not been practical or desirable since the natural tissues and organs have one major advantage over the man-made implants, i.e., their ability to adjust to a new set of circumstances by remodeling their micro- and macrostructure. Consequently, the mechanical fatigue of tissues is minimal unless a disease hinders the natural healing processes or unless they are overloaded beyond their ability to heal.
Joon B. Park, Roderic S. Lakes
Chapter 14. Hard Tissue Replacement II: Joints and Teeth
Abstract
The articulation of joints poses some additional problems as compared with long bone fracture repairs. These include wear and corrosion and their products, as well as complicated load transfer dynamics. In addition, the massive nature of the (total) joint replacements such as the knee and the elbow and their proximity to the skin also renders the greater possibility of infection. More importantly, if the replacement fails for any reason, it is much more difficult to replace the joint a second time since a large portion of the natural tissue has already been destroyed.
Joon B. Park, Roderic S. Lakes
Chapter 15. Transplants
Abstract
As we have seen in the previous chapters, biomaterials have many uses in aiding healing, restoring a lost form or function, and correcting a deformity. The limitations of artificial materials become apparent when we realize that only the simplest mechanical, structural, optical, and chemical functions can be assumed by nonliving materials. Functions that can only be performed by living tissues can be restored either by transplanting a new tissue or a new organ or by regenerating the tissue or organ that has lost its function.
Joon B. Park, Roderic S. Lakes
Backmatter
Metadaten
Titel
Biomaterials
verfasst von
Joon B. Park
Roderic S. Lakes
Copyright-Jahr
1992
Verlag
Springer US
Electronic ISBN
978-1-4757-2156-0
Print ISBN
978-1-4757-2158-4
DOI
https://doi.org/10.1007/978-1-4757-2156-0