Biomedical Engineering Reference
In-Depth Information
Figure 6.1
Uses of biomaterials.
However, interactions with cells and various cellular processes are discussed in
Chapter 7.
6.2
Types of Biomaterials
In general, a biomaterial is defined as a nonviable material, used in a medical device
that is intended to interact with biological systems [1]. A material that performs
with an appropriate host response in a specific application is termed as a
biocom-
patible
material. Currently used biomaterials can be grouped into five categories:
metals and alloys, ceramics, polymers, composites, and biological materials.
6.2.1 Metals and Alloys
Metals and their alloys (blended with other metallic or nonmetallic substances to
improve a specific quality) are used as biomaterials because of their strength and
toughness. Most important in this class are stainless steel, cobalt-chromium alloy,
titanium, nickel, aluminum, zinc, and their alloys. Metals and alloys are utilized in:
replacement devices for joints such as hips and knees; internal fixation devices such
as bone plates, screws, and pins for hard tissues and stents for the opening of blood
vessels [Figure 6.2(a)], the esophagus, and urinary tracks. After severe trauma in the
head region, the surgical removal of part of the cranium is often the only possibility
to save the patient. This leads to large defects and material is necessary to protect
the brain mechanically. Rebuilding the contours with long-term stability, the reduc-
tion of patient complaints, the easy handling of the implants, and the possibility of
the oncological follow-up with qualified imaging methods are the basic and most
important requirements. The best available material for this particular purpose is
pure titanium, which is used in the manufacturing of the required implants [Figure
6.2(b)]. Dental applications employ gold and its alloys. Tantalum is used in special
cases such as wire sutures in some plastic and neurosurgical applications. Alloys of
platinum and other noncorrosive metals in that group are used in pacemakers as
conducting leads and other components. Nickel containing stainless steel has been
used in early hip implants for its good strength, ability to work hard, and pitting
