From a medical point of view, a tooth with living pulp is a normal tooth, while a tooth with dead pulp is a tooth with a necrotic nerve that has no feeling and is more fragile and easy to break. The pulp is the main source of nutrient supply for the nerve and tooth. Once the nerve is necrotic, the tooth will lose its nutrient supply and become less tough and more brittle, and its ability to resist external forces will be reduced. If not protected, the tooth will easily split when biting hard objects. Because of the loss of nutrient supply, the color of the dead pulp tooth will gradually become darker and darker. In the case of front teeth, this can affect the aesthetics. A tooth with dead pulp is usually asymptomatic, but the crown may have deep cavities or other hard tissue disorders, or deep periodontal pockets in the filling. The crown is discolored to a dull yellow or gray color and has lost its luster. There is no response to the pulp vitality test, and the temperature test has a certain tolerance threshold for normal pulp to hot and cold stimuli, generally no significant response to water at 20℃-50℃. Dead pulp teeth, on the other hand, do not respond to any temperature stimulus. The periapical images of the affected teeth were not significantly abnormal as shown by radiographs.