title: Dentinal tubules revealed with X-ray tensor tomography.
abstract: Dentin is a mineralized material making up most of the tooth bulk. A system of microtubules, so called dentinal tubules, transverses it radially from the pulp chamber to the outside. This highly oriented structure leads to anisotropic mechanical properties directly connected to the tubules orientation and density: the ultimate tensile strength as well as the fracture toughness and the shear strength are largest perpendicular to dentinal tubules. Consequently, the fatigue strength depends on the direction of dentinal tubules, too. However, none of the existing techniques used to investigate teeth provide access to orientation and density of dentinal tubules for an entire specimen in a non-destructive way. In this paper, we measure a third molar human tooth both with conventional micro-CT and X-ray tensor tomography (XTT). While the achievable resolution in micro-CT is too low to directly resolve the dentinal tubules, we provide strong evidence that the direction and density of dentinal tubules can be indirectly measured by XTT, which exploits small-angle X-ray scattering to retrieve a 3D map of scattering tensors. We show that the mean directions of scattering structures correlate to the orientation of dentinal tubules and that the mean effective scattering strength provides an estimation of the relative density of dentinal tubules. Thus, this method could be applied to investigate the connection between tubule orientation and fatigue or tensile properties of teeth for a full sample without cutting one, non-representative peace of tooth out of the full sample.
authors.affiliation: Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching, Germany. Electronic address: christoph.jud@tum.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Jud
authors.affiliation: Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Schaff
authors.affiliation: Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching, Germany.
authors.forename: Irene
authors.initials: I
authors.lastname: Zanette
authors.affiliation: Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Wolf
authors.affiliation: Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fehringer
authors.affiliation: Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching, Germany; Institut für diagnostische und interventionelle Radiologie, Klinikum rechts der Isar, Technische Universität München, 81675 München, Germany; Institute for Advanced Study, Technische Universität München, 85768 Garching, Germany.
authors.forename: Franz
authors.initials: F
authors.lastname: Pfeiffer
mesh_terms: D003786:Dental Pulp Cavity; D003804:Dentin; D013718:Tensile Strength; D014054:Tomography; D014965:X-Rays
keywords: Dentin; Dentinal tubules; Tooth; X-ray dark-field; X-ray grating interferometry; X-ray tensor tomography