Management of Failed Apexification Associated with Internal Root Resorption and Apical Calcification: A 56-Month Case Report.

Objective: To report the conservative management of a complex failed apexification in a permanent premolar complicated by severe internal root resorption, irregular apical calcification, and exceptionally thin root canal walls and to evaluate its long-term (56-month) clinical and radiographic outcomes. Methods: A 27-year-old male presented with chronic apical periodontitis in the right mandibular first premolar. A previous apexification attempt had failed, resulting in arrested root development, an apical calcified bridge, and extensive internal root resorption. CBCT imaging revealed a critical root canal wall thickness of less than 1 mm in the middle and coronal thirds. To avoid extraction or invasive surgery, a non-surgical apical barrier technique was performed. Due to the severe structural compromise and high risk of root fracture, mechanical instrumentation was minimized; instead, chemomechanical debridement was optimized using Er:YAG laser-activated irrigation. The apical region was sealed with a bioceramic material (iRoot BP), and the weakened root structure was reinforced intraradicularly with dual-cure flowable resin, followed by progressive occlusal adjustments. Results: At the 3-month follow-up, the patient was completely asymptomatic, and radiographs indicated initial periapical bone healing. The 56-month follow-up demonstrated progressive formation of mineralized tissue, apparent thickening of the root canal walls at root apex, complete resolution of periapical radiolucency, and a stable, functional occlusion. Conclusions: This case demonstrates that teeth with severe structural compromise and internal resorption following failed apexification are not necessarily hopeless. A tailored conservative approach, integrating advanced laser-assisted disinfection, bioceramic apical barriers, internal resin reinforcement, and meticulous occlusal management, can yield highly successful long-term outcomes, ensuring the preservation of the natural dentition.