Retreatment or Surgery? Your Step-by-Step Decision Tree When a Root Canal Fails

Even with meticulous technique, root canal treatments may occasionally fail. 

Despite our best efforts, failure occurs, and the rates range between 10% to 20%.

When they do, clinicians must answer a critical question:

Do you retreat the canal or opt for surgical intervention?

Such decisions are rarely straightforward, but a clear framework can guide clinicians toward the most patient-centered solution.

Why Do Root Canals Fail?

Understanding the reason for failure is step one. The top causes of root canal failure include¹:

• Missed canals (especially MB2 in maxillary molars)
   
• Inadequate cleaning and shaping
   
• Persistent periapical infection
   
• Leakage from coronal restorations
   
• Instrument separation or ledges
   

Research highlighted that missed anatomy and persistent intraradicular infection were the most common causes of persistent apical periodontitis after RCT².

When Is Retreatment the Right Choice?

Retreatment is a non-surgical endodontic retreatment that involves removing the old filling, disinfecting the canal, and refilling.

Retreatment is Recommended When:

• There is access to the canal system
   
• The cause of failure is missed anatomy or inadequate previous treatment
   
• The restoration is either temporary or easily replaced
   
• The tooth is structurally sound and restorable
   

Retreatment success rates range from 75% to 88%, with the use of modern techniques such as CBCT, magnification, and bioceramic sealers³.

Retreatment preserves more of the natural tooth and is often preferred when feasible.

When Does Surgery Make More Sense?

Apicoectomy is the surgical option that involves root-end resection, curettage, and retrograde filling, with the help of magnifying tools.

Consider Surgery When:

• The canal is blocked by posts or ledges that cannot be bypassed
   
• Retreatment has failed or is not technically possible
   
• There is a persistent periapical lesion or cyst that does not resolve
   
• A perforation or complex resorption is present
   

Evidence-Based Stats:

Recent studies show that apicoectomy, especially when performed using modern microsurgical techniques delivers excellent short-term outcomes.

Healing rates in the first 2 to 4 years have been reported as high as 85% to 95%⁴.

However, long-term success tends to taper. Studies following up over 5 to 10 years report success rates in the range of 60% to 80%, depending on the clinical situation⁵.

What do we learn from this?

Apicoectomy can be highly successful, especially in the short term, but it is essential to set realistic expectations and choose cases wisely.

Decision-Making Guide: Retreatment vs Apicoectomy

How Modern Tools Improve Success Rates?

Old school struggles have now modern solutions, and they are changing success rates in a big way. Here are few examples-

• CBCT imaging: A systematic review and meta-analysis reported that CBCT has a sensitivity of 94% and specificity of 93.1% in detecting second canals in permanent teeth^6.

For the second mesiobuccal canal (MB2) in maxillary molars, the sensitivity was even higher at 96.6%, which promises the potential to make “missed canals’’ a thing in the past.

A study further analysed 208 CBCT scans and found that 40.7% of maxillary first molars had "missed canals". The numbers highlight the prevalence of undetected canals in conventional imaging and emphasise the importance of advanced diagnostic tools⁷.

• Magnification: Magnification tools, such as loupes and dental microscopes, make it easier to spot canal openings and perform treatments more precisely.

A 2018 review found that using magnification reduces errors and improves overall success in root canal procedures⁸.

• Glide path & crown-down techniques: Glide path and crown-down techniques are not just buzzwords; rather, they are essential steps in modern endodontics.

Utilizing rotary glide path files like ProGlider has been shown to significantly reduce apical debris extrusion compared to manual methods, which helps with fewer procedural errors and better patient outcomes⁹.

• Bioceramic sealers: They are changing the entire game with their superior sealing ability and contribute to better healing outcomes¹⁰.

It is proven that with the right tech, technique, and timing, even tough cases can turn out just fine.

Case Example: What Would You Do?

Case: A 42-year-old presents with a symptomatic maxillary molar with a post and crown. CBCT reveals missed MB2 and a periapical lesion.

If the post is easily removed and the crown is temporary:

-Retreatment.

If the post is long, cast, and removal may cause fracture:

-Surgery may be the safer route.

Final Thoughts

There is no straightforward answer to opt for retreatment or surgery.

Both retreatment and surgery are valid evidence-based options. The decision depends on anatomy, restorability, patient factors, and clinician experience.

Use a structured approach acknowledging clinical, radiographic, and patient-centered aspects to select the most predictable option.

References

1. Aljabri MK, Kensara JA, Mandorah AO, Sunbul MA. Causes of root canal treatment failure: A prospective study in Makkah City, Saudi Arabia. Saudi J Oral Sci. 2020;7(1):40–45.
2. ​​Siqueira JF Jr, Rôças IN, Ricucci D, Hülsmann M. Causes and management of post-treatment apical periodontitis. Br Dent J. 2014 Mar;216(6):305–312.
3. Torabinejad M, Corr R, Handysides R, Shabahang S. Outcomes of nonsurgical retreatment and endodontic surgery: a systematic review. J Endod. 2009 Jul;35(7):930–7.
4. Setzer FC, Kratchman SI. Present status and future directions: Surgical endodontics. Int Endod J. 2022;55(Suppl. 4):1020–1058.
5. Song M, Kim E, Kim RH, Lee SJ, Kim Y. Prognostic factors of clinical outcomes in endodontic microsurgery: a retrospective study. J Endod. 2011;37(7):927–33.
6. Aung NM, Myint KK. Diagnostic accuracy of CBCT for detection of second canal of permanent teeth: A systematic review and meta-analysis. Int J Dent. 2021;2021:1107471.
7. Alotaibi BB, Khan KI, Javed MQ, Dutta SD, Shaikh SS, Almutairi NM. Relationship between apical periodontitis and missed canals in mesio-buccal roots of maxillary molars: CBCT study. J Dent Sci. 2023;18(3):1034–1040.
8. Low JF, Mohd Dom TN, Baharin SA. Magnification in endodontics: A review of its application and acceptance among dental practitioners. Eur J Dent. 2018 Oct–Dec;12(4):610–616.
9. Akhlaghi NM, Aminsobhani M, Ghandi M, Norouzi N. Effect of different glide path establishing techniques on apical debris extrusion using two single-file systems: an in vitro study. Endodontology. 2023;35(4):123–130.
10. Zhang W, Li Z, Peng B. Assessment of a new root canal sealer's apical sealing ability and biocompatibility. J Endod. 2009 Jun;35(6):915–918.