The second time the nerve was killed and changed, the pain was less severe. Because of the acute inflammation, the inflammation was significantly reduced after the first pulp drainage was performed. The pain is less pronounced when the second change is performed. Some patients may have localized swelling and mild pain after the dressing change, and may consider taking anti-inflammatory medication in combination. After the root tip is really pain-free, then the next step of filling the root canal is performed. Therefore, killing the nerve is a gradual relief of the apical inflammation and there may be pain in between, but the pain is not very pronounced at this time and most of the pain does not recur. Therefore, if you have pulpitis or periapical inflammation, you need to have root canal treatment in a timely manner.