Dentigerous cysts are one 01the most prevalent types olodontogenic cysts. Its true histogenesis remains unclear, most authors support a developmental origin, but it has been suggested that exist also an inflammatory origin. The purpose 01 this paper is to present an inflammatory dentigerous cyst 01 the mandibular second premolar in a JO-year-old lemale related to pulpotomized primary tooth and to explain the pathogenesis 01a new type 01dentigerous cyst.