BSP 2017 Perio Staging and Grading: Free Calculator + Guide

The “Mental Maths” Problem

If you are like most dentists, the transition from the 1999 classification (Chronic/Aggressive) to the 2017 World Workshop classification has added a layer of cognitive load to every exam.

The new system reflects the biology better, but working out “% bone loss ÷ age” in your head while a patient waits is not easy.

The calculator below, based on the Healthy Gums DO Matter (HGDM) toolkit, does the maths for you. It is free and needs no sign-up.

The Cheat Sheet: How the Logic Works

This tool follows the BSP Implementation of the 2017 classification, which simplifies the World Workshop rules for UK general practice. Here is how the calculator reaches a diagnosis.

1. Staging (The Severity)

Staging is based on the worst site of interproximal bone loss in the mouth. The HGDM toolkit (Page 16) maps percentage bone loss to the anatomical thirds of the root:

• Stage I (Early/Mild): Bone loss <15% (or <2mm attachment loss).
• Stage II (Moderate): Bone loss in the coronal third (15% to 33%).
• Stage III (Severe): Bone loss in the middle third (33% to 66%).
• Stage IV (Very Severe): Bone loss in the apical third (>66%).

2. Grading (The Speed of Progression)

Grading estimates how quickly the disease is likely to progress. The BSP implementation uses one ratio: % Bone Loss ÷ Patient Age.

• Grade A (Slow): Ratio < 0.5
  (Example: A 60-year-old with 20% bone loss. 20÷60 = 0.33)
• Grade B (Moderate): Ratio 0.5 – 1.0
  (Example: A 50-year-old with 40% bone loss. 40÷50 = 0.8)
• Grade C (Rapid): Ratio > 1.0
  (Example: A 40-year-old with 50% bone loss. 50÷40 = 1.25)

3. Extent (Distribution)

Extent describes how widespread the disease is (HGDM page 18):

• Localised: Affecting <30% of teeth.
• Generalised: Affecting >30% of teeth.
• Molar/Incisor Pattern: A specific pattern often seen in Grade C cases.

What About Smokers and Diabetics?

In the BSP implementation, risk factors like smoking and diabetes are documented alongside the diagnosis, rather than changing the Grade calculation directly (HGDM Page 18).

A complete diagnosis statement should look like this (HGDM Page 19):

Beyond Stage and Grade

This calculator covers the radiographic part of the diagnosis. The rest of the Healthy Gums DO Matter pathway tracks plaque and bleeding scores, whether the patient is engaged after initial therapy, and whether the disease is stable after active treatment.

The thresholds for each, with worked examples, are in our BSP staging and grading cheat sheet.