Periodontitis Classification: AAP/EFP Staging and Grading

Core Review

The 2018 Classification Framework: Overview

The 2018 World Workshop (AAP/EFP) produced a comprehensive reclassification that is now the global standard. The framework defines three broad categories:

1. Periodontal Health and Gingival Health
2. Gingivitis: Dental Biofilm-Induced
3. Periodontitis (staged I-IV, graded A-C)

Plus additional categories for non-dental-biofilm-induced conditions, peri-implant diseases, and other conditions affecting the periodontium.

Category 1: Periodontal Health and Gingival Health

Periodontal health is defined as the absence of clinical signs of inflammation and the absence of progressive attachment loss.

Clinical Gingival Health on an Intact Periodontium:

• No bleeding on probing (<10% of sites)
• Probing depths ≤3 mm
• No attachment loss (no CAL from CEJ)
• No radiographic bone loss

Clinical Gingival Health on a Reduced Periodontium:

• A patient previously treated for periodontitis who is now stable
• No bleeding on probing (<10% of sites)
• Probing depths ≤4 mm (may have residual pockets)
• May have attachment loss (CAL) and radiographic bone loss from previous disease — these are historical, not current
• This is a "well-maintained" periodontitis patient

Category 2: Gingivitis — Dental Biofilm-Induced

Gingivitis is an inflammatory condition confined to the gingiva without attachment loss or bone loss.

Key features:

• BOP present (≥10% of sites) — the hallmark sign
• Probing depths may be normal or deepened (pseudopockets from gingival enlargement)
• No CAL — this is the critical distinction from periodontitis
• No radiographic bone loss
• Reversible with adequate plaque control

Gingivitis on an Intact Periodontium: No history of periodontitis, no CAL, no bone loss. This is "simple" gingivitis.

Gingivitis on a Reduced Periodontium: BOP in a patient with a history of treated periodontitis. This represents recurrent inflammation at a previously diseased site — a "relapse" that requires attention to prevent further attachment loss.

Gingivitis severity:

• Localized: 10-30% of sites with BOP
• Generalized: >30% of sites with BOP

Category 3: Periodontitis

Periodontitis is defined by the presence of interdental clinical attachment loss at ≥2 non-adjacent teeth, OR buccal/oral CAL ≥3 mm with pocketing >3 mm at ≥2 teeth. CAL must not be attributable to non-periodontal causes (traumatic toothbrushing, caries extending into the cervical area, endodontic lesions draining through the periodontal ligament, distal bone loss adjacent to an impacted third molar).

Periodontitis = CAL that is (a) interdental in nature, (b) not attributable to local causes, and (c) present at ≥2 non-adjacent teeth.

Staging (I-IV): Severity and Complexity

Staging answers: "How severe is the disease, and how complex is it to manage?"

Stage I — Initial Periodontitis

• CAL: 1-2 mm interdental at site of greatest loss
• Radiographic bone loss: Coronal third (<15% of root length)
• Tooth loss due to periodontitis: None
• Complexity: Probing depths ≤4 mm, mostly horizontal bone loss
• Treatment: Generally non-surgical; straightforward to manage

Stage II — Moderate Periodontitis

• CAL: 3-4 mm interdental at site of greatest loss
• Radiographic bone loss: Coronal third (15-33% of root length)
• Tooth loss due to periodontitis: None
• Complexity: Probing depths ≤5 mm, mostly horizontal bone loss
• Treatment: Generally non-surgical; moderately complex

Stage III — Severe Periodontitis with Potential for Additional Tooth Loss

• CAL: ≥5 mm interdental at site of greatest loss
• Radiographic bone loss: Extending to the middle third and beyond
• Tooth loss due to periodontitis: ≤4 teeth
• Complexity: Probing depths ≥6 mm, vertical bone loss ≥3 mm, furcation involvement Class II or III, moderate ridge defects
• Treatment: May require surgical intervention; complex to manage

Stage IV — Severe Periodontitis with Potential for Loss of Dentition

• CAL: ≥5 mm interdental at site of greatest loss (same CAL threshold as Stage III)
• Radiographic bone loss: Extending to the middle third and beyond
• Tooth loss due to periodontitis: ≥5 teeth
• Complexity: Need for complex rehabilitation due to masticatory dysfunction, secondary occlusal trauma (tooth mobility ≥Class II), severe ridge defects, bite collapse, drifting and flaring, less than 20 remaining teeth (10 opposing pairs)
• Treatment: Requires interdisciplinary management (periodontal, restorative, orthodontic, possibly surgical)

Staging Decision Matrix:

How to stage: Start with CAL → then check RBL → then tooth loss → then complexity. The highest applicable stage is assigned. If CAL and RBL suggest different stages, use the higher one.

Grading (A-C): Progression Risk

Grading answers: "How fast is the disease progressing, and what is the risk of future progression?"

