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Periodontics: INBDE study notes and practice questions

Periodontics questions test the current classification of periodontal health and disease, how you measure it, and what you do in each phase of treatment. Patient scenarios with probing depths and bleeding scores are common.

390 practice questions · 20 patient cases

Practice Periodontics

Where it fits in the official INBDE blueprint

Oral Health Management (periodontal disease). Nearest foundation knowledge areas: FK 6, FK 7. See the content outline for the official weights. This mapping is approximate: real items combine a clinical area with a foundation area.

What this area tests

High-yield checklist

Common traps

These notes are original study aids, not official exam content. Confirm clinical details against current guidelines.

Sample questions

1. An image shows gingival tissue that is red, edematous, and bleeds easily upon contact. Which term best describes the texture of this tissue?

  1. Friable
  2. Indurated
  3. Fibrotic
  4. Hyperkeratotic
Show answer and explanation

Correct answer: A. Friable

Friable describes tissue that is easily crumbled, torn, or bleeds spontaneously or on minimal contact — a hallmark of severely inflamed or pathological tissue. Inflamed gingival tissue loses its normal fibrotic architecture and becomes delicate, edematous, and friable. This is contrasted with fibrotic or indurated tissue, which is firm and resistant to manipulation. In the context of highly inflamed gingiva, friable is the most accurate descriptive term.

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2. GTR (Guided Tissue Regeneration) is BEST indicated for which periodontal defect?

  1. Generalized horizontal bone loss (1-wall defect)
  2. Class II furcation involvement and 2-3 wall vertical infrabony defects
  3. Class III furcation involvement (complete through-and-through)
  4. Suprabony pockets only
  5. Gingival recession on single-rooted teeth (CTG is better)
Show answer and explanation

Correct answer: B. Class II furcation involvement and 2-3 wall vertical infrabony defects

✓ B) Class II furcation and 2–3 wall vertical defects are the BEST indications for GTR.
GTR uses a barrier membrane (resorbable or non-resorbable) to exclude epithelium and connective tissue, allowing PDL progenitor cells to repopulate the defect → new cementum + PDL + alveolar bone. BEST outcomes with: (1) 2–3 walled vertical infrabony defects (more walls = better blood supply for clot stabilization); (2) Class II mandibular furcation; (3) Narrow, deep defects. POOR outcomes: (1) 1-wall defects (insufficient bone walls); (2) Class III furcation (complete); (3) Horizontal bone loss. Combined with bone grafts: even better results (enamel matrix derivative for regeneration).

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3. For the same case, what specific type of bony defect is this?

  1. Crater defect
  2. Circumferential defect
  3. Combined 1-3 wall defect
  4. Horizontal defect
Show answer and explanation

Correct answer: C. Combined 1-3 wall defect

Most vertical periodontal osseous defects are not a single, uniform wall pattern along their entire depth — they commonly present as combined defects, transitioning between different numbers of bony walls (e.g., 1, 2, or 3 walls) at different depths/levels of the same defect, which is the most common real-world presentation of a deep, narrow infrabony defect like the one described.

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4. What type of bacteria is found in a healthy gingival sulcus?

  1. Aerobic, non-motile, gram-positive organisms
  2. Spirochetes and fusiform bacteria
  3. Anaerobic, motile, gram-negative rods
  4. Facultative anaerobic, motile, gram-negative
Show answer and explanation

Correct answer: A. Aerobic, non-motile, gram-positive organisms

Healthy sulcus flora: aerobic/facultatively anaerobic, non-motile, gram-positive organisms (Streptococcus, Actinomyces). Diseased pockets shift toward anaerobic, motile, gram-negative bacteria.
  • A. ✅ CORRECT – Healthy sulcus: aerobic, non-motile, gram-positive cocci and rods.
  • B. ❌ Spirochetes and fusiform bacteria are periodontal pathogens in diseased pockets.
  • C. ❌ Anaerobic gram-negative motile bacteria characterize periodontal disease, not health.
  • D. ❌ Facultative anaerobic, motile gram-negative bacteria are associated with early periodontitis.

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5. A patient with periodontitis diagnosed two years ago (who never completed the recommended scaling/root planing) now has deep periodontal pockets, bone loss, pain, and a periapical radiolucency. What type of lesion is this?

  1. Combined endodontic-periodontal lesion
  2. Primary periodontal lesion
  3. Primary endodontic lesion
Show answer and explanation

Correct answer: A. Combined endodontic-periodontal lesion

This presentation — long-standing, untreated periodontal disease (deep pockets, bone loss) now combined with a new periapical (endodontic-origin) radiolucency — describes a combined endodontic-periodontal lesion, where both disease processes are present and may even communicate, rather than a purely periodontal or purely endodontic problem alone.

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6. Miller's classification of gingival recession predicts root-coverage outcomes. Which class describes recession extending to or beyond the mucogingival junction WITHOUT loss of interdental bone or soft tissue, so that 100% root coverage is still predictable?

  1. Class II
  2. Class I
  3. Class III
  4. Class IV
Show answer and explanation

Correct answer: A. Class II

Miller Class II = recession extends to or beyond the mucogingival junction, but the interproximal bone and soft tissue are intact, so complete (100%) root coverage is still predictable. Class I recession does not reach the MGJ (also 100% predictable). Classes III and IV have interdental attachment loss that limits coverage (partial in III, none in IV).Other options: Class I does not reach the MGJ; Classes III and IV involve interproximal bone loss and reduced coverage potential.Key exam takeaway: Miller I and II (no interdental loss) allow predictable full coverage; III (partial) and IV (none) have interproximal loss.

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7. Which surface of the maxillary first premolar is most difficult to clean and most prone to plaque accumulation, due to a developmental anatomic feature?

  1. Mesial surface
  2. Distal surface
  3. Buccal surface
  4. Occlusal surface
Show answer and explanation

Correct answer: A. Mesial surface

The maxillary first premolar classically has a developmental concavity/groove on its mesial surface, creating a localized plaque trap that makes this surface notably more difficult to clean than the other surfaces — a recognized local anatomic risk factor for periodontal breakdown in that specific area if oral hygiene is inadequate.

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8. For the same case, if a biopsy were performed on the surrounding bone marrow, what cell type would most likely be found (consistent with an underlying plasma cell disorder, e.g., multiple myeloma)?

  1. Lymphocytes
  2. Macrophages
  3. Neutrophils
  4. Plasma cells
Show answer and explanation

Correct answer: D. Plasma cells

Multiple myeloma is a malignancy of plasma cells, so a bone marrow biopsy in a patient with this underlying condition would show an abnormal, often sheet-like proliferation of plasma cells — distinguishing it from the other inflammatory cell types listed, which are not characteristic of a plasma cell neoplasm.

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Patient cases

All Periodontics questions (390)