In this retrospective study with limited cone-beam computed tomography (limited CBCT), we investigated the anatomic characteristics of the accessory mental foramina and accessory branches of the mandibular canal. The CBCT records of approximately 150 patients were evaluated, and 17 accessory mental foramina were found in 16 patients. The anatomic peculiarities of the mandibular canal that might be relevant to endodontic treatment were observed. Accessory mental foramina tended to exist in the apical area of the first molar and posterior or inferior area of the mental foramen. The accessory branches of the mandibular canal showed common characteristics in the course of gently sloping posterosuperior direction in the buccal surface area. Verification of the existence of accessory mental foramina would prevent accessory nerve injury during periapical surgery. In root canal treatment, the possibility of accessory mental foramina-related nerve paresthesia seems low unless the mental foramen and mandibular canal are injured. Limited CBCT is effective for presurgical 3-dimensional assessment of the neurovascular structures in dentoalveolar treatment.