There are several reasons why tooth extraction can cause swelling of the face: 1. The presence of chronic inflammatory lesions such as granulation tissue in the extraction sockets, and the spread of bacteria along the blood circulation to multiple gaps of the jaw and face after tooth extraction, causing swelling and pain of the face. 2. Inadvertent damage to tissue structures such as capillaries during tooth extraction, resulting in massive bleeding and increased exudate from the traumatic surface, which can enter the jaw gap and cause swelling. 3. The application of operations such as incision of gums, cutting mucosal flaps, separating soft tissues, removing alveolar bone, splitting crowns and other operations, which form a large trauma to the organism and cause tissue reaction.