A 40-year-old male patient was referred to a private clinic for endodontic treatment of teeth with a periapical lesion in his premolar region of mandible that was discovered during routine radiographic examination. Panoramic radiography revealed a unilocular periapical radiolucency below the apex of the mandibular left canine extending to the second premolar (Figure ). On the periapical radiograph, the lesion mimicked a radicular cyst; however, the teeth were asymptomatic and the periodontal ligament space and lamina dura were intact. The teeth also gave a positive response to the sensibility tests. The patient had no history of trauma to the jaw. Clinical examination revealed no facial asymmetry and no lymphadenopathy. The most likely diagnosis was a nonodontogenic cyst.\nIt was decided to examine the lesion by CBCT to evaluate the relationship of the lesion with its surrounding structures and reach a definite diagnosis. CBCT images were taken by NewTom CBCT system (NewTom VG) with the exposure settings of 110 kVp, 59.62 mA, 4.3 seconds exposure time, 5 × 5 cm field of view, and 14-bits gray scale. The CBCT scans revealed a well-defined lingual defect in the canine to second premolar region with no connection to the base of the mandible and a cyst-like appearance. Evaluation of axial, coronal, and sagittal sections confirmed a lingual wall defect; the buccal wall was intact and there was no expansion. The mental foramen was clearly demarcated from the radiolucency by cortical bone and was not part of the lesion. The root apices of the first and second premolars directly contacted the lesion with no sign of resorption (Figure ).\nFor more evaluation of the internal contents of the defect, we used the software's ability to determine the gray scale value. The gray scale value of the main contents of the defect in the middle section was approximately in the range of −78 to 202 with a mean (± standard deviation) of 108 (±31). The mean gray scale value for the adjacent lingual soft tissue was 108 (±52). The lesion was clearly related to the adjacent lingual soft tissue, which could be the anatomical location of sublingual gland with approximately similar gray scale value (Figure ). Thus, this defect could be classified into the group with range of soft tissues.\nConsidering the dental and clinical history of the patient and the radiographic features, the defect was diagnosed as a premolar region variant of lingual bone depression and regular follow-ups were scheduled for the patient.
A 76-year-old at death male Caucasian cadaveric head (fresh-frozen) was dissected. During routine dissection of the head, the mandible was dissected, and the soft tissues of the mandible were removed. After the mandible was separated from the head, a large bony defect was found on the lingual surface of the right mandible, which was located 25.2 mm anterior to the angle of the mandible and 3.3 mm superior to the inferior border of the mandible. The shape and size of the bony defect was oval and 10.8×6.0 mm, respectively (, ). The bony defect had a smooth surface and did not show any pathological condition. Therefore, it was determined to be an SBC. The SBC had continuity with the right mylohyoid groove. The depth of the SBC and width of the mandible at the SBC was 4.15 mm, 3.14 mm, respectively. The SBC was not observed on the left side.