Periodontology
What this domain tests
Questions focus on the 2017 classification (stage and grade), the difference between gingivitis and periodontitis, risk factors, and the sequence from non-surgical to surgical therapy and maintenance.
Core rules
- Gingivitis is reversible inflammation confined to the gingiva with no clinical attachment loss. Periodontitis requires clinical attachment loss plus radiographic bone loss.
- Staging uses severity (interdental CAL, bone loss percentage, tooth loss from periodontitis) and complexity (probing depth ≥6 mm, furcation, ridge defect, bite collapse). Stage I is CAL 1–2 mm, Stage II 3–4 mm, Stage III ≥5 mm, Stage IV adds complexity such as masticatory dysfunction.
- Grading uses progression rate: Grade A slow, Grade B moderate, Grade C rapid, judged by bone loss/age ratio and modified by smoking and diabetes.
- Probing depth alone does not define stage; you must convert to clinical attachment level using the gingival margin.
- Risk factors: smoking (dose-dependent, masks bleeding), poorly controlled diabetes (Grade C modifier), plaque biofilm as the necessary cause.
- Therapy: cause-related therapy with oral hygiene instruction and subgingival scaling and root planing, re-evaluation after 6–8 weeks, then surgery (flap, regenerative with grafts or GTR) or continued maintenance at individually set intervals.
- Systemic antibiotics (amoxicillin plus metronidazole) are an adjunct for specific aggressive cases, never a substitute for debridement.
Worked example
A 45-year-old smoker has 6 mm pockets on 16 and 26, CAL of 5 mm, 40% bone loss on the worst tooth, and no tooth loss. Reasoning: CAL ≥5 mm gives Stage III; bone loss/age is 40/45 ≈ 0.89, which combined with heavy smoking gives Grade C. Plan cause-related therapy, re-evaluate at 8 weeks, and consider regeneration only if the defect is suitable.
Traps
Staging from pocket depth without calculating CAL; forgetting to subtract recession; missing that smoking masks bleeding and worsens grade; using antibiotics instead of debridement; not re-evaluating before surgery.