Sodium hypochlorite (NaOCl) is widely utilized as an endodontic irrigant due to its antimicrobial efficacy and tissue-dissolving capabilities. Its mechanisms of action involve hypochlorous acid, chloramines, and the solution’s high alkalinity, which contribute to tissue dissolution through protein degradation and saponification of lipids. While effective for disinfecting root canals, unintended extrusion beyond the apical foramen can cause severe chemical injury. Although cases of NaOCl accidents have been reported, detailed serial clinical documentation of tissue responses following such incidents remains limited in the literature. This case report presents a 66-year-old female who developed acute pain during root canal irrigation of the mandibular left lateral incisor (#32) due to NaOCl extrusion. Initial findings included a mucosal opening suggestive of subepithelial necrosis, followed by bilateral chin ecchymosis and intraoral tissue degradation. Over the following days, signs of liquefactive and fat necrosis emerged, eventually progressing to tissue remodeling with re-epithelialization and fibrotic healing. Cone-beam computed tomography revealed a periapical lesion with buccal bone fenestration, indicating a possible anatomical route for extrusion. The root canal was obturated once soft tissue healing was evident, and by 12 weeks, the affected area had fully recovered with scar-like integration into surrounding mucosa. This case report highlights the importance of identifying anatomical risk factors such as buccal bone fenestration to prevent extrusion and underscores the value of timely, conservative management. Close follow-up is important for monitoring soft tissue changes and guiding appropriate intervention.

• 이명진(전북대학교 치과대학 치과보존학교실 구강생체과학연구소, 전북대학교 임상의학연구소, 전북대학교병원 의생명연구원) | Myung Jin Lee (Department of Conservative Dentistry, School of Dentistry and Institute of Oral Bioscience, Jeonbuk National University, Jeonju, 54896, Republic of Korea, Research Institute of Clinical Medicine of Jeonbuk National University, Jeonju, 54907, Republic of Korea, Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, 54907, Republic of Korea) Corresponding author