A 32-year-old woman presented to the Dental Hospital of Universitas Padjadjaran with what initially appeared to be an ordinary complaint: swelling of the gum on the left side of her lower jaw. She had noticed the swelling approximately three months earlier. It had grown slowly and was completely painless. The examining dentist initially suspected an osteoma and referred her for further examination. That decision ultimately changed everything.
The case report, written by drg. Rellyca Sola Gracea, Sp.RKG. Subsp. RDP (K) from the Department of Dental Radiology, Faculty of Dentistry, Universitas Gadjah Mada, together with her colleague from Universitas Padjadjaran, Ria Noerianingsih Firman, was published in the December 2019 edition of the Jurnal Radiologi Dentomaksilofasial Indonesia. The case is important not only because of the rarity of the tumor but also because it demonstrates how three-dimensional imaging technology can capture details that would not be visible on conventional radiographs.
A Tumor Hidden Behind an Unusual Appearance
Sementoblastoma is a benign tumor that accounts for less than one percent of all odontogenic tumors. It originates from ectomesenchymal tissue and develops from tissue resembling cementum, the hard layer covering the tooth root. It most commonly occurs in the mandible, particularly in the premolar and molar regions.
Its classic radiographic appearance is well established: a round, well-defined radiopaque lesion surrounded by a characteristic radiolucent halo. In this case, however, the appearance was different. Cone beam computed tomography (CBCT) revealed a round lesion with lower-than-usual density. Rather than being completely radiopaque, it appeared radiographically intermediate in density. The radial pattern commonly associated with the tumor was also absent.
Why? Because the lesion was still in its early developmental stage.
Sementoblastoma develops progressively, beginning as a radiolucent lesion, followed by a mixed radiolucent-radiopaque appearance, and eventually becoming completely radiopaque once mature. In this case, mineralization was not yet complete, resulting in a relatively low lesion density, with CBCT measurements showing an average value of 372.2 pixel values.
When 2D Imaging Is Not Enough
This is where CBCT played a crucial role. On conventional two-dimensional radiographs, such as panoramic or periapical images, early-stage lesions like this can easily overlap with surrounding anatomical structures. Image superimposition is a classic problem that can lead to diagnostic errors.
CBCT enables multiplanar reconstruction, including coronal, sagittal, and axial views, each providing different but complementary information. The coronal view showed that the lesion had expanded toward the buccal aspect and caused thinning of the cortical bone. The sagittal view revealed the lesion's dimensions, measuring 8.4 mm × 9.5 mm. The axial view showed that the lesion was directly attached to the root of tooth 44.
The most decisive finding was the inverted view on the coronal section. When this mode was activated, the lesion was clearly seen to be directly attached to the tooth root, with no periodontal ligament space or lamina dura separating the lesion from the cementum. There was no gap. This is a key distinguishing feature between sementoblastoma and osteoblastoma. Although the two lesions are histopathologically very similar, osteoblastoma typically retains a visible separation between the lesion and the tooth.
“CBCT examination allows assessment of the involvement of the affected tooth by the sementoblastoma lesion, the lesion margins, and its extent, thereby helping practitioners and clinicians establish a diagnosis of sementoblastoma by identifying its characteristic radiographic features.”
Clinical Diagnosis Requires a Trained Eye
The clinical examination already provided several clues: a hard swelling in the buccal region of teeth 44–45, soft tissue with the same color as the surrounding tissue, no caries, and both teeth remaining vital. Teeth affected by sementoblastoma are generally still vital, except in advanced cases.
However, clinical examination alone was insufficient to establish the diagnosis. Without radiographic imaging, sementoblastoma can easily be mistaken for osteoma, hypercementosis, cemento-ossifying fibroma, osteoblastoma, or other radiopaque lesions, particularly during its early stage. Histopathological examination remains the gold standard for definitive diagnosis, but CBCT provided strong diagnostic guidance before surgical treatment was performed.
The patient was ultimately referred to an oral surgery clinic for enucleation, removal of the tumor together with the affected tooth, curettage, and peripheral ostectomy. This treatment is important to prevent recurrence because, despite being benign, sementoblastoma can behave aggressively, causing root resorption, bone expansion, cortical perforation, and even pathological fractures in certain cases.
Lessons from a Case That Was Nearly Missed
This case report is about more than a rare tumor. It serves as a reminder that radiographic appearances do not always conform to textbook descriptions. Early-stage lesions may present differently from their classic appearance, and without appropriate imaging technology, diagnosis may be delayed until the lesion becomes more aggressive.
For the dental radiology community, the findings reinforce the diagnostic value of CBCT in evaluating atypical lesions. For general clinicians, the message is simpler: when clinical findings and two-dimensional radiographs do not provide a satisfactory answer, the next step is not to wait, but to refer the patient.
Source DOI: https://doi.org/10.32793/jrdi.v3i3.446
Authors: Anny Anggraini; drg. Achmad Zam Zam Aghasy, M.Kes.
Photo: Pexels