NBDE Periodontics and Endodontics 4 — Questions and Answers
Question 1: Which bacteria is considered a MAJOR periodontal pathogen and is characteristically associated with rapidly progressing periodontitis?
- Streptococcus mutans
- Porphyromonas gingivalis (Correct answer)
- Actinomyces viscosus
- Fusobacterium nucleatum
Correct answer: Porphyromonas gingivalis
Porphyromonas gingivalis is a Gram-negative anaerobic rod considered a keystone periodontal pathogen due to its ability to evade host defenses and produce destructive proteases.
Question 2: What type of root resorption occurs from the outside of the root inward and is often associated with trauma or orthodontic treatment?
- Internal inflammatory resorption
- External inflammatory resorption (Correct answer)
- Replacement resorption (ankylosis)
- Cervical root resorption
Correct answer: External inflammatory resorption
External inflammatory resorption occurs on the outer root surface, commonly triggered by trauma, orthodontic forces, or periapical infection stimulating osteoclastic activity.
Question 3: Which material is used as the gold standard for root canal obturation?
- Resilon
- Gutta-percha with sealer (Correct answer)
- Mineral trioxide aggregate (MTA)
- Zinc oxide eugenol paste
Correct answer: Gutta-percha with sealer
Gutta-percha combined with an endodontic sealer remains the gold standard for root canal obturation due to its biocompatibility, dimensional stability, and ease of removal if retreatment is needed.
Question 4: A patient taking phenytoin for seizure disorder is MOST likely to develop which periodontal complication?
- Necrotizing ulcerative gingivitis
- Drug-influenced gingival enlargement (Correct answer)
- Aggressive periodontitis
- Desquamative gingivitis
Correct answer: Drug-influenced gingival enlargement
Phenytoin (Dilantin) is one of the classic drugs causing drug-influenced gingival enlargement (overgrowth), along with cyclosporine and calcium channel blockers.
Question 5: What does the term 'weeping canal' indicate clinically?
- Excessive irrigant use during shaping
- Persistent exudate from the canal indicating active infection (Correct answer)
- Blood contamination from pulp exposure
- Overfilled canal with sealer extrusion
Correct answer: Persistent exudate from the canal indicating active infection
A weeping canal refers to persistent exudate (usually serous or purulent) flowing from the root canal, indicating active periapical infection requiring further debridement before obturation.
Question 6: Which probe is specifically designed for detecting furcation involvement in multirooted teeth?
- Williams probe
- UNC-15 probe
- Nabers probe (Correct answer)
- Michigan O probe
Correct answer: Nabers probe
The Nabers probe (curved furcation probe) is specifically designed to access and measure furcation defects on multirooted teeth.
Question 7: Which radiographic finding is MOST characteristic of a periapical cyst versus a periapical granuloma?
- Periapical cysts have a radiopaque border
- Periapical cysts tend to be larger with a well-defined corticated border (Correct answer)
- Granulomas appear larger than cysts
- Cysts show lamina dura intact while granulomas do not
Correct answer: Periapical cysts tend to be larger with a well-defined corticated border
While not definitively distinguishable radiographically, periapical cysts tend to appear larger with a well-defined corticated (sclerotic) border compared to the less defined margin of granulomas.
NBDE Periodontics and Endodontics 4
Which bacteria is considered a MAJOR periodontal pathogen and is characteristically associated with rapidly progressing periodontitis?