Biomedical Engineering Reference
In-Depth Information
531]. After immersion into Ringer's solution, the tensile strength was
not altered whereas the fatigue properties were significantly reduced.
The biocompatibility of PMMA/HA biocomposites was tested
in vivo
and enhanced osteogenic properties of the implants compared to
single-phase PMMA were observed [528, 532-535]. It was shown
that not only the mechanical properties of PMMA were improved but
the osteoblast response of PMMA was also enhanced with addition
of HA [532]. Thereby, by adding of calcium orthophosphates, a non-
biodegradable PMMA was made more bioactive and osteoconductive,
yielding a well-processible biocomposite concrete. As a drawback,
the PMMA/HA formulations possess a low flexural, compressive,
and tensile strength.
-phenol-α-
glycidylmethacrylate-based resin appeared to possess comparable
mechanical and biological properties to typical PMMA cement,
leading to potential uses for implant fixation [545]. To improve the
mechanical properties of calcium orthophosphate cements and
stabilize them at the implant site, various researchers have resorted to
formulations that set
A biocomposite made from HA granules and
bis
, primarily through cross-linking reactions
of the polymeric matrix. For example, TTCP was reacted with PAA,
forming a cross-linked CDHA/calcium polyacrylate biocomposite
[546]. In aqueous solutions, TTCP hydrolyzes to CDHA [27] and the
liberated calcium cations react with PAA, forming the cross-linked
network [546]. Reed et al
in situ
synthesized a dicarboxy polyphosphazene
that can be cross-linked by calcium cations and cement-based (TTCP
+ DCPD) CDHA/polyphosphazene biocomposites with a compressive
strength ~10 MPa and of ~65% porosity were prepared as a result
[547]. To mimic PMMA cements, PFF/β-TCP biocomposites were
prepared with addition of vinyl monomer to cross-link PPF. As a
result, quick setting and degradable biocomposite cements with a
low heat output and compressive strengths in the range of 1-12 MPa
were prepared by varying the molecular weight of PPF, as well as
the contents of the monomer, β-TCP, initiator, and NaCl, as a porogen
[548, 549]. An acrylic cement with Sr-containing HA as a filler [138],
an injectable polydimethylsiloxane/HA cement [550], biocomposites
consisting of PLGA microspheres and a calcium orthophosphate
cement [551, 552], as well as a hybrid cement formulation of
chitosan oligosaccharide/gelatin/calcium orthophosphate [553]
were prepared as well.
.
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