Fig. 1.

Tooth structure and neuron innervation. (Reprinted Quintessence International with permission from Europe PubMed Center.) (a) Cut-away image of a human tooth illustrating several key composite layers; (b) SEM image of dentine showing solid dentine material and dentinal microtubules running perpendicularly from the pulpal wall toward dentine-enamel junction; (c) schematic of the innervation of a dentinal microtubule. The pulpal terminus of a dentinal microtubule usually contains the terminus of a nociceptor and a process extended by an odontoblast. The terminal fibril of the nociceptor ends with a terminal bead that is rich in ion channels that are sensitive to noxious stimuli including heat and shear stress.