In the textbook classification, pulpal necrosis means that the entire nerve is in a state of necrosis, inactive and dead. If the pulp is judged to be in this state, root canal treatment should be performed in a timely manner to clean out the necrotic pulp tissue and restore the whole tooth. If left unattended, the necrotic tissue can cause apical inflammation and periapical inflammation, so such a process requires our attention. There are many reasons for pulpal necrosis, for example, some patients have necrosis of the nerve before the pulpal necrosis, without any sensation in between. There may be some reasons for this, such as a history of trauma to the tooth many years ago, especially to the front teeth, if the trauma may cause a slight displacement of the tooth, thus causing damage to the blood supply and nerve of the tooth, thus gradually reducing the blood supply inside the tooth in the middle of the process, slowly causing necrosis of the nerve tissue inside the pulp. The above is more common in the clinic, but also need to remind patients to pay attention to.