Tetracalcium phosphate-based materials and processes for their preparation

The invention provides (i) apatite-coated tetracalcium phosphate particles; (ii) a process for preparing the apatite- coated tetracalcium phosphate particles by hydration; (iii) a tetracalcium phosphate-based setting composition; (iv) a composition for forming a hardening material using coated tetracalcium phosphate particles and an acidic aqueous solution; and (v) the composition as defined in (iv) in which the acidic aqueous solution can satisfy the concentration relationships as represented below: (a) 25% </= citric acid </= 50% (b) 30% </= citric acid + phosphoric acid </= 70% (c) 10% citric acid - phosphoric acid </= 50%