Biomedical Engineering Reference
In-Depth Information
toughness, attaining the lower fracture-toughness limit of bone
without a decrease of bioactivity and biocompatibility [1094, 1095].
Besides, a dual HA biocomposite that combined two HA materials
with different porosities: HA with 75% porosity, for bone ingrowth
and HA with 0% porosity, for load bearing was manufactured. This
dual HA biocomposite appeared to be suitable for use as an implant
material for spinal interbody fusion as a substitute for iliac bone
grafts, which could eliminate the disadvantages associated with
autograft harvesting [1096]. A biodegradable biocomposite porous
scaffold comprising a β-TCP matrix and nano-sized fibers of HA was
developed and studied for load-bearing bone tissue engineering.
The nano-sized fibers of HA were prepared by a biomimetic
precipitation method, the inclusion of which significantly enhanced
the mechanical property of the scaffold, attaining a compressive
strength of 9.87 MPa, comparable to the high-end value (2-10 MPa)
of cancellous bone [1097]. Finally, it is interesting to mention on a
successful reinforcement of carbonateapatite porous blocks by newly
prepared carbonateapatite crystals (i.e., by the same compound;
thus, a biocomposite of two different carbonateapatites was
obtained) [1098]. First, a calcium salt was introduced to micropores
of carbonateapatite blocks. Then, the calcium salt was carbonated
to form calcite inside the micropores of the carbonateapatite blocks
by exposing the blocks to carbon dioxide at the second step. On
the third step, the blocks were immersed in a Na
aqueous
solution. In this process, calcite inside the micropores of the
carbonateapatite blocks was transformed to carbonateapatite and
the newly formed crystals of carbonateapatite entangled on those
of the existing carbonateapatite blocks. Due to bonding between the
newly formed carbonateapatite crystals and the existing ones in the
carbonateapatite blocks, a mechanical strength of the blocks became
~1.5 times higher when compared to that before the treatment
[1098].
HPO
2
4
6.4.8
Functionally Graded Biocomposites
Although, in most cases, the homogeneous distribution of filler(s)
inside a matrix is required [426], there are composites, where
this is not the case. For example, functionally graded materials
(commonly referred to as FGM) might be characterized by the
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