Biomedical Engineering Reference
In-Depth Information
1
mm
Figure 4.8.
MCPC implantation in a rabbit epiphysis femoral defect, SEM observation.
X-ray contrast performance also provides important data, as the radiopacity of
materials is required during the implantation process to ensure the location of
the fi lled material [58]. Various radiopaque agents (RA) such as barium sulfate,
zirconium oxide or iodine have been tested (mechanical properties, cytotoxicity
effects) [59]. In vertebroplasty, the non resorbable acrylic bone cements (poly-
methyl methacrylate, PMMA) contain barium sulphate [60]. To obtain a resorb-
able injectable bone substitute with rheological properties and x-ray contrast
characteristics, Serge Baroth et al. [61] have developed “rounded” calcium phos-
phate granules loaded with an RA such as barium salt or with rare earth elements
containing bismuth, lutetium and gadolinium. The four RA produced were:
barium sulphate (BaSO
4
), lutetium oxide (Lu
2
O
3
), bismuth oxide (Bi
2
O
3
) and
gadolinium phosphate (GdPO
4
). CDA (BCP 60-40) were mixed with RA (20%
w/w) to obtain radiopaque calcium phosphate composites. The composites were
shaped in 80 - 200
m “rounded” granules or pellets (ten mm in diameter, one mm
thickness). The materials were sintered according to specifi c processes. Steam
sterilisation (121 °C, 30 minutes for pellets) or dry sterilization (180 °C, four hours
for granules) were used for
in
vitro
and
in
vivo
tests.
X-ray diffraction (XRD) and infra-red spectroscopy (FTIR) showed integra-
tion of the Ba into the CaP crystal lattice, while no substitution was noticed for
the other RA used. SEM observation of the composite surfaces showed that the
addition of our RA to the calcium phosphate matrix had an infl uence on crystal
shape, crystal size and microporosity. With the addition of BaSO
4
, large crystals
were obtained with low microporosity and a smooth surface. With the addition of
Bi
2
O
3
, crystals grew in needle shapes with signifi cant microporosity. With Lu
2
O
3
and GdPO
4
, the microporosity was signifi cant with small crystals and a number of
fragments present on the BCP/Lu
2
O
3
matrix.
μ
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