Abstract: Periapical cyst was caused by missing MB2 of the maxillary first molar. This case underwent comprehensive treatment of the affected tooth using methods such as micro root canal retreatment, apical resection and retrograde filling, cyst removal, bone regeneration surgery, and crown restoration. Through clinical examination and CBCT observation, the clinical symptoms of the affected tooth disappeared, and CBCT showed a decrease of bone defect areas and an increase of density. After multidisciplinary joint treatment, the function of the maxillary first molar was successfully preserved, and periapical cysts were eliminated, promoting the regeneration and repair of bone defects.

Key words: MB2 omission, periapical cyst, multidisciplinary therapy