Biomedical Engineering Reference
In-Depth Information
earlier he was involved in a car accident and a piece of the windscreen
embedded in his chin, unbeknown to him. The inert glass would have
been sealed off from the body by fibrous tissue and over the years it was
pushed out through the soft tissue to the skin.
This topic will illustrate that, for biomedical applications, certain
glasses can be active in the body and stimulate the natural healing of
damaged tissues. The degradation of the glass is actually encouraged and
plays an important role, allowing space for tissue regrowth and actively
stimulating cells to produce tissue.
Glass is actually far from being a single composition but rather is a
state of matter, a subset of the solid state. A glass is a network of atoms
(most commonly silicon) bonded to each other through covalent bonds
with oxygen atoms. A silica-based glass is formed of silica tetrahedra
(Figure 1.1) bonded together in a random arrangement. Window glass
is usually based on the soda-lime-silica (Na
2
O-CaO-SiO
2
) system.
Bioactive glasses also often contains these components, but in different
proportions to inert glasses. Chapter 5 discusses the atomic structure in
more detail.
Si
Figure 1.1
Schematic of a silica tetrahedron, the basic component of a silica glass.
