| dc.description.abstract | Objectives. Mercury intrusion under very high pressures is used to study the distributions of dimensions of pores in permeable solids. We noted that archival calcified tissue samples which had been tested to 750 bar were permanently stained, had therefore retained mercury, and decided to investigate whether this could be a valuable morphological space stain for studies with backscattered electron imaging in scanning electron microscopy (BSE-SEM) and X-ray microtomography (XMT). Methods. Samples included human and rat teeth, African elephant tusk, and freeze-dried developing bovine teeth. Porosimetry tested samples were embedded in poly-methyl-methacrylate. Blocks were cut and polished for imaging, uncoated, with 20kV BSE-SEM and 90kV XMT. Results. Unmineralized space compartments were brought into great prominence in all tissues. In cementum, mercury filled non-mineralised cores of Sharpey fibres as well as cementocyte lacunae and canaliculi. Dentine tubules were extremely marked and often showed an astonishing number of fine side branches at a size just below the resolution limit of conventional optical microscopy: their continuity across the enamel dentine junction with enamel tubules and spindles was clearly shown. Interglobular dentine zones were heavily impregnated. Imaging the mercury revealed detailed information concerning the tubule curvature (odontoblast movement) patterns responsible for the wonderful chequer board arrangement in elephant ivory. In enamel, prism boundary discontinuities (‘sheaths’) were prominent in the known hypomineralisation tracts - tufts and lamellae - but also in developmental hypomaturation regions in MIH and ‘white spot’ caries. In rat incisor, defect non-mineralised zones were seen in innermost enamel. Conclusions. Hg staining is a useful method. Because of the extreme high density and signal levels from mercury, both XMT and BSE-SEM demonstrate its presence at below their normal spatial resolution limits giving rise to apparently higher resolution. | en_US |
