Calcium Phosphate Cements with Biomedical Applications

CALCIUM PHOSPHATE CEMENTS WITH BIOMEDICAL APPLICATIONS 

The major interest in calcium phosphate cements has always been in their potential for biomedical applications. This is because bone contains hydroxyapatite (Ca5(P04)30H), a calcium phosphate mineral. Any material that could be used to bond bone or produce an artificial graft should contain this mineral for compatibility. In fact, much of the research in producing calcium phosphate-based cements or sintered ceramics was motivated by their biomedical applications. We will discuss applications of calcium phosphate cements in detail in Chapter 18. This section describes their materials development. 

Brown and Chow [7] have listed the important calcium phosphate compounds arranged in the order of increasing basicity (Ca to P ratio). This list is reproduced in Table 13.5 along with a short form notation for each compound in the first column. We have also included in the list an additional mineral, dahllite, recently synthesized by Constantz et al [14], because this mineral is an important compound found in bones. 

Calcium Phosphate Compounds and their Solubility Product Constants (p/sTsp). 

Monocalcium phosphate monohydrate (MCPM) Ca(H2P04)2-H20 Soluble 

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CALCIUM PHOSPHATE CEMENTS WITH BIOMEDICAL APPLICATIONS... 

Calcium Phosphate Cements with Biomedical Applications... 

Calcium oxide is the main ingredient in conventional portland cements. Since limestone is the most abundant mineral in nature, it has been easy to produce portland cement at a low cost. The high solubility of calcium oxide makes it difficult to produce phosphate-based cements. However, calcium oxide can be converted to compounds such as silicates, aluminates, or even hydrophosphates, which then can be used in an acid-base reaction with phosphate, forming CBPCs. The cost of phosphates and conversion to the correct mineral forms add to the manufacturing cost, and hence calcium phosphate cements are more expensive than conventional cements. For this reason, their use has been largely limited to dental and other biomedical applications. Calcium phosphate cements have found application as structural materials, but only when wollastonite is used as an admixture in magnesium phosphate cements. Because calcium phosphates are also bone minerals, they are indispensable in biomaterial applications and hence form a class of useful CBPCs that cannot be substituted by any other. 

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