Apical closure of an immature root subsequent to apical curettage.

A 7-year-old female presented with a history of trauma to the mandibular central incisor resulting in pulpal necrosis and soft tissue swelling. During apexification treatment, an ultrasonic file was separated and lodged in the periapical tissues. Surgical retrieval of the broken instrument resulted in complete curettage of the periapical tissues. Apical closure occurred following intracanal calcium hydroxide therapy. The findings suggested that hard tissue barrier formation occurred despite the absence of Hertwig's epithelial root sheath and local periapical tissues.