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. Author manuscript; available in PMC: 2018 Oct 1.
Published in final edited form as: Dent Clin North Am. 2017 Oct;61(4):835–856. doi: 10.1016/j.cden.2017.06.003

Table 1.

Calcium phosphate compounds and their solubility/degradation properties

Name Chemical formula Symbol Ca/P ratio −log(Ksp) at 298 K
Monocalcium phosphate monohydrate Ca(H2PO4)H2O MCPM 0.5 1.14
Dicalcium phosphate anhydrous CaHPO4 DCPA 1.0 6.90
Dicalcium phosphate dihydrate CaHPO2H2O DCPD 1.0 6.59
Octocalcium phosphate Ca8H2(PO4)5H2O OCP 1.33 96.6
Hydroxyapatite Ca10(PO4)6(OH)2 HA 1.67 116.8
Fluorapatite Ca10(PO4)6F2 FA 1.67 120.0
Monocalcium phosphate anhydrous Ca(H2PO4)2 MCPA 1.67 1.14
α-Tricalcium phosphate α-Ca3(PO4)2 α-TCP 1.5 25.5
β-Tricalcium phosphate β-Ca3(PO4)2 β-TCP 1.5 28.9
Tetracalcium phosphate Ca4(PO4)2O TTCP 2.0 38.0

The parameter −log(Ksp) denotes the solubility product. The lower the −log(Ksp) value, the higher is the solubility. Similarly, it can also be noted that acidic products (MCPM) with lower Ca/P ratio have higher solubility compared to basic compounds, such as hydroxyapatite with higher Ca/P ratio.