An abscess in the gums after root canal treatment should not be left alone. Due to the imperfect root canal treatment root tip may appear inflammation, inflammation occurs without effective treatment, extended to the alveolar bone and gums above, it will lead to localized inflammation of the gums, the formation of pus resulting in pus phenomenon. After the patient’s pulp is treated with root canal therapy, if an abscess forms, it means that there is inflammation at the root tip, and it is necessary to carry out a second root canal therapy to take out the root canal material that was originally filled, and then fill it again after anti-inflammatory treatment. If the original material cannot be removed, surgery may be needed to remove the inflamed area of the root tip. After root canal treatment, patients need to have regular follow-ups and pay attention to oral care, and when discomfort occurs, it is recommended to go to the dental hospital in a timely manner, so that the cause of the disease can be clarified and then reasonably treated.