In brief
Tooth discolouration has three broad causes: surface (extrinsic) stains from coffee, tea, red wine, dark foods and tobacco; internal (intrinsic) changes from trauma, certain medications, excessive fluoride during childhood or decay; and age itself, as enamel thins and reveals the naturally yellower dentin beneath. The distinction matters because it determines the fix — surface stains respond to cleaning and whitening, while internal discolouration often needs other approaches entirely.
Key takeaways
- Surface stains come from dark foods, drinks and tobacco — the most common and most treatable type.
- Internal discolouration arises from trauma, medications, fluorosis or decay and resists ordinary whitening.
- Aging yellows everyone's teeth as enamel thins over softer, yellower dentin.
- A single dark tooth usually signals an internal cause worth examining, not just staining.
Tooth discolouration usually comes from one of three sources: surface stains from food, drinks and tobacco; internal changes inside the tooth from injury, medications, fluoride or decay; and natural aging, as enamel thins and the yellower layer underneath shows through. The type matters, because it decides what will work. Surface stains and age-related yellowing often respond to cleaning and whitening, while internal discolouration usually needs a different approach.
This guide explains each type, what the colour of a stain can suggest, which treatments tend to help, and when a change in tooth colour is a reason to see a dentist rather than just a cosmetic concern.
What are the main types of tooth discolouration?
Dentists usually group discolouration into three types.
| Type | Where it sits | Common causes | What usually helps |
|---|---|---|---|
| Extrinsic (surface) | On or in the outer enamel | Coffee, tea, red wine, dark foods, tobacco, plaque and tartar | Professional cleaning, whitening, habit changes |
| Intrinsic (internal) | Inside the tooth structure | Injury, certain medications, fluorosis, decay, old fillings, root canal treatment | Internal whitening for some teeth, bonding, veneers or crowns |
| Age-related | Enamel thins, dentin shows through | Normal wear over decades | Whitening often helps; bonding or veneers for more change |
Many people have more than one type at the same time. Someone in their fifties who drinks coffee daily, for example, may have both surface staining and age-related yellowing.
What causes surface stains on teeth?
Enamel looks smooth, but under magnification it is slightly porous. Coloured compounds in food and drinks settle into it over time. Common culprits include:
- coffee and tea (tea is often a stronger stainer than people expect)
- red wine and cola
- dark berries, such as blueberries and blackberries
- tomato sauce, soy sauce, curry and balsamic vinegar
- tobacco, whether smoked or chewed
Tobacco tends to cause the most stubborn yellow-brown staining. Plaque and tartar make any staining worse. They hold pigment themselves, and their rough surface gives stains more to cling to.
Acidic drinks, such as soft drinks, sports drinks and some juices, can also play a part. They soften the surface of the enamel briefly, which may make it easier for pigments to settle in if you have something dark soon after.
How to reduce surface staining
The good news is that this is the most common and most treatable type.
- Rinse your mouth with water after coffee, tea or red wine.
- Use a straw for iced coffee, iced tea and dark soft drinks.
- Brush twice a day with fluoride toothpaste and clean between your teeth daily.
- Wait a little while after acidic drinks before brushing, rather than scrubbing softened enamel straight away.
- Keep up with professional cleanings. Polishing removes much of the surface stain that brushing leaves behind. Our guide to what a routine dental cleaning includes explains that part of the visit.
- If you smoke or vape, quitting helps your gums and overall health as well as the colour of your teeth.
What causes internal tooth discolouration?
Intrinsic discolouration sits inside the tooth rather than on its surface. That is why brushing, polishing and standard whitening often have limited effect.
Injury to a tooth
A tooth that was knocked, even years ago, can slowly darken. If the injury damaged the nerve and blood supply inside the tooth, breakdown products can stain the dentin from the inside. The result is often a single tooth that looks grey, brown or darker than its neighbours.
This matters for health, not just appearance. A tooth whose nerve has died can develop an infection at the root tip, sometimes without pain. A darkened tooth after an injury deserves an exam and often an X-ray. If a tooth is ever knocked out or loosened, see what to do if a tooth is knocked out.
Medications and early development
Some medications taken while teeth were still forming in childhood, including certain antibiotics, can leave grey, brown or banded discolouration in the adult teeth. Some medications taken later in life can also contribute to staining. If you think a medication may be involved, bring your medication list to your appointment.
Too much fluoride in early childhood
Fluoride helps protect teeth from decay. But swallowing too much fluoride while teeth are forming, for example from swallowing large amounts of toothpaste as a young child, can cause dental fluorosis. It usually shows up as white flecks, streaks or chalky patches, and in more noticeable cases brown spots. This is why young children are generally advised to use only a small amount of fluoride toothpaste, with an adult helping them brush and encouraging them to spit.
