There are usually two reasons for the darkening of tooth roots: one is the soft tissue cause of tooth roots and the other is the hard tissue cause of tooth roots. The soft tissue cause of tooth roots is mainly soft tissue pigmentation spots, a few normal people can be seen on the surface of the soft tissue of tooth roots with diffuse cloud-like deposits of melanin, caused by excessive production of melanin in the oral mucosa or various pigmentation abnormalities from hemoglobin; this pigmentation varies from person to person, has no pathological significance and does not require treatment. The cause of hard tissue of tooth roots is divided into external coloring and bacterial infection caused by: a small amount of food residue deposited in the recesses of teeth to form soft scale, due to the presence of various bacteria on the surface of teeth, they secrete sticky substances attached to the soft scale, and metabolize sugar to produce lactic acid to corrode the surface of tooth enamel, over time will form yellow or black plaque, calculus, so that the roots of teeth black, like to drink tea, smoke, drink coffee People will also form melanin deposits on the root of teeth, called tea scale, tobacco stains, etc., which will make the root of teeth black; another situation is that the root of teeth is exposed due to gum atrophy in old patients, and the root surface of teeth is infected with bacteria secondary to form root surface caries, which causes the root of teeth black, which is a kind of tooth decay. It is recommended to diagnose and treat the tooth root blackening under any reason in time to avoid complications and serious consequences.