Biology of Tooth Structures

Visualizing the interplay between the dentinal tubules and the pulp is helpful in understanding the development of hypersensitivity. The dentin layer that is surrounded by the enamel of the crown and cementum of the root is comprised of a succession of dentinal tubules reaching from the pulp to the dentin enamel junction (Figure 4). The tubular structure of dentin makes it porous with the tubules serving as the portal through which stimuli enter the pulp (Figure 3). The pulp is highly innervated, with fibers that enter the dentinal tubules.28,33,34 The question for a very long time was how far the nerve fibers reach into the dentin. It is now known that nerve fibers are located only in the dentin that is closest to the pulp.28 The question then becomes how stimuli to the outside of the tooth are received by these circumpulpal nerve fibers. Additionally, the odontoblasts, which are the dentin-producing cells, are located near the pulp with the odontoblastic processes being restricted to the inner one-third of the dentinal tubules.35,36 Since neither the odontoblastic processes nor the nerve fibers extend throughout the dentin, one might question whether or not there is another yet unknown mechanism for transmission of the information provided by the stimulus to the pulp.