Biomedical Engineering Reference
In-Depth Information
Metal-ceramic systems for dental restorations have been
available since the 1960s. They rely on the application and iring
of a veneering ceramic onto a metal substructure to produce an
esthetically acceptable restoration. Veneering ceramics for metal-
ceramic restorations, commonly named feldspathic porcelains, are
usually leucite (KAlSi
2
O
6
)-based [138]. Feldspar-derived glass alone
exhibits a low coeficient of thermal expansion, around 8.6
×
10
-6
/°K
[133]. The addition of leucite to feldspar glass led to the production
of veneering ceramics with a coeficient of thermal expansion
compatible with that of the metal substructure.
With the success of zirconia as a dental restorative material,
manufactured 3Y-TZP abutments and implants have recently been
introduced on the dental market. Low-temperature degradation
of 3Y-TZP involves microstructural changes such as grain pull-out,
microcracking, and surface roughening [31, 34]. It has also been
demonstrated that surface inish and residual surface stresses
strongly inluence the response of 3Y-TZP to low-temperature
degradation [35]. Ceria-stabilized zirconia/alumina nanocomposites
for dental applications have been shown to exhibit high lexural
strength (1422 ± 60 MPa), high reliability, and an excellent resistance
to low-temperature degradation [91].
3
.
3
.
1
.
3 Carbon
Over the past years, various carbon materials have been investiga-
ted in many areas of medicine [6, 7, 130]. Carbon occurs in different
lattice forms, from amorphous through intermediate to crystalline,
e.g., hexagonal or regular lattice diamond. The broad range of
applications of carbon materials in medicine is also the outcome
of many preparation methods. Carbon implant materials can be
produced by pyrolysis of solid, liquid, and gaseous carbon precursors.
The pyrolysis method applied to carbon compounds allows the
production of carbon of different structure and microstructure
in the form of thin ilms or thick layers, solid pyrolytic carbon,
powders, and in the form of ibers. The different forms of carbon
that have received attention are artiicial graphites, glasslike carbon,
carbon ibers, pyrolytic carbon, and vapor-grown carbon coatings.
Among pure forms of carbon, the pyrolytic carbons and carbon
coatings on various substrates have found clinical applications in the
cardiovascular, orthopedic, and dental areas as well as in long-term
transcutaneous applications [10
−
12, 18, 77]. Most of the studies on
