Micro & Immunology · single question
Which bacteria is most commonly associated with FAILED root canal treatment?
Show answer and explanation
Correct answer: B. Enterococcus faecalis
Enterococcus faecalis is found in up to 77% of persistent/failed root canal infections. It is uniquely resistant to: calcium hydroxide intracanal medicament (high pH resistance), desiccation, nutrient starvation, and many antibiotics. It survives in dentinal tubules long after other bacteria are eliminated.
- A. ❌ P. gingivalis is a primary periodontal pathogen — not specifically associated with failed RCT.
- B. ✅ E. faecalis — the classic organism in persistent root canal infections; resistant to most standard intracanal medicaments.
- C. ❌ Fusobacterium is part of the primary endodontic flora but not specifically the failed RCT organism.
- D. ❌ Prevotella is also primary endodontic flora but not the key failed-treatment organism.
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