The Interpretation of the X-Ray Diffractograms Obtained from Human Dental Enamel

Abstract

Various types of X-ray diffractograms of dental tissues, on flat film, are illus. and a logical approach to their interpretation is given. A specimen having randomly oriented crystallites (powdered enamel and dentin) gives a "powder pattern" of concentric rings with diameters and intensities characteristic of the crystallin substance (apatite). "Preferred" orientation of the crystallites with one of their axes (c-axis) more or less parallel gives a "fiber pattern": the rings are split into arcs. When the "fiber axis" is perpendicular to the X-ray beam, the positions of the arcs make identification of the reflections easy and definite. The pattern of the apatite fiber structure (dental enamel) is illustrated with all reflection arcs indexed. When the fiber axis is tilted the arcs shift their positions. Any preferred orientation of the crystallites in the specimen is likely to cause severe changes in the intensities of the individual reflections; its effect must be considered before any attempt is made to employ observed intensity variations for other deductions. From profiles of the 002 reflection, measured with a Geiger counter diffractometer, a particle size of 870 A is calculated for enamel and 290 A for dentin. Non-apatitic lines in the diffractograms of enamel and dentin occasionally reported by others are due to insufficient monochromatization of the incident X-rays.