The most common cause of a blister on the edge of the tooth bed is tooth decay, dental caries caused by pulpal infection, and further to the root tip to form an apical abscess, apical abscess rupture after the formation of a chronic fistula manifestation, if you do not get timely treatment may be reoccurring, the formation of an apical abscess. When there is an apical abscess, first of all, you should take a picture to see the apical lesion, alveolar bone destruction, usually can do root canal treatment to control the inflammation of the root tip to achieve the purpose of healing, if the apical lesion is very serious, the alveolar bone destruction is more serious, may need to extract the tooth. When there are no symptoms, the apical abscess enters the chronic phase, not necessarily with clinical symptoms, but also need to be treated, no symptoms just no acute inflammation, if this repeated apical inflammation occurs in the milk teeth, it may affect the growth and development of the permanent teeth, so it should also be actively treated.