An unusual dentigerous cyst in a young child.

A dentigerous cyst is an odontogenic developmental cyst associated with the crown of an unerupted tooth. This article describes the case of a 7-year-old girl with painful swelling in the left facial region, prolonged retention of tooth No. 9d, and a displaced tooth No. 9 in eruption. Radiographic examination revealed an extensive radiolucent lesion of approximately 28 mm and displacement of teeth No. 10 and 11. Marsupialization was performed, teeth No. 8d and 9d were removed, and the swelling reduced immediately. At a 2-year follow-up, radiographs revealed that teeth No. 10 and 11 had erupted but were displaced. Routine radiographic examinations are important for children during the eruption phase to prevent and detect any alterations that could damage the permanent dentition and occlusion.