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Periodontal Staging and Grading in Practice: A Hygienist's Walkthrough of the 2017 Classification

10/21/2026 9:45:00 PM   |   Comments: 0   |   Views: 7
The 2017 classification of periodontal diseases from the American Academy of Periodontology (AAP) and the European Federation of Periodontology (EFP) replaced the old "chronic versus aggressive" model with a system of stages and grades. Years later, many offices still use it inconsistently. One hygienist charts "Stage II," another writes "moderate chronic," and a third leaves the diagnosis blank for the dentist. In busy urban practices, where new patients arrive with records from many different offices, that inconsistency makes it hard to compare findings over time.

This walkthrough breaks the system into steps you can apply chairside.

Step 1: Confirm It Is Periodontitis

Staging and grading only apply once periodontitis is established. A patient is a periodontitis case when:

  • Interdental clinical attachment loss (CAL) is detectable at two or more non-adjacent teeth, or

  • Buccal or oral CAL of 3 mm or more, with probing depths over 3 mm, is present at two or more teeth.

The attachment loss must not be explained by another cause, such as trauma-related recession, a vertical root fracture, an endodontic lesion draining through the sulcus, or a third molar extraction site.

If attachment is intact and bleeding on probing is present at 10 percent or more of sites, the patient has gingivitis rather than periodontitis. A patient with a reduced but stable periodontium who has been successfully treated can also present with gingivitis, and that distinction is worth charting.

Step 2: Assign the Stage

The stage describes severity and how complex the case will be to manage. Start with the worst interdental site, then check complexity factors.

Severity

  • Stage I: interdental CAL of 1 to 2 mm; radiographic bone loss in the coronal third, under 15 percent; no tooth loss from periodontitis.

  • Stage II: interdental CAL of 3 to 4 mm; bone loss of 15 to 33 percent; no tooth loss from periodontitis.

  • Stage III: interdental CAL of 5 mm or more; bone loss extending to the middle third of the root or beyond; four or fewer teeth lost to periodontitis.

  • Stage IV: the same CAL and bone loss as Stage III, with five or more teeth lost to periodontitis.

Complexity

  • Stage I: maximum probing depth of 4 mm or less, mostly horizontal bone loss.

  • Stage II: maximum probing depth of 5 mm or less, mostly horizontal bone loss.

  • Stage III: probing depths of 6 mm or more, vertical bone loss of 3 mm or more, Class II or III furcation involvement, or a moderate ridge defect.

  • Stage IV: everything in Stage III plus a need for complex rehabilitation, such as masticatory dysfunction, secondary occlusal trauma, bite collapse, drifting or flaring, or fewer than 20 remaining teeth.

A single complexity factor can move a patient up a stage. Severity sets the starting point; complexity can raise it.

Step 3: Describe the Extent

Add the extent to the stage:

  • Localized: fewer than 30 percent of teeth involved.

  • Generalized: 30 percent of teeth or more.

  • Molar/incisor pattern: when the distribution follows that classic presentation.

Step 4: Assign the Grade

The grade estimates how fast the disease has progressed and how likely it is to progress further. Every case starts at Grade B and is then shifted up or down based on evidence.

Primary criteria

  • Direct evidence: if prior radiographs or charting are available, look at bone or CAL loss over five years. No loss suggests Grade A, less than 2 mm suggests Grade B, and 2 mm or more suggests Grade C.

  • Indirect evidence: divide the percentage of bone loss at the worst site by the patient's age. Under 0.25 suggests Grade A, 0.25 to 1.0 suggests Grade B, and over 1.0 suggests Grade C.

  • Case phenotype: heavy biofilm with modest destruction leans toward A, while destruction out of proportion to the biofilm present leans toward C.

Grade modifiers

  • Smoking: fewer than 10 cigarettes a day supports Grade B; 10 or more supports Grade C.

  • Diabetes: an HbA1c under 7.0 percent in a patient with diabetes supports Grade B; 7.0 percent or higher supports Grade C.

This is one more reason to keep the medical history current. A smoking history or a recent HbA1c can change the grade on its own.

A Worked Example

A 52-year-old patient smokes about 12 cigarettes a day. The worst interdental CAL is 5 mm, radiographic bone loss at that site reaches roughly 40 percent of root length, and the deepest pocket is 6 mm. No teeth have been lost to periodontal disease, and about 40 percent of teeth are involved.

  • CAL of 5 mm and a 6 mm pocket put the case at Stage III.

  • With 40 percent of teeth involved, it is generalized.

  • Bone loss divided by age is 40 / 52, or about 0.77, which points to Grade B.

  • Smoking 10 or more cigarettes a day moves the case to Grade C.

The diagnosis reads: generalized periodontitis, Stage III, Grade C, current smoker. That single line tells the next clinician how advanced the disease is, how aggressive it has been, and which risk factor matters most.

Communicating the Diagnosis to Patients

Patients do not need the full framework, but stage and grade translate well into plain language. "Stage" tells them how much support has been lost. "Grade" tells them how quickly it is happening and whether something like smoking or blood sugar is speeding it up. Framed that way, a Grade C modifier becomes a concrete reason to talk about tobacco cessation or diabetes control rather than an abstract label.

Making It Consistent Across the Team

The classification works best when every clinician in the office applies it the same way. A short internal guide taped inside a cabinet, or built into the charting software, keeps everyone aligned. In a high-volume general practice with a multi-provider dental team, where several providers may see the same patient over the years, a shared routine makes charting comparable from one visit to the next and from one hygienist to another.

Staging and grading also guide the recall interval. A Stage I, Grade A patient and a Stage III, Grade C patient should not be on the same maintenance schedule, and a clear diagnosis makes that case to the patient and to their insurer.

The Bottom Line

Confirm periodontitis, stage it by the worst site and complexity, add the extent, and grade it using history and risk factors. With a little practice, the process takes a minute or two at the end of a full charting, and it leaves a diagnosis that is precise, defensible, and useful to everyone who treats that patient afterward.
Category: Periodontics
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