Longitudinal study of the three-dimensional development of subsurface enamel lesions during in vitro demineralisation

A longitudinal study was made of the 3D development of subsurface enamel lesions in whole human molars. X-ray microtomography (XMT) was used to measure the 3D distribution of linear attenuation coefficients in the tissue at 8-15 stages during cumulative times of 36-107 days demineralisation through approximately 1-mm-wide windows. Although lesion morphology was consistent with preferential anisotropic dissolution parallel to enamel prisms at the advancing front, detail (at a scale of approximately 100 microm) varied in relation to exposed surface sites separated by <1 mm. The distribution of mineral in the most superficial region varied across the exposed face of each lesion. Within lesions, localised foci of low mineral concentration (at a scale of approximately 200 microm) retained their general form through successive stages of demineralisation before coalescing. The most advanced regions within a lesion seemed to correspond with surface regions with lowest mineral concentration. These findings indicate that local variations in fractional pore volume of partially demineralised enamel influence the subsequent spatial development of lesions.