Essential periodontal glossary
Terms used in the EFP/AAP 2017 classification, the Lang–Tonetti PRA and the Bonebenders periodontal diagnosis calculator.
Why this glossary
Clinics often mix English and local terms (CAL, BOP, staging, grading, PRA). A shared lexicon reduces charting and referral errors and smooths hygienist–dentist handovers. The definitions below are those used by the Bonebenders calculator and related clinical guides.
Diagnosis terms
- Stage (I–IV)
- Severity and complexity of periodontal damage, based on interdental CAL, radiographic bone loss, teeth lost and complexity factors. Assigned from the worst site.
- Grade (A–C)
- Rate of progression estimated from the bone-loss/age ratio and from smoking and diabetes (HbA1c) modifiers.
- Extent
- Localised (<30% of teeth), generalised (≥30%), or molar–incisor pattern.
- CAL
- Clinical Attachment Loss: attachment loss from the cemento-enamel junction to the base of the pocket. A key staging parameter.
- Radiographic bone loss (RBL)
- Percentage of root height lost on radiographs; used for staging and for the bone-loss/age ratio in grading and PRA.
Inflammation and risk terms
- BOP
- Bleeding on Probing: percentage of sites that bleed on probing. Marker of active inflammation; a PRA factor and a stability criterion.
- Residual pockets ≥5 mm
- Deep sites remaining after active therapy; predictors of progression and tooth loss if left unmonitored.
- PRA
- Periodontal Risk Assessment (Lang–Tonetti 2003): a six-factor profile that stratifies progression risk in SPT (low / moderate / high).
- Recall interval
- Maintenance visit frequency (typically 2–12 months) driven by individual risk and capped for Stage IV, Grade C and instability.
Stability after therapy
- Stable
- BOP <10%, PD ≤4 mm, no 4 mm site with BOP, no progressive bone loss.
- In remission / control
- BOP ≥10% but PD ≤4 mm and no 4 mm sites with BOP.
- Unstable
- PD ≥5 mm, or ≥4 mm with BOP, or progressive bone loss — indicates tighter recalls or retreatment.
Other useful terms
- SPT
- Supportive Periodontal Therapy: the maintenance phase after active therapy.
- Furcation involvement
- Involvement of the root furcation (classes I–III); a complexity factor in staging.
- HbA1c
- Glycated haemoglobin; ≥7% typically shifts grade toward C as a modifier.
How the terms connect in the clinical flow
In a typical visit you measure BOP and probing depths, estimate CAL and RBL, count teeth lost, and review smoking/diabetes. From those data come stage and grade (2017 diagnosis), the PRA profile (SPT risk), and the recall interval. Post-treatment stability tells you whether to maintain or retreat.
Shared thresholds keep operators in the same practice consistent: the same meaning of “high BOP,” the same residual-pocket criterion, the same definition of instability. The glossary exists to share that language.
Recurring numeric thresholds
- CAL 1–2 / 3–4 / ≥5 mm → Stage I / II / III–IV (with other criteria)
- Bone-loss/age ratio <0.25 / 0.25–1 / >1 → Grade A / B / C (with modifiers)
- BOP <10% among stability criteria
- PD ≥5 mm (or ≥4 mm with BOP) → unstable
- Typical recalls 2–12 months by PRA and caps
These thresholds should not be memorised at the expense of context: 5 mm CAL at a single site with occlusal trauma is not the same as generalised CAL with high BOP. The glossary fixes word meanings; the visit integrates numbers into the real patient.
For full criteria, use the dedicated guides on staging and grading, PRA and recall intervals, then apply the values in the calculator.
Frequently asked questions
Are CAL and probing depth the same?
No. Probing depth measures from the gingival margin to the pocket base; CAL measures attachment loss relative to the CEJ and better reflects historical damage.
Does high BOP always mean high PRA risk?
BOP is one of six vectors. High BOP raises risk, but the final category also depends on pockets, teeth lost, bone-loss/age, systemic factors and smoking.
Where can I compute these parameters?
In the periodontal diagnosis calculator: enter clinical values to obtain stage, grade, PRA and recall interval.
Open the free calculator and get stage, grade, PRA and recall interval from clinical parameters.
Open the calculatorThis guide does not replace a specialist examination. It is clinical decision support, to be interpreted within professional judgement.
Scientific references
- Tonetti MS, Greenwell H, Kornman KS. Staging and grading of periodontitis. J Periodontol. 2018;89 Suppl 1:S159-S172. PubMed
- Lang NP, Tonetti MS. Periodontal risk assessment (PRA) for patients in supportive periodontal therapy (SPT). Oral Health Prev Dent. 2003;1(1):7-16. PubMed
- 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