To explore the discovery and treatment of multiple root canals in the maxillary second premolar to provide a reference for root canal therapy.

A case of maxillary second premolar occlusal discomfort accompanied by cold and heat stimulation pain and spontaneous pain was analyzed retrospectively.

In this case, the number of roots and root canals in the tooth was determined by CBCT to be three roots with four canals. Root canal therapy was performed with Ni-Ti endodontic files and thermoplastic gutta-percha via root optical microscopy. The clinical symptoms disappeared after the operation.

The maxillary second premolar root canal system is complex, and additional root canals can be found and located with CBCT and optical microscopy. High-quality root canal therapy was completed.

To investigate treatment strategies for chronic periapical periodontitis in prematurely erupted premolars and provide guidance for managing pulp and periapical diseases in young permanent teeth with immature roots.

A regenerative endodontic procedure (REP) was performed on a prematurely erupted maxillary left first premolar (tooth 24) at Nolla stage Ⅶ with chronic apical periodontitis, following standardized protocols including root canal irrigation, disinfection, and coronal sealing. The case was followed up, and a literature review was conducted.

Clinical resolution of symptoms was observed on tooth 24, with sustained root development. After a 20-month follow-up, the tooth had restored biological function. Literature synthesis revealed that periapical infections in prematurely erupted permanent teeth predominently arise from pulp exposure and bacterial infection, with retrograde infection being rare. For young permanent teeth with necrotic pulp, regenerative endodontic procedures has been established as the treatment of choice to promote apical closure and root maturation. The critical steps of regenerative endodontic procedures include thorough disinfection, induced bleeding to form a fibrin scaffold, and coronal sealing to facilitate stem cell recruitment and differentiation.

Regenerative endodontic procedures represents an effective and viable treatment option for prematurely erupted young permanent teeth with chronic periapical periodontitis.