Grading considers:

1. Direct evidence of progression (longitudinal CAL or RBL data)
2. Indirect evidence (RBL as a percentage of root length divided by patient age)
3. Risk factors: smoking, diabetes

Grade A — Slow Rate of Progression

• Direct evidence: No CAL or RBL loss over 5 years
• Indirect evidence: RBL/age ratio <0.25
• Risk factors: Non-smoker, no diabetes (or normoglycemic)
• Phenotype: Heavy biofilm deposits with relatively low destruction — the patient's immune response is fairly controlled

Grade B — Moderate Rate of Progression

• Direct evidence: <2 mm CAL or RBL loss over 5 years
• Indirect evidence: RBL/age ratio 0.25-1.0
• Risk factors: Smoker <10 cigarettes/day, HbA1c <7% in diabetic patients
• Phenotype: Destruction is commensurate with biofilm deposits

Grade C — Rapid Rate of Progression

• Direct evidence: ≥2 mm CAL or RBL loss over 5 years
• Indirect evidence: RBL/age ratio >1.0
• Risk factors: Smoker ≥10 cigarettes/day, HbA1c ≥7%
• Phenotype: Destruction exceeds expectations given biofilm deposits — the patient's immune response is hyper-reactive

RBL/age ratio calculation:

• Percentage of bone loss at the most affected tooth / patient's age
• Example: 40% bone loss in a 50-year-old → 40/50 = 0.8 → Grade B
• Example: 40% bone loss in a 30-year-old → 40/30 = 1.33 → Grade C (rapid progression for the patient's age)

Extent:

• Localized: <30% of teeth affected
• Generalized: ≥30% of teeth affected
• Molar/incisor pattern: When grade C presents with a specific pattern (previously called "localized aggressive periodontitis" or "localized juvenile periodontitis")

Putting It Together: Example Classifications

Case 1: A 45-year-old non-smoker with CAL of 3 mm interdental, RBL in coronal third (~20%), no tooth loss, probing depths ≤5 mm, horizontal bone loss. Classification: Stage II, Grade A, Generalized Periodontitis

Case 2: A 55-year-old smoker (1 pack/day) with CAL of 7 mm interdental, RBL to middle third (~50%), lost tooth #14 due to periodontitis, Class II furcation on #19 and #30, PD ≥6 mm, vertical bone defect on #30 mesial. Classification: Stage III, Grade C, Generalized Periodontitis

Case 3: A 30-year-old non-smoker with CAL of 2 mm interdental, RBL 10% (coronal third), no tooth loss, probing depths ≤4 mm, horizontal bone loss. Classification: Stage I, Grade A, Localized Periodontitis

Case 4: A 62-year-old diabetic (HbA1c 8.5%) with CAL of 8 mm interdental, RBL to apical third, lost 6 teeth due to periodontitis, Class III furcation on #3, mobility Class II on several teeth, bite collapse, drifting, 18 remaining teeth. Classification: Stage IV, Grade C, Generalized Periodontitis

Grading Modifiers

After establishing the base grade, modifiers are applied to reflect specific risk factors:

• Smoking: Never (Grade A), <10 cigs/day (Grade B), ≥10 cigs/day (Grade C)
• Diabetes: Non-diabetic/normoglycemic (Grade A), HbA1c <7% (Grade B), HbA1c ≥7% (Grade C)
• Shift to Grade C from any existing risk factor: If either smoking or diabetes qualifies for Grade C, the overall grade becomes Grade C

Important: What Changed from the 1999 Classification

The NBDHE no longer uses these obsolete terms (and neither should you):

Implant Health and Disease

The 2018 classification also introduced standardized definitions for peri-implant conditions:

• Peri-implant health: No BOP, no suppuration, no bone loss beyond initial remodeling
• Peri-implant mucositis: BOP (+), erythema, swelling; no bone loss beyond remodeling
• Peri-implantitis: Inflammation + progressive bone loss beyond initial remodeling

Clinical Application

A 48-year-old new patient presents. Full mouth assessment reveals:

• Interdental CAL of greatest loss: 6 mm (#30 mesial)
• Radiographic bone loss: approximately 45% (middle third) at #30 mesial
• Tooth loss: #3 extracted 3 years ago "because it was loose" (likely periodontitis-related)
• Probing depths: generalized 4-7 mm
• Furcation: Class II buccal on #19, #30
• Smoking: 15 cigarettes/day (37.5 pack-year history)
• Medical history: no diabetes

Staging: CAL ≥5 mm → qualifies for Stage III. RBL to middle third → consistent with Stage III. Tooth loss = 1 tooth → Stage III. Complexity: Class II furcation, PD ≥6 mm → Stage III.

Grading: Direct evidence not available (new patient). Indirect: RBL/age = 45/48 ≈ 0.94 → Grade B. Modifier: smoking ≥10 cigs/day → Grade C. Final grade: C.

Extent: >30% teeth affected → Generalized.

Final Classification: Stage III, Grade C, Generalized Periodontitis

Common Traps

• TRAP: Using old terminology. The NBDHE has transitioned to the 2018 classification. Answers using "chronic" or "aggressive" are incorrect.
• TRAP: Staging based on probing depth rather than CAL. Staging is driven by interdental CAL at the site of greatest loss.
• TRAP: Confusing CAL and probing depth. In Stage I, CAL is 1-2 mm, but probing depths may be ≤4 mm. They are not the same.
• TRAP: Forgetting that grading includes risk factor modifiers. A patient with RBL/age = 0.4 (Grade B) but who smokes 1 pack/day shifts to Grade C.
• TRAP: Staging a GINGIVITIS case as periodontitis. Check for CAL and bone loss first — no CAL and no bone loss = gingivitis, not periodontitis.