Why Teeth Discolour: Intrinsic and Extrinsic Staining Explained
Wondering why teeth look yellow, grey or stained? This page explains surface (extrinsic) and internal (intrinsic) stain, and change from age, tetracycline, fluorosis and injury. Reviews suggest stain type can affect whether whitening helps: surface stain can be removed; some internal stain may not fully respond. Whitening does not change crowns, veneers or fillings. Composite bonding, veneers or crowns can cover a discoloured tooth instead, with their own risks.
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Medical disclaimer: This page is for general information only. It does not replace an examination or treatment by a dentist.
This page was reviewed by Dr Ibraheem Ijaz, principal dentist at Deepcar Dental Care, a General Dental Practitioner registered with the GDC under number 301711.
Why are my teeth yellow?
Teeth can look yellow or darker from stain on or inside the tooth, and because more of the dentine under the enamel can show through.
A 2022 International Endodontic Journal review explains that tooth colour comes mainly from the dentine, under the enamel. NHS guidance says teeth can become stained or darker because of getting older, regularly having drinks that can stain teeth, such as coffee, tea or red wine, and smoking.
What is extrinsic staining?
Extrinsic staining is discolouration on the outer surface of the tooth, usually from food, drink or smoking.
A 2019 Dentistry Journal review explains that the coloured compounds behind it, which a 2025 review calls chromogens, attach to the tooth directly or, more likely, collect in plaque, tartar and the pellicle, a layer of mainly salivary proteins on enamel. It says abrasive techniques, such as brushing with toothpaste or professional dental cleaning, and peroxides can remove extrinsic stain. How peroxide acts on stains is covered among the whitening science pages in this section.
What is intrinsic staining?
Intrinsic staining is discolouration inside the tooth, in the enamel or dentine, so it cannot be brushed away at home.
A 2019 review describes intrinsic stain forming while teeth develop, from too much fluoride, tetracycline or some metabolic and systemic conditions, and after teeth come through mainly from bleeding inside the tooth after an injury, or from dental procedures.
Why do teeth change colour with age?
Teeth tend to look darker with age because, a 2019 review explains, wear makes enamel thinner and more translucent, so more dentine shows through.
A 2006 Journal of Dentistry review concluded that age is among the factors that can influence the outcome of bleaching, with the type of stain and the starting tooth colour.
Questions about this treatment? Book online or call the practice.
How do tetracycline and fluorosis stain teeth?
Both are mainly built into the tooth as it forms, from tetracycline antibiotics or from too much fluoride.
Tetracycline staining
A 2004 International Journal of Dermatology review explains that tetracyclines are taken up by teeth forming when the drug is given, causing lasting yellow or grey to brown colour, depending on the dose or type of drug relative to body weight. Discolouration starting in adulthood after long-term tetracycline or minocycline has also been reported, though most of the literature it reviewed was case reports. In general, if teeth change colour during long-term medicine use, show them to a dentist.
A 2019 chemistry review says intrinsic stain in the dentine is almost impossible to remove by chemical or mechanical means from outside the tooth. A 2006 review concluded that the literature suggests peroxide lightens coloured compounds particularly within the dentine. A small 1999 study concluded that tetracycline-stained teeth can be whitened using extended treatment time. In it, 12 people (80%) who completed six months of 10% carbamide peroxide nightguard bleaching were surveyed 54 months later: 10 reported no obvious colour change since treatment or only slight darkening not noticed by others, and 2 slight darkening probably noticeable to others.
Fluorosis
Dental fluorosis is a change in the enamel from too much fluoride while teeth form. The Oral Health Foundation says it can cause faint white marks, is usually mild, does not affect how teeth work, and is rare. A 2019 review says bleaching will not completely remove most discolouration built into the enamel, such as fluorosis.
How do injury and root canal treatment discolour a tooth?
An injury or root canal treatment can darken a single tooth from the inside.
A 2022 review explains that bleeding inside an injured tooth can stain it brown, reddish or black, especially where the pulp has died, though a tooth that stays alive may regain its normal colour. Pulp remnants and some root canal materials can also discolour a root-filled tooth.
