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Abstract

There are no universally accepted guidelines for general dental practitioners regarding when endodontic referral to a specialist service may be indicated. UK NHS specialist endodontic services do not have national standardised criteria for which patient cases will be accepted for specialist care, and it is therefore important that more complex cases can be identified by general practitioners and referred accordingly, decreasing the likelihood of avoidable iatrogenic errors occurring, which reduce treatment outcome.

There have been a number of indices developed to help ascertain the complexity of endodontic cases. Part 2 discusses tips for identifying endodontic case complexity and examines indices available to guide clinicians as to when referral to an endodontic specialist service may be warranted.

Introduction

Increased tooth retention in an ageing population1 poses challenges for specialist endodontic services. Older adults may have more complex medical histories which impact on dental care, such as frailty, dementia, and multi-morbidity (two or more chronic conditions including respiratory or coronary heart disease, and type 2 diabetes).2 Due to the coexistence of multiple long-term conditions, patients increasingly experience polypharmacy, with 44% of patients over 65 taking five or more medications.3 In addition, tooth-related challenges in an ageing population can present difficulties: treating the increased prevalence of root caries increases the risk of pulpal exposure;4 secondary and tertiary dentine deposits can make root canals more tortuous to negotiate;4 and restorative cycles result in multiple pulpal insults, reducing the pulp's regenerative capacity.5

Today, it is desirable to retain one's natural dentition in a comfortable, functional and aesthetically acceptable state to allow engagement in normal, everyday activities.6 This demands clinicians provide more complex endodontic treatment, frequently including dismantling indirect restorations, root canal retreatment and periradicular surgery.

This article discusses tips for identifying more complex cases and discusses tools available to guide assessment and identification of complex cases which may benefit from referral.

Referral of endodontic cases

There is variation between UK health boards on what is considered suitable for specialist services and/or secondary care, complicating the issue of when to treat or refer. Thorough, structured dental assessment allows clinicians and patients to make decisions about teeth regarding benefits, risks, predictability and cost-effectiveness of treatment, and whether referral is warranted and beneficial to achieve a predictable outcome, minimising treatment risk and harm. The outcome of endodontic treatment is known to be influenced by the dentist's skill7 and thus pre-treatment identification of endodontic case complexity is essential. Difficult endodontic cases pose increased risk of iatrogenic error, which can directly reduce treatment success.8

Assessing endodontic case complexity: patient factors

Patient factors can affect tooth prognosis. For example, cases with restricted mouth opening, patients who cannot lie supine or who have a tremor tend to increase the complexity of care. Individuals who cannot or will not tolerate dental dam make endodontic treatment an impossibility due to safety risks such as inhalation or ingestion of irrigants or files. Reduced endodontic outcomes are associated with microbial contamination of the root canal system from saliva if a dental dam is not used. In addition, some studies suggest medical conditions, such as diabetes, may reduce endodontic treatment success,9 thought due to the alterations in immune functions and gingival crevicular fluid.10

Furthermore, the use of medications such as bisphosphonates, antiplatelet or anticoagulants or a pre-existing bleeding condition may influence the decision on whether to try retaining a tooth in order to avoid risking development of medication-related osteonecrosis of the jaw (MRONJ) or risk of post-operative bleeding following extraction.11 It is noteworthy that the placement of subgingival rubber dam clamps are considered invasive dental procedures for those patient cases at risk of infective endocarditis.12

Assessing endodontic case complexity: radiographic interpretation

An up-to-date, appropriate radiograph is an essential part of the pre-operative endodontic assessment. The gold standard view for diagnosing and treatment planning endodontic cases is a paralleling periapical.2,13 This should clearly show the radiographic apex of the root(s) and at least 2-3 mm of surrounding periradicular tissues, allowing analysis of pathology and root morphology.14 This is the image of choice due to high sensitivity identifying periradicular pathology (being almost twice that of panoramic radiographs) and specificity is similarly high, indicating a high probability of a true negative rate.15

Two-dimensional imaging allows visualisation in a mesiodistal plane only and diagnostic yield may be improved by taking two periapical views of the same tooth, at different angles (using parallax shift).13 Both horizontal and vertical parallax shifts can be useful. Using this, the more distant object appears to move in the same direction as the tube shift, while the closer object appears to move in the opposite direction. Figure 1 shows examples of the benefit of using horizontal and vertical parallax shifts in assessing endodontic cases. Table 1 summarises key features usually identifiable from paralleling periapical views which impact endodontic case complexity and therefore treatment planning.

Fig. 1
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Image A and B show an example of horizontal parallax shift during assessment of a patient referred with pain from previously root canal treated tooth 46. The x-ray tube head is more mesially positioned in image B which reveals there are four previously obturated canals, not the three suggested in image A. Image C is of tooth 11 referred by the patient's GDP stating a perforation and internal root resorption in tooth 11 was identified when root canal treatment was commenced. The patient relates a history of trauma and describes a lateral luxation of tooth 11. A maxillary occlusal radiograph (Image D) sheds light on a different diagnosis: an unhealed mid-third horizontal root fracture and periradicular changes are seen. This is an example of a vertical parallax shift which shows the horizontal root fracture more clearly than the periapical image (C), clarifying the diagnosis and steering treatment planning

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Table 1 Relevant radiographic features for endodontic treatment planning
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Cone-beam computed tomography systems (CBCT)

In recent years, advantages of CBCT for endodontic treatment planning have emerged, for example, in cases of possible non-odontogenic pain when conventional radiography has been insufficient in identifying pathology, which could account for symptoms. However, the radiation dose is generally higher with CBCT than conventional radiography,34 although the advent of limited volume (where the field of view is limited to the area of interest), high-resolution CBCT reduces the effective dose of radiation to the patient.34

Limited volume CBCT can be of use in the assessment of dental trauma, complex root canal morphology, resorption, endodontic complications and planning for surgical endodontic management.34 However, significant radiographic artefacts from metallic restorations and even gutta-percha can compromise the detail gained.13

Conclusion

Several patient-related, clinical and radiographic factors impact on endodontic treatment planning and case complexity. In the next part, the assessment tools available and their benefits and limitations for guiding endodontic case complexity will be considered.