Trauma-induced dentigerous cyst involving an inverted impacted mesiodens: case report.

There have been only a small number of studies on the association of dentigerous cysts with supernumerary teeth. The purpose of this article was to report the case of a dentigerous cyst associated with an impacted inverted mesiodens that developed secondary to trauma to its predecessor, a non-vital permanent maxillary central incisor. As a consequence of trauma, the central incisor's root development was prematurely arrested and the open apex lay close to the follicle of the underlying inverted mesiodens. The negligent attitude of both the child and parent in seeking dental treatment was a contributing factor. The case was further complicated by impaction of the adjacent permanent central incisor due to the presence of another unerupted but normally oriented mesiodens. Occlusal and Intraoral periapical radiographs revealed a well-defined radiolucent area surrounding the inverted mesiodens. Microscopic examination revealed a cystic cavity that was lined by 2-3 cell thick non-keratinized stratified squamous epithelium resembling reduced enamel epithelium. Dentigerous cysts associated with impacted permanent teeth are not uncommon but the cysts which are induced by trauma are uncommon. Development of trauma-induced dentigerous cyst around an inverted impacted mesiodens associated with the periapical area of a traumatized, non-vital, immature permanent central incisor is a rare occurrence.