A calcium oxide-silica composite biomaterial either in amorphous state or crystalline state having an average pore size, as determined by the BET method, in the range of from 0.8 to 4 nm, wherein the calcium oxide-silica content of the biomaterial is at least 80 wt %, the balance being optionally one or more other materials and wherein the molar ratio of calcium oxide to silica is at least 0.1.