Inflammatory diseases in the dental periapical region are prevalent reactive disorders associated with necrotic dental pulps, more often secondary to dental caries or dental trauma. Radicular periapical abscesses and granulomas are characterized by an acute inflammatory infiltrate rich in neutrophils or by a chronic inflammatory process, respectively. The fibrous capsule of radicular periapical cysts also contains a dense chronic inflammatory component, while its non-keratinized epithelial lining usually leads to the correct diagnosis. The periodontal tissue is also frequently affected by inflammatory or immunologic processes. The current classification of periodontal and peri-implant diseases is comprehensive and recognizes many pathological conditions. Biofilm-induced gingivitis and periodontitis are more often observed among adult patients with a wide age range and no sex predilection. Plasma cell gingivitis is a rare, benign inflammatory condition usually associated with allergic processes. Pyogenic granuloma is characterized by a nonspecific chronic inflammatory infiltrate associated with a local etiologic agent. Microscopically, all these periodontal processes present polymorphous inflammatory infiltrates where plasma cells and lymphocytes predominate. Treatment of these reactive dental and periodontal inflammatory processes is usually local and includes the removal of the irritative agent that is imparting the aggression.