Biomedical Engineering Reference
In-Depth Information
human tissues, e.g., bone and teeth, are composites. The amount, morph-
ology, distribution and characteristics of the components determine the
overall behavior of the resulting tissue.
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Over the last 50 years, the use of composites has progressively increased.
Applications include aeronautical, automotive, naval and, more recently,
biomedical. Many biomedical composites are now commercially available,
but many more are under investigation. New applications include drug de-
livery devices and tissue engineering scaffolds. For biomedical applications,
biocompatibility and biomimicity are important.
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7.1.1 Biomedical Applications of Composites
Synthetic composites can be designed to reproduce the form, mechanical
characteristic and function of a damaged tissue.
1
This section focuses on
orthopedic and dental applications of composites.
7.1.1.1 Orthopedic
Composites are regarded as third-generation biomaterials for orthopedic
applications.
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They are commonly employed as bone fixation resorbable
plates,
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hip joint replacement implants,
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bone cements,
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and bone grafts.
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Commercially available composite bone plate examples include laminated
continuous carbon fiber reinforced poly(
L
-lactide)
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and continuous poly(
L
-
lactide) fiber reinforced poly(
L
-lactide) composites.
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These are commonly
used for fixing comminuted zygomatic arch
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and distal femur fractures.
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Furthermore, they are employed in craniofacial surgery
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and to correct the
form of soft tissues as in cleft lips.
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Other composites developed as po-
tential bone plates include phosphate glass fiber reinforced polylactide
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and cross-linked polypropylene fumarate-poly(lactide-co-glycolide)-hydroxy-
apatite.
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Furthermore, polyether ether ketones (PEEK), which have become a
polymer of choice for fixation of hard tissue, primarily in spinal applications,
has been combined with hydroxyapatite, carbon fillers and fibers to enhance
the material integration within the body.
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The use of some fillers (e.g.,
carbon fibers) reinforces the material, thus allowing the fabrication of even
stronger devices for load bearing applications.
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.
7.1.1.2 Dental
Non-degradable dental resin composites are extensively used in restorative
dentistry. These consist of a polymerizable resin matrix, typically high mo-
lecular weight hydrophobic dimethacrylate monomers, silane-treated silica-
based inorganic filler particles, and an initiator-activator system. They set
via free radical polymerization upon exposure to a blue light source. The
polymerized composites are cross-linked three-dimensional networks with
suitable esthetic, physical and mechanical properties for dental appli-
cations.
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Dental composites can be bonded to tooth structure using resin
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