In the beginning of November 2015, a male Asian patient (52 years old) noticed major discomfort and pain in his left TMJ. A week later, as the symptoms got worse and the patient began to experience difficulties in fully opening his mouth. He visited his general dentist, who observed that the patient had an evident limitation in fully opening his mouth (maximum mouth opening of 16 mm), with a discrete clicking noise and without deviation when opening.\nAn extraoral examination demonstrated the absence of asymmetry or bulging, but pain was confirmed when the left-side TMJ was palpated. An intraoral examination did not evince any disease of odontogenic etiology. The patient's medical history was not significant.\nThe general dentist suspected that the patient was affected by temporomandibular disorder and disc displacement. The patient was then medicated with analgesics (500 mg of paracetamol twice a day for 1 week) and radiographic examinations were carried out, with a provisional diagnosis of temporomandibular dysfunction.\nThen, on the radiographic examination, the clinician observed a radiolucent lesion in the superior posterior border of the mandibular ramus (left side). Considering that lesions in mandibular ramus may cause neurological disorders, the dentist checked whether the patient had any neurological complaints, such as paresthesia on the left side of the mandible, but the patient did not report any neurological symptoms. The patient was therefore referred to the university clinic.\nThe panoramic radiograph revealed an oval-shaped radiolucency with well-defined borders that was unilocular and located near the upper third of the ramus, posterior to the mandibular foramen, and close to the mandibular posterior margin. The lesion was homogeneously radiolucent, had no sclerotic margins, no contiguity with the mandible border, and measured about 1 cm in its largest diameter. No alterations were observed in the surrounding tissues, such as periosteal reaction or anatomical structure displacement, as demonstrated in .\nOpen- and closed-mouth TMJ radiographs of the patient were also available, and they confirmed the presence of the oval radiolucency on the left border of the mandibular ramus with radiographic characteristics similar to those observed in the panoramic radiograph (). The TMJ evaluation established that the position of the mandibular condyles was posterior to the articular eminence when the patient's mouth was open, suggesting a reduction of condylar translation.\nThe patient was then referred for MRI to investigate TMJ alterations that might explain the symptoms and confirm the diagnosis of temporomandibular dysfunction. For the radiolucent area, provisional diagnoses of traumatic bone cyst and parotid MBD were also considered.\nMRI was performed in a 3-T system (Siemens Magnetom Skyra, Siemens, Munich, Germany) using dedicated head and neck surface coils. Axial T1- and T2-weighted images were obtained. The section thickness was 4 mm.\nOn MRI, abnormal findings of the bilateral joint discs were not observed, despite the limitation of mouth opening, and the patient's symptoms were relieved by analgesic medications. At the same time, the radiolucent lesion was also further investigated. An axial scout image () demonstrated a tiny hyperintense image eroding the left mandibular ramus on the lingual side, which corresponded to continuous glandular tissue from the parotid gland. A proton-weighted image () and T2-weighted images () exhibited a well-defined hyperintense signal area on the mandibular ramus, surrounded by a thick cortical bone-like area with a hypointense signal.\nDue to the imaging characteristics demonstrated by MRI, it was concluded that the well-defined hyperintense area observed in and was glandular tissue, and other types of bone lesions were then disregarded. The bone cavity was filled by soft tissue, clearly continuous to the parotid gland. The adipose tissue within the glandular cells was responsible for the hyperintense image detected in the T2-weighted sequences.\nAfter the final diagnosis of parotid MBD was made by MRI and the TMJ symptoms completely disappeared, the patient did not come back for regular follow-up visits.
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.