The healthy root pulp, degradation and regeneration

2. In the root, the Hopewell-Smith and Tomes granular layers constitute the outer limits (each of these layers being 8-15μm thick, with a total thickness approximately of 30μm). Both layers are located beneath the dentino-enamel or the dentinocementum junctions. In the outer mantle dentin, they contain a few tubules that are bent, and display minute diameter. In the granular layer, the peripheral layers include unfilled interglobular spaces (or calcospheritic structures), apparently empty but actually containing GAGs. These outer layers constitute the limits of the sound circumpulpal dentin (primary and secondary dentins). The pulp volume displays variable thickness, depending the age of the tooth.1