Top tips for treatment planning: tooth-by-tooth prognosis - Part 3: endodontic prognosis

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Introduction

In Part 3, we continue our discussion by exploring additional intra-operative factors and post-operative considerations. To recap, Fig. 1 illustrates the intra-operative factors we have covered thus far: achieving apical patency and preserving peri-cervical dentine. In this part, we will further discuss intra-operative factors such as the length, density, and taper related to obturation, as well as managing intra-operative flare-ups. We will also address post-operative considerations that influence the overall success and longevity of endodontic treatments. Our aim is to provide comprehensive prognostic guides for clinicians, ensuring well-informed decision-making throughout the treatment process.

Fig. 1

Intra-operative factors influencing endodontic prognosis

Intra-operative factors

• 1. Obturation

  • a. Length of the root canal filling

Numerous studies have investigated various aspects of filling length, including short, flush, and long fillings, as well as comparisons between overfilled and overextended fillings, and studies on leakage. However, only a few studies have examined the impact of leaving a chemo-mechanically debrided root canal unfilled on treatment outcomes. These studies attributed about 40% to 60% of endodontic treatment failures to inadequate obturation of the root canal system.¹ Traditionally, these failures were believed to arise from issues such as overfilling, underfilling, and the overall poor quality of root fillings.

Initially, it was believed that an unfilled root canal would cause stagnation of tissue fluids within the ‘hollow tube', leading to sustained periapical inflammation. Later studies refuted this, finding no significant differences in periapical healing between teeth with and without obturation.² The quality of the coronal restoration was found to be more crucial for periapical health than the root filling.³

Given the current evidence, it is premature to disregard the obturation step. Root canal filling should still be performed to address any lingering infection after cleaning and shaping. Additionally, it may help prevent microbial leakage to the periapex if the coronal seal is compromised, though evidence for this is limited. Clinical decision-making should prioritise the patient's specific needs rather than rigidly adhering to a single method.

Root fillings extending to within 2 mm of the apex have been associated with success rates of 81%.² This could be attributed to the effective disinfection of the canals, particularly at the apical portion, achieved through thorough instrumentation and irrigant penetration, which allowed the root fillings to extend similarly.^1,4

Tips

• Use electronic apex locators as suggested previously to determine the precise working length.⁵ This helps in avoiding over- or under-preparation of the canals and placement of the final root filling at the desired length

• If uncertain, always double-check the working length (WL). A cone-fit radiograph with the master gutta-percha (GP) point in place can be extremely helpful if the WL is in question or if a WL radiograph was not been previously taken. Ensure that the filling material is within the optimal range of 0-2 mm from the apex

• Obturation techniques such as warm vertical compaction or continuous wave condensation can help achieve optimal fill even in complex canal anatomies.

• b. Density of root canal obturation

Obturation aims to provide a satisfactory apical seal and three-dimensional filling of the canals. Although the concept of a ‘hermetic seal' has been questioned by recent studies, achieving a good three-dimensional fill can mitigate residual infection after chemo-mechanical debridement.^4,6 While assessing three-dimensional obturation with two-dimensional imaging is challenging, technically ‘satisfactory' obturations (absence of voids) are associated with significantly improved success rates.^1,4 A radiographically dense root filling has been considered to additionally aid in preventing microbial seepage for a short while, in the event the coronal seal is compromised.⁷

Tips

• In addition to the tips provided above for achieving good obturation, integrating strategies such as utilising magnification and illumination, employing specific obturation techniques like lateral condensation or warm vertical compaction to achieve a uniform and void-free obturation, and confirming void absence with radiographs, further enhances the quality of obturation and contributes to improved prognosis

  A radiographically dense root filling has been considered to additionally aid in preventing microbial seepage for a short while, in the event the coronal seal is compromised.

• Sealers fill the vacant space between the prepared dentinal wall and the core filling material, establishing a good seal in the root canal system.

