Biomedical Engineering Reference
In-Depth Information
pathway for the cell reaction was proposed according to the surface treatment
used:
(1) metal ion release changes the time course of gene expression in the focal
adhesion kinase pathway;
(2) once the accumulation of metal ions released from the Ti surface exceeds
a threshold value, cell growth is diminished and apoptosis may be
activated;
(3) protein tyrosine kinase up-regulation is also induced by metal ion release;
(4) expression of the Bc1-2 family and Bax may suggest that metal ions
induce apoptosis.
5.5 INTEGRATED IMPLANT SYSTEM
In order to achieve the aforementioned three requirements for successful implants
[Oshida et al., 1994] titanium implant surfaces need to be modifi ed. They can be
treated by additive methods (to form surface convex texturing), such as the tita-
nium beads plasma spray procedure, to increase effective surface area. They have
also been modifi ed by subtractive methods (to form surface concave texturing)
such as acid pickling, acid etching, sandblasting, and other small particle-blasting
to change the texture, as well as to increase the surface area. The development
and use of these surface modifi cations have been based on the fact that an
improved osseointegration can be achieved by increasing the topography or
roughness of the implant surface [Klokkevold et al., 1997]. Mechanical and mor-
phological compatibilities can be achieved by surface texturing by means of
chemical, physical, mechanical or combined processes. Ti materials have modulus
of elasticity value of about 150 - 250 GPa while bone structure has only 10 - 20 GPa,
as seen in Figure 5.4. Also it is already known that successful implant systems
possess optimum surface roughness (see Figure 5.5), ranging from 1
m.
To achieve both mechanical and morphological compatibilities, new concept such
as GAF-C/D (gradually altering function concept and design) should be taken
into serious consideration [Jetro, 1994; Bogdanski et al., 2002; Oshida, 2007d].
Technologies supportive to the implant developments have been well
advanced. They should include:
μ
m to 50
μ
(1) coating (such as sol-gel coating [Kim et al., 2004], plasma immersion ion
implantation method [Maitz et al., 2005], etc.),
(2) laser surface engineering, including amorphous phase formation
[Agarwal et al., 2000], laser alloying [Draper et al., 1985; Galerie et al.,
1992], and direct laser forming [Hollander et al., 2006],
(3) near net shape forming (NNS) [Ringeisen et al., 2001; Finke et al., 2002;
Klug et al., 2004] and nanotechnology [Frosch et al., 2004; Macak et al.,
2005 ; Oh et al., 2005 ],
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