Ultrastructural studies of synthetic apatite crystals.
In this paper a survey is given of some ultrastructural properties of synthetic hydroxyapatite. The preparation method by which single crystals with a length in the range of 0.1-3.0mm and a defined purity and stoïchiometry can be produced is given. Two groups of materials are considered in detail: carbonate-rich (greater than 0.1% CO3) and low-carbonate hydroxyapatites. The experiments on carbonate-rich material, being the most interesting from a biological point of view, show that acids attack at an active site in the hexagonal basal-plane of the crystals. Later on the crystals dissolve in the center of the crystal parallel to the c-axis forming tube-like structures. The active site can be protected from dissolution if the crystals are pretreated by EHDP or MFP. A comparison with lattice defect theory shows that most likely dislocations of the "hollow-core" type are responsible for the preferential dissolution.
D000143:Acids; D002118:Calcium / Q000032:analysis; D002254:Carbonates / Q000032:analysis; D003461:Crystallography; D006801:Humans; D006882:Hydroxyapatites / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D012995:Solubility; D013499:Surface Properties
D000143:Acids; D002254:Carbonates; D006882:Hydroxyapatites; D010710:Phosphates; D002118:Calcium