Hydroxyl apatite crystal size

Mention has already been made of substitution within the crystal lattice. A foreign ion, provided that it is similar in size to the ion which it replaces, may exchange for a normal hydroxyapatite constituent. This process is called heteroionic exchange, whereas the exchange of like ion for like is called isoionic exchange. There are, thus, two ways in which ions other than calcium, phosphate or hydroxyl may become part of the structure of biological apatite. Firstly,... 

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