Biomedical Engineering Reference
In-Depth Information
Carbonate substituted apatites for use as bone substitute material has
been prepared from biologic materials. For example, commercial coralline HA
(Prosteon ®
Interpore Co, Irvine, California) is prepared by the hydrothermal
conversion of coral,
Porites
(CaCO
3
in aragonite form) in the presence of
ammonium phosphate [15,35,110] . Bovine bone - derived commercial products
are prepared by special treatment of bovine bone such as removal of organic
phase without sintering (BioOss®, Geitslich, Switzerland) or by special treatment
including sintering at 900 °C or above (Endobon®, Darmstad, Germany) [16].
Experimental CHA for bone repair were prepared by hydrolysis method [111]
and by hydrothermal conversion. Carbonate apatite (CHA) blocks can be pre-
pared by the hydrothermal conversion of calcite or gypsum blocks in the presence
of (NH
4
)
2
HPO
4
or Na
2
HPO
4
[117,118] or hydrothermal conversion of
<
- TCP in
the presence of carbonate-containing solutions [121]. Conversion of calcite block
to carbonate apatite block is time dependent (Figure 2.12) and also dependent on
the concentration of the phosphate solution.
Commercial calcium phosphate cements consist of a powder and liquid
component. The powder component is usually a mixture of two or more kinds
of calcium phosphates (e.g.,
α
-TCP, TTCP, DCPD, ACP) that when mixed with
the liquid component sets into a product consisting of CDA, CHA or DCPD
[11,48,51,74,101] .
Experimental calcium phosphates recommended as biomaterials or as coat-
ings on implants include: CHA, CFA, OCP, Mg-TCP, Zn-TCP, calcium phosphate
glass, etc [4,39,68,71,99,111].
α
100
B
80
60
40
20
A
0
0
2
4
6
8
Time (hr)
Figure 2.12.
Transformation of calcite to carbonate apatite by hydrothermal conversion of
calcite in the presence of 1 mol/L Na
2
HPO
4
, 60 °C. The amount of calcite decreased while the
amount of carbonate apatite increased with time.
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