Orientation and deformation of mineral crystals in tooth surfaces

概要

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Tooth enamel is the hardest material in the human body, and it is mainly composed ofhydroxyapatite (HAp)-like mineral particles. As HAp has a hexagonal crystal structure,X-ray diffraction methods can be used to analyze the crystal structure of HAp in teeth.Here, the X-ray diffraction method was applied to the surface of tooth enamel to measurethe orientation and strain of the HAp crystals. The c-axis of the hexagonal crystal structureof HAp was oriented to the surface perpendicular to the tooth enamel covering the toothsurface. Thus, the strain of HAp at the surface of teeth was measured by X-ray diffractionfrom the (004) lattice planes aligned along the c-axis. The X-ray strain measurements wereconducted on tooth specimens with intact surfaces under loading. Highly accurate strainmeasurements of the surface of tooth specimens were performed by precise positioningof the X-ray irradiation area during loading. The strains of the (004) lattice plane weremeasured at several positions on the surface of the specimens under compression alongthe tooth axis. The strains were obtained as tensile strains at the labial side of incisortooth specimens. In posterior teeth, the strains were different at different measurementpositions, varying from tensile to compressive types.