Biomedical Engineering Reference
In-Depth Information
Interestingly, but bioactivity of HA bioceramics might be enhanced
by a high-energy ion irradiation [640]. The effect was attributed to
formation of a unique 3D macroporous apatite layer of decreased
crystallinity and crystal size on the irradiated surfaces. To conclude
this topic, the atomic and molecular phenomena occurring at the
bioceramic surface in aqueous solutions and their effects on the
relevant reaction pathways of cells and tissues must be elucidated in
more details. However, further investigation of this topic requires a
careful analysis of the available experimental data, which is beyond
the scope of this review.
4.6.5
Cellular Response
Fixation of an implant in the human body is a dynamic process that
remodels the interface zone between the implant and living tissues
at all dimensional levels, from the molecular up to the cell and
tissue morphology level, and at all time scales, from the first second
up to several years after implantation. Immediately following the
implantation, a space filled with bio-fluids appears next to the implant
surface. With time, proteins will be adsorbed at the bioceramic
surface that will give rise to osteoinduction by cell proliferation
and their differentiation towards bone cells, revascularisation and
eventual gap closing. Ideally, a strong bond will be formed between
the implant and surrounding tissues [54]. A detailed study on
interfacial interactions between calcined HA and substrates have
been performed recently [641], where the interested readers are
referred for further details.
Osteoblasts cultured on HA bioceramics are generally reported to
be completely flattened and difficult to distinguish the cytoplasmic
edge from the HA surfaces after ~2 h incubation [642]. These
observations underscore an expected bioactivity of HA and make HA
bioceramics well suited for bone reconstruction. Osteoblasts cultured
on porous HA bioceramics appeared to exhibit a higher adhesion, an
enhanced differentiation and suppressed proliferation rates when
compared to the non-porous controls [643, 644]. Furthermore,
formation of distinct resorption pits on HA [645] and β-TCP [634]
surfaces in the presence of osteoclasts was observed. Moreover, a
surface roughness of calcium orthophosphate bioceramics was
reported to strongly influence the activation of mononuclear
precursors to mature osteoclasts [645].
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