Abstract
RATIONALE: There is an increasing tendency for case reports to reveal anatomical aberrances in mandibular first molars, such as the lateral and accessory canals. Thus, clinicians should pay special attention to anatomic variances when dealing with mandibular first molars requiring endodontic treatment to prevent reinfection within the root canal system, which is responsible for the failure of root canal treatment. PATIENT CONCERNS: This article presents the clinical report and successful root canal treatment of a 24-year-old healthy female patient with an extensive periapical lesion in a 6-canal first mandibular molar. The patient was admitted to the endodontic department because of a periapical abscess found 1 month ago in her left mandibular first molar. DIAGNOSIS: Chronic apical periodontitis was diagnosed based on clinical examination coupled with radiographic and cone-beam computed tomography images. INTERVENTIONS: The treatment plan was to first perform root canal therapy and then perform clinical observation. OUTCOMES: During 1-year follow-up period, the treated tooth was asymptomatic, and complete resolution of the extensive apical lesion was eventually achieved, as shown in the postoperative cone-beam computed tomography images and clinical examination. LESSONS: The present case emphasizes the importance of a comprehensive understanding of root canal morphology, especially rare anatomical variations, to ensure successful root canal treatment. Additionally, the case report adds to the library of previously reported cases of extensive periapical lesions with a direct connection to the root canal system, which demonstrates the potential clinical advantages of root canal therapy as a conservative nonsurgical approach in these cases.