Periodontology
What the exam tests
Use of the current classification, differentiation of gingivitis from periodontitis, and construction of a risk-based treatment and maintenance plan.
Core rules
- Periodontitis is defined by interdental clinical attachment loss (CAL) of 2 mm or more, or buccal/oral CAL of 3 mm or more with pocketing above 3 mm.
- Staging by severity and complexity: Stage I = CAL 1-2 mm; Stage II = CAL 3-4 mm; Stage III = CAL 5 mm or more with up to four teeth lost to periodontitis; Stage IV adds bite collapse, mobility, ridge defects or fewer than 20 teeth.
- Grading by rate of progression: Grade A = radiographic bone loss/age <0.25; Grade B = 0.25-1.0; Grade C = >1.0. Smoking and HbA1c above 7.0% shift the grade upward.
- Probing depth is not attachment loss: recession and gingival margin position must be recorded to calculate CAL.
- Treatment sequence: behaviour change and oral hygiene instruction, then supra- and subgingival instrumentation, re-evaluation at 6-8 weeks, then surgery only for residual sites. Adjunctive systemic antibiotics (amoxicillin plus metronidazole) are considered in Grade C or aggressive cases, never as a substitute for debridement.
- Supportive periodontal care intervals follow risk; smokers and diabetics need shorter recalls.
Worked example
A 52-year-old smoker has 6 mm pockets on molars, 40% bone loss on the worst tooth, no tooth loss, and HbA1c 6.0%. Reasoning: CAL of 6 mm gives Stage III; bone loss/age = 40/52 = 0.77, giving Grade B, but smoking raises the risk profile and justifies Grade C-level vigilance. Treatment: hygiene phase, full-mouth instrumentation, smoking cessation, re-evaluation at 8 weeks, and 3-monthly maintenance.
Traps that cost marks
- Staging from probing depth alone.
- Calling a Grade C case 'aggressive periodontitis' - that category no longer exists.
- Prescribing antibiotics without instrumentation.