Numerical density and distributional pattern of dentin tubules.

By a new method the numerical density and distributional pattern of transversely cut dentin tubules and the diameters of their peritubular dentin walls were measured in sections near the dentin-enamel junction (DEJ), midway to the pulp, and near the pulp wall in human premolars. For each section the mean and standard deviation of these variables were expressed. At all three levels the measurements comprised the same bundle of tubules from the DEJ to pulp in the coronal dentin. The number of tubules per square millimeter increased more than three times, and the diameters of peritubular dentin decreased one-tenth, whereas central distances between tubules were halved from DEJ to pulp. Thus the pulpward reduction of intertubular dentin is quantified. The distribution of the tubules is not regularly hexagonal, but the distances between them at each given depth are still very uniform in all directions. The pattern of cross-cut tubules often showed distinct short curved rows. The quantitative method might be used to determine taxonomic affinities.