Proper removal of the diseased tissue, debriding the canal system, and sealing the defect or cavity, the surgeon prevents or reduces the spread of microorganisms within the periradicular tissues. Treatment modalities following the failure of root canal treatment (RCT) are root canal retreatment (ReRCT). Regeneration of periapical defects may have a significant problem in periradicular surgery. In such circumstances, the gingival connective tissue can proliferate, or the oral epithelium can migrate into the defect, preventing the development of normal trabecular bone. Hard tissue can be restored using guided tissue regeneration (GTR) in conjunction with endodontic treatment for endodontic-periodontal lesions. Treatment of large periapical defects using GTR increases overall treatment success.