Micro & Immunology · patient case question
How many bacterial species are typically implicated in a periapical lesion?
Patient case: Abandoned periodontal therapy with pain at tooth #29
Patient: Female, 55 years old
Chief Complaint: Pain in the lower right premolar region.
Background: Began scaling and root planing two years ago but never completed the course and did not return for review.
Current Findings: Generalised heavy subgingival calculus with profuse bleeding on probing. Deep pockets and generalised horizontal bone loss. A panoramic shows a periapical radiolucency associated with tooth #29 continuous with the marginal bone loss. Tooth #29 has no caries and no restoration.
Show answer and explanation
Correct answer: D. More than three
- A. Two species does not reflect the observed microbial diversity of the necrotic canal.
- B. Single-organism endodontic infection is essentially unknown. Even a lesion apparently dominated by one species has others present.
- C. Three understates it. The community is characteristically larger, and its complexity increases with the duration of the infection.
- D. CORRECT. Endodontic infections are POLYMICROBIAL. Culture and molecular studies typically recover four to twelve species from an infected canal, predominantly obligate anaerobes acting in synergy — one organism's metabolic products become another's substrate, which is why the community is far more pathogenic than any single member.
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