Amelogenesis Imperfecta (AI) is a genetically and clinically heterogeneous group of inherited disorders characterised by defective enamel quality and/or quantity. Disturbances during tooth development can disrupt the correct formation of hydroxyapatite crystallites during the biomineralisation of enamel, which ultimately can affect the structure and clinical appearance of teeth.
Novel insights into the mechanistic understanding of AI pathogenesis can be gained using a suite of physical characterisation techniques including synchrotron X-ray diffraction (SXRD), microfluorescence (XRF) and X-ray microtomography (XMT) to comprehensively characterise and spatially quantify crystallographic, chemical, and mineral density distributions respectively.
Method:
High resolution 3D images of three intact human premolars: two clinically diagnosed as hypomaturation AI and one sound type matched control, were collected using an in-house developed microtomography system (MuCAT), with time-delay integration readout to eliminate ring artefacts.
Synchrotron X-ray diffraction was used to evaluate the orientation of hydroxyapatite crystallites in enamel. 2D diffraction and microfluorescence measurements were taken on beamline 2-ID-D at the Advanced Photon Source (APS). A 10µmx10µm beam spot was used to collect images in the cuspal region at high resolution in order to detect changes across small areas of interest.
Result:
Hypomature AI specimens exhibited healthy enamel thickness but overall lower mineral concentration than sound enamel. Mineral concentration was at its lowest at the surface and EDJ, differences in severity were noticed between teeth from the same patient. Rietveld refinement of SXRD patterns has shown variations in HA preferred orientation and lattice parameters.
Conclusion:
The spatial variation of crystallite organisation and mineral distribution has been mapped in enamel affected by hypomaturation AI. The specialised X-ray techniques used in combination have provided complementary information on the crystallographic and microstructural properties of AI affected enamel, showing differences in texture, chemical and mineral distribution as a function of position that occur across this subtype of AI.