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X-ray microdiffraction of the crystalline structure forming a tooth


X-ray diffraction measurements of enamel and dentin, which are the major tissues of a tooth, indicate that they are mostly made of hydroxyapatite. It is not very well known that external treatments, such as laser irradiation, may alter the structure of these components. X-ray microdiffraction is useful to observe the localized influence of laser irradiation on the enamel.


Microdiffraction measurements with ø100 μm X-ray beam were performed on three positions of a section of enamel (labeled 1, 2, 3 in the picture below) using a D/MAX RAPID II diffractometer. The measurement conditions were: X-ray generator output: 40 kV, 36 mA; target: Cu; exposure time: 300sec.

The resulting diffraction patterns indicate that hydroxylapatite polycrystals, the major component of the enamel, became amorphous—not only at the irradiated surface but deeper into the tooth. The amorphous component was largest on the surface (3).

Tooth 1
Left: Enamel of a tooth that has been altered due to
laser irradiation at three labeled measurement points.
Center: Two-dimensional X-ray diffraction data.
Right: Tooth schematic (Ø100 µm each at measurement
sites 1, 2, and 3)


Tooth 2
2θ-I profiles converted from two-dimensional data.


Professor Fumio Hirota of The Nippon Dental University supplied the sample and the data



F. Hirota, Lasers in Dentistry, Revolution of Dental Treatment in the New Millennium, (Elsevier Science B.V.) pp.301-311 (2003)