Abstract: This article reports a novel clinical approach for root canal treatment in a case of periapical periodontitis. The patient presented with a buccal wedge-shaped defect exposing the pulp and persistent sinus tract drainage in the mandibular premolar. Radiographic and cone-beam computed tomography (CBCT) evaluation revealed complex root canal anatomy, rendering conventional root canal therapy ineffective for managing the lingual canal. The Department of Stomatology, Peking Union Medical College Hospital (PUMCH) developed an innovative minimally invasive technique—Photoacoustic-steaming United Minimal-invasive Chemomechanical-prepara-tion Hydramatic-obturation(PUMCH) Therapy, which successfully addressed this clinical challenge. This technique employs enhanced chemical disinfection to partially replace mechanical debridement and utilizes negative pressure-guided hydraulic obturation with bioceramic materials. At the 1-month follow-up, complete sinus tract healing and significant symptomatic improvement were observed. This represents the first reported application of PUMCH Therapy in complex root canal anatomy, demonstrating its minimally invasive nature, high efficiency, and precision advantages in endodontic treatment, thereby providing new insights for endodontic therapy.