Prism arrangement in human cusp enamel deduced by X-ray diffraction.

Analysis of the many X-ray diffractograms obtained from the regions along the bands of Hunter-Schreger, and a series of X-ray patterns taken by tilting the specimen with respect to the incident X-ray beam over a wide range of tilt angles, showed that the fibre axis of the crystal aggregates in each zone of the bands not only deviated in opposite directions but also tilted at an angle of about 50 degrees with respect to the central axis of tooth enamel. Comparison with previous studies enabled a fundamental and simplified three-dimensional model of human cusp enamel to be constructed, consisting of two groups of spirally-arranged structure which would probably be elastic enough to fulfil its unique functions in occlusion and mastication.