NBDE Periodontics 3 — Questions and Answers
Question 1: Which microorganism is most strongly associated with localized aggressive periodontitis (formerly localized juvenile periodontitis)?
- Porphyromonas gingivalis
- Aggregatibacter actinomycetemcomitans (Correct answer)
- Tannerella forsythia
- Treponema denticola
Correct answer: Aggregatibacter actinomycetemcomitans
Aggregatibacter actinomycetemcomitans (Aa) is the primary pathogen in localized aggressive periodontitis, found in up to 90% of affected sites.
Question 2: A free gingival graft harvested from the palate primarily provides which benefit?
- Increases zone of attached gingiva (Correct answer)
- Eliminates periodontal pockets
- Regenerates alveolar bone
- Corrects gingival embrasures
Correct answer: Increases zone of attached gingiva
Free gingival grafts are used primarily to widen the zone of keratinized/attached gingiva in areas of inadequate tissue.
Question 3: Chlorhexidine gluconate reduces supragingival plaque primarily through which mechanism?
- Competitively inhibiting glucosyltransferase
- Disrupting bacterial cell membranes via electrostatic binding (Correct answer)
- Chelating calcium in salivary pellicle
- Blocking bacterial fimbriae adhesion receptors
Correct answer: Disrupting bacterial cell membranes via electrostatic binding
Chlorhexidine's cationic molecule binds to negatively charged bacterial cell membranes, altering permeability and causing cell death.
Question 4: Which of the following best describes the biologic width?
- The distance from the free gingival margin to the alveolar crest
- The combined dimension of junctional epithelium and supracrestal connective tissue attachment (Correct answer)
- The sulcus depth plus the attached gingiva width
- The distance from the CEJ to the base of the pocket
Correct answer: The combined dimension of junctional epithelium and supracrestal connective tissue attachment
Biologic width (~2 mm) is the combined height of the junctional epithelium (~1 mm) and supracrestal connective tissue attachment (~1 mm).
Question 5: Osseous resective surgery is most indicated when the goal is to:
- Regenerate lost attachment using membranes
- Create a positive architecture by eliminating infrabony defects (Correct answer)
- Increase the width of keratinized gingiva
- Treat furcation Class III defects with GTR
Correct answer: Create a positive architecture by eliminating infrabony defects
Osseous resective surgery reshapes bone to create a positive (scalloped) architecture that allows better plaque control.
Question 6: Which of the following is a contraindication to periodontal surgery?
- Probing depth of 6 mm unresponsive to SRP
- Furcation involvement Class II
- INR of 3.8 in a patient on warfarin therapy (Correct answer)
- Residual horizontal bone loss of 30%
Correct answer: INR of 3.8 in a patient on warfarin therapy
An INR above 3.5 indicates excessive anticoagulation and a significant bleeding risk, requiring medical consultation before elective surgery.
Question 7: The pinkish stippled appearance of healthy attached gingiva is due to:
- Melanin pigmentation from melanocytes
- Rete peg interdigitation and collagen bundles in the lamina propria (Correct answer)
- Dense capillary network close to the surface
- Parakeratinized epithelium overlying thin submucosa
Correct answer: Rete peg interdigitation and collagen bundles in the lamina propria
Stippling results from the interdigitation of epithelial rete pegs with connective tissue papillae and underlying dense collagen bundles.
NBDE Periodontics 3
Which microorganism is most strongly associated with localized aggressive periodontitis (formerly localized juvenile periodontitis)?