EFFECTIVE FORMULATIONS FOR THE PREPARATION OF CALCIUM-PHOSPHATE BONE CEMENTS

In the system CaO-P2O5-H2O 13 different solids with varying Ca/P ratio s are known. In addition calcium phosphates containing other biocompat ible constituents like Na, or K, or Mg or Cl or carbonate, are known. Therefore, a large number of combinations of such compounds is possibl e which might result in the formation of calcium phosphate cements upo n mixing with water. However, the number of calcium phosphates possibl y formed by precipitation at room or body temperatures is limited to 1 2, which should limit the number of suitable combinations. In this stu dy more than 450 different combinations of reactants have been investi gated. The results were evaluated on the basis of the following criter ia: (a) was the intended reaction product formed? (b) was the final se tting time shorter than 60 min? (c) was the compressive strength after soaking for 1 day in Ringer's solution at 37-degrees-C higher than 2 MPa? We found that 15 formulations satisfied all of these criteria. Th e distribution of cements synthesized in this way was 3 DCPD type, 3 C MP type, 6 OCP type and 3 CDHA type cements. The DCPD type cements wer e acidic during setting and remained that for a long time afterwards. CDHA type cements were neutral or basic during setting, and remained n eutral after completion of the reaction. The OCP type cements were neu tral both during and after setting. Two CMP type cements were basic bo th during and after setting. In this study compressive strengths were found up to 90 MPa. Also, in the literature values up to 90 MPa have b een reported for this type of cement. Taking into account the excellen t biocompatibility and the good osteoconductivity of calcium phosphate s and the fact that these calcium phosphate cements can be injected in to the site of operation, it may be expected that these materials will become the materials of choice for bone replacement and augmentation. Their suitability for the fixation of metal endoprostheses for joint replacement should be investigated as well.