Endodontics: The Sequel or the Surgical

Background

Root canal treatment is highly successful for managing peri-radicular pathologies related to an infected root canal system, with up to 96% of cases resolved with primary, non-surgical root canal treatment alone.¹ However, there are cases where initial treatment fails to resolve symptoms or eliminate infection. This leaves practitioners with the decision to either perform non-surgical root canal re-treatment, extract the tooth or refer for surgical intervention. NSRCreT involves revisiting the root canal system to address persistent symptoms and eliminate residual infection. Where the cause of failure is clear, this may be achievable in a general practice setting, but may sometimes require more advanced clinical techniques.^2,3

Alternatively, endodontic microsurgery may be more appropriate. This involves surgically resecting the apical portion of the root, followed by sealing the root-end to prevent further infection, with the aim of removing the part of the root housing complex anatomy and eliminating residual bacteria.⁴ This procedure is reserved for cases where NSRCreT is less likely to succeed, among other factors discussed throughout this article. In contrast, cases with a hopeless prognosis must be identified, where extraction and replacement should be considered as first-line treatment.

Endodontic failure

Following initial root canal treatment (RCT), success can be determined in several ways, with abatement of pre-operative symptoms being the most obvious. Post-endodontic treatment pain is typically transient, and eases within the first few days following obturation.⁵ Should pain persist, or increase in the days and weeks following the RCT, failure of the root canal treatment is the most likely cause. However, mechanical irritation of peri-apical tissues can cause similar symptoms, with overinstrumentation of the root canal and extrusion of material through the apical foramen being the likely causative factors.⁶

Other signs and symptoms of recurrent infection include the presence or persistence of an apical abscess. The use of a GP point inserted into a draining abscess often allows localization of the tooth from which pathology originates.

Radiological examination of the RCT provides important information regarding the quality of endodontic treatment provided, indicating potential reasons for failure, and aiding in the decision on further treatment options. Simple factors, including obturation in relation to the radiographic apex, homogeneity of obturation and a wellsealed coronal restoration typically result in favourable outcomes (Figures 1 and 2).⁸ The gutta percha should be closely adapted to the canal walls, with no visible canal space beyond the endpoint of the root canal filling and without extensive extruded obturation material.¹⁴ Additionally, it is desirable to obtain information on the previous RCT concerning the quality of isolation and irrigation. This may be done through the review of records or during history taking (Table 1).

Care must be taken when interpreting the size of apical pathology as a marker for disease regression with two-dimensional radiographic imaging (e.g. peri-apical or dental panoramic tomography). Differing angulation of the X-ray beam, altered exposure, angulation of the film, processing errors and image processing can give the illusion of a change in size of pathology.⁷

Clear deficiencies in a previous root filling (including voids, lack of patency, etc.) and lack of adherence to guidelines for root treatment (e.g. use of rubber dam isolation), would require non-surgical root canal re-treatment should the patient be keen to retain the tooth.⁸ The predictability of NSRCreT may reduce if previous high-quality treatment has failed. This requires clinicians to investigate the potential reasons for failure to inform subsequent treatment planning (common reasons for endodontic failure are outlined in Table 1). Attempting peri-radicular surgery as first-line treatment in these cases may be inappropriate, introducing risks associated with surgery, and increasing post-operative morbidity.

When to consider surgical endodontics

Systematic reviews indicate that non-surgical re-treatment, when attempted first, may yield a more favourable long-term outcome compared with surgical endodontic treatment.^9,10 However, advances in modern tricalcium silicate cements and microsurgical techniques have improved the predictability of surgical approaches. Varying success rates for peri-apical microsurgery are reported, with a systematic review reporting 77% success,¹² and a recent narrative review reporting 48–93%, with a trend of increased success in more recent studies.^11,12 Moreover, in cases of symptomatic and progressive peri-radicular disease, apical surgery can be considered a preferred first-line treatment option under specific circumstances (Tables 2 and 3).

The nature of the peri-apical lesion, classified as peri-apical abscesses, granulomatous, or cystic, may also be a cause of primary RCT failure, and compromise outcomes of orthograde re-RCT.¹⁵ True cysts separated from the root are an example of lesions that require surgical intervention as the first-line treatment (enucleation, marsupialization or decompression).

