NBDE Periodontics 4 — Questions and Answers
Question 1: In guided tissue regeneration (GTR), the membrane barrier functions primarily to:
- Deliver antibiotics directly to the defect
- Exclude epithelial and gingival connective tissue cells from the root surface (Correct answer)
- Stabilize the blood clot during healing
- Stimulate osteoblast differentiation via growth factors
Correct answer: Exclude epithelial and gingival connective tissue cells from the root surface
GTR membranes create a secluded space that prevents fast-migrating epithelial and connective tissue cells from occupying the defect, allowing slower PDL and bone cells to repopulate.
Question 2: A patient presents with painful erythematous gingiva, interdental necrosis, and a punched-out papilla appearance. The most likely diagnosis is:
- Herpetic gingivostomatitis
- Necrotizing ulcerative gingivitis (NUG) (Correct answer)
- Desquamative gingivitis
- Linear gingival erythema
Correct answer: Necrotizing ulcerative gingivitis (NUG)
NUG is characterized by the classic triad of pain, interdental necrosis/pseudomembrane, and fetid odor, with punched-out papillae being pathognomonic.
Question 3: Which bone morphology is most favorable for periodontal regeneration using GTR or bone grafts?
- Horizontal bone loss with flat interproximal septum
- Narrow three-wall infrabony defect (Correct answer)
- Wide one-wall infrabony defect (hemiseptal)
- Class III furcation involvement
Correct answer: Narrow three-wall infrabony defect
Three-wall infrabony defects have the most surrounding bone walls to provide cellular progenitors and structural containment for the graft, yielding the best regenerative outcomes.
Question 4: The primary blood supply to the free gingival graft recipient site derives from which source during initial healing (0–3 days)?
- Anastomosis with vessels in the graft
- Plasmatic diffusion from the recipient bed (Correct answer)
- Periosteal vessels penetrating the graft
- Collateral circulation from adjacent papillae
Correct answer: Plasmatic diffusion from the recipient bed
During the first 1–3 days (avascular phase), the graft survives by absorbing plasma directly from the recipient bed via diffusion.
Question 5: Enamel matrix derivative (Emdogain) promotes periodontal regeneration primarily by mimicking which developmental process?
- Intramembranous bone formation
- Hertwig's epithelial root sheath signaling during cementogenesis (Correct answer)
- Endochondral ossification of alveolar bone
- Osteoclast inhibition via RANKL blockade
Correct answer: Hertwig's epithelial root sheath signaling during cementogenesis
Emdogain (amelogenin proteins) recapitulates root development signals from Hertwig's root sheath to promote acellular cementum and PDL regeneration.
Question 6: Which of the following findings on a periapical radiograph is MOST consistent with aggressive periodontitis affecting the first molar?
- Generalized horizontal bone loss at 10% of root length
- Arc-shaped (saucer-shaped) bone loss around the first molar (Correct answer)
- Dense sclerotic bone at the apex
- Widened PDL space at the apical third only
Correct answer: Arc-shaped (saucer-shaped) bone loss around the first molar
Localized aggressive periodontitis classically shows vertical arc-shaped bone loss in an 'arcuate' pattern around first molars and incisors.
Question 7: A connective tissue graft (subepithelial connective tissue graft) is preferred over a free gingival graft for root coverage because it:
- Provides greater width of keratinized tissue
- Offers better esthetics due to color matching with recipient tissue (Correct answer)
- Is less technique-sensitive to perform
- Requires no periosteal bed at the recipient site
Correct answer: Offers better esthetics due to color matching with recipient tissue
The connective tissue graft is covered by the recipient's own epithelium, resulting in superior color and texture match compared to the free gingival graft.
NBDE Periodontics 4
In guided tissue regeneration (GTR), the membrane barrier functions primarily to: