EFP/AAP 2017 classification: staging and grading

The 2017 World Workshop replaced the 1999 Armitage system with a two-axis diagnosis: stage (severity and complexity) and grade (rate of progression). This guide summarises the criteria used by the Bonebenders clinical calculator.

Why it matters clinically

Staging and grading align communication between clinicians, treatment planning and prognosis. Stage describes how much damage is present and how complex it is to manage; grade estimates how fast disease may progress. Both inform treatment intensity and supportive-care recall frequency.

How stage is assigned (I–IV)

Stage is set by the worst site and by complexity factors. Teeth are not averaged: a single severe site can raise the stage for the whole dentition.

Stage I — initial

• Interdental CAL 1–2 mm
• Radiographic bone loss (RBL) in the coronal third (<15%)
• No tooth loss due to periodontitis
• Maximum probing depth ≤4 mm; mostly horizontal bone loss

Stage II — moderate

• Interdental CAL 3–4 mm
• RBL in the coronal third (15–33%)
• No tooth loss due to periodontitis
• Maximum probing depth ≤5 mm

Stage III — severe, with potential for additional tooth loss

• Interdental CAL ≥5 mm
• RBL extending to the mid-third of the root or beyond
• ≤4 teeth lost to periodontitis
• Possible complexity: PD ≥6 mm, vertical defects ≥3 mm, furcation II/III, moderate ridge defects

Stage IV — severe, with potential for loss of dentition

• As Stage III plus masticatory dysfunction
• Secondary occlusal trauma (mobility ≥ grade 2), bite collapse, drifting, ≥5 teeth lost to periodontitis, or <20 remaining teeth (10 opposing pairs)

How grade is assigned (A–C)

Grade typically starts at B and shifts with direct/indirect evidence of progression and with systemic/environmental modifiers.

• Grade A (slow): no bone loss over 5 years, or bone-loss%/age ratio <0.25; non-smoker; no diabetes.
• Grade B (moderate): bone-loss/age ratio 0.25–1.0; smoker <10 cigarettes/day; diabetes with HbA1c <7.0%.
• Grade C (rapid): ratio >1.0; smoker ≥10 cigarettes/day; diabetes with HbA1c ≥7.0%.

Heavy smoking and poorly controlled diabetes shift the grade toward C even when the bone-loss/age ratio is intermediate.

Extent and distribution

• Localised: <30% of teeth involved
• Generalised: ≥30% of teeth involved
• Molar–incisor pattern: characteristic distribution affecting molars and incisors

Recommended diagnostic sequence

First confirm the diagnosis of periodontitis (detectable interdental clinical attachment loss at more than one non-adjacent site, or buccal/lingual CAL ≥3 mm with pocketing >3 mm). Only then assign stage, grade and extent. Staging does not create the diagnosis: it characterises severity, complexity and progression risk.

In practice: collect history (smoking, diabetes/HbA1c), six-site probing, CAL at worst sites, targeted radiographs, teeth lost attributable to periodontitis, and complexity factors (furcation, vertical defects, mobility, occlusal collapse). Then assign stage from the worst site, grade from ratios and modifiers, and extent from the percentage of teeth involved.

Common pitfalls

• Relying on probing depth alone without CAL or radiographs.
• Averaging sites instead of using the worst site.
• Counting teeth lost to caries/trauma as periodontitis-related losses.
• Ignoring modifiers (smoking ≥10/day, HbA1c ≥7%) when assigning grade.
• Treating stage and grade as permanent labels rather than reassessing over time.

Using it in the calculator

Enter age, teeth present, interdental CAL, radiographic bone loss, teeth lost, BOP, residual pockets, smoking and glycaemic control. The tool returns stage, grade and extent according to these criteria, together with PRA and the recall interval. Read the output as decision support: diagnostic responsibility stays with the clinician who examined the patient.

After computing, reconcile the output with the full clinical picture: if the tool suggests Stage III but masticatory dysfunction is obvious, reconsider Stage IV; if grade looks like B but the patient smokes ≥10 cigarettes/day, the modifier should push toward C. The calculator automates thresholds; it does not replace clinical synthesis.

Frequently asked questions

Does staging replace the diagnosis of periodontitis?

No. It characterises periodontitis that has already been diagnosed. Staging/grading do not replace history-taking, full-mouth probing or clinical judgement.

If only one site is severe, which stage do I use?

Use the stage of the worst site, unless complexity factors elevate the category further.

Can grade change over time?

Yes. Grade reflects current progression risk; at recall, new radiographs or modifiers (smoking, HbA1c) may reassign it.

This guide does not replace a specialist examination. It is clinical decision support, to be interpreted within professional judgement.

Scientific references

1. Tonetti MS, Greenwell H, Kornman KS. Staging and grading of periodontitis. J Periodontol. 2018;89 Suppl 1:S159-S172. PubMed
2. Papapanou PN, Sanz M, et al. Periodontitis: Consensus report of workgroup 2 of the 2017 World Workshop. J Periodontol. 2018;89 Suppl 1:S173-S182. PubMed
3. Tonetti MS, Sanz M. Implementation of the new classification of periodontal diseases: decision-making algorithms. J Clin Periodontol. 2019;46(4):398-405. PubMed

Clinical guide by Dr. Ernesto Bruschi — bonebenders.com

Last clinical review: 1 August 2026