Gum swelling after filling may be due to two common diseases: 1, local bad stimulation leads to gingival inflammation is common after tooth adjacent caries filling, due to filling process not placed adjacent forming piece leads to filling material formation overhang, also can be adjacent to restore too loose leading to food embedding, these two situations can cause gum swelling and bleeding in the gap, accompanied by biting pain and hot and cold stimulation discomfort, this kind of affected teeth should be 2, due to the wrong diagnosis, mistakenly treat the tooth with periapical infection as caries for filling treatment, the pulp of this kind of tooth has necrosis due to bacterial infection leading to apical inflammation, there will be no obvious discomfort when it is in chronic stage, once filling treatment will make the original aerobic environment of bacteria in root canal suddenly change causing acute attack of inflammation, the clinical manifestation is severe tooth The clinical manifestation is a severe tooth throbbing pain with varying degrees of tooth loosening and swelling of the apical part of the tooth, pus, and pus often breaks through the bone wall and periosteum to reach the subgingival area to form a subgingival abscess, in which case root canal treatment should be performed on the affected tooth.