Biomedical Engineering Reference
In-Depth Information
the long-term failure of titanium-based hip implants after 10-15 years remains unresolved. This has
been attributed to insufficient early osseointegration and corrosion wear particles at a later stage
[6-8]
.
Titanium dental implants fail due to various factors like insufficient early osseointegration, bacterial
infection, surgical trauma, premature overloading, micro-movements caused by inadequate prosthesis
design, improper surgical placement, metal fatigue, and inadequate quality and quantity of bone sur-
rounding the implant
[9,10]
. Over the past decade, various techniques of titanium surface modification
have been employed to fabricate implant surfaces in order to promote osseointegration, faster healing
time, higher bone-to-implant contact (BIC) ratio and longevity of titanium implants. These approaches
are reviewed in the following sections of this chapter.
6.2
TITANIUM SURFACE MODIFICATION METHODS
To formulate novel titanium implant surface that could enhance early osseointegration, an overall
knowledge of the research work done so far is essential. Titanium known as a “valve metal,” when
exposed to air, water, or other oxygen containing atmosphere it forms an oxide layer having 2-5 nm
thickness
[11]
. The spontaneously formed oxide layer (TiO
2
) provides resistance to corrosion and pro-
tection of the underlying metal
[12]
. Titanium being relatively inert, cannot directly bind to the bone
and therefore osseointegration via the oxide layer (TiO
2
) becomes relatively a long process
[13,14]
. In
an effort to enhance cell-implant surface interaction, many surface modification methods have been
investigated in the past to optimize surface topography and accelerate osseointegration with the host
tissue
[15-20]
. The process of new bone formation at the implant-bone interface has been summa-
rized in
Figure 6.1
[16]
. It is well established that physical or chemical changes of titanium surface
Bone
g
d
c
h
b
e
g
a
f
Biomaterial
FIGURE 6.1
Representation of events at the bone-implant interface. (a) Protein adsorption from blood and
tissue fluids, (b) protein desorption, (c) surface changes and material release, (d) inflammatory
and connective-tissue cells approach the implant, (e) possible targeted release of matrix proteins
and selected adsorption of proteins such as bone sialoprotein (BSP) and Osteopontin (OPN),
(f ) formation of lamina limitans and adhesion of osteogenic cells, (g) bone deposition on both
the exposed bone and implant surfaces, (h) remodeling of newly formed bone
[16]
.
