Pulp inactivators cause gradual necrosis of the nerve of the tooth, during which time the patient may experience little or no pain. Current pulp inactivators, also known as deciduous inactivators, are not inherently toxic and are self-limiting; even if sealed for too long, they will not leak outside the apical foramen and will not damage the alveolar bone. Toxic inactivators containing arsenic used in the early years have been eliminated, and the current inactivators mainly contain formaldehyde, cresol, etc., which can make the pulp lose water and die. After the pulp is deactivated, the subsequent root canal treatment can be carried out and the patient will not have any pain.