Periodontal Staging and Grading (2017 AAP/EFP) for the INBDE
The 2017 AAP/EFP classification labels every periodontitis patient with a stage (I to IV: how severe the damage is and how hard it will be to treat) and a grade (A to C: how fast the disease is moving). You stage from the worst interdental attachment loss, then adjust for tooth loss and complexity; you grade from bone loss divided by age, then adjust for smoking and blood sugar control.
Classify 20 cases until it is automatic
The Study Boards INBDE course drills staging and grading the way the exam asks it: inside a patient box, mixed in with other subjects. The Periodontics Module and Master File teach every stage and grade, and the Master Tests, daily tasks and nightly live tests at 9 PM New York time make you apply them. The course is extremely personalised: red lines and assignments are given to you on the go, it learns from the way you study, and faculty are there to assist you. US-licensed dentists answer your doubts.
What the 2017 classification changed
The 2017 World Workshop, run jointly by the American Academy of Periodontology (AAP) and the European Federation of Periodontology (EFP), replaced the 1999 system. Three changes matter most for the exam.
“Chronic” and “aggressive” are goneBoth are now grouped under one name: periodontitis. Severity and speed are described with stage and grade instead.1
Health, gingivitis or periodontitis?
Before you stage anything, decide which bucket the patient is in. The 2017 numbers are simple: bleeding on probing (BOP) as a percentage of sites, and probing depth.
| Diagnosis | Bleeding on probing | Probing depth | Attachment loss |
|---|---|---|---|
| Gingival health, intact periodontium | Under 10% of sites | 3 mm or less | None |
| Gingivitis, intact periodontium | 10% or more (localized 10-30%, generalized over 30%) | 3 mm or less | None |
| Health on a reduced periodontium, stable treated periodontitis patient | Under 10% | 4 mm or less | Present (from past disease) |
| Gingivitis in a patient with a history of periodontitis | 10% or more | Shallow sites | Present (from past disease) |
| Periodontitis | Usually present | Often deepened | Interdental CAL at 2 or more non-adjacent teeth |
Health and gingivitis thresholds from the Workgroup 1 consensus report; periodontitis case definition from the Workgroup 2 report.23
The full periodontitis case definition
A patient is a periodontitis case if either of these is true:3
Interdental CALDetectable interdental clinical attachment loss at 2 or more non-adjacent teeth.
Buccal or oral CALCAL of 3 mm or more with pocketing of 3 mm or more on the buccal or oral surface, at 2 or more teeth.
- gingival recession of traumatic origin
- caries reaching the cervical area of the tooth
- CAL on the distal of a second molar linked to a malposed or extracted third molar
- an endodontic lesion draining through the marginal periodontium
- a vertical root fracture
Staging periodontitis: Stage I to IV
Stage describes how much tissue the disease has already destroyed and how complex long-term care will be. It is set at the patient’s worst site, not their average.
| Factor | Stage I | Stage II | Stage III | Stage IV |
|---|---|---|---|---|
| Worst interdental CAL | 1-2 mm | 3-4 mm | 5 mm or more | 5 mm or more |
| Radiographic bone loss (RBL) | Coronal third (under 15%) | Coronal third (15-33%) | Middle third of root and beyond | Middle third of root and beyond |
| Teeth lost to periodontitis | None | None | 4 or fewer | 5 or more |
| Complexity | Max probing depth 4 mm or less; mostly horizontal bone loss | Max probing depth 5 mm or less; mostly horizontal bone loss | Stage II complexity plus: probing depth 6 mm or more, vertical bone loss 3 mm or more, Class II or III furcation, moderate ridge defects | Stage III complexity plus a need for complex rehabilitation: masticatory dysfunction, secondary occlusal trauma (mobility degree 2 or more), severe ridge defects, bite collapse, drifting or flaring, fewer than 20 teeth (10 opposing pairs) |
| Extent (add to every stage) | Localized (under 30% of teeth involved), generalized, or molar/incisor pattern | |||
Adapted from the AAP staging chart and Tonetti et al. 2018.46
The staging flowchart
Drawn by our faculty from the AAP staging chart and the 2017 consensus papers.
