Claudia Hoffman, D.D.S.
Diagnosing a Radiolucent Lesion in the Posterior Mandible
Claudia Hoffman

Claudia Hoffman

AS ALL DENTISTS KNOW, accurate diagnosis is crucial and can be challenging.  A 46-year-old African American female presented to me with the chief complaint,  “I went for my regular check-up, and my dentist told me I need a root canal.”  The patient had an unremarkable medical history, and she had seen her dentist annually for the past 20 years. 
     Upon clinical presentation, no nodes, masses, or swelling were apparent. The patient had good oral hygiene with a dental history of endodontics, restorative, fixed, and extractions. 
 The patient was referred for evaluation of tooth #19.  Radiographically, #19 had a large 2 cm well-delineated periapical radiolucency at the apex of the distal root. The tooth had been restored many years earlier with a MOD amalgam.  (See Figure 1.)
    The clinical exam revealed an asymptomatic molar that tested vital with a normal response to cold stimuli. Number 19 was negative to percussion and palpation. There was a mild buccal expansion at the apex of #19. The tooth exhibited no mobility and pockets less than 3 mm.  The fact that the tooth tested vital was unusual, but there was the possibility that only the distal root had been necrotic and that the mesial roots may have remained vital. 
    The patient was referred to an oral and maxillofacial surgeon for consultation regarding the lesion on #19.  The oral surgeon evaluated #19 and reported that the lesion of the distal root was likely a granuloma with a small amount of buccal expansion with over-lying mucosa intact. The oral surgeon recommended root canal therapy and re-evaluation in three to six months; if the lesion increased or did not respond to treatment, #19 would receive an incisional biopsy, exploration, or both.
    The differential diagnosis for this radiolucent lesion in the posterior mandible is:
  • Periapical granuloma: involves a nonvital tooth
  • Periapical cyst: nonvital tooth
  • Periapical cemento-osseous dysplasia (early stages): mostly in African American females; usually apical to mandibular anteriors; teeth are vital
  • Odontogenic keratocyst: unilocular radiolucency
  • Ameloblastoma: especially in the posterior mandible; often associated with an impacted tooth (multilocular radiolucency)
  • Traumatic bone cyst: mandibular lesion that scallops up between roots of teeth; usually in younger patients
  •     The root canal therapy was performed as indicated, and upon access into the canals vital tissue was evident in the distal and mesial canals.  The tooth was completed, and the patient remained asymptomatic.  The patient was then referred back to the oral and maxillofacial surgeon for re-evaluation, and the pre-operative treatment was to biopsy the lesion and possibly to perform an apicoectomy on the distal root.  The results of the biopsy would determine future proceedings. 
        After the biopsy, the surgical report came back showing a diagnosis of viable bone and connective tissue consistent with a traumatic (simple) bone cyst in the area around #19.  This is a benign, empty, or fluid-containing cavity within bone devoid of an epithelial lining, a  pseudocyst.  The lesion is more common than the literature indicates, and the etiology is uncertain.  The typical presentation is a well-delineated radiolucent defect that can range from 1 to 10 cm, with domelike projections that scallop upward between roots.  The treatment is surgical exploration and curettage, the prognosis is excellent, and reoccurrence is rare.  Figure 2 shows the tooth at the time of the four-month recall, illustrating that the majority of the lesion has filled in.
    Summer 2004
    Figure 1

    FIGURE 1: Radiograph of #19, showing a large well-delineated periapical radiolucency at the apex of the distal root. 

    Figure 2

    FIGURE 2: Showing the tooth at the time of the four-month recall.

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