Endodontic Retreatment and Management of Failures
This domain tests whether you can diagnose why treatment failed and choose retreatment, surgery, or extraction.
Causes of failure
- Intraradicular: missed or untreated canals, inadequate cleaning, persistent E. faecalis biofilm, untreated isthmuses.
- Extraradicular: Actinomyces biofilm, foreign body, true cyst.
- Coronal leakage from a failed restoration or delayed restoration.
- Vertical root fracture or an untreated crack, where retreatment will not help.
Diagnosis before re-entry
History, pulp and periapical tests, probing, and a small-field CBCT to look for untreated anatomy, perforation, fracture and lesion size. Retreating without a diagnosis is the commonest error in this domain.
Technique
Access through the existing restoration, remove gutta-percha with rotary retreatment files, heat or solvents (chloroform, orange oil), remove paste, re-instrument larger, restore patency, locate untreated canals, repair perforations with MTA or a bioceramic. Posts are removed with ultrasonics and trephines; separated instruments are bypassed where possible. Reported retreatment success is roughly 70-85%, below primary treatment.
Choosing surgery versus retreatment
Surgery is preferred for extraradicular infection, unreachable complex anatomy, biopsy needs, or persistent symptoms after adequate retreatment. Intentional replantation is a last resort.
Worked example
A molar treated 5 years ago now has a sinus tract and a periapical lesion on the mesial root. CBCT shows an untreated MB2. Diagnosis: persistent intraradicular infection from missed anatomy. Plan: nonsurgical retreatment, locate and instrument MB2, medicate, and obturate when asymptomatic.
Traps
Retreating a cracked tooth; creating a new perforation during post removal; assuming a new lesion means the previous treatment was technically poor rather than anatomically incomplete.