Guide to the Causes of Tooth Discoloration: How to Tell Surface Stains from Discoloration Inside the Tooth

The causes of tooth color change can be divided into pigment attaching to the tooth surface and color changing inside the tooth, either when the tooth forms or after an injury. Depending on the cause, cleaning and polishing may be enough, or whitening or laminates may be needed. If only one tooth suddenly darkens, it is best to have a dentist find the cause first.

Published 2026-11-08 · Updated 2026-11-08 · DentalStatics editorial team

Key facts

Foods that cause surface staining	Strongly pigmented foods such as coffee, black tea, green tea, wine and curry, and tobacco (source: Korea Disease Control and Prevention Agency (KDCA, 질병관리청) National Health Information Portal)
Dental fluorosis	Caused by excess fluoride intake in infancy while permanent teeth form; does not occur after permanent teeth have erupted (source: Korea Disease Control and Prevention Agency (KDCA) National Health Information Portal)
Tetracycline-class drugs	Given during tooth development (late pregnancy, infancy, under age 8), they can cause permanent yellow, gray or brown discoloration (source: Ministry of Food and Drug Safety (MFDS, 식품의약품안전처) (approved drug labeling))
Chlorhexidine mouthwash	Increased staining of teeth and oral surfaces is listed as an adverse reaction in the approved labeling (source: Ministry of Food and Drug Safety (MFDS) (approved drug labeling))
Amalgam fillings	Can cause staining of the tooth (source: Korea Disease Control and Prevention Agency (KDCA) National Health Information Portal)

How is tooth discoloration classified?

Tooth discoloration is easy to understand if you separate causes outside the tooth from causes inside it. Staining in which food pigments, tobacco or some medicines stick to the tooth surface has an outside cause, while a change in the color of the tooth tissue itself, such as from effects during tooth growth, trauma or old fillings, has an inside cause.

Outside staining often improves with professional cleaning, polishing or whitening at the dental clinic. For discoloration inside the tooth, the response to whitening is inconsistent, so covering treatments such as resin, laminates or crowns may be considered as well.

The KDCA also mentions tooth color changed by congenital or acquired causes when explaining the indications for laminates. In other words, the cause and extent of discoloration are the starting point for choosing treatment.

What can be done about stains caused by food, tobacco or mouthwash?

In KDCA material, the representative strongly pigmented items are wine, green tea, black tea, curry, tobacco and coffee. These pigments build up on the surface of teeth and of fillings such as resin, making them look yellow or brown.

For mouthwash containing chlorhexidine, used in gum treatment, the approved labeling from the Ministry of Food and Drug Safety (MFDS) lists increased staining of teeth and oral surfaces as an adverse reaction. Staining can also appear on prostheses and the back of the tongue, so it is best not to use it beyond the prescribed period.

Surface stains can be largely removed by cleaning and polishing at the dental clinic, but stain removal for cosmetic purposes is not covered by national health insurance in Korea. As habits that prevent discoloration, the MFDS recommends quitting or cutting down on tobacco and brushing right after eating strongly colored food.

What kinds of discoloration form while the teeth are being made?

Dental fluorosis is a condition in which a problem occurs while enamel, the outermost layer of the tooth, is forming and spots appear. The KDCA explains that it occurs when too much fluoride is taken in infancy while the permanent teeth are forming, and that once permanent teeth have erupted into the mouth, taking a lot of fluoride does not cause it.

The approved labeling for tetracycline-class antibiotics from the MFDS states that giving them during tooth development, that is, in late pregnancy, in infancy, or to children under 8, can cause permanent yellow, gray or brown discoloration of the teeth. If this is a concern when a child is prescribed an antibiotic, you can ask the prescribing doctor or pharmacist.

This kind of discoloration is set inside the tooth, so it does not go away with surface cleaning. If fluorosis is suspected, an experienced dental professional can differentiate it and decide on treatment, so a consultation is advisable.

What should be suspected if only one tooth has darkened?

If a front tooth that was hit in the past has gradually darkened, the state of the tooth nerve may have changed after the trauma, and a dental examination is needed. A tooth that has suffered trauma is monitored over time, including its color change.

A gray look around an old amalgam filling is because amalgam can cause staining of the tooth. The border of resin or laminates can also discolor over time, so it is checked together whether this is a tooth that was treated before.

A dark filling margin may be simple staining or secondary decay underneath. It is hard to tell by appearance alone, so it is confirmed with tests such as X-rays.

Which treatment is chosen for each cause of discoloration?

The dental clinic compares the methods below according to the cause, the extent and the number of discolored teeth. If one method is not enough, they may be combined, for example whitening followed by resin or laminates to finish.

In every case, cosmetic treatment is not covered, so choose after having the expected cost, how long it lasts and how much tooth is cut explained for each method.

Surface staining: cleaning and polishing, and whitening if needed
All teeth evenly yellow: whitening is considered first
Partial spots or small discoloration: resin bonding
Wide discoloration that whitening cannot fix: laminates or crowns
Discoloration of a single tooth after trauma: decide treatment after checking the nerve state

Common myths and facts

Myth: Yellow teeth are caused by neglecting brushing.

Some discoloration forms inside the tooth regardless of brushing habits, such as fluorosis, tetracycline-class drugs and trauma.

Myth: The more often you gargle, the whiter your teeth get.

The approved labeling for chlorhexidine mouthwash from the MFDS lists increased staining of teeth and oral surfaces as an adverse reaction.

Myth: Any discoloration disappears with a single whitening.

The response to whitening is inconsistent for discoloration inside the tooth, so resin, laminates or crowns may be considered as well.

Frequently asked questions

Can antibiotics taken in childhood change tooth color?

The MFDS approved labeling states that tetracycline-class antibiotics given during tooth development can cause permanent discoloration. Discoloration that has already formed is a change inside the tooth, so the dentist checks the response to whitening and decides whether covering treatment is needed.

There is a white spot on my tooth. Is it from fluoride?

Excess fluoride intake in infancy can cause fluorosis spots, but white spots can also come from other causes such as early decay. The KDCA recommends a visit for consultation because an experienced dental professional can tell them apart.

Does brushing right after coffee reduce staining?

Brushing right after strongly colored drinks like coffee is the same as the discoloration prevention method the MFDS advises. If you cannot brush right away, rinsing your mouth with water also shortens the time pigment stays on the teeth.

Only one front tooth turned gray. Will whitening fix it?

If only one tooth has darkened, the cause may be a nerve change after trauma or an old filling, so an examination comes before whitening. Depending on the cause, treatment to check the nerve state may be needed, and the whitening method also differs.

My teeth turned brown after using a gum-care mouthwash.

Mouthwash containing chlorhexidine can cause staining of the teeth and oral surfaces, and the approved labeling states that the stain may not come off easily even with dental preventive treatment. Tell the dentist who prescribed it how long you have used it and discuss whether to continue.

References

Korean version →