<unk>  or apical<unk>  (AP) is an acute or chronic inflammatory lesion around the apex of a tooth root, most commonly caused by bacterial invasion of the pulp of the tooth. It is a likely outcome of untreated dental caries (tooth decay), and in such cases it can be considered a sequela in the natural history of tooth decay, irreversible pulpitis and pulpal necrosis. Other causes can include occlusal trauma due to 'high spots' after restoration work, extrusion from the tooth of root filling material, or bacterial invasion and infection from the gums.<unk>  may develop into a<unk>  abscess, where a collection of pus forms at the end of the root, the consequence of spread of infection from the tooth pulp (odontogenic infection), or into a<unk>  cyst, where an epithelial lined, fluid-filled structure forms. Etymologically, the name refers to inflammation (Latin, -itis) around (peri- ) the root tip or apex (-apical) of the tooth (-odont-). Periradicular<unk>  is an alternative term.
Periapical periodontitis
Chronic periodontitis
Periodontal abscess
Periodontal disease
Drug-related gingival hyperplasia
Dental fluorosis
Denture-related stomatitis
Desquamative gingivitis