2D Mapping of Dental Enamel Affected by Caries

Methods: Synchrotron X-ray diffraction was used to evaluate the orientation of hydroxyapatite crystallites in enamel. Four types of tooth samples have been studied: 1) enamel with demineralised artificial lesion, 2) artificially remineralised enamel, 3) healthy control and 4) naturally carious enamel. Samples were treated with acetic acid then buffer solution to create lesions, before preparing 500µm sections. 2D X-ray diffraction patterns were collected on the XMaS beamline at the European Synchrotron Radiation Facility (ESRF). A 20µmx20µm beam spot was used to collect images at high resolution in order to detect changes across small areas of interest.

Results: 2D diffraction images have been analysed using Fit2D software. Variations in the intensity around the (002) reflection are indicative of texture in enamel. For each diffraction image, intensity was plotted against the azimuthal angle and fitted to a Gaussian peak. Changes in the Full Width Half Maximum (FWHM) were monitored from enamel surface to EDJ. In demineralized enamel, a systematic decrease in FWHM was seen from surface to EDJ, indicating a rise in texture. Both remineralised and healthy control enamel followed a similar trend of low FWHM at enamel surface.

Conclusion: The direct site of demineralisation results in a lack of texture and less orientation as compared to unaffected enamel. Similarities in higher texture observed in remineralised and healthy control enamel suggests that remineralisation may potentially restore crystallites to their original orientation.

Funding: QMUL/MRC PhD studentship