Bacteria can penetrate through various access portals in the deeper tissue layers of the cheek, lip and mouth base. These portals are, for example, the root tips in the case of infected root canals, parodontal pockets as well as infected alveolar bone after extractions. The contact between connective tissue and bacteria triggers severe inflammation. If this serous exudate cannot drain, it results in swelling. Increased immigration of lymphocytes and granulocytes causes an infiltrate. Tissue melting causes a cavity filled with pus, an abscess, after two or three days.

Therapy consists in removal of the accumulated secretion and bacteria combat. An abscess tends to spontaneously open and drain pus after a few days. If therapy is not applied, a fistula will often remain, through which the inflammatory secretion can drain. The opening of an abscess with a scalpel is called incision. An excision, on the other hand, is understood as the excavation of pathologically altered tissue.  

Complicated dentition (Dentitio difficilis) predominantly affects the lower wisdom teeth, as the tooth cannot penetrate fully due to lack of space. However, as gingiva is not conjoined with enamel, this incomplete breakthrough creates a dirt niche. The mucosa forms a hood over a part of the chewing surface. Antibiotic therapy and surgical opening of the niche is performed when severe cases are accompanied by trismus and soft-part swelling. The prophylactic removal of such wisdom teeth prevents the recurrence of this clinical picture.

If the cause of the infiltrate or abscess formation is a parodontal pocket, secretion is achieved through incision or by opening the pocket. In severe cases the inflammation has to be combated with antibiotics. Parodontitis is treated or the tooth is removed after the acute symptoms have abated.