← All explanationsApproximal plaque index

What does the API show during an oral-hygiene review?

The approximal plaque index, or API, describes the proportion of examined interdental sites with visible plaque, often after disclosing. It supports a focused oral-care discussion; it does not diagnose caries or periodontitis.

For training & practice ↓

Fictional front teeth with purple-disclosed plaque at gum margins and between teeth. — Disclosure principle; no personal index is calculated from this image.

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Make plaque visible

Disclosed plaque highlights areas that brushing or interdental cleaning may miss.

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Record systematically

Examined sites are recorded as plaque-present or plaque-free, allowing a percentage to be calculated.

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Target oral care

Suitable aids and their use can be discussed. Later measurements need comparable conditions for interpretation.

Read the full explanation

Make plaque visible
Disclosed plaque highlights areas that brushing or interdental cleaning may miss.
Record systematically
Examined sites are recorded as plaque-present or plaque-free, allowing a percentage to be calculated.
Target oral care
Suitable aids and their use can be discussed. Later measurements need comparable conditions for interpretation.

Notes on the teaching images

Disclosure principle; no personal index is calculated from this image.
Symbolic illustration of recording examined sites; not a real chart.
Example cleaning aid; suitable size and technique are discussed individually.

For your visit: open the communication cards

Watch the short explanation ↓

At a glance

Purpose?

Record interdental plaque.

Diagnosis?

Not a standalone disease diagnosis.

Use?

Discuss targeted oral care.

Knowledge in motion

Explained in 36 seconds.

Three steps. No audio.
Each scene can also be selected manually.

Landscape film (MP4) · Portrait film (MP4)

Silent educational film with German on-screen text and simplified teaching images. Not a patient case or a promised treatment outcome. The full English explanation is available as text.

Go to film text

Often confused

Plaque versus bleeding index

The API records plaque at examined interdental sites. A bleeding index records a different gingival observation.

Quick answers

Does the API measure pocket depth?

No. Pocket depth requires a different examination.

Does a plaque-positive site prove decay?

No. It records plaque, not established tooth damage.

Why might my next value differ?

Plaque changes with oral care. Timing and examination conditions also matter when comparing results.

At the practice

For a personal discussion

Editorially suggested question to discuss with Dr Niusha Barahmand Pour:

Which aids suit my interdental spaces?

Ask which interdental aids fit and how to use them if cleaning is difficult.

Discuss interdental cleaningAppointment selection at Doctolib

Meet Dr. Niusha Barahmand Pour ↗

Learning layer for training & practiceUnderstand terminology and deepen knowledge

Approximal: Facing an adjacent tooth.
Dichotomous recording: Recording two possible states, here plaque present or absent.
Index: A value summarising observations under a defined method.

Make the distinction

The API records plaque at examined interdental sites. A bleeding index records a different gingival observation.

Knowledge questionWhat does the API directly describe?

For learning, not for assessing personal symptoms. Your answer is not stored or sent.

Plaque at examined interdental sites.
Bone height throughout the jaw.
The number of teeth certainly affected by decay.

View answer

Plaque at examined interdental sites.

A plaque index is not a caries or bone measurement.

Sources and context

Editorial research: 2026-11-06. General information, not an individual diagnosis or treatment recommendation. Teaching illustrations are simplified and do not depict a patient case.