• When using traditional sealers like resin-based and calcium hydroxide-based sealers, ensure that the core filling material occupies most of the canal space, minimising the amount of sealer used. This helps prevent sealer-related problems such as disintegration, dissolution, or shrinkage. Newer calcium silicate-based sealers, with their superior biomechanical properties, can simplify this process and reduce the time needed for obturation.⁸

• c. Taper of root canal obturation

Preparing and creating a taper in the root canals enhances irrigation dynamics and effective chemo-mechanical debridement.^9,10 This tapering also reduces the risk of extruding irrigants, and obturating materials. While over tapering can lead to weakening of roots by compromising the peri-cervical dentine (PCD), under shaping can result in compromising the prognosis.

• 2. Intra-appointment pain and swelling

The presence of pain and swelling between operative appointments, often termed as inter-appointment flare-ups, has been associated with poorer treatment outcomes deteriorating endodontic prognosis.¹¹ These flare-ups are considered as exacerbations of periapical inflammation or infections and can occur due to various reasons such as inadequate asepsis, disinfection, improper irrigation, or material extrusion during the root canal procedure.

Extensive inter-appointment swelling can impair mouth opening, compromising the quality of subsequent treatments. Additionally, damage to the provisional restoration during a prolonged inter-appointment period for pain and swelling to subside can lead to coronal microbial leakage, further affecting the tooth's prognosis.

Current evidence suggests that inter-appointment flare-ups may indicate a more aggressive host-microbial interaction at the periapical region.⁴ This interaction involves the persistence or proliferation of microorganisms within the periapical tissues despite initial treatment attempts. These microorganisms can provoke an inflammatory response, leading to symptoms such as pain and swelling. These errors can cause tissue irritation and exacerbate periapical inflammation.^4,11

Tips

To avoid the complication of intraoperative pain and swelling and improve prognosis, we can follow these additional tips:

• Utilise rubber dam isolation for an aseptic operating field, which helps prevent contamination of the root canal system and reduces the risk of postoperative complications (Fig. 2)

  Fig. 2

  

  Utilise rubber dam isolation for an aseptic operating field

• Adopt a conservative and gentle approach during canal instrumentation to avoid excessive pressure or trauma to periapical tissues. This helps minimise tissue irritation and reduces the likelihood of postoperative pain and swelling

• Employ intermittent irrigation techniques using side-vented needles to flush debris and disinfect the root canal system effectively. This reduces the risk of extrusion of irrigants beyond the apex while enhancing irrigation efficacy without causing irritation to the periapical tissues

• Provide clear postoperative instructions to patients, including guidance on managing discomfort, swelling, and any potential complications following the procedure. Prescribe appropriate analgesics and recommend adjunctive measures such as cold compresses or anti-inflammatory medications to alleviate postoperative symptoms.

Prognosis based on these various intra-operative factors is presented in Table 1

Table 1 Prognosis based on various intra-operative factors

• 3. Post-operative factors (Fig. 3)

  Fig. 3

  

  Post-operative factors for endodontic prognosis

  • a. Coronal seal and post endodontic restorations

Coronal leakage is a major cause of endodontic failure in a tooth with thoroughly disinfected root canals.³ Even a well-obturated canal does not provide an enduring barrier to bacterial penetration for extended durations; thus, we rely on the restoration for the long-term integrity of the coronal seal. Inadequate quality of the coronal restoration contributes to unsuccessful outcomes.

After access cavity restoration, endodontically treated teeth are often restored with full-coverage crowns to ensure optimal structural support and protection.¹² Restorations should serve primarily three functions: the protection of the root canal treatment from microleakage and subsequent failure, as well as fracture protection from occlusal forces, and provide the contacts and contours to support a healthy attachment apparatus around the treated tooth.

The necessity for cuspal coverage should be assessed on a tooth-by-tooth basis, considering factors such as remaining tooth structure, presence of cracks, and opposing dentition. According to the latest recommendations from the European Society of Endodontology,¹³ most posterior teeth with at least one missing proximal wall require cuspal coverage restorations.

