Biomedical Engineering Reference
In-Depth Information
porosity (~84
−
87%), while retaining excellent compressive
strength (~7
−
8 MPa), which has been unachievable in the
case of
pure apatite scaffolds (~74% porosity with ~2 MPa strength).
All of
the specimens show a good healing response without adverse
tissue
reactions. Good healing is shown at 4 weeks post-surgery
with the
ingrowth of new bone into the macropore-channels of
the scaffolds.
The apatite-coated
zirconia scaffolds show good bone forming ability
and are considered
to be a promising scaffolding material for bone
regeneration
since they possess a high level of both mechanical and
biological
properties [73].
Dental implants for load bearing applications require the use of
materials that are both bioactive and have signiicant mechanical
strength [13]. There are no existing materials that readily it
these two criteria. While titanium and titanium-based alloys have
excellent mechanical properties and are generally well tolerated
in a physiological environment, they have negligible capacity for
osteointegration. Two approaches have been taken to improve the
osteointegration: a surface modiication approach and a composite
approach. In the surface modiication approach, the surface of
the primary material is modiied by chemical or electrochemical
methods to make the surface bioactive, or a bioactive coating
is applied using, for example, plasma deposition techniques. In
the composite approach, the primary material is combined with
bioactive materials, such as bioglass or bioceramics. Conventional
powder metallurgy methods [23, 98], or plasma-assisted processes
[30, 87] are commonly used for fabricating the composites.
The biocomposites prepared from powder mixtures of titanium
(
α
-Ti), hydroxyapatite (HA), and bioactive glass (BG) (SiO
2
-CaO-
P
2
O
5
-B
2
O
3
-MgO-TiO
2
-CaF
2
) were investigated, too [99]. The
results showed that complex reactions among the starting materials
mainly depended on the initial Ti/HA ratios as well as the sintering
temperatures.
Although titanium (Ti) and its alloys are the preferred metal
materials for orthopedics and dentistry because of their high strength
and good biocompatibility [132, 136], they are bioinert biomaterials
and cannot directly bond to the bone. Moreover, HA coatings to
improve the surface bioactivity of titanium and its alloys often lake
off as a result of poor ceramic/metal interface bonding, which may
make the surgery fail [19, 144]. The problems mentioned above can
