Why Is One Tooth Darker Than the Others?

When every tooth but one looks the same, the odd one out is telling you something happened inside it.

Quick Answer

A single tooth turning gray, brown, or darker than its neighbors usually means the nerve inside has died, often years after a knock or injury. Blood breakdown products stain the tooth from within. External whitening does not work on it. Treatment is usually a root canal followed by internal bleaching, a veneer, or a crown.

The injury you may have forgotten

A blow to the tooth, even one from childhood, can damage the blood supply inside. The nerve slowly dies, and the byproducts of the trapped blood darken the tooth from the inside. The color change can appear months or years after the incident.

Front teeth take these hits most often, which is why they are the usual suspects.

Other causes worth ruling out

Deep decay under an old filling, a large silver filling showing through thin enamel, or a previous root canal that stained the tooth can all darken a single tooth. A crack that lets in stain does the same.

Only an exam and an X-ray sort out which one you have, and whether the tooth is still alive.

Why whitening will not fix it

Whitening gel works on the outer surface. This stain lives inside the tooth. Bleach the whole smile and the dark tooth stays dark while everything else gets lighter, which makes it stand out more.

The fix has to come from inside or cover the tooth entirely.

The real options

If the nerve is dead, a root canal removes the source, and internal bleaching placed inside the tooth can lighten it from within. Where that is not enough, a veneer or crown covers it and matches your other teeth.

See tooth discoloration causes, root canal treatment, and porcelain veneers.

Frequently Asked Questions

Can a dead tooth be saved?

Often yes. A root canal removes the dead pulp and preserves the tooth, which can then be lightened internally or covered with a veneer or crown.

Will whitening fix one dark tooth?

No. The stain sits inside the tooth, so external whitening lightens the surrounding teeth and makes the dark one more noticeable. Internal bleaching or a veneer is the answer.

Does a dark tooth always mean infection?

Not always, but it often means the nerve has died, which can lead to infection later. An exam and X-ray determine whether treatment is needed now.