DentAIstudy
Periodontology

Periodontitis Staging & Grading Simplified (OSCE & Viva Guide)

A clear, examiner-friendly breakdown of staging and grading using the 2017 classification.

Quick Answers

What is “staging” in periodontitis?

Staging describes how severe the disease is now and how complex it is to manage.

What is “grading” in periodontitis?

Grading estimates how fast the disease is likely progressing and considers risk factors.

What are Stage I–IV based on?

Mainly clinical attachment loss (CAL), radiographic bone loss, tooth loss, and complexity factors.

What are Grade A–C based on?

Rate of progression (bone loss/age), plus modifiers like smoking and diabetes.

1. Why examiners love staging & grading

The new classification replaced the old “chronic vs aggressive” system, because it gives a clearer clinical picture and supports treatment planning.

In OSCE/viva you’re scored on:

  • Choosing the right stage
  • Choosing the right grade
  • Giving a short justification

2. The 2-step mindset

Always answer in this order:

Exam Approach

Step 1: Stage it (severity + complexity)
Step 2: Grade it (speed + risk)

3. How to Stage periodontitis (I → IV)

Start with the WORST affected site (your maximum CAL or radiographic bone loss).

Staging (very high-yield)

  • Stage I (initial): CAL 1–2 mm, bone loss limited to coronal third, PD ≤4 mm.
  • Stage II (moderate): CAL 3–4 mm, bone loss coronal third, PD ≤5 mm.
  • Stage III (severe): CAL ≥5 mm, bone loss to middle third, PD ≥6 mm, possible furcation.
  • Stage IV (advanced): Stage III + functional problems (drifting, bite collapse, <20 teeth remaining).

After choosing I–IV, add extent: Localized (<30% teeth), Generalized (≥30%), or molar-incisor pattern.

4. Complexity factors that push Stage III/IV

Even if CAL is borderline, complexity can upgrade the stage. Examiners expect this line.

  • PD ≥6 mm
  • Vertical bone loss ≥3 mm
  • Furcation class II/III
  • Tooth loss because of periodontitis
  • Less than 20 remaining teeth = automatic Stage IV

These “upgrade clues” are emphasized in clinical decision trees.

5. How to Grade periodontitis (A → C)

Grading estimates progression and future risk. If you have old radiographs, compare them; if not, use bone loss/age ratio.

Grading (simple rules)

  • Grade A (slow): bone loss/age <0.25, heavy plaque but little destruction.
  • Grade B (moderate): bone loss/age 0.25–1.0, expected progression.
  • Grade C (rapid): bone loss/age >1.0, destruction out of proportion to plaque.

6. Risk modifiers that upgrade Grade

You pick a grade, then modify based on risk:

  • Smoking: <10 cigarettes/day → at least Grade B; ≥10/day → Grade C.
  • Diabetes: HbA1c <7% → at least Grade B; ≥7% → Grade C.

7. OSCE / Viva model answer

Example Examiner Answer

“This patient has maximum CAL of 5–6 mm with radiographic bone loss into the middle third and a class II furcation, so I would diagnose Stage III periodontitis. Bone loss/age ratio is around 0.6 with no heavy risk modifiers, so this is Grade B. Extent is generalized because more than 30% of teeth are involved.”

8. Common student mistakes

  • Staging based on average CAL instead of maximum site
  • Ignoring complexity upgrades
  • Forgetting extent (localized vs generalized)
  • Grading without checking smoking/diabetes

9. How DentAIstudy helps

DentAIstudy can instantly transform perio charts into:

  • Stage + grade diagnosis
  • Justified OSCE summaries
  • Flashcards for rules and risk modifiers
  • MCQs for boards

Try Study Builder →

References

  • Tonetti MS, Greenwell H, Kornman KS. Staging and grading of periodontitis: framework and proposal. J Periodontol. 2018.
  • American Academy of Periodontology / European Federation of Periodontology. Staging and Grading Periodontitis guideline summary. 2019.
  • EFP Clinical decision tree for staging and grading. 2019.
  • ADA overview of 2017 World Workshop classification. 2022.