You notice it gradually at first. Perhaps one tooth looks darker than the others. Maybe a brown mark has become black, or you have suddenly noticed that several teeth no longer look the colour they used to.

Teeth turning black can happen for several reasons, and the pattern of the colour change often matters. A dark line affecting the surface of several teeth is different from one tooth that gradually turns grey or black. The important question is not simply what colour is the tooth? It is why has the colour changed?

Is One Tooth Turning Black or Several?

This is often one of the first things a dentist will consider.

One tooth turning dark

When a single tooth changes colour while the surrounding teeth look normal, the cause may be something happening inside that particular tooth. Previous trauma, deep decay or damage to the pulp can all lead to internal discolouration. A tooth may become grey, brown or black as changes inside it become visible through the outer tooth structure.

Several teeth becoming darker

When multiple teeth appear darker, surface staining or gradual changes in tooth colour are more likely explanations. Food, drinks, tobacco and certain products can contribute to external staining over time. The pattern alone cannot provide a diagnosis, but it can help explain why one person’s colour change needs a very different assessment from another’s.

Why Has One Tooth Suddenly Turned Black?

A sudden or noticeable colour change in one tooth should not be ignored. One possible explanation is damage to the pulp—the soft tissue containing nerves and blood vessels inside the tooth. Trauma, infection or advanced decay can affect this tissue. As the internal tissues change, the tooth may gradually become darker. This can happen after:

  • A fall or blow to the mouth
  • A sports injury
  • Deep tooth decay
  • A significant crack
  • Previous dental procedures affecting the tooth

Sometimes, the injury happened long ago. You may have knocked a front tooth years earlier and completely forgotten about it. The colour change can appear later, which makes the connection difficult to recognise.

Why is My Tooth Turning Black at the Gum Line?

It may be a surface stain or hardened deposit, particularly if the colour appears as a line or small dark marks close to the gums. Black staining can also develop in this area and should be distinguished from tooth decay. However, decay can also produce brown or black areas. The NHS notes that tooth decay may cause white, brown or black spots, particularly as the damage progresses. This is why a black tooth at the gum line should not automatically be treated as a cosmetic stain. You can read more about the possible causes in what causes black teeth?.

Can a Cracked Tooth Turn Black Inside?

A crack can sometimes allow bacteria to reach deeper into the tooth. If the internal pulp becomes infected or damaged, changes inside the tooth can eventually affect its colour. Cracks can also become stained, making the damaged area itself appear darker.

Why Are My Gums Turning Black?

Why are my gums black? For some people, the answer is simply natural pigmentation. Melanin can give healthy gums a brown or darker appearance, and this colour may be present across larger areas of the mouth rather than appearing as a new isolated patch.

But if you are asking, “Why are my gums darkening?”, because the colour has changed recently, the situation is different. A new dark area deserves closer attention, particularly if it is limited to one area or appears alongside swelling, soreness, bleeding or another visible change. For a more detailed explanation, see what does it mean when gums are black?

A Tooth Can Change Colour Without Becoming “Black” Overnight

Colour changes do not always follow a simple pattern. A tooth may first appear:

  • Yellowish or brown
  • Grey
  • Dark grey
  • Increasingly dark over time

This is particularly common when the discolouration originates inside the tooth. The exact colour depends on the underlying cause and the way light passes through the tooth structure. If you are also wondering, “Why do I have black gums?”, it is important to remember that gum pigmentation and tooth discolouration may have different causes. Photographs alone are therefore rarely enough to identify the problem accurately.

The Cause Determines What Happens Next

A surface stain may require professional cleaning. A tooth darkened by decay needs the decay treated. Internal changes following damage to the pulp may require a completely different approach. In some suitable cases where a tooth has changed colour because of an underlying dental problem, root canal treatment may be considered to treat infection or damage within the tooth. The right treatment always depends on the diagnosis.

Don’t Wait for a Changing Tooth to Explain Itself

A long-standing surface stain and a tooth that is actively changing colour are not the same thing. If you have noticed that one tooth is becoming darker, particularly after an injury or alongside pain, sensitivity or swelling, arrange a dental examination. The sooner the cause is identified, the clearer it becomes whether you are dealing with surface staining, decay or a problem developing inside the tooth.

The same applies if you have noticed changes to the surrounding gum tissue and are asking, “Why are my gums turning black?” New or unexplained changes in colour should be assessed rather than assumed to be harmless.