AAWSAP DIRD, Biomaterials, January 2010

Text

This text came with the file. It may have mistakes. When the text and the image disagree, the image is right.

UNCLASSIFIED//FOR OPPICIAL Y§liii Ql'IL¥
An appropriate selection of the polymer matrix is necessary in order to develop a
successful drug delivery system. The most commonly used polymers for this
application, polylactide (PLA) and poly(lactide-co-glycolide) (PLGA), have been used in
biomedical applications for more than 20 years and are known to be biodegradable,
biocompatible, and nontoxic. A vast amount of literature is available on the
characterization of these polymers and their biodegradation and drug-release
properties.
MEDICAL TITANIUM AS A BIOMATERIAL
Titanium metal has qualities of strength, inertness, and a biological compatibility that
make it desirable as a biomaterial. Essentially all pacemakers, neurostimulators, and
various other implanted medical devices use titanium as a packaging case material.
Titanium metal exposed briefly to the atmosphere oxidizes to form a microscopically
thin layer of titania (titanium oxide) . Titania is a hard, adherent, and inert ceramic-like
compound and is thought to be largely responsible for titanium's acceptability in
biomedical applications where metal corrosion in warm, salty body fluids ordinarily
would be a problem.
Titanium is used for its high strength in replacement hip and knee joints. In these
cases, it is important how the metal integrates with living tissue and bone because load
must be transferred from the metal to the bone. Titanium generally does exceedingly
well and is used as the metal of choice in nearly all biomedical applications where high
strength and impact resistance is important.
Titanium has a particular ability among the various metals that might otherwise be
chosen in that it can integrate itself well with living bone. The recognition of this dates
back to 1952, when Swedish Professor Per-Ingvar Branemark conducted an experiment
in which he studied blood flow in living rabbit bone. The bone was fixed in a roughly
machined titanium holder. At the conclusion of the experiment, after many days, he
found that the bone had integrated so completely with the titanium that removing it
was impossible. He called this osseointegration and saw the possibilities for human use.
Figure 29 shows a photomicrograph of a titanium-bone interface. The close
approximation of the titanium (black) to the tissue is an indicator of a close-metal­
tissue integration. Osseointegration was first implemented in dentistry to fixate teeth. It
is now also is used for head and jaw reconstruction.
UNCLASSIFIED/,6FOA OFFICIOL Uili OPIL¥
22