Periapical radiograph

The periapical radiograph of the LL7 (Figure 5.1.1) revealed:

• Good bone levels.
• Large amalgam restoration with the core build‐up extending into the mesial and distal canals and satisfactory margins.
• Both roots have a slightly curved morphology.
• Existing root filling in both roots, terminating short of the radiographic apices.
• A uniform and intact periodontal ligament.

Conventional two‐dimensional (2D) radiographs have limitations and are affected by superimposition, geometrical distortion and anatomical noise. If the periapical lesion is confined to the cancellous bone it may not be detected with conventional radiographs. Cone beam computed tomography (CBCT) scans are three‐dimensional (3D) and have a higher sensitivity and specificity for the detection of periapical pathology when compared to conventional radiographs. The ionising radiation associated with CBCT needs to be justified such that the additional information from the scan provides beneficial information for the management of the case. A high‐resolution, small field‐of‐view CBCT (Morita 3De) was warranted in this case to check for pathology (Figure 5.1.2).

Findings from cone beam computed tomography for the LL7

• The mesial root has an S‐shape morphology. There is radiolucent bone in the furcation, but essentially a normal lamina dura.
• In the sagittal plane, there is a slightly widened apical lamina dura around the distal root.

What is the diagnosis?

The symptoms (specifically, tenderness to chewing) are consistent with periradicular inflammation, possibly due to infection. The differential diagnosis could include (i) post‐treatment endodontic infection, (ii) a crack, or (iii) occlusal trauma. However, there were no corroborating findings seen clinically or radiographically, so the precise aetiology was uncertain.

As clinicians, we are accustomed to operative intervention; indeed, many patients expect it. Yet when there is an uncertain aetiology due to a mismatch in history, symptoms and clinical findings, or when the findings are inconclusive, it is certainly acceptable to wait, monitor and review.

Depending on the diagnosis, the potential treatment options might include monitor and review, endodontic retreatment or extraction. In this case, as the symptoms were settling and the diagnosis was uncertain, in discussion with the patient the decision was to recall in one year but review at any time if there were recurrent symptoms or signs.

Review

One year later, the patient returned for review. Over the year, there had been intermittent mild symptoms with occasional tenderness to chewing.

A new periapical radiograph revealed a developing periapical radiolucency (Figure 5.1.3). Therefore, with this new radiographic finding it was then possible to clarify the diagnosis as symptomatic apical periodontitis associated with the previously root‐filled lower left second molar.

What is the most likely aetiology?

The possible reasons for the recurrent periapical infection could be renewed endodontic infection via coronal microleakage, or a crack, or infection that persisted after the previous root canal treatment and some ecological disturbance that allowed the infection to reach a clinical level. Special properties are required by microorganisms for long‐term survival in the inhospitable environment of the filled root canal (Table 5.1.1).