Why Teeth Change Colour — A Simple Guide

Yellow, grey, brown or spotted teeth are a common concern. But not all stains are the same. Some sit on the surface and come off with a professional cleaning. Others are inside the tooth and need a completely different approach.

Here is what causes tooth discolouration, and what can be done about it.

First, What Gives a Tooth Its Colour?

A tooth has two main layers:

Enamel — the hard, slightly see-through outer shell.
Dentine — the layer underneath, which is naturally yellow.

The shade you see is mostly dentine showing through the enamel. So teeth are never naturally pure white — and anything that thins the enamel or darkens the dentine will change the colour, even if the surface is perfectly clean.

Dentists group discolouration into three types.

1. Surface Stains (Extrinsic)

These sit on the outside of the enamel and usually clean off well.

Common causes and how they look

Tea, coffee, red wine, cola — yellow-brown.
Turmeric and spiced foods — yellow-orange.
Tobacco, smoked or chewed — brown to black.
Chlorhexidine mouthwash, used long term — brown.
Iron supplements or iron-rich water — a black line near the gum.
Certain bacteria, common in children — a black or dark green gum line.
Plaque and tartar — yellow-brown, and rough to the tongue.

What helps

Professional scaling and polishing, plus good daily brushing and cleaning between the teeth.

A note on whitening toothpastes. They can reduce surface stain, but they cannot change your natural tooth shade. Highly abrasive ones can wear the enamel and eventually make teeth look more yellow.

2. Stains Inside the Tooth (Intrinsic)

Polishing will not help here, because there is nothing on the surface to remove.

Stains that formed in childhood

Fluorosis — too much fluoride while the teeth were forming, from high-fluoride water or swallowed toothpaste. Chalky white flecks, or brown mottling in more severe cases.
Tetracycline staining — these antibiotics, taken in pregnancy or before about age eight, leave grey, yellow or blue-brown bands.
Weak or thin enamel — from a high fever, poor nutrition, vitamin D deficiency, or an injury to a baby tooth. Shows as white, yellow or brown patches, often pitted.
Inherited conditions — some families have naturally defective enamel or dentine, affecting all the teeth.

Stains that develop later

A tooth that has died after an injury — a knock damages the blood supply inside. The tooth slowly turns grey or dark brown, sometimes years later. A single dark front tooth is nearly always this, and needs checking.
Decay — starts as a chalky white spot, then turns brown or black and softens.
Old fillings and root canal materials — amalgam can grey the tooth around it, and old fillings pick up stain at the edges.
A pink patch on a tooth — rare, but needs urgent dental attention.

3. Age-Related Change

Completely normal. Over the years, enamel gradually thins while the tooth lays down more dentine inside. Thinner enamel over a darker core means a deeper shade, helped along by years of accumulated stain.

Quick Colour Guide

General yellow — age, diet, or thin enamel.
Brown patches — tobacco, tea and coffee, fluorosis, or early decay.
Black at the gum line — bacteria, iron, or tartar.
Chalky white spots — early decay or fluorosis.
One grey or dark tooth — a past injury; the tooth is probably no longer alive.
Grey-blue overall — tetracycline staining.
A pink patch — needs urgent review.

This is a guide, not a diagnosis. A proper assessment usually needs an examination and an X-ray.

Treatment Options

Treatment depends on how deep the stain is.

Scaling and polishing — the first step for all surface stain.
Whitening (bleaching) — professionally supervised gel, in custom trays at home or applied in the clinic. Works best on yellowing; grey and banded stains take longer. Mild sensitivity is common and settles afterwards.
Internal bleaching — for a single dark tooth after root canal treatment. The gel is sealed inside the tooth.
Microabrasion — gently removes a very thin surface layer to fade white or brown marks.
Resin infiltration — a resin is soaked into white spots so they blend in. No drilling needed.
Composite bonding — tooth-coloured material to mask small defects.
Veneers or crowns — for deep stains or damaged teeth where whitening will not be enough.

If decay or a failing filling is the cause, that is always treated first.

How to Prevent It

Brush twice daily with fluoride toothpaste, and clean between the teeth once a day.
Rinse with water after tea, coffee, wine or strongly coloured food.
Stop tobacco in every form.
Supervise young children’s brushing and use only a small amount of toothpaste.
Wear a mouthguard for contact sports.
Keep to the check-up interval your dentist advises.

See a Dentist Soon If You Notice

One tooth going dark, especially after an old injury.
A pink patch showing through a tooth.
A dark spot with sensitivity, pain, or a rough edge.
Discolouration with gum swelling or a bad taste.
Several teeth changing colour quickly.

In Short

Tooth colour is a clinical sign, not only a cosmetic one. Surface stain and age-related yellowing are easily managed. Colour coming from inside the tooth may be harmless, or the first sign of injury, decay or a developmental problem.

Get your teeth examined before buying any whitening product. The right answer may be a polish, a bleach, a filling, or root canal treatment.

For general information only; this does not replace a dental consultation. To book an appointment, please contact our reception.