Effect of the calcium to phosphorus ratio on the setting properties of calcium phosphate bone cements

摘要

α -Tricalcium phosphate (α -TCP) has become the main reactant of most experimental and commercial ceramic bone cements. It has calcium-to-phosphorus (Ca/P) ratio of 1.50. The present study expands and reports on the microstructures and mechanical properties of calcium phosphate (CP) cements containing sintered monolithic reaetants obtained in the interval 1.29 < Ca/ P < 1.77. The study focuses on their cement setting and hardening properties as well as on their microstructure and crystal phase evolution. The results showed that: (a) CP-cements made with reaetants with Ca/P ratio other than 1.50 have longer setting and lower hardening properties; (b) CP-cements reactivity was clearly affected by the Ca/P ratio of the starting reactant; (c) reaetants with Ca/P < 1.50 were composed of several phases, calcium pyrophosphate and a- and J5-TCP. Similarly, reaetants with Ca/P > 1.50 were composed of a-TCP, tetracalcium phosphate and hydroxyapatite; (d) only the reactant with Ca/P = 1.50 was monophasic and was made of a-TCP, which transformed during the setting into calcium deficient hydroxyapatite; (e) CP-cements developed different crystal microstructures with specific features depending on the Ca/P ratio of the starting reactant.