SEM study on the dentin and cementum of oreodont teeth.

An SEM study on the dental hard tissue was conducted on the canines and molars removed from a fossil oreodont. The orthodentin was densely distributed with dentinal tubules measuring 2.2 microns in diameter; the tubules were filled with their related odontoblastic processes. They coursed in a parabolic fashion from the pulpal aspect towards the tooth surface. There were many fine lateral offshoots that branched from the tubules, such that the mantle dentin measuring 50 microns in thickness was mostly distributed with these terminal branches measuring 0.7 micron in diameter. However, they did not intrude into the enamel to form spindles and rods. SEM study indicated that the uneven surface of the tubular wall was due to a crisscross of the underneath dentinal matricial fibers, and the peritubular dentin was not observed. The superficial circumpulpal dentin was distributed with interglobular dentin, while the radicular dentin beneath the cementum was additionally distributed with a granular layer. We also observed concentric lamellae corresponding to incremental lines in the dentin, as well as a flat wavy dentinoenamel junction. We noticed the radicular dentin was covered with an acellular cementum except at the apical portion, where it was paved with cellular cementum.