A well-done root canal can last a lifetime. But sometimes — for various reasons — a root canal treatment fails months or years later. The good news: in most cases, the tooth can be saved with endodontic retreatment instead of going straight to extraction.
What is endodontic retreatment?
It's the procedure where an endodontist re-accesses a tooth with a previous root canal, removes the old filling material (gutta-percha, pastes, posts), cleans the canals again, disinfects with advanced irrigation, and seals it again hermetically. It can be done weeks, months or decades after the original treatment.
Why does a root canal fail?
The most frequent causes:
- Unlocated canals: complex anatomy with accessory canals the original treatment didn't detect — the most common cause of failure.
- Incomplete obturation: the material didn't reach the apex or empty spaces remained.
- Coronal leakage: the restoration on top of the tooth lost its seal and allowed bacteria to enter the treated canals.
- Root fracture: a crack allows bacterial colonization of the periapical space.
- New cavity: a recurrent cavity reaches the already-treated canals.
- Persistent reinfection: bacteria that survived the original treatment, lodged in dentinal tubules or non-instrumented isthmuses.
Signs your root canal is failing
- Pain when chewing on the treated tooth — new or recurring.
- Sensitivity to percussion: it hurts when the tooth is gently tapped.
- Fistula (small bump with pus) on the gum near the tooth.
- Recurring swelling in the area.
- Progressive darkening of the tooth.
- Persistent unpleasant taste around the tooth.
- Radiographic finding: new or persistent periapical lesion on routine check.
In many cases there are no symptoms and the problem is discovered only by radiograph — that's why periodic check-ups matter even on already-treated teeth.
Retreatment vs. extraction
Before proceeding, we evaluate: remaining tooth structure, root condition, bone support, identifiable cause of the failure and realistic prognosis. If retreatment has a favorable prognosis, it is preferable to extraction + implant for the same reasons that apply to any natural tooth: proprioception, bone preservation, cost and total time of the process.
The process step by step
- Diagnostic evaluation with digital radiography.
- Access: the previous crown or restoration is removed.
- Disobturation: all previous material is removed using solvents, ultrasonics and microscope.
- Re-instrumentation: cleaning with modern rotary files, looking for canals that may have been missed.
- Advanced irrigation: ultrasonically activated to reach areas mechanically inaccessible.
- Intracanal medication: in cases of active infection, calcium hydroxide for 1-4 weeks.
- Final obturation: three-dimensional sealing with thermoplastic gutta-percha.
- Definitive restoration: new crown — critical to prevent reinfection.
Retreatment usually requires 2-3 visits and is technically more complex than the original treatment.
The microscope in retreatment
The endodontic microscope transforms retreatment. It allows you to visualize remnants of previous material, detect untreated canals, remove posts without damaging the root, retrieve fractured instruments and identify internal fractures invisible to the naked eye. Without a microscope, retreatment depends on touch; with a microscope, it's a visually guided procedure.
Success rate
Studies report success rates of 70-85% for retreatments with a specialist and adequate technology. When retreatment isn't enough, apicoectomy (apical microsurgery) can be a third option before considering extraction.
Don't resign yourself to extraction without a second opinion
At Clínica Endodontics in San Miguel, we perform retreatments with a microscope and evaluate each case with clinical honesty: if it can be saved, we save it; if not, we explain why with evidence you can see on the screen.
Last updated: .