Cavern (synonymous with cavernitis) is the process of resorption of the root apex or neck of the tooth pulp with an inflammatory focus in dentin, characterized by the appearance of apical periodontitis caused by hypothermia and hypovitaminosis with poor nutrition and insufficient thermal conditions. The cavernous process, without external reaction, developed up to 3–5 years, after which it took a chronic course with the formation of fibrous tissue in the apical part of the root system, thickening of the walls of the root canal, and reactive gingivitis. At the same time, the color of the tooth changed from bluish to gray, which is associated with the polycyclic activity of a specific enzyme.