Biomedical Engineering Reference
In-Depth Information
TABLE 2.1. Calcium Phosphates in Biologic Systems
Calcium phosphate
Chemical formula
Occurrence
Carbonate apatite,
Carbonate- F -
apatite
(Ca,Z)
10
(PO
4
,Y)
6
(OH,Z)
2
enamel, dentin, bone, fi sh
enameloids, special shells,
pathologic calcifi cations (dental
calculus, urinary stone, sof-tissue
calcifi cations), fossil teeth &
bones, calcifi cation on heart valve
prostheses
Octacalcium
phosphate, OCP
Ca
8
H
2
(PO
4
)
6
.5H
2
O
pathologic calcifi cations (dental
calculus urinary stones)
Brushite, dicalcium
phosphate
dihydrate, DCPD
CaHPO
4
.2H
2
O
pathologic calcifi cations:dental
calculus, chondrocalcinosis,
crystalalluria; human enamel and
dentin caries
Whitlockite,
Mg - substituted
beta tricalcium
phosphate, β - TCMP
(Ca,Mg)
3
(PO
4
)
2
pathologic calcifi cations: dental
calculus urinary stones, arthritic
cartilage, soft tissue calcifi cations;
arrested dentin caries.
Amorphous calcium
phosphate, ACP
(Ca,Mg)
x
(PO
4
,Y ′ )
y
soft tissue calcifi cation (skin, joint)
associated with uremia
Calcium
pyrophosphate
Dehydrate, CPPD
C a
2
P
2
O
7
.2H
2
O
pseudo - gout deposits in synovium
fl uid
Z = Na, Mg, K, Sr, etc; Y = CO3, HPO4; X = Cl, F; Y
′
= P2O7, CO3. [57,63,64,68,72,86,89,90,97,112]
Calcium phosphates occurring in biologic systems (Table 2.1) include: carbonate
apatite (CHA), amorphous calcium phosphate (ACP), dicalcium phosphate dihy-
drate (DCPD), dicalcium phosphate anhydrous (DCPA), octacalcium phosphate
(OCP), magnesium-substituted tricalcium phosphate (
- TCMP), and calcium py-
rophosphate dihydrate (CPPD) [13,64,112] . Other non - phosphatic compounds
that also occur in urinary stones with or without calcium phosphates include cal-
cium oxalates, struvite (magnesium ammonium phosphate) or uric acid.
Synthetic apatites and biologically relevant calcium phosphates (for example,
ACP, DCPD, OCP,
β
-TCP) have been extensively studied in the early 1950s and
1960s to gain insights into:
β
(a) the formation of the bone mineral;
(b) demineralization - remineralization of tooth mineral (enamel or dentin)
associated with dental caries;
(c) ways of preventing formation of different types of calcium phosphates
associated with pathologic calcifi cations (for example, dental calculus,
urinary stones, soft tissue calcifi cations (heart, lung, joint, skin), or calci-
fi cation of prostheses (for example, heart valve prosthesis).
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