Decay, old fillings and past dental work
- Decay can show up as chalky white spots in its early stage, then brown or black areas as it progresses.
- Older metal fillings can make the surrounding tooth look grey.
- Tooth-coloured fillings and bonding can pick up stain over time, or no longer match nearby teeth if those teeth have been whitened.
- Root-canal-treated teeth sometimes darken over the years.
Enamel that did not form fully
Some people have thinner or weaker enamel from birth or from illness in early childhood. Affected teeth may look yellow, white-spotted or brown, and they may also be more sensitive or prone to wear.
Why do teeth get more yellow with age?
Even without stains or injury, teeth tend to look more yellow as we get older. Two things happen together:
- Enamel wears thinner. The white, slightly see-through outer layer gradually wears from decades of chewing and brushing.
- Dentin becomes more visible. The layer underneath, called dentin, is naturally yellow. As enamel thins, more of that colour shows through.
This is normal, and it happens regardless of habits. Age-related yellowing often responds well to whitening, because whitening works through the enamel to lighten the tooth.
What does the colour of a stain suggest?
Colour alone cannot diagnose a problem, but it can offer clues your dentist will look into.
- General yellowing across all teeth: often aging, surface staining or both.
- Brown staining along the gumline or between teeth: often tea, coffee, tobacco or tartar.
- One grey or dark tooth: often an old injury, a damaged nerve or an older filling.
- White spots or streaks: can be fluorosis, early decay, or marks left after braces.
- Brown or black spots on the chewing surface or between teeth: can be stain or decay, which only an exam can tell apart.
- Grey or brown bands across several teeth: can point to medications taken during tooth development.
Anything new, spreading or limited to one tooth is worth having checked.
How is tooth discolouration treated?
The right treatment depends on the cause, which is why an assessment comes first.
Professional cleaning
For surface stains, a professional cleaning and polish is often the first step. Many people are surprised by how much lighter their teeth look afterward, especially if stain has built up with tartar.
Teeth whitening
Teeth whitening uses bleaching agents to lighten the colour of the tooth. It tends to work best on surface staining and age-related yellowing. It does not change the colour of fillings, crowns, veneers or bonding, so existing dental work may stand out afterward. Results vary from person to person, and some people notice temporary sensitivity.
Internal whitening
For some root-canal-treated teeth that have darkened, whitening can be done from inside the tooth. Your dentist can tell you whether this is suitable for your tooth.
Dental bonding
Bonding covers discolouration with a thin layer of tooth-coloured material. It can suit small spots, patches or a single stained tooth. Learn more in what dental bonding can help improve or on our dental bonding page.
Porcelain veneers and crowns
For discolouration that whitening cannot reach, veneers cover the front of the teeth with thin custom shells, and crowns cover the whole tooth when it is also weakened. The trade-offs are compared in teeth whitening vs veneers.
Why matching treatment to cause matters
Choosing the wrong treatment can waste money and sometimes make things look worse. Whitening teeth with fluorosis patches, for example, can lighten the enamel around the patches while the patches themselves stay the same, making the contrast more noticeable. A plan that starts with the cause avoids this.
Is whitening toothpaste or an over-the-counter kit enough?
Whitening toothpastes can help remove fresh surface stains, mainly through mild polishing. They do not change the natural shade of your teeth or reach internal discolouration. Over-the-counter kits may lighten some teeth, but results vary, and they cannot tell you whether a dark spot is stain or decay.
Before starting any whitening, it is worth having a checkup. Whitening over an untreated cavity, a cracked tooth or receding gums can cause sensitivity and does nothing for the underlying problem.
Why do children’s teeth become discoloured?
Children’s teeth can change colour too, and the causes are a little different from adults’.
- A bump to a baby tooth. Falls are common in young children. A baby tooth that turns grey, pink or dark after a knock may have an injured nerve. Some settle on their own, but the tooth should be checked, because an infection can affect the adult tooth developing underneath.
- Early decay. Chalky white lines near the gumline are often the first sign of decay in young children. Brown or black spots can follow.
- Fluorosis. White flecks on new adult teeth can come from swallowing too much toothpaste when younger.
- Plaque and diet. Some children develop green, orange or dark surface stains, often linked to plaque buildup or certain foods, drinks and supplements.
Whitening products are generally not recommended for children. If you notice a colour change in your child’s teeth, a checkup is the best first step. Our guide on how to help prevent cavities in children covers daily habits that also help limit staining.
