Periodontitis Staging and Grading
Practical chairside reference for the 2018 (2017 World Workshop) classification of periodontitis. Source: Periodontitis Consensus report of workgroup 2 of the 2017 World Workshop on the Classification of Periodontal and Peri‐Implant Diseases and Conditions (Papapanou et al. 2018), with the staging/grading framework from Tonetti, Greenwell & Kornman 2018.
A complete diagnosis = Stage (I–IV) + Extent/distribution + Grade (A/B/C), e.g. “Generalised Stage III, Grade B periodontitis”.
Staging
Stage reflects severity at presentation and anticipated complexity of management. Set the initial stage from interdental CAL at the worst site; if CAL is unavailable, use radiographic bone loss (RBL). Tooth loss attributable to periodontitis and complexity factors can then shift the stage upward.
| Feature | Stage I (Initial) | Stage II (Moderate) | Stage III (Severe) | Stage IV (Very severe) |
|---|---|---|---|---|
| Severity | ||||
| Interdental CAL at worst site | 1–2 mm | 3–4 mm | ≥5 mm | ≥5 mm |
| Radiographic bone loss | Coronal third (<15%) | Coronal third (15–33%) | Extends to mid or apical third of root | Extends to mid or apical third of root |
| Tooth loss (due to periodontitis) | None | None | ≤4 teeth | ≥5 teeth |
| Complexity | ||||
| Max probing depth | ≤4 mm | ≤5 mm | ≥6 mm | ≥6 mm |
| Bone-loss pattern | Mostly horizontal | Mostly horizontal | Vertical bone loss ≥3 mm | Vertical bone loss ≥3 mm |
| Furcation | — | — | Class II or III | Class II or III |
| Ridge defects | — | — | Moderate ridge defect | Severe ridge defect |
| Additional (Stage IV only) | — | — | — | Need for complex rehab: masticatory dysfunction; secondary occlusal trauma (mobility ≥ degree 2); bite collapse, drifting, flaring; <20 remaining teeth (10 opposing pairs) |
| Extent / distribution (descriptor) | Localised (<30% of teeth), generalised, or molar/incisor pattern |
- The Stage III vs IV distinction is driven primarily by complexity factors (e.g. severe masticatory dysfunction or posterior bite collapse → Stage IV), not by CAL alone.
- For post-treatment patients, CAL and RBL remain the primary determinants; if treatment eliminates a stage-shifting complexity factor, the stage does not regress (carry the original complexity into maintenance planning).
Grading
Grade estimates the rate of progression and risk for future progression / poor outcomes. Use direct evidence when longitudinal data exist; otherwise use indirect evidence (%RBL ÷ age). Start every case at Grade B, then shift to A or C on evidence, then apply risk-factor modifiers.
| Criterion | Grade A (Slow) | Grade B (Moderate) | Grade C (Rapid) |
|---|---|---|---|
| Direct evidence — longitudinal RBL or CAL over 5 yrs | No loss over 5 yrs | <2 mm over 5 yrs | ≥2 mm over 5 yrs |
| Indirect evidence — % bone loss ÷ age | <0.25 | 0.25–1.0 | >1.0 |
| Case phenotype | Heavy biofilm, low destruction | Destruction commensurate with biofilm | Destruction exceeds biofilm; molar/incisor or early-onset pattern; poor response to standard therapy |
| Modifier — smoking | Non-smoker | <10 cigarettes/day | ≥10 cigarettes/day |
| Modifier — diabetes | Normoglycaemic / no diabetes | HbA1c <7.0% | HbA1c ≥7.0% |
Practical tips
- Quantify radiographic bone loss as a percentage of root length at the worst-affected tooth: measure bone loss from ~2 mm below the CEJ to the bone crest, expressed as a fraction of total root length.
- Convert to grade via the %RBL ÷ age ratio (indirect evidence): <0.25 → A, 0.25–1.0 → B, >1.0 → C. Example: 30% bone loss in a 60-year-old = 0.5 → Grade B; the same 30% in a 25-year-old = 1.2 → Grade C.
- Stage = the highest qualifying feature. A single severity or complexity factor that meets a higher stage sets the stage — e.g. Class II/III furcation alone shifts a case to ≥ Stage III regardless of CAL.
- One complexity factor shifts the stage up. Not all factors need be present; use clinical judgement.
- Grade modifiers only move the grade upward. Begin at Grade B, refine with direct/indirect evidence, then bump up for smoking or poorly-controlled diabetes (a Grade A/B case with HbA1c ≥7.0% or ≥10 cig/day becomes Grade C).
- New umbrella term: the single diagnosis “periodontitis” now replaces the former “chronic” and “aggressive” categories, since current evidence does not support them as distinct diseases. Necrotising periodontal diseases and periodontitis as a manifestation of systemic disease remain separate categories.