Lang & Tonetti Periodontal Risk Assessment (PRA)
The 2003 PRA stratifies individual progression risk in supportive periodontal therapy (SPT). Together with stage and grade, it drives the recall interval in the Bonebenders clinical calculator.
Role of PRA in SPT
After active therapy, patients enter supportive care. Progression risk is not uniform: some remain stable with longer recalls; others lose attachment if intervals stretch. PRA converts measurable clinical parameters into a risk category (low, moderate, high) used to personalise recall frequency.
Using PRA systematically avoids two symmetric errors: treating every post-therapy patient with the same habitual recall, or changing frequency only after an obvious relapse. Stratification anticipates risk instead of chasing it.
The six factors
The classic model plots six vectors on a functional radar diagram:
- Bleeding on probing (BOP) — percentage of bleeding sites (≤9% low, ≤25% moderate, >25% high).
- Residual pockets ≥5 mm — residual deep sites after therapy (≤4 / ≤8 / >8).
- Missing teeth — count out of 28 (excluding third molars), any cause — distinct from periodontitis-related tooth loss used for staging.
- Bone loss / age ratio — worst-site RBL divided by age (≤0.5 low, ≤1.0 moderate, >1 high).
- Systemic / genetic conditions — diabetes, IL-1 polymorphism, stress or immunosuppression: present → high on this vector.
- Environmental factors — smoking: non-smoker/former (>5 years) low; occasional/moderate medium; ≥20 cig/day high.
The overall profile yields the risk category (low: at most one moderate vector; moderate: ≥2 moderate or 1 high; high: ≥2 high), aligned with Lang–Tonetti and reference tools such as periostools.org / perio-tools.com/pra.
Clinical interpretation
- Low risk: favourable BOP, residual pockets and modifiers; typically longer recalls.
- Moderate risk: mixed residual factors; closer monitoring.
- High risk: several unfavourable vectors (inflammation, deep pockets, smoking, high bone-loss/age); short recalls and reinforced behaviour change.
What this calculator adds
The PRA core stays compatible with periostools.org. On top, the tool integrates EFP/AAP 2017 staging/grading, post-treatment stability, and a month-based recall interval (with caps for Stage IV, Grade C and instability), rather than only the qualitative “maintain / increase / refer” message.
PRA and the 2017 classification
Staging/grading describe the current diagnosis; PRA estimates future progression risk in SPT. They are complementary: Stage III, Grade C with high PRA needs more intensive supportive care than Stage II, Grade A with low PRA. Staging uses tooth loss due to periodontitis; PRA uses total missing teeth out of 28.
Data collection at supportive visits
PRA is only as good as the current data. At each SPT visit record at least: full-mouth BOP, count of pockets ≥5 mm, teeth present/lost, updated radiographic estimate when indicated, smoking status and systemic control. A PRA built on years-old data under- or overestimates present risk.
When a factor improves (smoking cessation, falling BOP, fewer deep pockets), risk may drop and recall intervals may lengthen — but only after recalculating the whole profile, not from a single clinical impression.
Model limitations
PRA does not capture every determinant (compliance, access to care, hygiene skill, bisphosphonates, pregnancy, and so on). It remains a stratification aid, not a substitute for judgement. In patients with a history of rapid progression despite a “moderate” profile, shorter recalls remain appropriate.
In the calculator
Enter BOP, pockets ≥5 mm, teeth lost, bone loss, age, systemic factors and smoking to obtain the PRA profile, risk category and proposed recall interval, with adjustments for Stage IV, Grade C and post-treatment instability. Use the output to explain why recalls are not one-size-fits-all and to document the rationale for maintenance.
In a multidisciplinary team (hygienist + dentist + periodontist) PRA becomes a shared language: everyone sees the same six vectors and risk category. That reduces operator variability when setting recalls and makes handovers clearer when the patient’s reference clinician changes.
If a vector is uncertain (e.g. outdated radiograph or incomplete BOP count), note it and do not force a “precise” category: a PRA refreshed at the next visit beats a seemingly complete profile built on fragile data.
Frequently asked questions
Does PRA replace staging?
No. PRA does not grade anatomical severity; it stratifies progression risk to plan recalls.
Should I recalculate PRA at every visit?
Yes, whenever BOP, residual pockets, smoking or systemic control change. Risk is not a permanent label.
Do I need dedicated software?
No. The six factors are collected in routine visits; the free calculator combines them using Lang–Tonetti logic and the tool’s clinical adjustments.
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
- 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
- Matuliene G, et al. Influence of residual pockets on progression of periodontitis and tooth loss. J Clin Periodontol. 2008;35(8):685-695. PubMed
- Trombelli L, et al. Supportive periodontal therapy. J Clin Periodontol. 2015;42 Suppl 16:S161-S170.