The effects of temperature on the behaviour of an apatitic calcium phosphate cement

An apatitic calcium phosphate cement is obtained by mixing alpha-tricalcium phosphate (alpha-TCP) and precipitated hydroxyapatite into a cement powder, and by then mixing this powder with an aqueous solution of Na2HPO4 as an accelerator. Setting times were reduced by about 30% by increasing the temperature from 22 to 37 degrees C. Compressive strength reached higher intermediate and final values at 37 degrees C. Degrees of transformation of the alpha-TCP in the resulting calcium-deficient hydroxyapatite (CDHA) were much higher at 37 degrees C after 24 h of storage in Ringer's solution according to X-ray diffraction. Differential scanning calorimetry indicated that the rate of reaction increased by a factor of about 5 when the temperature was increased from 25 to 37 degrees C. Scanning electron microscopy showed that the microstructure was more homogeneous and that a more tight entanglement of the precipitated CDHA crystals occurred after storage at 37 degrees C than at room temperature.