Five staging rules the exam loves
The initial stage comes from clinical attachment loss at the site of greatest loss. Use radiographic bone loss only if CAL is not available.6
A single 6 mm interdental site makes the patient at least Stage III, even if every other site is 2 mm. Extent (localized or generalized) is how you describe the spread.
One or more complexity factors may shift the stage to a higher level.6 A Class II furcation in a patient with 4 mm CAL makes them Stage III, not Stage II.
If treatment removes a complexity factor (for example, a deep pocket closes), the stage does not go back to a lower one.4
Both start at 5 mm. What separates them is tooth loss (5 or more teeth) and the need for complex rehabilitation.6
Grading periodontitis: Grade A, B or C
Grade estimates how fast the disease is progressing, how well it is likely to respond to treatment, and its possible effect on general health. Clinicians start by assuming Grade B, then look for evidence to move to A or C.6
| Criterion | Grade A (slow) | Grade B (moderate) | Grade C (rapid) |
|---|---|---|---|
| Direct evidence: bone loss or CAL over 5 years | No loss | Under 2 mm | 2 mm or more |
| Indirect evidence: % bone loss / age | Under 0.25 | 0.25 to 1.0 | Over 1.0 |
| Case phenotype | Heavy biofilm, little destruction | Destruction matches the biofilm | Destruction exceeds what the biofilm explains; signs of rapid or early-onset disease |
| Modifier: smoking | Non-smoker | Under 10 cigarettes a day | 10 or more cigarettes a day |
| Modifier: diabetes | No diabetes, normal glucose | HbA1c under 7.0% | HbA1c 7.0% or more |
From the AAP grading chart.6 Use direct evidence (old radiographs or charts) whenever you have it.
How to work out bone loss divided by age
Take the worst-affected tooth. Estimate the radiographic bone loss as a percentage of root length, then divide that number by the patient’s age in years.4
20% at age 8020 ÷ 80 = 0.25. Just at the B line, so Grade B. A result of 10% at 80 (0.125) would be Grade A.
30% at age 5030 ÷ 50 = 0.6. Between 0.25 and 1.0, so Grade B.
45% at age 3045 ÷ 30 = 1.5. Over 1.0, so Grade C.
Peri-implant health, mucositis and peri-implantitis
The 2017 workshop gave implants their own case definitions. The key question is always the same: is there bone loss beyond the normal remodelling after placement?
| Condition | Bleeding or pus on gentle probing | Probing depth | Bone loss beyond initial remodelling |
|---|---|---|---|
| Peri-implant health | Absent | No increase from earlier exams | Absent |
| Peri-implant mucositis | Present | May or may not be increased | Absent |
| Peri-implantitis | Present | Increased compared with earlier exams | Present |
From the Workgroup 4 consensus report.5
No baseline records?Peri-implantitis can still be diagnosed from the combination of bleeding and/or suppuration on gentle probing, probing depths of 6 mm or more, and bone levels 3 mm or more apical to the most coronal part of the intraosseous implant.5
Who gets peri-implantitis?There is strong evidence for higher risk in patients with a history of severe periodontitis, poor plaque control and no regular maintenance after implant therapy. Data on smoking and diabetes are inconclusive.5
Three worked cases, step by step
These are original cases written by our faculty for practice. Write your full diagnosis, then open the walk-through.
Patient: 34-year-old woman. Non-smoker. No medical conditions.
Findings: Interdental CAL of 3 to 4 mm on #3, #14, #19 and #30. Maximum probing depth 5 mm. Bleeding on 35% of sites. Bone loss is horizontal and reaches about 20% of root length at #30. No furcation involvement. No teeth lost. 28 teeth present.
Show the step-by-step diagnosis
1. Periodontitis case? Yes. Interdental CAL is present on several non-adjacent teeth.
2. Starting stage. Worst interdental CAL is 4 mm, which is Stage II. Bone loss of 20% (coronal third, 15-33%) agrees.
3. Tooth loss. None, so no change.
4. Complexity. Probing depth is 5 mm at most, bone loss is horizontal, no furcations. Nothing pushes the stage up.
5. Extent. 4 of 28 teeth is about 14%, which is under 30%, so localized.
6. Grade. Start at B. Bone loss/age = 20 ÷ 34 = 0.59, which is in the 0.25 to 1.0 band. She does not smoke and has no diabetes. Grade B.
