Biomedical Engineering Reference
In-Depth Information
TABLE 6.2 Various Methods to Create Nanofeatures on cpTitanium
Implants
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Methods
Characteristics
Self-assembly
The available functional group could serve multiple functions
such as an osteoinductive or cell-adhesive molecule.
Ion beam deposition Creates nanofeatures on the surface of the material used.
Acid etching
Creates surface nanofeatures and destroy contaminants when
combined with sandblasting and/or peroxidation.
The topography of titanium implant surfaces may be affected by nanoscale
modification as well as the chemistry of the surface. Implant surface quality has
been divided into three categories
136
:
(1)
mechanical properties
(2)
topographic properties, and
(3)
physicochemical properties.
These characteristics are indicated to be relative and changing any of these
groups also affected the others. One limitation that is usually encountered in
studies comparing nano- and micron-level surface topography is the extreme
difficulty to isolate chemistry or charge effects induced by the nanotopography.
However, atomic-level control of surface topography during material assem-
bly is influenced by quantum phenomena that do not govern traditional bulk
material behavior.
137
It is very extremely important to distinguish topography-
specific effects from allied changes in surface energy or chemical reactivity.
Nanotechnology provides novel ways of atomic-scale manipulation of matter.
Some approaches are currently prevalent in the experimental application to
endosseous implants (
Table 6.2
).
138
Physical method of compaction of nanopar-
ticles of TiO
2
versus micron-level particles that yield surfaces with nanoscale
grain boundaries is one such approach.
139
This offers conservation of the chem-
istry of the surface among different topographies.
Molecular self-assembly is one other factor that affects surface topog-
raphy. Spontaneous chemisorption and vertical close-packed positioning of
molecules onto substrates allowing the exposure of functional or active end-
chain groups at the interface leads to self-assembled monolayers (SAMs).
140
The exposed functional group serves as active site for osteoinductive or cell-
adhesive molecule. One such example is the use of cell-adhesive peptides
(RGD domains or arginine-lysine-aspartic acid) attached to SAMs com-
posed of polyethylene glycol (PEG) and applied to the titanium surfaces.
141
The chemical treatment of different surfaces to expose reactive groups on
