Conservative management of a traumatic large cyst-like periapical lesion with a separated apical root structure in a young permanent tooth: a case report

Traumatic dental injury in immature permanent teeth may compromise pulp vitality and root development. Separated apical root formation, also described as phantom or detached root, is uncommon, and its occurrence with a large cyst-like periapical lesion after trauma is rarely reported. This case describes a young permanent incisor with post-traumatic pulp necrosis, a large cyst-like periapical lesion, and a radiographic structure consistent with separated apical root formation, highlighting its diagnostic and treatment-planning implications. An 11-year-old girl was referred for a large periapical radiolucency in the maxillary anterior region three years after traumatic crown fracture. Teeth 11 and 12 were non-vital. Radiographic examination showed incomplete apical closure of tooth 11, a 17 × 9 × 13 mm cyst-like periapical lesion involving the adjacent root area, and a separated apical root structure at the lesion periphery. Tooth 12 had complete root development. Root canal therapy was performed for tooth 12, and conservative non-surgical endodontic management was performed for tooth 11, including intracanal drainage, irrigation, calcium hydroxide medication, and subsequent Vitapex placement as an interim intracanal medicament. At 26 months, radiographic follow-up showed substantial but incomplete lesion regression, followed by definitive apical barrier placement and permanent composite resin restorations for teeth 11. This case documents a rare radiographic presentation consistent with separated apical root formation after traumatic injury in an immature permanent tooth with pulp necrosis and a large cyst-like periapical lesion. Recognition of this pattern may help clinicians distinguish it from root fracture and inform conservative, case-specific treatment planning.