Figure 1. Schematic of convergence of tubules toward the pulp. (A) Periphery of the dentin. Most surface area is occupied by intertubular dentin (), with a few tubules surrounded by hypermineralized peritubular dentin (). (B) Near the pulp, the increase in tubule diameter has occurred largely at the expense of the peritubular dentin. This substrate has a high protein content. As the remaining dentin is made thinner (from A to B), the permeability of the dentin increases, because both diameter and density of dentinal tubules are increased. Reprinted with permission from Elsevier.