You are brushing your teeth and you notice it: a dark spot on one of your teeth that was not there before, or maybe it has been there for a while and you have been wondering about it. Your first thought is probably cavity. And it might be. But dark spots on teeth have several possible causes, and not all of them require a filling.
Here is what the different causes look like, how to tell them apart, and when you need to see a dentist.
The most common causes of a black spot
1. Early or active tooth decay (cavity)
This is the cause most people worry about, and it is a legitimate concern. Tooth decay occurs when bacteria in your mouth produce acids that dissolve the mineral structure of your enamel. In the early stages, this can appear as a white spot (demineralisation). As the decay progresses, it darkens to brown or black.
Signs that a dark spot may be a cavity:
- It is soft or sticky when you run your tongue over it
- You feel a rough texture or a small hole
- The tooth is sensitive to sweet, hot, or cold food and drink
- The spot is located in a groove on a molar, between teeth, or at the gum line
If decay has broken through the enamel into the softer dentine underneath, it needs treatment. A dental filling is the most common solution for small to moderate cavities. Larger cavities may need a crown.
2. Extrinsic staining
Not all dark marks are decay. Your teeth can pick up stains from:
- Coffee, tea, and red wine
- Tobacco
- Dark-coloured foods (berries, soy sauce, balsamic vinegar)
- Certain mouthwashes containing chlorhexidine
- Iron supplements
Extrinsic stains sit on the outer surface of the tooth. They are usually removable with a professional clean, and in some cases, with teeth whitening. The key difference from a cavity is that staining does not create a hole, soft spot, or sensitivity.
3. Arrested (inactive) decay
Sometimes early decay begins but then stops progressing. This can happen when oral hygiene improves, fluoride exposure increases, or the environment around the tooth changes. The result is a dark spot that looks concerning but is no longer active.
Arrested decay is hard and smooth to the touch. Your dentist can test this with a probe and an X-ray. If the decay is confirmed as inactive, it may not need a filling. It does need monitoring at regular check-ups to ensure it stays inactive.
Other dark marks that may not be active decay
4. Amalgam show-through
If you have old silver amalgam fillings, the metal can darken the surrounding tooth structure over time. This creates a grey or black shadow visible through the enamel, even though the tooth itself may be healthy.
If the filling is intact and the tooth is structurally sound, no treatment is needed. If the appearance bothers you, the old amalgam filling can be replaced with a tooth-coloured composite restoration.
5. Calculus (tartar)
Hardened plaque (calculus or tartar) can build up along the gum line and between teeth. When calculus forms below the gum line, it often has a dark brown or black colour. This is called subgingival calculus and it cannot be removed with brushing alone. It requires professional removal during a dental clean.
6. Dental fluorosis or developmental marks
Some people have natural variations in tooth colour that developed during childhood when the teeth were forming. These can include brown or dark spots, particularly if the teeth were exposed to high fluoride levels during development. These marks are cosmetic only and do not indicate disease.
How your dentist tells the difference
When you come in with a dark spot on a tooth, your dentist will:
- Examine the spot visually under magnification and strong lighting
- Test the surface with a dental explorer to check if it is soft (active decay) or hard (staining or arrested decay)
- Take an X-ray to see if there is decay beneath the surface that is not visible from the outside
- Review your history for risk factors like diet, oral hygiene habits, and previous dental work
This process takes a few minutes and gives a clear answer. The difference between a cavity that needs treatment and a stain that needs a clean is usually obvious to a clinician with the right tools.
What treatment looks like
Active decay: A dental filling using tooth-coloured composite resin. If the cavity is large, a crown or onlay may be needed. If the decay has reached the nerve, root canal treatment may be required.
Extrinsic staining: Professional cleaning (scale and polish) removes most surface stains. For deeper or more persistent staining, teeth whitening can improve overall tooth colour. Veneers are an option if the staining is intrinsic and cannot be removed by whitening.
Arrested decay: Monitoring at regular check-ups. No treatment unless the decay reactivates.
Amalgam show-through: Optional replacement of the old filling with composite if the appearance is a concern.
Calculus: Professional scaling to remove tartar deposits, followed by a discussion about improving oral hygiene to prevent buildup.
When to see a dentist
See a dentist if:
- The dark spot is new or has changed in size or colour
- You feel a rough texture, hole, or sticky surface
- The tooth is sensitive to sweet, hot, or cold
- The spot is in an area you cannot see well (between teeth or on a back molar)
- You have not had a dental check-up in more than 12 months
If the spot has been there for years and has not changed, it may be benign. But the only way to confirm this is with a clinical examination.
How to prevent dark spots and cavities
- Brush twice daily with fluoride toothpaste
- Floss or use interdental brushes daily
- Limit sugary and acidic food and drink
- Attend regular dental check-ups every six months for early detection
- Consider dental sealants for children's permanent molars
At Ivy Dental in Everton Park and Nundah, we can assess any dark spot on your tooth in a single appointment and give you a clear answer about whether treatment is needed.
Book a check-up at Ivy Dental. Call (07) 3266 7120 or visit us at Everton Park or Nundah. Open 7 days.
