Guides · Cosmetic
Why do teeth turn yellow? Types of discolouration and the solution for each
External stains, the natural darkening that comes with age, intrinsic discolouration from medicines and trauma; when cleaning is enough, and when whitening or veneers are needed.
Tooth discolouration has three main causes: surface stains (tea, coffee, tobacco — removed by cleaning and polishing), thinning of enamel with age revealing the yellow dentine beneath (lightened by whitening), and discolouration from within the tooth (tetracycline, fluorosis, root-treated or traumatised teeth — limited response to whitening; veneers or crowns may be needed). The right solution depends on the cause.
The natural colour of teeth
Teeth are not white but a slightly yellowish ivory: the outer enamel is semi-translucent and the colour is largely set by the yellow dentine beneath. The shade varies from person to person and even from tooth to tooth in the same mouth (canines are darker). "Snow white" is not a natural colour; the aim is a natural brightness in harmony with the face and the whites of the eyes.
1. Extrinsic (surface) stains
Tea, coffee, red wine, cola, dark fruits, tobacco and some mouthwashes (chlorhexidine) bind to the plaque and pellicle on the enamel surface. Brushing does not remove them entirely; scaling and polishing in the clinic remove most of them. Whitening toothpastes work on light surface stains but do not lighten the tooth's own colour; abrasive ones damage enamel with frequent use.
2. Age-related darkening
Over time enamel thins while dentine thickens and darkens; teeth look more yellow and less bright. This is the commonest reason for whitening, and dentist-supervised whitening responds well. More: Teeth whitening and How long does whitening last?
3. Intrinsic discolouration
- Tetracycline: Certain antibiotics taken in childhood (or by the mother in pregnancy) leave grey-brown bands in the teeth. Limited response to whitening; veneers or crowns in marked cases.
- Fluorosis: Excess fluoride during tooth development; chalky white spots, brown pits in severe cases. Microabrasion and resin infiltration in mild cases, whitening plus composite in moderate cases, veneers in severe ones.
- A single dark tooth: After trauma or root canal treatment. In a root-treated tooth, internal bleaching (placing the agent inside the tooth) is usually effective; if not, a veneer or crown.
- Developmental enamel defects (MIH, amelogenesis imperfecta): Paediatric and aesthetic assessment; protective restorations.
- Old fillings and amalgam: Make the tooth look grey; the restoration is replaced.
Which solution for which case?
| Cause | First option | If insufficient |
|---|---|---|
| Surface stains | Cleaning + polishing | Whitening |
| Age-related yellowing | Whitening (in-office/at-home) | Veneers |
| Tetracycline (mild) | Extended at-home whitening | Veneers / crowns |
| Fluorosis | Microabrasion, resin infiltration | Composite / veneers |
| A single dark (root-treated) tooth | Internal bleaching | Veneer / crown |
Common mistakes
- Bicarbonate, lemon, strawberries, charcoal: Acids and abrasives thin the enamel; brighter in the short term, yellower and more sensitive teeth in the long run.
- Whitening strips/pens: Low-dose peroxide; mild effect, gum irritation and risk of uneven results. Dentist-supervised home whitening is more predictable.
- Assuming fillings will whiten too: Whitening lightens only natural tooth; fillings and crowns in the front region are matched afterwards.
Slowing down yellowing
Take dark drinks through a straw and with meals, rinse with water afterwards, don't smoke, brush twice a day with fluoride toothpaste, polish every 6 months. Treating reflux and clenching, which cause enamel erosion, also helps preserve the colour.
This article is for general information only; diagnosis and treatment tailored to you require a dental examination.
How long does teeth whitening last, and who should not have it?
Causes of discolouration, the difference between in-office and at-home methods, sensitivity, how long results last and when whitening is not suitable.
Teeth clenching and grinding (bruxism): symptoms and the night guard
The common cause behind morning jaw pain, worn teeth and headaches; the signs and harms of bruxism and protection with a night guard.
Tooth sensitivity: why teeth twinge in the cold, and what helps
The causes of the short, sharp twinge from cold, heat and sweets; what you can do at home, how desensitising toothpastes work and the situations that need an examination.