It is made up of 70 % inorganic materials ( mainly hydroxylapatite and some non-crystalline amorphous calcium phosphate ), 20 % organic materials ( 90 % of which is collagen type 1 and the remaining 10 % ground substance, which includes dentine-specific proteins ), and 10 % water ( which is absorbed on the surface of the minerals or between the crystals ).
32.
"' Apatite "'is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of PO 4 ) 6 ( OH, F, Cl ) 2, and the crystal unit cell formulae of the individual minerals are written as Ca 10 ( PO 4 ) 6 ( OH ) 2, Ca 10 ( PO 4 ) 6 ( F ) 2 and Ca 10 ( PO 4 ) 6 ( Cl ) 2.
