Biomedical Engineering Reference
In-Depth Information
of the target composition, lack of contamination, and fine control of
the film properties [15]. The introduction of a reactive gas atmosphere
allows composition modulation and preserves the bonding configuration
of the final coatings. The choice of the reactive atmosphere in which the
plasma plume was generated affects the bonding configuration of the
resulting film in terms of the presence of non-bonding oxygen groups,
which are important for bioactive behavior. A disadvantage of PLD
technique is that the films are not as dense as those deposited by other
techniques, such as magnetron sputtering.
8.7 SUMMARY
Many different systems to produce bioactive glass coatings on metals
and ceramics have been developed. Each of them has several advantages
and disadvantages, beside different features, in terms of compositional
homogeneity, coating thickness, ease of application, and tailoring of
properties. Some of them, such as plasma spraying, can be used at an
industrial scale to produce implantable devices, for both orthopedic and
dental applications. A lot of data have been collected about the inter-
face reactivity between the glass coating and the substrate, especially in
the field of glass-to-metal bonding, and about the thermo-mechanical
properties of the bonded materials. Several efforts are focused on the
optimization of their composition to induce good bonding to the sub-
strate as well as good biological properties. However, a word of caution
is necessary: the glass coatings will degrade slowly over time (several
years) and it is unclear exactly what will happen to a metal implant when
that happens. This is also the case for hydroxyapatite-coated implants.
Metal implants are therefore made to have a porous or pitted surface
prior to coating, to try to stimulate bone ingrowth into the surface prior
to the completion of degradation of the coating.
REFERENCES
[1] Hench, L.L. (1998) Bioceramics. Journal of the American Ceramic Society , 81 ,
1705-1728.
[2] Lopez-Esteban, S., Saiz, E., Fujino, S. et al . (2003) Bioactive glass coatings for ortho-
pedic metallic implants. Journal of the European Ceramic Society , 23 , 2921-2930.
[3] Di Nunzio, S., Vitale-Brovarone, C., Spriano, S. et al . (2004) Silver containing
bioactive glasses prepared by molten salt ion-exchange. Journal of the European
Ceramic Society , 24 , 2935-2942.
[4] Vitale-Brovarone, C. and Verne, E. (2005) SiO 2 -CaO-K 2 O coatings on alumina
and Ti6Al4V substrates for biomedical applications. Journal of Materials Science:
Materials in Medicine , 16 , 863-871.
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