24.3 Staging and Grading Periodontitis
Key Takeaways
- A periodontitis case requires interdental clinical attachment loss at two or more non-adjacent teeth.
- Stage is assigned from interdental attachment loss or radiographic bone loss at the worst site, from stage I through stage IV.
- Grade is assigned from direct five-year radiographic evidence or indirectly from the percentage bone loss divided by age.
- A bone loss to age ratio below 0.25 is grade A, 0.25 to 1.0 is grade B and above 1.0 is grade C.
- Extent is localised at under 30% of teeth, generalised at 30% or more, or a molar-incisor pattern.
4. Periodontitis: Definition, Staging, and Grading
Formal Case Definition of Periodontitis
According to the 2018 Classification, a patient is formally defined as a periodontitis case if:
- Interdental clinical attachment loss (CAL) is clinically detectable at $\ge 2$ non-adjacent teeth; OR
- Buccal or oral CAL $\ge 3\text{ mm}$ with pocketing $> 3\text{ mm}$ is clinically detectable at $\ge 2$ teeth.
Exclusion Rule: The observed clinical attachment loss must not be attributable to non-periodontitis causes, including:
- Gingival recession of traumatic origin (e.g., severe toothbrush abrasion, oral piercings).
- Dental caries extending cervically into the subgingival radicular third.
- Attachment loss on the distal aspect of a mandibular second molar associated with an impacted, partially erupted, or extracted third molar.
- An endodontic lesion draining via the marginal periodontium (true endo-perio lesion).
- The occurrence of a vertical root fracture.
Patient Presents with Interdental Attachment Loss
│
├── Does CAL occur at ≥ 2 non-adjacent teeth?
│ ├── NO ──> Exclude non-periodontal causes (caries, trauma, 3rd molar, fracture)
│ └── YES ─> CONFIRMED PERIODONTITIS CASE
│ │
│ ├── Determine STAGE (I, II, III, IV) based on Severity & Complexity
│ ├── Determine GRADE (A, B, C) based on % Bone Loss / Age & Risk Factors
│ └── Determine EXTENT (Localised <30%, Generalised ≥30%, Molar-Incisor)
Staging of Periodontitis (Severity and Complexity)
Staging categorises the severity of tissue destruction and the complexity of required clinical management, ranging from Stage I (early disease) to Stage IV (advanced breakdown threatening total dentition loss).
| Staging Parameter | Stage I: Initial | Stage II: Moderate | Stage III: Severe with Potential for Additional Tooth Loss | Stage IV: Advanced with Potential for Dentition Loss |
|---|---|---|---|---|
| Interdental CAL (Worst Site) | $1-2\text{ mm}$ | $3-4\text{ mm}$ | $\ge 5\text{ mm}$ | $\ge 5\text{ mm}$ |
| Radiographic Bone Loss (RBL) | Coronal third ($< 15%$) | Coronal third ($15-33%$) | Extending to mid-third of root and beyond ($\ge 33%$) | Extending to mid-third of root and beyond ($\ge 33%$) |
| Tooth Loss (Due to Periodontitis) | $0\text{ teeth}$ | $0\text{ teeth}$ | $\le 4\text{ teeth}$ | $\ge 5\text{ teeth}$ |
| Maximum Probing Depth | $\le 4\text{ mm}$ | $\le 5\text{ mm}$ | $\ge 6\text{ mm}$ | $\ge 6\text{ mm}$ |
| Bone Loss Pattern | Horizontal only | Mostly horizontal | Vertical bone loss $\ge 3\text{ mm}$; Class II/III furcations | Vertical bone loss $\ge 3\text{ mm}$; Class II/III furcations |
| Masticatory & Occlusal Complexity | None | None | Moderate alveolar ridge defect | Masticatory dysfunction; secondary occlusal trauma; mobility $\ge$ Class II; bite collapse; $< 20$ teeth remaining ($< 10$ opposing pairs) |
Grading of Periodontitis (Biological Rate of Progression)
Grading estimates the future risk of disease progression, anticipates responsiveness to standard therapy, and evaluates systemic impacts. Clinicians calculate grading using direct evidence (longitudinal radiographic bone loss over 5 years) or indirect evidence (the ratio of percentage bone loss to patient age at the most severely affected tooth).
