Why Do Teeth Turn Yellow? Tooth Stains and Causes

Short answer

Teeth turn yellow because of pigments that stick to the surface, such as tea, coffee and smoking (extrinsic discolouration), changes in the internal structure of the tooth such as tetracycline, fluorosis and trauma (intrinsic discolouration), and enamel that thins with age. Surface stains mostly lessen with cleaning, and yellow tones usually respond well to whitening. Grey and white stains, however, often need other treatments.

Why do teeth turn yellow?

Teeth turn yellow because of pigments that build up on the surface (external discolouration), changes in the internal structure of the tooth (internal discolouration) and enamel that thins with age. In most people, several of these causes are present together.

Two layers determine the colour of a tooth: the semi-translucent enamel on the outside and the yellowish dentine inside. The thinner or more translucent the enamel, the more the yellow of the dentine shows through. Stains that stick to the surface add further darkness to the picture.

To choose the right treatment, you need to know where the discolouration comes from. Some stains come off with cleaning, some respond well to whitening and some need other treatments.

What is extrinsic (external) discolouration?

Extrinsic discolouration is staining caused by pigments that stick to the surface of the tooth. It is the most common type of discolouration and often lessens considerably with cleaning.

Drinks: Tea, coffee, red wine and cola.
Tobacco: Cigarettes, cigars and shisha; these leave yellow-brown and dark stains.
Some mouthwashes: Chlorhexidine mouthwashes used over a long period can cause brown staining.
Pigment-producing bacteria: Can form thin black, green or orange lines along the gum line.
Tartar and plaque: Tartar built up on the surface holds on to pigments and looks dark.

Over time, surface stains can penetrate the enamel. In that case cleaning alone may not be enough; for details, see our page smoking, tea and coffee stains.

What is intrinsic (internal) discolouration?

Intrinsic discolouration is a colour change within the internal structure of the tooth that cannot be cleaned from the surface. It can appear during or after tooth development.

Tetracycline discolouration: Tetracycline-group antibiotics taken while the teeth are developing, that is during pregnancy or childhood, can cause grey, brown or banded discolouration.
Fluorosis: White opaque spots caused by excess fluoride intake while the teeth were developing; in advanced cases brown areas may be seen.
Trauma: If the nerve of a tooth that has taken a knock is damaged, the tooth may gradually turn grey, brown or dark.
Root canal treatment and old fillings: Some filling and root canal materials can darken the tooth from the inside.
Developmental enamel defects: Defects in the enamel structure can create white, yellow or brown areas.

Why do teeth turn yellow with age?

As we age, enamel thins and dentine thickens and darkens, so teeth naturally look more yellow. This process progresses at a different rate in everyone.

Pigments that build up over the years settle into micro-cracks in the enamel. Inside the tooth, new layers of dentine form and the colour darkens. As a result, teeth can look both more yellow and duller.

Age-related yellowing is among the types of discolouration that usually respond well to whitening. However, exposed root surfaces and worn areas may be more sensitive, so they are assessed before treatment.

Possible causes by stain colour

The colour of a stain gives an important clue to its cause. The table below is only a general guide; the definitive distinction is made at the examination.

Stain colour	Possible causes
Yellow, overall	Dentine colour, age, thin enamel, surface build-up
Brown	Tea, coffee, smoking, tartar, advanced fluorosis
Thin black line	Pigment-producing bacteria, iron supplements, tartar
Green or orange	Pigment-producing bacteria, inadequate oral hygiene
Grey or blue-grey	Tetracycline, nerve death, show-through from an old amalgam filling
Darkening of a single tooth	Trauma, nerve death, root canal treatment
White opaque spots	Mineral loss from enamel, fluorosis, developmental enamel defects
Dark brown-black spot	Decay; an examination is needed to tell it apart from staining

Shade guide showing tooth colour tones, comparing yellow and brown tooth stains — A shade guide helps record the starting shade. · Illustrative AI-generated image; not a patient.

Which stains respond to whitening?

Yellow and yellow-brown tones usually respond well to whitening; grey, blue-grey and white stains respond more modestly. The expected result is different for each type of discolouration.

Discolouration	Response to whitening
Age-related yellowing	Usually good
Tea, coffee or smoking colour that has penetrated the enamel	Usually good; cleaning is needed first
Mild tetracycline discolouration	Slow and limited; long-term at-home treatment may be needed
Severe tetracycline discolouration	Often insufficient
Darkening of a single tooth due to nerve death	Limited from the outside; internal whitening may be needed
White spots	Whitening does not remove the spots; they may look more noticeable at first

We explain how much lightening can be expected on our page how many shades lighter.

Which situations need other treatment?

For discolouration that does not respond, or responds only modestly, to whitening, other treatments can be used alone or together with whitening.

White spots and mild fluorosis: Resin infiltration (popularly known as ICON treatment) or microabrasion can be used. Details are on our page white spot treatment.
A single darkened tooth: Internal whitening can be used on teeth that have had root canal treatment.
Severe tetracycline discolouration or irregular shape: Porcelain veneers or crowns may be considered.
Stains caused by decay: The decay is removed and a filling is placed first.
Colour caused by tartar: A scale and polish may be enough.

For some people, several methods are planned together. For example, whitening may be done first, followed by resin infiltration for white spots. This order matters, because resin infiltration and fillings do not lighten with whitening; their colour is chosen to match the new shade after whitening.

White opaque spots on the front teeth, discolouration due to fluorosis or mineral loss from enamel — White spots do not go with whitening; different treatments may be needed. · Illustrative AI-generated image; not a patient.

How is the cause of discolouration identified at the examination?

The cause of discolouration is determined by visual inspection, shade measurement, the patient's history and, where needed, X-rays. This assessment helps you avoid unnecessary or ineffective treatment.

We look at whether the stain is on all the teeth or on a single tooth.
We ask about medicines taken in childhood, use of fluoridated water or supplements, and any past knocks to the teeth.
The starting shade is measured with a shade guide and photographed.
If a single tooth has darkened, nerve vitality is tested and an X-ray is assessed.
Once surface stains have been removed by cleaning, the true colour of the tooth is reassessed.

The first step is often a scale and polish. An assessment made on clean teeth gives a more accurate picture of what can be expected from whitening.

Frequently asked questions

Does tooth yellowing go away?

It depends on the cause. Surface stains lessen with cleaning, and the tooth's own yellow colour can be lightened with whitening. Some internal discolouration needs other treatments.

I have a brown stain on my tooth – is it decay?

It could be, but not every brown stain is decay. Tea, coffee, smoking and tartar also cause brown stains. The distinction is made at the examination.

What causes black lines on the teeth?

Thin black lines along the gum line are often caused by pigment-producing bacteria and are seen especially in children. They are removed with professional cleaning but may come back.

Does tetracycline staining go with whitening?

In mild cases it can be partly lightened with long-term at-home whitening. With severe discolouration the result is often limited, and options such as veneers are considered.

Why has one of my teeth darkened?

Darkening of a single tooth is mostly linked to a past knock or nerve death. It is assessed with X-rays and vitality tests; if needed, root canal treatment and internal whitening are planned.

Does toothpaste whiten yellow teeth?

Whitening toothpastes can reduce surface stains but do not noticeably change the tooth's own colour.