Staging & Grading Step by Step (2017 AAP/EFP)

Step 1: Is it a periodontitis case?

Interdental clinical attachment loss (CAL) is detectable at 2 or more non-adjacent teeth, OR buccal/oral CAL of 3 mm or more with pocketing over 3 mm at 2 or more teeth.
Exclude attachment loss from other causes: trauma-related recession, cervical caries, a third molar extraction site, an endodontic lesion draining through the PDL, or a vertical root fracture.

Stage	Worst interdental CAL	Bone loss on radiograph	Teeth lost to periodontitis	Complexity flags
I (initial)	1–2 mm	Under 15% (coronal third)	0	PD up to 4 mm, mostly horizontal loss
II (moderate)	3–4 mm	15–33% (coronal third)	0	PD up to 5 mm, mostly horizontal loss
III (severe, can still lose teeth)	5 mm or more	Middle third or beyond	4 or fewer	PD 6 mm or more, vertical defects 3 mm or more, class II/III furcation, moderate ridge defect
IV (severe, can lose the dentition)	5 mm or more	Middle third or beyond	5 or more	Needs complex rehabilitation: masticatory dysfunction, mobility degree 2 or more from secondary occlusal trauma, bite collapse, drifting or flaring, fewer than 20 teeth (10 opposing pairs)

Pick the stage from the worst-site severity first; any complexity flag can push the stage up, never down.
Add the extent: localized (under 30% of teeth), generalized (30% or more) or molar/incisor pattern.

Evidence	Grade A	Grade B	Grade C
Bone or CAL loss over 5 years	None	Under 2 mm	2 mm or more
Percent bone loss ÷ age	Under 0.25	0.25 to 1.0	Over 1.0
Smoking	Non-smoker	Under 10 cigarettes a day	10 or more a day
Diabetes	No diabetes (normoglycemic)	HbA1c under 7.0%	HbA1c 7.0% or higher

Smoking and diabetes are grade modifiers: they can only raise the grade.
Worked ratio: 40% bone loss at age 32 → 40 ÷ 32 = 1.25 → grade C. 30% at age 60 → 0.5 → grade B. 10% at age 45 → about 0.22 → grade A evidence.

Format: 'Generalized periodontitis, stage III, grade B' (extent, stage, grade). Add the risk factors that drove the grade.
Other 2017 terms to use: periodontal health and gingivitis on an intact or reduced periodontium; necrotizing periodontal diseases; periodontitis as a manifestation of systemic disease; 'chronic' and 'aggressive' are retired.

Staging from probing depth: use interdental CAL first (and bone loss if CAL is unavailable).
Giving a patient grade A because the ratio is low while they smoke 15 cigarettes a day: smoking 10 or more a day sets grade C.
Lowering a stage because only one site is severe: the worst site sets the stage.
Counting teeth lost for orthodontic or caries reasons toward stage IV: only teeth lost to periodontitis count.

Stage = Severity + complexity (how bad, how hard); Grade = Growth rate (how fast).

Pick an answer to see right away whether it is correct and why.

A 50-year-old non-smoker without diabetes has worst interdental CAL of 6 mm, bone loss into the middle third, 2 teeth lost to periodontitis and no need for complex rehabilitation. Stage?
A 32-year-old has 40% bone loss at the worst site. What grade does the percent-bone-loss/age ratio suggest?
Which finding alone would raise an otherwise stage III case to stage IV?
A patient with HbA1c of 8.2% is otherwise grade B. The grade becomes:
Periodontitis involves 4 of 26 teeth. The extent is:

0 of 5 answered

Answer key: 1 D · 2 A · 3 D · 4 B · 5 D

Dental School Map · Original study material, written and checked by our team; always confirm clinical decisions against current guidelines.