PURPOSE: To maintain physical properties of an obtained hardened object and to control only the hardening time without changing the composition of Ca- phosphate cement itself in order to control the hardening time since the hardening time can easily be controlled only by adjusting quantities of quart. Ca- phosphate and/or α-type tert. Ca-phosphate which are modified the surfaces, and to drasticaly shorten the hardening time by modifying the surface, compared with the case free from an operation of the surface modification.

CONSTITUTION: In the Ca-phosphate cement consisting of sec. Ca-phosphate, the quart. Ca-phosphate and/or the α-type tert. Ca-phosphate, when the total quantity of the sec. Ca-phosphate is mixed with the quart. Ca-phosphate and/or the α-type tert. Ca-phosphate to modify the surface by a high speed in-air flow impact process, the hardening time of the Ca-phosphate cement is controlled by adjusting the mixed quantities of the quart. Ca-phosphate and/or the α-type tert. Ca-phosphate which are mixed.