Introduction: Complex root canal anatomies challenge the limits of our skills, techniques, and abilities to clean the root canal system and achieve a successful endodontic outcome. Background: The following case report depicts a first mandibular molar indicated for root canal treatment after diagnosis of pulpal necrosis and asymptomatic apical periodontitis due to caries. Pre-operative radiographic analysis revealed two distinct periapical lesions and a Periapical Index (PAI) Score of 3. Methods: The tooth was accessed for root canal treatment and instrumented to a final apical size of #20. Additional cleaning and disinfection were performed utilizing the GentleWave® System. After the GentleWave® Procedure, the tooth was obturated with gutta-percha and an epoxy resin based sealer by warm vertical condensation and thermoplasticized gutta-percha backfill. Post-operative radiographs revealed a middle mesial canal not previously visualized during instrumentation or prior to performing the GentleWave Procedure. The newly located, uninstrumented, middle mesial canal was filled with sealer. Results: Recall was performed over a 9-month period. Both clinical and radiographic assessments showed complete healing, no clinical signs or symptoms, and a PAI score of 1 at the 9-month recall. This case illustrates healing after root canal treatment utilizing minimal instrumentation and the GentleWave Procedure, suggesting that GentleWave Procedure can clean and disinfect complex root canal anatomy.