In cases of failed non-surgical root canal re-treatment, further non-surgical re-treatment becomes less predictable, making a surgical approach advisable.^8,16 Extra-radicular infections with biofilms on the root surface and colonies of resilient species, such as Actinomyces and Propionibacterium, within the soft tissue lesion may also hinder the success of NSRCreT, although this may not be known until the treatment has failed.¹⁷

Further challenges to non-surgical root canal re-treatment include accessing the root canal system through complex restorations such as Nayyar cores, fibre posts or cast metal posts. Although posts can often be safely removed with appropriate techniques to avoid root fractures,^18,19 where post removal may compromise the structural integrity of the tooth, or the benefits of further chemo-mechanical disinfection through NSRCreT cannot be justified. These cases will often benefit from surgical approaches as a first-line option.

Successful RCT relies heavily on thorough disinfection throughout the canals.¹⁴ This may be challenging with complex canal anatomy, such as significant curvatures (>30°), multiple roots and root canal systems, or long roots (>25 mm), posing considerable challenges.²⁰ Additional factors, including calcifications, resorptions, and iatrogenic errors (including file fractures and perforations), can further hinder effective chemo-mechanical debridement, making non-surgical treatment increasingly challenging. These issues are further enhanced the closer they occur to the apex.²¹

Should any of the above factors be present when clinically or radiologically examining a patient's previously root-treated tooth, referral to a secondary or tertiary care setting is advised for consideration of surgical intervention. These factors are summarized in Figure 3.

Restorability of the tooth: the bigger picture

Considering technical limitations, anatomical complexities, and iatrogenic errors, the feasibility of restoring a tooth should be the primary concern before considering either non-surgical root canal re-treatment or apical surgery. To aid in the decision-making process about restorability and effectively communicating them to patients, the dental practicality index (DPI) proves to be a valuable tool.^22,23 The DPI evaluates the structural integrity of the tooth, its periodontal stability, endodontic requirements, and other contextual factors, such as overall restorative needs, social aspects, dental history, and medical considerations.

At the level of the tooth

An initial step in assessing restorability may involve the removal of existing restorations, because this can help identify the cause of failure and most importantly, the restorability of the tooth. By removing restorations, issues, including caries, cracks, and marginal breakdowns become more apparent. This can be a critical step, with one study identifying caries in 19.2% of teeth, which increased to 86.1% following complete removal of the coronal restoration.²⁴ Furthermore, this procedure allows for direct visualization of supra- and subgingival margins, facilitating decisions between extraction, deep marginal elevation, or the possibility of placing an indirect restoration margin.²⁵ Additionally, this enables the examination of the ferrule and improves the visualization of angulation for access of the root canal system, reducing the risk of iatrogenic errors.²⁶

The presence of fractures extending to the root surface reduces the prognosis of the tooth, and treatment options become limited to extraction.²⁷ Clinically, the presence of a single, deep, narrow periodontal pocket around the affected tooth, along with mobility in a post or coronal restoration, may indicate a fracture. Additionally, a ‘J-shaped’ lesion seen radiologically, or the loss of the periodontal ligament space could also suggest a fracture.²⁸ More advanced imaging techniques, such as cone beam computed tomography (CBCT), can predictably demonstrate patterns of bone loss that are indicative of a fracture.^29,30

Bony support and root length must also be considered part of this assessment. Extensive crestal bone loss, or the presence of vertical bony defects in the region of the tooth in question would be likely to contraindicate apical surgery. Teeth with already compromised bony support or a decreased crown:root ratio would lose further support following apical surgery and as such, NSRCreT or extraction may be favourable.¹³ The same concept applies to teeth with shortened roots. Considering the 3 mm lost for apical surgery, if the remaining crown:root ratio would be less than 1:1, endodontic surgery would not be a viable treatment option.

When teeth do not meet the criteria of restorability, consideration of non-surgical root canal re-treatment or surgical endodontics is futile. The most pragmatic option would be extraction, with a discussion with the patient about replacement options, whether fixed or removable.

Other considerations of peri-apical surgery include potentially negative consequences. Any form of surgery requiring the raising of a full-thickness periosteal flap can lead to localized gingival recession. This must be considered when planning surgery in the aesthetic zone, especially around crown margins (Figure 4). Recession in patients with high smile lines can lead to poorer aesthetic outcomes, and in the most aesthetically driven patients, preferential outcomes may be acquired through extraction and prosthetic replacement.

Conclusion

Navigating the decision between NSRCreT and surgical intervention is a critical aspect of endodontic care. By staying informed of the latest advances and considering patient-specific factors, GDPs can provide their patients with all viable treatment options. By understanding each approach's indications, limitations, and outcomes, practitioners can deliver optimal care and achieve successful patient treatment outcomes.