THE MICRO MACROPOROUS BIPHASIC CALCIUM PHOSPHATE CONCEPT FOR BONE RECONSTRUCTION AND TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 108

4.3.4.1 Composition. XRD analysis showed the fi nal HA/ β TCP ratios for

all BCP specimens to be 60/40 2, independent of the sintering conditions. No

differences in relative intensities or broadening of the diffraction peaks were ob-
served in any of the BCP specimens. In the FTIR spectra, only absorption bands
attributed to the OH group for the HA and to the PO 4 groups for the HA and
the

±

-TCP were observed. An apparent decrease in the intensity of the OH ab-
sorption bands, loss of resolution and broadening of the OH and PO 4 absorption
bands were observed in the FTIR spectra of BCP specimens D4 and D5 com-
pared to those of D1, D2, and D3.

β

4.3.4.2 Dissolution Properties. Dissolution experiments in an acidic buf-
fer (0.1 M KAc, pH 6, 37 °C) showed differences in the extent of dissolution as
refl ected by the concentration of Ca ions released into the acidic buffer over time.
Maximum dissolution (maximum change in Ca concentration in the buffer) was
observed in the fi rst ten minutes after exposing the BCP discs to the acidic buf-
fer, and no signifi cant change in Ca concentration was observed after 60 minutes.
The BCP discs in groups D1 and D2 behaved almost identically followed by D3,
indicating greater solubility than the BCP discs in groups D4 and D5.

4.3.4.3 Cell Proliferation and Colonization. An established mouse fi bro-
blast cell line L929 was used. After seven days of culture, it was observed that
percentage cell coverage on the BCP disc surfaces differed: much higher percent-
age coverage was observed on the surfaces of D1 and D2 discs (80 and 60%, re-
spectively) than on the surfaces of D3, and even lower for surfaces of D4 and D5
discs (about 10 to 20%), as shown in Table 4.3. The cells on BCP discs D1 and D2
were observed to have proliferated and to be present all over the surface of the
discs while the cells on the D4 and D5 discs showed much less proliferation and
were observed only on the areas where they were originally deposited. The cells
on the surface of the D1 and D2 discs had polygonal shapes while the cells on
D4 and D5 appeared to be more rounded and contracted. Furthermore, the cells
on D5 were characterised by long fi lopodia. The surfaces of the D1 and D2 discs
appeared grainy and rougher while the surfaces of the D5 discs appeared smooth
and similar to the surface as it was before the in vitro experiment.

4.3.4.4 In Vivo Experiment. The right and left epiphyses of rabbits were
implanted, and two defects created, one in the upper part (cancellous bone) and
one in the diaphysis (no bone trabeculae, only bone marrow). After three weeks,
the implants were processed for histology. All the implanted BCP discs showed
good biocompatibility. However, bone growth and bone contact were very differ-
ent for the discs implanted in the cancellous bone of the epiphysis compared to
those in bone marrow: the higher the density, the lower the osteogenicity, particu-
larly for the discs implanted in the bone marrow site. Moreover, the higher the
density (D5 discs), the lower the amount of newly-formed bone in direct contact
with the implant surface (Figures 4.3, 4.4 and 4.5).