| abstract |
The rod-shaped apatite crystals of the formula Ca 5 (PO 4 ) 3 (OH) x F y have the following featuresn a) the length-to-breadth ratio of the crystals is at least ≧5 and b) x+y=1, where if x or y≠0 the total amount of the crystals is present as a mixture of individual hydroxyapatite crystals and fluoroapatite crystals and/or as mixed crystals, such that, based on the total amount of the crystals, (1−x)·100% of the hydroxide ions present if y=0 are replaced by fluoride ions. nn The invention furthermore describes dispersions which contain such rod-shaped apatite crystals, and a process for the preparation of the dispersions or of the apatite crystals. |