“…In addition to this trace amounts of elements such as strontium, barium, copper, zinc, and iron are commonly associated with biological apatite and may be seen as substituents in the apatite structure [2]. Therefore, one approach to control the osteoblastic response of HA coatings, both in vitro and in vivo, could involve the use of substituted HA, incorporating different ions, such as silicon (Si) [3], lithium (Li) [4] magnesium (Mg) [5], carbonate (CO 3 ) [6], zinc (Zn) [7], silver (Ag) [8], fluoride, (F) [9], chloride (Cl) [10], potassium (K) [11], copper (Cu) [12], sulphate (SO 4 ) [13], tantalum (Ta) [14], cerium [15] or strontium (Sr) [16] into the HA lattice, in order to mirror the complex chemistry of human bone. Many reports of the use of these substituted materials can be found in the literature, both as bone substitute materials and as coatings [17][18][19].…”