| Grading Parameter | Grade A: Slow Progression | Grade B: Moderate Progression | Grade C: Rapid Progression |
|---|---|---|---|
| Direct Evidence (5-year RBL) | No bone loss over 5 years | $< 2\text{ mm}$ loss over 5 years | $\ge 2\text{ mm}$ loss over 5 years |
| Indirect Evidence (% RBL / Age) | $< 0.25$ | $0.25\text{ to }1.0$ | $> 1.0$ |
| Biofilm vs Destruction Phenotype | Heavy biofilm deposits with low levels of tissue destruction | Destruction commensurate with biofilm deposits | Destruction exceeds expectations given biofilm deposits; early-onset patterns |
| Risk Factor: Tobacco Smoking | Non-smoker | Smoker $< 10\text{ cigarettes/day}$ | Heavy smoker $\ge 10\text{ cigarettes/day}$ |
| Risk Factor: Diabetes Mellitus | Normoglycaemic / No diabetes | Diagnosed diabetes with $\text{HbA1c} < 7.0%$ ($< 53\text{ mmol/mol}$) | Diagnosed diabetes with $\text{HbA1c} \ge 7.0%$ ($\ge 53\text{ mmol/mol}$) |
[!NOTE] The Grade Modifier Upgrade Rule: Grade assignment begins with the calculation of the bone loss/age ratio (or direct evidence). If a systemic grade modifier (smoking or diabetes) reflects a higher biological grade than the bone loss/age ratio, the grade must be upgraded to the higher grade. For example, a 50-year-old patient with $30%$ bone loss has a ratio of $30 / 50 = 0.60$ (Grade B); however, if the patient smokes 15 cigarettes daily, the definitive grade becomes Grade C.
Extent and Distribution
Extent describes the proportion of teeth affected by attachment loss corresponding to the assigned Stage:
- Localised: $< 30%$ of remaining teeth involved.
- Generalised: $\ge 30%$ of remaining teeth involved.
- Molar-Incisor Pattern: Tissue breakdown is restricted classically to the first permanent molars and incisors (representing the phenotype formerly designated as localized aggressive periodontitis).
Complete BSP Diagnostic Statement Format
Under BSP guidelines, a complete, legally robust periodontal diagnostic statement must incorporate four distinct descriptors:
Clinical Example: "Generalised Periodontitis; Stage III, Grade C; currently unstable; active risk factors: cigarette smoking (15/day), poorly controlled Type 2 Diabetes Mellitus (HbA1c 8.4% / 68 mmol/mol)."
Making the Diagnosis in the UK
UK practice follows the British Society of Periodontology implementation of the 2017 World Workshop classification, which sets out a defined pathway. A patient screened with the Basic Periodontal Examination who has codes 3 or 4, or evidence of interdental recession, proceeds to a full periodontal assessment with radiographs. Periodontitis is diagnosed where there is interdental clinical attachment loss at two or more non-adjacent teeth, or buccal or oral attachment loss of 3 mm or more with pocketing greater than 3 mm at two or more teeth, provided the loss is not attributable to a non-periodontal cause such as recession from trauma, caries, a malpositioned third molar, an endodontic lesion or a root fracture.
Once periodontitis is confirmed, the BSP pathway asks whether it is molar–incisor pattern, localised (under 30 per cent of teeth) or generalised; then the stage from the worst site's radiographic bone loss measured at the mid-root level — Stage I up to 15 per cent, Stage II coronal third, Stage III mid-third, Stage IV apical third; then the grade from the ratio of maximum percentage bone loss to the patient's age — Grade A below 0.5, Grade B 0.5 to 1.0, Grade C above 1.0; then current status, stable, in remission or unstable; and finally risk factor documentation such as smoking and diabetes control.
Stability as a Treatment Endpoint
The pathway also defines the endpoint of treatment, which is what makes it clinically useful rather than merely descriptive. A patient is stable when bleeding on probing is under 10 per cent, there are no probing depths of 4 mm or more that bleed, and the maximum probing depth is 4 mm or less. A patient is in remission when bleeding on probing is 10 per cent or more but the probing depth criteria are otherwise met. A patient is unstable when there are probing depths of 5 mm or more, or 4 mm pockets that bleed on probing. These exact thresholds are reliably examined, and they also determine whether treatment moves on to the next step or returns to re-treatment.