The Solubility of Calcium Phosphate Bone Grafts in Medicine
- Page ID
- 418909
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| Type of Calcium Phosphate Material Used in Bone Grafts | Chemical Equation of Formation |
| Hydroxyapatite | \[6H_3PO_{4 (aq)} + 10Ca(OH)_{2 (s)} \xrightarrow {rxn} Ca_{10}(PO_4)_6(OH)_{2 (s)} + 18H_2O_{(l)}\] |
| Tricalcium Phosphate | \[CaCO_{3 (aq)} + Ca_2P_2O_{7 (s)} \xrightarrow {rxn} Ca_3(PO_4)_{2 (s)} + CO_{2 (g)}\] |
| Biphasic Calcium Phosphate | Mixture of \[Ca_{10}(PO_4)_6(OH)_{2 (s)}\] and \[Ca_3(PO_4)_{2 (s)}\] |
\[K_{sp} \propto SA^{-1}\]
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Solubility Constant
A solubility constant is the measure of how well a solid dissociates in a liquid. There are many factors that can affect a molecule’s solubility such as pH, pressure, and temperature. Moreover, the polarity of a solvent that the solute is in can greatly affect its solubility – like polarities dissolve like solvents. For example, nonpolar solvents dissolve nonpolar solutes and polar solvents dissolve polar solutes. The solubility constant is equal to the equilibrium concentrations of the products divided by the equilibrium concentrations of the reactants. Bone grafts are used when bones are damaged or a patient has bone loss. As the bones in the body are absorbing the calcium ions that have slightly dissolved from the bone graft, the equilibrium of calcium phosphate (reactant) and calcium (product) constantly changes because of Le Chatelier’s Principle, which states that when a system at equilibrium experiences a change, the direction of the chemical equilibrium will shift to counteract that change and return the system to equilibrium. The reason why calcium phosphate is used as a main component in bone grafts is because it has a very low Ksp value of 2.07e-33, and therefore does not rapidly decompose in the body and enhances bone regeneration. This allows the bone to still have access to the calcium it needs to grow at a steady pace.
\[K_{sp} = [Ca_{(aq)}^{2+}]^{10}[PO_{4 (aq)}^{3-}]^6\]
Looking Towards the Future
Due to lack of adequate technology, there is still little research on some of the materials that are used in bone grafts, as they are difficult to synthesize. Looking to the future, scientists researching the advancement of bio-materials hope to learn more about these materials and come up with innovative ways to apply them better for higher functioning bone grafts that maximize biocompatibility and graft strength.