Acute conditions in periodontology are diseases of the periodontium that cause its destruction, and are characterized by sudden onset, rapid progression and severe pain. These conditions include periodontal abscess, necrotizing diseases and endo-perio lesions. The main cause of these diseases are anaerobic bacteria from the genera Porphyromonas, Prevotella, Fusobacterium, Treponema and Actinobacillus. In addition to bacteria, predisposing factors such as stress, smoking and poor oral hygiene also play an important role in the development of the disease. A periodontal abscess is a localized and limited accumulation of pus within the gingival wall. It manifests itself as a round protrusion of the gingiva, and the exudation of pus is clinically visible. Necrotizing diseases include necrotizing gingivitis, periodontitis and stomatitis. Necrotizing gingivitis leads to the destruction of the gingiva in the area of the interdental papillae. In necrotizing periodontitis, the destruction leads to the loss of attachment. Necrotizing stomatitis means the extension of destruction to the mucous membrane of the tongue, palate and cheeks. Endodontic periodontal lesions are the result of pathological communication between the pulp and the periodontal pocket, which results in the formation of bone defects, loss of attachment and necrosis of the pulp. Therapy works towards the treatment of the acute condition and pain control. After the acute condition subsides, it is necessary to perform adequate periodontal and endodontic therapy, depending on the condition. In case of systemic symptoms, the patient is prescribed antibiotics.