Real-time monitoring of the setting reaction of brushite-forming cement using isothermal differential scanning calorimetry.

The setting behavior of a brushite-forming cement (beta-tricalcium phosphate/mono calcium monophosphate) was investigated using an indentation technique (the Gillmore needles method) and isothermal differential scanning calorimetry (DSC). The two objectives of the study were to investigate whether DSC could be used to real-time monitor a fast-setting calcium phosphate cement (CPC) and to determine if it is possible to correlate DSC results directly with conventional setting-time measurements. Best-fit linear correlation analysis revealed that both the initial and final setting time (T(i) and T(f)) measured by indentation were strongly correlated to the maximum heat flow measured with DSC. It seems therefore possible to predict the setting times, usually achieved with user dependent indentation methods, of this specific fast setting CPC on the basis of objective DSC measurements. The drawbacks of DSC, however, are its overall complexity and expense and the fact that only exothermal reactions can be investigated in comparison to the Gillmore needles method, furthermore, it is not possible to monitor the complete reaction as the first 2 or 3 min are lost due to sample preparation and apparatus set up.