= Dentinal tubule
A \b[dentinal tubule] is a microscopic channel in <dentine>, within the mineralized material formed by <odontoblasts>. The tubule network records the paths of <odontoblast> processes as <dentine> is deposited. A tubule is a structural channel; whether a prepared specimen contains fluid, a cellular process or an empty space depends on the tissue and its preparation.<Relation between the Macroscopic Pattern of Elephant Ivory and Its Three-Dimensional Micro-Tubular Network by M. Albéric and others>[Introduction: tubules as evidence of odontoblast migration during tusk growth]{ref}
Elephant <ivory> provides a useful structural example. In a2017 study, observations of different cut planes and <computed tomography> using <synchrotron radiation> connected visible tubule profiles with their three-dimensional trajectories. A tube cut across, along or obliquely does not present the same two-dimensional profile. Consequently, a collection of oval profiles in a section need not consist of isolated oval cavities.<Relation between the Macroscopic Pattern of Elephant Ivory and Its Three-Dimensional Micro-Tubular Network by M. Albéric and others>[Abstract; Materials and Methods; Discussion: microtubule network]{ref}
A deliberately simplified transport example makes the channel size matter. For steady <laminar flow> through a straight circular tube, the <Hagen-Poiseuille equation> gives $Q=\pi r^4\Delta p/(8\mu L)$, where $r$ is tube radius, $L$ length and $\mu$ fluid <dynamic viscosity>. Doubling $r$ would multiply $Q$ by16 at fixed pressure difference and length. Real <dentinal tubules> branch, vary in width and may be obstructed, so this ideal calculation illustrates sensitivity to geometry rather than predicting a whole <tooth>'s permeability.
Back to article page
