Periodontics
The largest single diagnosis category on the OSCE — and an exam loved for its multi-answer questions where one missed pick costs the whole mark. The trick is reading BOP, CAL, and PD as a triangle, not three separate numbers.
14%
Largest Dx Category
01
Diagnosis Decision Map
Three numbers decide everything: BOP %, PD, CAL. Read them as a triangle.
The diagnostic triangle
Diagnostic categories — full reference
Health
| Type | BOP | PD | CAL | Description |
|---|---|---|---|---|
| Clinical Gingival Health | < 10% | ≤ 3 mm | 0 | No clinical inflammation |
| Intact Periodontium | < 10% | ≤ 3 mm | 0 | No CAL, no recession, no periodontitis history |
| Reduced Periodontium (non-perio) | < 10% | ≤ 3 mm | may exist | Aggressive brushing, crown lengthening |
| Reduced Periodontium (Stable Perio Pt) | < 10% | ≤ 4 mm | may exist | Treated periodontitis. No 4 mm pocket WITH BOP. |
Gingivitis
| Type | BOP | PD | CAL | Description |
|---|---|---|---|---|
| Biofilm-induced gingivitis | ≥ 10% | ≤ 3 mm | 0 | Plaque-mediated |
| Mediated by systemic / local risk factors | ≥ 10% | ≤ 3 mm | 0 | Hormones (puberty/pregnancy), hyperglycemia, malnutrition; subgingival restorations, hyposalivation |
| Drug-influenced gingival enlargement | ≥ 10% | ≥ 3 mm | 0 | Pseudo-pocketing from nifedipine, phenytoin, cyclosporine |
Periodontitis
| Type | Threshold |
|---|---|
| Periodontitis | CAL at ≥ 2 non-adjacent teeth OR buccal CAL > 3 mm with PD > 3 mm at ≥ 2 teeth |
M
Memory Hook · The two gates
BOP < 10% = health lane. BOP ≥ 10% = inflammation lane. Then ask: any CAL? PD > 3? That's three questions in 5 seconds.
i
OSCE pattern · "Select ONE OR MORE"
Multiple boxes can be correct simultaneously — e.g., "Clinical Gingival Health" + "Reduced Periodontium" + "Stable Periodontitis Patient" all check together for a treated patient.
02
Staging & Grading
Stage = "How far gone?" (worst CAL + RBL + tooth loss). Grade = "How fast?" (rate of bone loss, modified by smoking and diabetes).
Stages I → IV
I
Initial
- Interdental CAL
- 1–2 mm
- RBL
- Coronal third < 15%
- Tooth loss
- None
- Max PD
- ≤ 4 mm
II
Moderate
- Interdental CAL
- 3–4 mm
- RBL
- Coronal 15–33%
- Tooth loss
- None
- Max PD
- ≤ 5 mm
III
Severe
- Interdental CAL
- ≥ 5 mm
- RBL
- Middle/apical 1/3
- Tooth loss
- ≤ 4 teeth
- Complexity
- PD ≥ 6 · vertical > 3 · furcation II/III
IV
Advanced
- Interdental CAL
- ≥ 5 mm
- RBL
- Middle/apical 1/3
- Tooth loss
- ≥ 5 teeth
- Complexity
- Mob ≥ 2 · bite collapse · < 20 teeth
Grades A · B · C
| A: Slow | B: Moderate | C: Rapid | |
|---|---|---|---|
| RBL or CAL over 5 yr | None | < 2 mm | ≥ 2 mm |
| % RBL / age (indirect) | < 0.25 | 0.25 – 1.0 | > 1.0; or destruction exceeds biofilm |
| Smoking | Non-smoker | < 10 cig/day | ≥ 10 cig/day |
| Diabetes | Normoglycemic | HbA1c < 7.0% | HbA1c ≥ 7.0% |
M
Memory Hook · Two questions
Stage = "How far gone?" Grade = "How fast?" RBL/age: <0.25 slow → 0.25-1 moderate → >1 rapid.
03
Recession (Cairo) & Necrotizing Diseases
Cairo classifies recession by interproximal CAL. The number tells you whether root coverage is even possible.
Cairo Recession Types — root coverage prognosis
M
Memory Hook · The comparison
Compare interproximal CAL to buccal CAL: none → RT1 (full cover possible). ≤ buccal → RT2 (partial). > buccal → RT3 (no full coverage).