In general, a tooth that darkens should be shown to a dentist, who can check the cause; the page on a dark or dead tooth explains more.
Internal whitening for a dark root-treated tooth is offered at Deepcar Dental Care; see internal whitening for a dark root-filled tooth.
What can cover a discoloured tooth instead of whitening?
Composite bonding, a veneer or a crown can cover a discoloured tooth instead of whitening.
A 2022 review lists these as alternatives to bleaching that involve more loss of tooth structure, expense, risks, and repair and replacement over time. It notes direct composite veneers are less invasive than porcelain but more likely to lose colour over time, and consistently ideal results are hard to achieve on a discoloured tooth.
Composite bonding, composite veneers, porcelain veneers, ceramic crowns for cosmetic reasons and replacing old discoloured fillings are among the cosmetic treatments offered at Deepcar Dental Care. Composite bonding has its own section, as does improving how your teeth look with veneers or crowns.
Which types of discolouration respond to whitening?
Whether whitening helps depends partly on the type of stain. A 2001 British Dental Journal review concluded that, in some instances, how a stain formed may affect the outcome of treatment and the options a dentist can offer.
| Type of discolouration | How it responds to whitening |
|---|---|
| Tea, coffee, red wine or smoking | Can be removed by abrasive cleaning and peroxides (2019 review) |
| Darkening with age | A reason to consider whitening (NHS); age can influence the outcome (2006 review) |
| Fluorosis | Not completely removed by bleaching (2019 review) |
| Tetracycline staining | Mixed: almost impossible to remove from outside (2019 chemistry review); lightened with extended treatment in one small study, though 2 of 12 later reported slight darkening probably noticeable to others (1999) |
| One dark tooth after injury or root canal | Internal whitening is an option for a root-filled tooth, though outcomes are not predictable (2022 review) |
| Crowns, veneers and fillings | Will not change colour, as whitening only lightens natural teeth (NHS) |
A 2019 review says bleaching will not completely remove fluorosis. Nor can whitening change the colour of crowns, veneers or fillings, because NHS guidance says it can only lighten natural teeth.
When is whitening not suitable at Deepcar Dental Care?
At Deepcar Dental Care, reasons whitening is not suitable include:
- under-18s
- pregnancy or breastfeeding
- active decay or gum disease
- heavy tetracycline staining
- patients with many front crowns or veneers
See whitening age limits and pregnancy and gum disease, decay and whitening. If you are considering whitening, see choosing a treatment, realistic teeth whitening results and the comparison of professional whitening and shop-bought kits. The page on professionally whitening your teeth describes whitening with a dentist.
Frequently asked questions
Why is one tooth darker than the others?
There are several possible causes. A 2025 British Dental Journal review says localised intrinsic discolouration is usually confined to a single tooth, commonly caused by trauma and tooth resorption. It concludes that a complete dental history, with clinical and X-ray examination, is important to confirm the cause, so show the tooth to a dentist.
Can mouthwash or toothpaste stain your teeth?
Some can. A 2019 review says chlorhexidine rinses and stannous toothpastes may stain teeth, especially after long-term use. The NHS says chlorhexidine staining goes when you stop using it, and to brush regularly; speak to a doctor, dentist or pharmacist if this does not help and it still bothers you or does not go away. Toothpaste staining: ask a dentist.
Can you reduce surface staining between dental visits?
Partly. Brushing with toothpaste can remove surface stain, which a 2019 review says collects most on hard-to-clean surfaces. It warns that hard abrasives may damage enamel and gums, especially with heavy brushing, so toothpastes are always a compromise between cleaning and wear.
Can old fillings discolour a tooth?
They can. A 2019 review lists dental procedures such as amalgam fillings among causes of intrinsic discolouration after teeth come through. Whitening does not change the colour of fillings, so a discoloured or mismatched filling keeps its colour unless it is replaced.
Why do my teeth look a different colour in different light?
Tooth colour is partly perception. A 2004 Journal of Dentistry review concluded that tooth colour and appearance are complex, with lighting conditions, translucency, opacity, light scattering, gloss and the human eye and brain all influencing how tooth colour is perceived.
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