Biomedical Engineering Reference
In-Depth Information
C. Glaser in 1885 [10]. In 1880s, occurrence of a calcium apatite [11]
and calcium orthophosphate [12-14] in a metallurgical slag was
discovered. Chemical reactions between calcium orthophosphates
and other chemicals were investigated as early as in 1891 [15].
Research papers on bone repairing are known since, at least, 1892
[16], while the earliest well-documented systematic studies of
calcium orthophosphates were performed at the beginning of the
twentieth century by F. K. Cameron with co-workers [17-21] and
H. Bassett [22-25]. The majority of the aforementioned researchers
already operated with individual chemical compounds. Further,
historical details might be found in Chapter 8.
By definition, all calcium orthophosphates consist of three
major chemical elements: calcium (oxidation state +2), phosphorus
(oxidation state +5) and oxygen (reduction state −2), as a part
of orthophosphate anions. These three chemical elements are
present in abundance on the surface of our planet: oxygen is the
most widespread chemical element of the earth's surface (~47
mass%), calcium occupies the fifth place (~3.3-3.4 mass%) and
phosphorus (~0.08-0.12 mass%) is among the first twenty of the
chemical elements most widespread on our planet [26]. In addition,
the chemical composition of many calcium orthophosphates
includes hydrogen, as an acidic orthophosphate anion (for example,
HPO
4
2−
or H
PO
4
−
), hydroxide (for example, Ca
(PO
)
(OH)
)
2
10
4
6
2
and/or incorporated water (for example, CaHPO
·2H
O). Diverse
4
2
combinations of CaO and P
(both in the presence of water and
without it) provide a large variety of calcium phosphates, which are
distinguished by the type of the phosphate anion: ortho-(PO
O
2
5
4
3−
),
meta-(PO
). In the case of multi-
charged anions (orthophosphates and pyrophosphates), calcium
phosphates are also differentiated by the number of hydrogen ions
attached to the anion. Examples include mono-(Ca(H
3
−
), pyro-(P
O
7
4−
), and poly-((PO
)
n
n−
2
3
PO
)
), di-
2
4
2
(CaHPO
) calcium phosphates
[27-29] (here, prefixes “mono”, “di”, “tri” and “tetra” are related to
the amount of hydrogen ions replaced by calcium). However, only
calcium orthophosphates are considered and discussed in this topic.
They are listed in Table 1.1 [30, 31]. Since all of them belong to calcium
orthophosphates, strictly speaking, all abbreviations in Table 1.1 are
incorrect; however, they are extensively used in literature and there
is no need to modify them.
), tri-(Ca
(PO
)
) and tetra-(Ca
P
O
4
3
4
2
2
2
7
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