Diagnosis and treatment planning

What is the diagnosis?

The diagnosis reached was chronic periapical periodontitis, associated with an existing (inadequate) root canal treatment.

The long post-treatment period and recent symptoms preclude the possibility that this is a healing lesion. Most radiolucent lesions heal within 6 months to 2 years, although some lesions may take 4–5 years to resolve. The size of the periapical radiolucency, together with the fact that the root canal treatment was done 7 years earlier, suggests that the infection has been present for a considerable time, probably many years.

What is the most likely aetiology?

The most likely explanation is infection that persisted after the previous root canal treatment (although new infection via coronal microleakage is a possibility that cannot be ruled out). It is interesting to consider the special properties required by microorganisms for long-term survival in the inhospitable environment of the filled root canal (Table 5.1.1).

Table 5.1.1 Properties required by microorganisms to survive in the root filled canal and cause post-treatment apical periodontitis

What are the treatment options?

The potential treatment options to be discussed with the patient are:

• Root canal re-treatment.
• Surgical endodontics.
• Extraction.
• Leave alone.

Although the antibiotic treatment had resolved the patient’s symptoms, it was a temporary solution. The ideal approach was to save this tooth as a functional unit within the dentition, and retention was the patient’s preference. This left two options: either root canal re-treatment or surgical endodontics.

Surgical endodontics has the advantage that the post-retained crown can be left undisturbed; in addition, patient treatment time is less compared with (non-surgical) re-treatment. A general disadvantage of this option is that surgery does not allow an opportunity for control of infection within the entire root canal system, and the outcome depends on the quality and depth of the root end filling. Additional issues specific to surgical endodontics on a lower molar are the thickness of the buccal bone which hampers access and vision. Also, the proximity of the periapical lesion to the inferior alveolar canal affects the risk level. In this case, the pre-operative radiograph shows that the lower border of the periapical lesion is within a few millimetres from the inferior alveolar canal.

Root canal re-treatment has the advantage of access to the infected root canal system, which provides the best opportunity for elimination of the microbial aetiology. Re-treatment to a high standard, based on infection control, invariably provides the best chances for long-term success. A disadvantage of re-treatment is the complexity and risks of post-removal before endodontic retreatment which increases the treatment time compared with endodontic surgery. There is also a risk of damage to the existing crown, which may necessitate fabrication of a new crown after completion of root canal re-treatment.

Before attempting re-treatment, the patient should be advised that the prognosis of
re-treatment depends on: firstly, being able to retrieve the existing filling materials (i.e. posts and root filling material), and secondly, on identification and subsequent negotiation of all root canals to their ideal working length. They should also be advised that, after dismantling the restoration, extraction might be necessary if the tooth is found to be unrestorable as a result of extensive caries and/or fractures.

It is important that the patient has a realistic understanding of the complexity of both the problem and the treatment. Neither approach offers a 100% certain successful outcome, and there is a small risk that the disease may not resolve or the tooth may fail and require extraction.

Should the posts be removed through the access cavity, or by removal of the crown?

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