Biomedical Engineering Reference
In-Depth Information
Historically, Nery and lynch with co-workers first used the term
biphasic calcium phosphate (BCP) in 1986 to describe a bioceramic,
that consisted of a mixture of HA and β-TCP [237]. Based on the results
of X-ray diffraction analysis, these authors found that the “tricalcium
phosphate” preparation material used in their early publication
[238] was in fact a mixture of ~20% HA and ~80% β-TCP. Currently,
only biphasic and triphasic calcium orthophosphate formulations
are known; perhaps, more complicated formulations would be
manufactured in future. Furthermore, nowadays, multiphasic and/
or polyphasic compositions consisting of high-temperature phases
of calcium orthophosphates, such as α-TCP, β-TCP, HA and, perhaps,
high-temperature ACP, OA and TTCP, are known only. No information
on multiphasic compositions, containing mCPm, mCPA, DCPD, DCPA,
low-temperature ACP, OCP and CDHA has been found in literature.
Perhaps, such formulations will be produced in future.
All BCP formulations might be subdivided into two major groups:
those consisting of calcium orthophosphates having either the same
(e.g., α-TCP and β-TCP) or different (e.g., β-TCP and HA) molar Ca/P
ratios. Among all known BCP formulations, BCP consisting of HA and
β-TCP is both the most known and the best investigated [312-323].
In 1986, leGeros in uSA and Daculsi in France initiated the basic
studies on preparation of this type of BCP and its
properties.
This material is soluble and gradually dissolves in the body, seeding
new bone formation as it releases calcium and orthophosphate ions
into the biological medium. Presently, commercial BCP products
of different or similar HA/
in vitro
-TCP ratios are manufactured in many
parts of the world (see partly overlapping Tables 4.2, 5.2 and 6.4) as
bone-graft or bone substitute materials for orthopaedic and dental
applications under various trade marks and several manufacturers
[322]. A similar combination of α-TCP with HA forms BCP as well
[252, 253, 255, 501-504].
recently the concept of BCP has been extended by preparation
and characterization of biphasic TCP (BTCP), consisting of α-TCP and
β-TCP phases [505-509]. The biphasic TCP is usually prepared by
heating ACP precursors [507-509], in which the α-TCP/β-TCP ratio
can be controlled by aging time and pH value during synthesis of the
amorphous precursor [508]. Furthermore, triphasic formulations,
consisting of HA, α-TCP and β-TCP [510] or HA, α-TCP and TTCP [499,
500] have been prepared.
β
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