Recent advancements in adhesive dentistry and biomimetic principles are challenging the routine use of full-coverage crowns for endodontically treated teeth.¹⁴ Biomimetic dentistry focuses on preserving as much tooth structure as possible and replicating natural biomechanics through minimally invasive preparations and selective caries removal.

The biomimetic restoration protocol emphasises modern adhesion techniques and stress-reduced cavity preparation to minimise the configuration factor (C-factor) and reduce stress in dental composite restorations.¹⁵

Tips

• Familiarise yourself with biomimetic dentistry principles aimed at preserving natural tooth structure and biomechanics. Incorporate minimally invasive techniques and selective caries removal to enhance long-term outcomes of restorative procedures

• Recognise that the approach to restorative treatment for endodontically treated teeth may vary depending on factors such as remaining wall volume and type of access cavity preparation. Customise treatment plans to suit each patient's unique needs and circumstances

• For anterior teeth, consider direct composite restoration for intact marginal ridges, while previously heavily restored teeth may require either direct composite or indirect restoration

• In posterior teeth, direct composite restoration is suitable for those with intact marginal ridges, while previously heavily restored teeth may benefit from direct composite with reinforced ultra-high molecular weight polyethylene fibre (UHMWPEF), possibly leading to indirect restoration or crown placement.¹³

Previously crowned posterior teeth with lost marginal ridges may require a reinforced core with either a conventional post, UHMWPEF fibre post, or an endo crown.

• 4. Timing of cuspal coverage

Pratt et al. (2016)¹⁵ examined the impact of the timing of cuspal coverage after root canal treatment and found that teeth receiving crowns more than four months after the procedure were almost three times more likely to be extracted compared to those restored within four months. Interestingly, after the four-month mark, the failure rate did not significantly increase until 18 months post-treatment, at which point the rate of failure surged, suggesting a critical period for fracture development.¹⁵

Teeth restored with indirect restorations within six months of root canal treatment had a higher survival rate (93.1%) compared to those with direct fillings (89.8%).¹⁵ It was also noted that teeth with a more favourable prognosis might have been preferentially restored with indirect restorations.

Survival rate of root-filled teeth without crowns was satisfactory up to three years (84% ± 9%) but declined thereafter. Outcomes after five years between teeth restored with direct and indirect restorations showed no difference. However, at the ten-year mark, teeth with indirect restorations had superior outcomes.¹⁶

Tips

• Periodically assess the need for cuspal coverage restoration during follow-up appointments, especially for teeth with delayed restoration, to prevent complications and ensure optimal prognosis

• Educate patients about the importance of timely restoration after root canal treatment and encourage compliance with recommended treatment timelines to improve treatment outcomes and long-term tooth survival.

Occlusion

Occlusion plays a significant role in the prognosis of endodontically treated teeth although conclusive evidence is lacking.¹⁷ Proper occlusion ensures that forces are distributed evenly across the dental arch, reducing the risk of excessive stress on individual teeth, including those that have undergone endodontic treatment. Occlusal forces can impact the longevity of restorations placed on endodontically treated teeth. Proper occlusion ensures the stability and durability of restorations, reducing the risk of failure.

Tips

When considering occlusal guidance, it's important to note that, in cases where it is desirable to avoid lateral forces on compromised posterior teeth, canine guidance is preferred as it redirects forces away from these teeth. Alternatively, group function is ideal when the goal is to distribute these forces across multiple teeth.

Prognosis based on these various post-operative factors is presented in Table 2.

Table 2 Prognosis based on various post-operative factors

Conclusion

In conclusion, the comprehensive evaluation of endodontic prognosis involves a meticulous consideration of pre-operative, intra-operative, and post-operative factors. Each phase contributes uniquely to the long-term success of root canal therapy, emphasising the importance of patient-specific assessments and tailored treatment plans. By integrating advanced diagnostic tools and adhering to evidence-based practices, dental practitioners can enhance treatment outcomes and patient satisfaction. Effective communication with patients regarding prognosis classifications - whether ‘good', ‘questionable', or ‘poor' - is essential in fostering informed decision-making and achieving optimal oral health outcomes.