SPACE-GROUP DETERMINATION OF HUMAN TOOTH-ENAMEL CRYSTALS

In the present work, we have determined the space group of human tooth-enamel crystals using - for the first time for a biological crystal - convergent beam electron diffraction (CBED). The symmetries observed in the different patterns we have obtained lead us to the P6(3)/m hydroxyapatite space group. Disorder, most likely situated in the columns formed by the hydroxyl ions of the crystals, is suggested as a cause of weak intensity in the otherwise forbidden 0001 (l odd) reflections and low visibility of first-order Laue zone (FOLZ) reflections in the CBED pattern from crystals oriented along the [0001] zone axis. A monoclinic phase was not observed.