Broken pins are a complication of root canal treatment, and the incidence of broken pins in clinical practice is not high. However, when a broken pin occurs, the doctor will usually try to remove the broken pin. When the broken pin cannot be removed, it may be kept in the root canal as a filling material. A broken needle in the root canal is different from a broken needle left inside the body during surgery because the root canal is a closed system, so even if the broken needle remains in the root canal, it will not flow with the blood and will only be fixed in one location. Therefore, even if a broken needle occurs, if the inflammatory condition can be controlled, it will not cause excessive side effects if left in the root canal.