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Plaque Index Calculator

Work out plaque index instantly with clear inputs, formula shown and shareable results.

About Plaque Index Calculator

Averages the Silness-Loe surface scores of 0 to 3 across all surfaces examined to give the plaque index.

Formula

Silness-Loe plaque index

Index = sum of surface scores / number of surfaces examined, where each surface scores 0 (none) to 3 (abundant plaque)

Worked example

With the default values below, Plaque Index Calculator returns Silness-Loe plaque index of 1.500. Change any input above and every figure here is recalculated in your browser.

Inputs used

Sum of surface scoresaccepts 0–600
24
Surfaces examinedaccepts 1–200
16

Results

Silness-Loe plaque index
1.500
Interpretation
Fair — moderate accumulation
Index as a share of the maximum
50.0%
Surfaces examined
16

Step by step

  1. 1Values used
  2. 2Silness-Loe plaque index
  3. 3Silness-Loe plaque index= 1.500
  4. 4Interpretation= Fair — moderate accumulation
  5. 5Index as a share of the maximum= 50.0
  6. 6Surfaces examined= 16

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

How does it differ from the O'Leary index?

The O'Leary plaque control record reports the percentage of surfaces with any plaque rather than a graded mean.

Which surfaces are scored?

Classically four surfaces on each of six index teeth, though full-mouth scoring is also used.

Related Calculators

Plaque Index Calculator – Calculate Silness-Loe plaque index