After the tooth is decayed, only the residual root is left, which needs to be extracted, patients do not need to worry too much, such a root is better to be extracted clinically, as long as the root is anesthetized locally through Ativan, and then through the apical tappet, the root can be tapped out, and the whole process does not have any pain, and the trauma is also very small. If the root is left in the mouth for a long period of time, it will not only cause apical inflammation and resorption of the alveolar bone, but also the sharp part of the stump may stimulate the mucous membrane of the mouth and gums, which may induce oral cancer. Therefore, the residual root left in the mouth is harmful but not beneficial, it is recommended that the patient timely extraction, three months after the extraction can be normal restoration of teeth.