Biomedical Engineering Reference
In-Depth Information
Ti 2 O 3 , and Ti 3 O 4 on its surface [60]. The average thickness of
the dense titanium oxide ilm is 10 nm [59]. This oxide thickness
increases more rapidly when in contact with bone. Additionally,
calcium and phosphorus ions increase and modify the oxide layer.
It has been shown that titanium oxide acts as a nucleation substrate
for calcium phosphate crystals [28, 109, 110]. The biological activity
of TiO 2 also inluences protein adsorption to the titanium surface
[36]. The chemical composition and microstructure of a surface
can regulate the adsorption of components present in extracellular
luid as a result of alterations in surface energy. In vitro studies have
shown that rough and chemically activated surfaces provide the ideal
conditions for direct protein adsorption and alter the adsorption of
ibronectin and albumin due to modiications in their ionic state
[119].
12.3 NanostructuredBiomaterials
Nanostructured biomaterials possess unique surface and mechanical
properties similar to the bone and hence are considered to be the
future generation biomaterials [39, 40, 132, 137, 144]. Owing to
very high number of atoms on the surface, nanograined materials
possess large surface energy. Thus, they exhibit entirely different
behavior compared to the micron sized grains. The bone-forming
cells generally attach themselves to the surface whose roughness is
of nanometer range.
The nano roughness arises because of the fact that human bones
consist of inorganic minerals of grain size varying from 20 to 80 nm
long and 2 to 3 nm in diameter [34]. The variation in the surface
energy due to the nanosurface roughness leads to desirable cellular
responses on nanostructured titanium and other materials resulting
in high osseointegration [65, 70, 71, 132, 137, 144]. The cell adhe-
sion behavior on submicron, nanometer structured titanium surface
was investigated and the obtained results were compared with a lat
smooth titanium surface [65]. The study demonstrated that both
nanometer and submicron surfaces have very high surface energy
and adhesion of bone cells was very high. Additionally, nanograined
alloys made of Cp Ti, Ti-6Al, 4V, and CoCr as well as nanoceramic
biomaterials such as alumina, titania, and hydroxyapatite also
exhibit increased cell adhesion [135, 142]. When the grain size was
 
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