Diagnosis: Periodontitis, Stage II, localized, Grade B
Patient: 52-year-old man. Smokes 15 cigarettes a day. Type 2 diabetes, latest HbA1c 6.4%.
Findings: Generalized interdental CAL of 4 to 7 mm. Probing depths up to 7 mm. A 4 mm vertical bony defect on #14. Class II furcation on #3 and #30. Mobility degree 1 on #24 and #25. Two molars were extracted because of periodontitis; 26 teeth remain. Worst bone loss is about 50% of root length on #14. 20 of 26 teeth are affected.
Show the step-by-step diagnosis
1. Periodontitis case? Yes.
2. Starting stage. Worst interdental CAL is 7 mm, so Stage III or IV.
3. Tooth loss. 2 teeth lost to periodontitis, which is 4 or fewer, so this does not make it Stage IV.
4. Complexity. Pockets of 7 mm, a vertical defect of 4 mm and Class II furcations are Stage III complexity factors. Is there a need for complex rehabilitation? Mobility is only degree 1, there is no bite collapse, and he has 26 teeth (more than 20). So it stays Stage III.
5. Extent. 20 of 26 teeth is well over 30%, so generalized.
6. Grade. Bone loss/age = 50 ÷ 52 = 0.96, which on its own is Grade B. His HbA1c of 6.4% is also a Grade B finding. But he smokes 15 cigarettes a day, which meets the Grade C criterion (10 or more a day). Grade C.
Diagnosis: Periodontitis, Stage III, generalized, Grade C
The lesson: do not stop at bone loss/age. One modifier can change the grade.
Patient: 23-year-old man. Non-smoker. Healthy. Very little visible plaque.
Findings: Interdental CAL of 6 to 7 mm limited to the first molars (#3, #14, #19, #30) and the central incisors (#8, #9, #24, #25). Vertical defects of 3 to 4 mm on the first molars. Bone loss reaches about 45% of root length on #30. No teeth lost. Other teeth are healthy.
Show the step-by-step diagnosis
1. Periodontitis case? Yes.
2. Starting stage. Worst interdental CAL is 7 mm, so Stage III or IV.
3. Tooth loss. None.
4. Complexity. Vertical defects of 3 mm or more are Stage III factors. No need for complex rehabilitation. Stage III.
5. Extent. The damage is confined to first molars and incisors, so describe it as a molar/incisor pattern.
6. Grade. Bone loss/age = 45 ÷ 23 = 1.96, well over 1.0. The phenotype also fits Grade C: destruction far exceeds the small amount of biofilm. Grade C.
Diagnosis: Periodontitis, Stage III, molar/incisor pattern, Grade C
The lesson: under the 1999 system, a young patient like this was often called “aggressive periodontitis”. That label no longer exists; it has been merged into periodontitis and is described with stage and grade.1
Want more cases in exam format? Try our free INBDE practice questions, and see the Stage III question in our DLOSCE practice set (preparing for the DLOSCE? See The Study Boards DLOSCE course).
Three quick questions
1. A 45-year-old has a worst interdental CAL of 4 mm and a Class III furcation on #19. What is the stage?
- Stage I
- Stage II
- Stage III
- Stage IV
Show answer
C. Stage III CAL alone says Stage II, but a Class II or III furcation is a Stage III complexity factor, and complexity moves the stage up.
2. An implant shows bleeding on gentle probing and a 5 mm probing depth. Radiographs match the bone level recorded at crown delivery. What is the diagnosis?
- Peri-implant health
- Peri-implant mucositis
- Peri-implantitis
- Periodontitis, Stage II
Show answer
B. Peri-implant mucositis Bleeding is present but there is no bone loss beyond the initial remodelling, so it is mucositis, not peri-implantitis.
3. A non-smoker without diabetes has 40% bone loss at age 32. Which grade fits the indirect evidence?
- Grade A
- Grade B
- Grade C
- It cannot be graded without old radiographs
Show answer
C. Grade C 40 ÷ 32 = 1.25, which is over 1.0. Indirect evidence is used when direct evidence (old records) is missing, so D is wrong.
