Whether the nerve of a tooth has been killed can be judged by the following aspects: 1. A pulp vitality test is performed, and the tooth does not respond to temperature stimulation such as cold or heat, indicating that the tooth has killed the nerve. 2. The clinician uses a high-speed drill to cut the tooth tissue, or uses an expanding needle to probe the root canal without soreness, indicating that the nerve has been killed. 3. The color of the affected tooth tooth compared with the neighboring teeth and teeth of the same name Significant yellowing and darkening indicates that the pulp has lost vitality. 4, X-rays show that the tooth root canal is empty or has been occupied by fillings such as gum tips, indicating that the nerve has been killed and then removed.