Texture Mapping the Spatial and Temporal Progression of Enamel Biomineralisation

Objectives: During the maturation stage of amelogenesis, the majority of enamel mineralization occurs. The long needle-like hydroxyapatite crystallites formed in the secretory stage grow laterally to fill the space of retreating protein molecules. In the present study we used 2D synchrotron x-ray diffraction to compare crystal orientation of developing enamel at different points during the maturation stage to track lateral crystal growth and therefore the spatial and temporal progression of enamel maturation. For dental research gaining an in-depth understanding into the temporal and spatial processes of biomineralisation will provide useful insights for developing successful reparative or regenerative technologies.

Methods: Several archaeological tooth specimens at different stages of maturation were selected and sectioned into 500µm thick slices. Synchrotron x-ray diffraction measurements were collected on the XMaS beamline at the European Radiation Synchrotron Facility. 20-150µm resolution maps for unerupted crown-half; unerupted crown-complete; and erupted fully mature intact tooth sections were collected for comparison. Through analysis of diffraction patterns, the crystallographic texture distribution in enamel has been determined for different stages of maturation.

Results: Through cuspal enamel, a general trend of increasing orientation of crystallites from the enamel-dentine junction (EDJ) towards the enamel surface was observed. The greatest increase is seen in fully mature enamel. The unerupted crown-complete specimen exhibited a slight increase in texture as a function of distance from the EDJ, albeit less than fully mature enamel. In contrast, the unerupted crown-half specimen showed a decrease in orientation approximately halfway through the cusp followed by an increase at the surface, indicating a non-linear gradation of texture through the cusp.

Conclusion: Our results suggest that the texture distribution at different stages of enamel maturation starts with a non-linear, heterogonous trend at the early stage of maturation becoming a smoothly-graded structure at full enamel maturation.

Funded by Wellcome Trust Value in People Award.