Criteria for Staging and Grading according to the description of the 2018 classification
| Stage | Criteria | ||||||
| CAL (mm) | Bone loss (%) | Tootd loss (n) | Max. PPD (mm) | Furcation involvement | |||
| Stage I | 1–2 | <15 | No | ≤4 | No | ||
| Stage II | 3–4 | 15–33 | No | 4–5 | Class II, III | ||
| Stage III | ≥5 | ≥33 | ≤4 | ≥6 | Class II, III | ||
| Stage IV | ≥5 | ≥33 | ≥5 | ≥6 | Class II, III | ||
| Grade | Bone loss/age (%/y) | Smoking statue | Diabetes | ||||
| Grade A | <0.25 | Non-smoker | Normoglycemic | ||||
| Grade B | 0.25–1.0 | <10 cigarettes/d | HbA1c <7% | ||||
| Grade C | >1.0 | ≥10 cigarettes/d | HbA1c ≥7% | ||||
CAL, clinical attachment level; PPD, probing pocket depth.