Necrotizing diseases & perio-systemic manifestations
| Type | Description | Initial Management |
|---|---|---|
| Periodontitis as Manifestation of Systemic Disease | Diabetes, HIV, Down syndrome → influence inflammation | SRP + CHX + systemic abx if indicated |
| Necrotizing Gingivitis | Acute gingival necrosis, bleeding, pain. Punched-out papillae. | Gentle debridement + CHX + systemic abx if systemic signs |
| Necrotizing Periodontitis | + bone loss + halitosis. Often immunocompromised. | SRP + CHX + systemic abx |
| Necrotizing Stomatitis | Necrosis beyond gingiva — soft tissue / bone. | Debridement + CHX + abx + urgent medical referral |
!
Trap · Necrotizing buzzwords
Spontaneous bleeding + pain + halitosis + papillary necrosis (punched-out papillae). Immunocompromised history → strongly favor necrotizing diagnosis.
04
Treatment Phases
Three phases. Restorative work waits until perio is stable.
Treatment phase flow
Surgical procedures — when to pick which
| Procedure | Does what | Indication |
|---|---|---|
| Coronally Positioned Flap | Repositions flap to cover root | Recession with sensitivity; aesthetic root coverage |
| Laterally Positioned Flap | Slides donor flap from neighbour | Isolated recession with adequate adjacent attached gingiva |
| Free Gingival Graft | Palatal graft to widen keratinized tissue | ↑ keratinized gingiva; multiple sites; less esthetic demand |
| Subepithelial CT Graft | CT graft, bilaminar/envelope recipient | Gold standard for esthetic root coverage |
| GTR / Regenerative | Membrane → selective regeneration | Grade II furcation; 2- or 3-wall vertical defects 4-5 mm |
| Gingivectomy | Excise gingiva to remove pocket | Drug-induced enlargement; pseudo-pockets |
| Distal Wedge | Eliminate distal pocket on terminal molar | Distal pocket on most distal tooth |
| Root Amputation / Hemisection | Remove one root or split molar | Severe perio loss / VRF / furcation on one root |
| Frenectomy | Remove abnormal frenum | High frenum → recession; midline diastema |
| Surgical Crown Exposure | Expose impacted/unerupted tooth | For ortho traction |
| Sinus Lift | Elevate sinus floor + graft | Insufficient bone height for posterior maxillary implant |
| Occlusal Therapy | Reduce traumatic forces | Adjunct when traumatic occlusion → mobility, fremitus |
05
Flap Designs
Three extraction flaps; named for their vertical incisions. More access = more verticals.
Extraction flap geometry
M
Memory Hook · "E-T-R" extraction flaps
Envelope (no verticals) → Triangular (one mesial vertical) → Rectangular (two verticals). More access = more verticals.
Periodontal & mucogingival flaps
| Flap | Description & indication |
|---|---|
| Semilunar | Curved incision in alveolar mucosa apical to gingiva. Requires adequate vestibular depth. Used in periapical/apical surgery to preserve interdental papilla. |
| Coronally Positioned | Split-thickness, repositioned coronally to cover recession. Requires 3 mm keratinized gingiva. |
| Apically Positioned | Repositioned apically to expose more tooth or reduce pocket. Crown lengthening; pocket reduction; ↑ keratinized gingiva. |
| Laterally Positioned | Slide donor tissue from adjacent tooth. Isolated recession with adequate donor attached gingiva. |
06
Contributing Factors
| Type | Description |
|---|---|
| Dental biofilm / calculus | Bacterial biofilm → host inflammatory response (primary etiology) |
| Periodontal phenotype | Thin → recession risk; thick → resistant |
| Toothbrush trauma | Aggressive horizontal brushing + hard bristles → recession + cervical abrasion |
| Self-induced trauma | Fingernail biting, foreign objects → localized injury |
| Intraoral jewellery | Lip/tongue piercings → localized recession (often mandibular anterior) |
| Caries | Subgingival caries → disrupts supracrestal attachment |
| Non-carious cervical lesions | Abrasion / erosion → recession + plaque retention |
| Tobacco use | ↓ bleeding (vasoconstriction!), impairs immune response, ↑ progression |
| Pulpal status | Necrosis → endo-perio lesion via accessory canals |
| Denture-induced trauma | Ill-fitting dentures → mechanical trauma + plaque |
| Traumatic occlusal forces | Does NOT initiate periodontitis but exacerbates attachment loss when inflammation exists |
| Systemic factors | Diabetes, phenytoin, cyclosporine, CCBs |
| Pro-inflammatory cytokines | IL-6, TNF-α, PGE₂; ↑ in poorly controlled diabetes, smoking, obesity |
!
Trap · The smoker's paradox
A smoker may have severe periodontitis with very LITTLE bleeding due to vasoconstriction. Don't be reassured by low BOP if pockets are deep + smoking history.
✓
Key · Occlusal trauma alone doesn't cause periodontitis
It only worsens disease when biofilm-driven inflammation already exists. Always look for the inflammatory trigger first.