PÁGINA DEL RESIDENTE

What should the diagnosis and treatment be?

¿Cuál sería su diagnóstico y su manejo terapéutico?

A 58-year-old woman without any medical history of interest for this case visited her dentist for an annual dental check-up. The orthopantomography disclosed an unexpected image of bone rarefaction of the mandibular symphysis from tooth apexes 3.4 to 4.4. She was referred to our department with a diagnosis of mandibular cyst (Figs. 1 and 2). The dentist’s therapeutic plan was cystectomy and tooth extraction, associated or not with filler and rehabilitation by dental implantation surgery in a second phase.

We decided to complete the preoperative study with radiography of the floor of the mouth and CT due to the size of the cyst.

Atrophy of the mandibular symphysis (B-w bone)

Atrofia de sínfisis mandibular (hueso B-an)

A. Riaño Argüelles¹, M.A. Bada García², Gorriarán Terreros³

1 Médico Residente.
2 Médico Adjunto.
3 Jefe de Servicio.
Servicio de Cirugía Oral y Maxilofacial.
Hospital Virgen del Camino. Pamplona, España

Correspondence

In the patient’s CT ordered with a clinical-radiologic diagnosis of suspected mandibular cyst, we were surprised to find that the lesion was missing. No cyst was found and the image in the plain radiograph was attributed to severe atrophy of the mandibular symphyseal region (Figs. 3, 4, and 5).

Since the patient was asymptomatic, conservative treatment and follow-up by her dentist-stomatologist was advised, despite her periodontal disease.

The patient had severe grade atrophy in an area of cortical bone, the mandibular symphysis, that is more resistant and has bone-conducting capacity. Nevertheless, this area is deficient in osteogenic cells. The way that the dental pieces that the patient still conserved protected against atrophy was noteworthy. The mandibular symphysis measured 20 mm in height to the dental nerve canal. At the mandibular base, the width was 10 mm, whereas in the area immediately below the apexes, where the atrophy was more marked, the bone width was 4 mm.

Discussion

The patient’s bone atrophy was division B (B-w), which corresponds to a clinical situation of mild-to-moderate atrophy that affects ridge width more than ridge height (ridge height was equal to that of division A > 12 mm).¹ As the bone is resorbed, the available bone width diminishes. This particularly affects vestibular cortical bone because the mandibular cortical bone is thicker on the lingual face (Table 1).

In our opinion, the patient was a candidate for an implant-supported total prosthesis. Different therapeutic options can be proposed, depending on whether we want to take advantage of the residual bone or to generate bone of sufficient width:

• Narrow diameter (3-3.5 mm) root implants can be inserted. However, these implants transfer more stress to ridge bone and carry more risk of fatigue fracture. Consequently, angles of more than 20º are not allowed.

• We could perform osteoplasty to convert her division B status into division A with sufficient width (assuming that a ratio of coronary height to bone height of less than 1 can be achieved). The resected fragment could even be used as an on-lay graft to augment thickness.

• The third therapeutic option was to obtain division A bone using a graft technique (using autogenous bone or bone substitutes, with or without membrane). This requires a healing period of 4-6 months. Bone augmentation is more predictable when only a minimal volume increase is sought and we are trying to widen the bone. It is less predictable for increasing height. We concluded that our patient should take the last therapeutic option and then be fitted for dentures.

Symphyseal mandibular atrophy can radiologically simulate, as in this case, an osteolytic lesion. This raises the problem of differential diagnosis with:

• Unmineralized odontogenic lesions.²

- Ameloblastoma. This benign epithelial neoplasm originates in the follicular epithelium and behaves aggressively. It is frequent in the third to fifth decades of life and it presents as a painless mass. However, it usually is located in the posterior mandible.

- Odontogenic keratocyst. This lesion originates in the dental lamina and parakeratinized caseous material often is found inside the cyst. The tumor has a high rate of recurrence due to the large number of minimal cysts associated with the main cyst.

- Odontogenic or follicular cyst. This cyst is associated above all with impacted teeth, particularly the third molar.

- Radicular cyst. This is the last stage in the progression of secondary periapical inflammation to pulpalnecrosis after inflammatory stimulation of Malassez epithelial remains (residual epithelial cells in the periodontal ligament).

Solitary central myofibroma This infrequent neoplasm affects the muscle and subcutaneous cellular tissue, but rarely bone. When it affects the mandible, it causes cortical expansion with dental mobility. After the tumor is resected, the recurrence rate is low.

Langerhans cells histiocytosis (Hand-Schuller-Christian disease). This low-grade carcinoma originates in Langerhans cells and responds well to surgery. It can be unifocal or multifocal.

Aneurysmal bone cyst.³ This is a pseudocyst that usually is located more in the mandibular corpus and ramus than in the midline, as in our case, because it prefers sites where the venous pressure is relatively high. As for its controversial etiopathogenesis, it is thought that it may be a neoplasm or response to trauma, chronic infection, arteriovenous anomalies, or a degenerative lesion.

Giant-cell granuloma.⁴ This non-neoplastic lesion occurs around the second decade of the life, with a female/male ratio of 2:1. It is particularly frequent during pregnancy and the postpartum period, which suggests that it is hormonedependent. It is characterized by slow-growing masses. When symptomatic, the mass is usually painful. The treatment is surgical and the recurrence rate is 10-15%.

Mandibular fibromyxoma. This is a rare neoplasm that appears between 10 and 50 years of age. This tumor has an aggressive lytic behavior that belies its benign histologic appearance.

Metastatic tumors (clear-cell renal carcinoma, multiple myeloma, brown tumors, etc. ).

To conclude, in our opinion, preoperative CT should be performed when extensive osteolytic lesions are discovered on plain radiography because there is a possibility that the condition may be confused with bone atrophy of atypical distribution.

Correspondence:
Ana Riaño Argüelles
Plaza Rafael Alberti nº9 1ºC
31010 Barañain, Navarra, España

References

1. Misch CE. Disponibilidad de hueso e implantología dental. En: Misch CE. Prótesis Dental sobre implantes. Madrid: Elsevier Mosby 2007;105-29.        [ Links ]

2. Scholl RJ, Kellet M, Neumann DP, Curie AG. Cysts and Cystic lesions of the mandible: Clinical and Radiologic-Histopathologic Review. Radiographics 1999;19: 1107-24.        [ Links ]

3. Goyal A, Tyagi I, Syal R, Agrawal T, Jain M. Primary aneurysmal bone cist of coronoid process. BMC Ear, Nose and Throat Disorders 2006;6:4.        [ Links ]

4. Nackos JS, Wiggins RH, Harnsberger HR. CT and MR Imaging of Giant Cell Granuloma of the Craneofacial Bones. Am J Neuroradiol 2006;27:1651-53.        [ Links ]