Histopathological Study of Regenerative Endodontic Therapy on an Immature Mandibular Second Premolar With Pulp Necrosis: A Case Report

Regenerative endodontic therapy (revascularization) for immature permanent teeth with pulp necrosis and/or apical periodontitis is an effective treatment to promote root maturation. Previous histological studies have reported the formation of cementoid or osteoid tissue and periodontal ligament-like tissue within the root canals. This case report presents the histopathological findings of a human immature permanent tooth with pulp necrosis following revascularization. A 11-year-old male patient presented with tenderness on biting and the formation of a sinus tract in the mandibular right second premolar (tooth #29), diagnosed as pulp necrosis with symptomatic apical periodontitis. Revascularization was performed using calcium hydroxide as an intracanal medicament, with reference to the American Association of Endodontists (AAE) 2018 Position Paper on Regenerative Endodontics. At the 12-month follow-up, radiographs showed thickening of the canal walls, apical narrowing, root elongation, and recovery of pulp sensibility. The tooth was later extracted for orthodontic reasons at 42 months and processed for histological examination. Histological evaluation revealed cementum-like hard tissue continuous with the existing dentin in the apical region, suggesting apical closure. In contrast, the coronal portion showed less mature cementum-like tissue accompanied by loose connective tissue and neovascularization. These findings indicate that revascularization with calcium hydroxide can induce the formation of cementum-like and dentin-like tissues with vascular regeneration in immature permanent teeth with pulp necrosis.