How can you keep teeth brighter after whitening or cleaning?
Once stains are removed, a few habits help keep them from returning quickly:
- Keep brushing twice daily and cleaning between teeth, since plaque holds stain.
- Rinse with water after dark drinks, or drink them with meals rather than sipping over hours.
- Cut back on tobacco, or better, stop.
- Keep up with regular cleanings, which remove new stain before it builds up.
- Ask your dentist before using whitening products repeatedly, especially if your teeth become sensitive.
Whitening results fade gradually for most people. How long they last depends on your habits and the natural colour of your teeth.
Does insurance cover treatment for discolouration?
It depends on the reason for treatment.
- Cosmetic treatment, such as whitening to brighten healthy teeth, is usually not covered by dental plans. The Canada Revenue Agency also does not accept purely cosmetic procedures, including teeth whitening, as eligible medical expenses for the medical expense tax credit.
- Treatment for disease or damage, such as a filling for decay or treatment for a tooth with a damaged nerve, may be covered under your plan like any other restorative care.
Costs depend on the cause, how many teeth are involved and the option you choose. Your dentist can explain the estimated fees for each option before treatment, and your office can send a predetermination to your insurer for larger treatment.
When should you see a dentist about tooth discolouration?
Book an exam if you notice:
- a single tooth that has turned darker, grey or brown
- discolouration with pain, sensitivity or swelling
- brown, black or chalky white spots you cannot explain
- a change in colour after an injury, even if it happened long ago
- discolouration in a child’s tooth
- staining that returns quickly after cleaning
It is also sensible to have an exam before starting any whitening, so the cause is confirmed and the approach suits your teeth. A dental exam can tell stain from decay and check whether a darkened tooth is healthy inside.
Getting tooth discolouration checked in Cornwall
If a stained or darkened tooth has been bothering you, the first step is finding out why. At York Street Dental Centre, 118 York Street, we look at the colour change, check the health of the tooth, and explain the options that fit the cause, along with estimated fees, before any treatment. We welcome patients from Glenview Heights, Eamer’s Corners and the downtown area, and from nearby Lakeview Heights and Glen Walter. New patients are welcome, and no referral is needed.
Call (613) 932-1620 or request an appointment to book an exam. You can also read more about our cosmetic dentistry options.
Frequently asked questions
Why is one of my front teeth darker than the rest?
A single dark tooth usually means an internal cause — most often an old injury that damaged the nerve. It deserves an examination, both because standard whitening rarely fixes it and because a dead nerve can hide infection.
Do whitening toothpastes work?
They help with fresh surface stains through mild abrasives and low-level agents, but they cannot change the tooth's internal shade or remove established staining. Expect maintenance-level results, not transformation.
Does smoking really stain that badly?
Yes — nicotine and tar produce deep yellow-brown staining that accumulates faster than dietary stains and resists brushing. Quitting is the single most effective stain-prevention step a smoker can take, with benefits well beyond colour.
Can children's teeth become discoloured?
Yes — from decay, trauma to baby teeth, excessive swallowed fluoride toothpaste or certain medications. Any unexplained colour change in a child's tooth is worth a dental visit rather than watchful waiting.
Can tooth discolouration be reversed?
It depends on the cause. Surface stains can often be removed with a professional cleaning, and many stains and age-related yellowing can be lightened with whitening. Internal discolouration from trauma, medications or fluorosis usually does not respond fully to whitening and may be covered with bonding or veneers instead. An exam identifies which type you have.
Is teeth whitening covered by insurance or the tax credit?
Usually not. Most dental plans treat whitening as cosmetic and do not cover it, and the Canada Revenue Agency does not accept purely cosmetic procedures such as teeth whitening as eligible medical expenses. Treatment for decay or a damaged nerve that is causing discolouration is a different matter, so ask your office what applies.
Sources
- Canadian Dental Association — Tooth Whitening
- Cleveland Clinic — Tooth Discoloration
- Mayo Clinic — Tooth Discoloration
- Canada Revenue Agency — Eligible medical expenses you can claim on your tax return
About the author
This article was written by the York Street Dental Centre Team and reviewed for clinical accuracy by the York Street Dental Centre dental team. York Street Dental Centre is a family dental office at 118 York Street, Cornwall, Ontario K6J 3Y8, providing general, preventive, restorative, and cosmetic dental care for patients of all ages.
Our articles explain common dental questions in plain language, cite reputable health and government sources where relevant, and are updated when guidance changes. Read our editorial policy or learn more about our practice.
This content is intended for general educational purposes and does not replace an examination, diagnosis or personalized treatment recommendation from a dental professional.