How to prepare: our full plan
Staging and grading is one topic in Periodontics, and Periodontics is one subject out of many on the INBDE. Here is how to cover all of it in order.
The Study Boards INBDE courseINBDE Premium Boards, a complete course built by US-licensed dentists:
- 12 course sections with Modules and Master Files
- 35,000+ focused questions
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- Live tests every night at 9 PM New York time
Build your study planRead these next, in this order:
Related high-yield topics
Frequently asked questions
What are the 4 stages of periodontitis?
Stage I (worst interdental CAL 1-2 mm), Stage II (3-4 mm), Stage III (5 mm or more, up to 4 teeth lost to periodontitis) and Stage IV (5 mm or more with 5 or more teeth lost, or a need for complex rehabilitation). Complexity factors such as deep pockets, vertical defects and furcations can move a patient to a higher stage.
How do you grade periodontitis?
Start at Grade B. Use direct evidence of progression over 5 years if you have old records; otherwise divide the percentage bone loss at the worst tooth by the patient’s age. Under 0.25 is Grade A, 0.25 to 1.0 is Grade B, over 1.0 is Grade C. Then check the modifiers: smoking 10 or more cigarettes a day or HbA1c of 7.0% or more meets Grade C.
Is aggressive periodontitis still a diagnosis?
No. The 2017 classification grouped the forms previously called “chronic” and “aggressive” into a single category, periodontitis, described by stage and grade. A young patient with damage limited to first molars and incisors is described with a molar/incisor pattern.
Can the stage go down after treatment?
No. If treatment removes a complexity factor that shifted the stage, the stage does not go back to a lower level.
What is the difference between peri-implant mucositis and peri-implantitis?
Both show bleeding and/or suppuration on gentle probing. Peri-implantitis also has bone loss beyond the initial remodelling after placement and increased probing depth. Mucositis has no such bone loss and can resolve.
How does The Study Boards help you prepare for perio classification on the INBDE?
Our INBDE course teaches staging and grading in the Periodontics Module and Master File, then tests it in patient-box questions across the Master Tests, Grand Tests and nightly 9 PM New York time live tests. US-licensed dentists answer your questions in the Queries and Help Section.
Stuck on a perio case?
Send it to us on WhatsApp. Our Admin Team with Dr. T and Dr. Kaur will contact you over WhatsApp, and a US-licensed dentist will walk you through it.
References
- Caton JG, Armitage G, Berglundh T, et al. A new classification scheme for periodontal and peri-implant diseases and conditions: Introduction and key changes from the 1999 classification. J Periodontol. 2018;89(Suppl 1):S1-S8. doi.org/10.1002/JPER.18-0157
- Chapple ILC, Mealey BL, Van Dyke TE, et al. Periodontal health and gingival diseases and conditions on an intact and a reduced periodontium: Consensus report of workgroup 1 of the 2017 World Workshop. J Periodontol. 2018;89(Suppl 1):S74-S84. doi.org/10.1002/JPER.17-0719
- Papapanou PN, Sanz M, Buduneli N, et al. Periodontitis: Consensus report of workgroup 2 of the 2017 World Workshop. J Periodontol. 2018;89(Suppl 1):S173-S182. doi.org/10.1002/JPER.17-0721
- Tonetti MS, Greenwell H, Kornman KS. Staging and grading of periodontitis: Framework and proposal of a new classification and case definition. J Periodontol. 2018;89(Suppl 1):S159-S172. doi.org/10.1002/JPER.18-0006
- Berglundh T, Armitage G, Araujo MG, et al. Peri-implant diseases and conditions: Consensus report of workgroup 4 of the 2017 World Workshop. J Periodontol. 2018;89(Suppl 1):S313-S318. doi.org/10.1002/JPER.17-0739
- American Academy of Periodontology. Staging and Grading Periodontitis (chart). perio.org
- The Study Boards. INBDE Premium Boards Course Blueprint. parmjitllc.com
Current as of October 2026. The 2017 AAP/EFP classification is still the current system. The cases and questions on this page are original teaching material, not real exam items.