Endodontic Treatment of a Mandibular Premolar Tooth with Two Canals and Extra Lateral Canals ¹Emek Bayındır ¹Öznur Sarıyılmaz ¹Çanakkale Onsekiz Mart University, Faculty of Dentistry, Department of Endodontics Aim: The purpose is to present the treatment of a twocanalled mandibular premolar tooth with periapical and lateral lesions using conventional canal treatment techniques. Case Description: A 40-year-old female patient presented to our clinic with a complaint of pain in tooth number 44. In the clinical examination, percussion was observed and in the radiographic examination, lesions were identified at the apex and mesial aspect of the tooth's middle third. In the radiograph, it was determined that the root canal has Vertucci Type V morphology and the presence of a separate lesion in the mesial middle region of the root suggested the existence of a lateral canal. Therefore, a cone beam computer tomography was requested to confirm the canal configuration of the patient. The canal treatment was started under the dental operating microscope, progress was made in the canals that bifurcate in the apical 2/3 and then calcium hydroxide was placed, and the patient was scheduled for a follow-up appointment one week later. In the second session, it was determined that the patient's complaints had subsided and the filling session was initiated. The lateral canal filling was achieved using EDDY activation applied to the root canal sealer, and the shaped canals were filled using the warm vertical compaction technique (down pack + back fill). Findings: It was determined that the lesion had decreased in the patient's 3 and 6-month follow-up radiographs, and her complaints had completely disappeared. Conclusion: It has been demonstrated that a two-canalled lower premolar tooth with additional lateral canals can be successfully treated with recent endodontic methods. Keywords: lateral canal, activation of sealer