← All explanationsRestoration margin

What does a dark line around a filling mean?

A restoration margin is the boundary between filling material and tooth tissue. Fit, surface condition and possible caries are assessed there. Discolouration alone does not establish a cavity or a need to replace the whole filling.

For training & practice ↓

Chewing-surface model with a tooth-coloured filling and limited marginal staining without a depicted open cavity. — Restoration boundary on a model · staining is not automatically caries

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Locate the boundary

The filling meets the tooth along an edge, which may lie on the chewing surface or between teeth.

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Distinguish findings

Staining, material fracture and a carious lesion are different findings.

03 / 03

Choose appropriate care

Review, refurbishment, repair or replacement depends on the whole tooth and the type of defect.

Watch the short explanation ↓

At a glance

What is the margin?

The tooth–filling boundary.

Does colour decide?

No.

Rough edge?

Have the margin checked.

Knowledge in motion

Explained in 36 seconds.

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

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 below.

Read the film text in English

Locate the boundary
The filling meets the tooth along an edge, which may lie on the chewing surface or between teeth.
Distinguish findings
Staining, material fracture and a carious lesion are different findings.
Choose appropriate care
Review, refurbishment, repair or replacement depends on the whole tooth and the type of defect.

Often confused

Staining versus recurrent caries

Staining describes colour; recurrent caries is a carious change in tooth tissue adjacent to a restoration.

Quick answers

Must a dark margin be replaced?

Not because of colour alone. First assess whether a defect needs intervention.

What if floss catches?

A rough edge or another cause is possible. Have it checked rather than filing the margin yourself.

Can only part be repaired?

Some limited defects are suitable for repair, but not every filling is repairable.

At the practice

For a personal discussion

Editorially suggested question to discuss with Dr Niusha Barahmand Pour:

Could this finding be reviewed or repaired, or does it need replacement?

An unusual margin can be assessed before deciding whether replacement is appropriate.

Have a filling checkedAppointment selection at Doctolib

Meet Dr. Niusha Barahmand Pour ↗

Learning layer for training & practiceUnderstand terminology and deepen knowledge

Marginal: Relating to an edge.
Marginal adaptation: How a restoration fits the tooth.
Repair: Targeted addition to correct a limited defect.

Make the distinction

Staining describes colour; recurrent caries is a carious change in tooth tissue adjacent to a restoration.

Knowledge questionWhat does staining alone establish?

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

No automatic replacement decision.
A need to replace every filling.
Certain pulp infection.

View answer

No automatic replacement decision.

Colour, adaptation and tissue condition are assessed separately.

Sources and context

Editorial research: 2026-11-02. General information, not an individual diagnosis or treatment recommendation. Teaching illustrations are simplified and do not depict a patient case.