Why Teeth Discolor: How the Cause Decides Whether Teeth Whitening Will Work

The mug was the problem. Someone rinses their coffee cup at the sink, catches their reflection in the dark kitchen window and notices, not for the first time, that their teeth are no longer the color of the porcelain in their hand. A quick search suggests strips, trays, gels and a dozen promises. What almost none of those pages ask is the only question that actually matters: what is the cause of tooth discoloration in this particular mouth?

That question decides everything. A tea drinker’s dulling film and a single gray front tooth that took a knock at a school football match twenty years ago look different, sit in different layers of the tooth and respond to completely different treatments. One may lift with a hygienist’s polish and a supervised course of gel. The other may need an X-ray before anyone reaches for a whitening tray.

This explainer walks through the layers of a tooth, the ways each layer changes color, and what the evidence says peroxide can and cannot reach.

What is the cause of tooth discoloration, in plain terms?

A tooth is built like a layered candle. The outer shell is enamel, a hard, mostly mineral coating that is slightly translucent, a little like frosted glass. Beneath it sits dentin, a softer, more porous tissue that is naturally yellow. At the core is the pulp, the soft center that holds the nerve and blood vessels. The color you see in the mirror is light passing through the enamel and bouncing back off the dentin, tinted by whatever is stuck to the surface along the way.

That anatomy explains why teeth can change color in only three fundamental ways. Something can coat the outside. The enamel can wear thinner so more of the yellow dentin shows through. Or the dentin and pulp themselves can change, because of bleeding after an injury, a dying nerve, decay, or a pigment that was locked into the tooth while it was still forming in childhood.

MedlinePlus groups the everyday triggers into a long list: coffee, tea, colas and red wine; tobacco; poor brushing that leaves plaque to hold stains; illness affecting enamel; certain medicines; dental materials such as silver-colored fillings; aging; genetics; excess fluoride during childhood; and trauma to a tooth. Several of these can be present at once.

Here is the practical point, and it is the argument of this whole article. Whitening gel is a chemical that can only alter what it physically reaches and what it can chemically break apart. Pigment sitting in enamel and outer dentin is within reach. A ceramic crown, a metal filling or an area of decay is not. So before anyone decides whether whitening will work, a dentist has to answer the prior question: which layer changed, and why?

Extrinsic vs intrinsic tooth stains: the distinction that predicts results

Dentists sort discoloration into two families, and learning the two words will make every later conversation clearer.

Extrinsic stains sit on the outside of the tooth, in the thin protein film that coats enamel and in the microscopic roughness of the enamel surface. They arrive from outside the body: coffee, tea, wine, curry, berries, tobacco smoke, some antiseptic mouth rinses. Because they are on or near the surface, a professional cleaning removes a good deal of them, and what remains is generally within the reach of peroxide.

Intrinsic stains live inside the tooth structure, in the deeper enamel or the dentin. Some were built in while the tooth was forming, such as the gray or brown bands caused by antibiotics of the tetracycline class given in early childhood, or the white and brown flecks of fluorosis, which is enamel altered by too much fluoride during development. Others develop later: dentin that darkens with age, a tooth that bled internally after a knock, or a nerve that quietly died.

Many clinicians add a third, blended category for age-related change, where thinning enamel and darkening dentin combine with decades of accumulated surface stain.

Telling the families apart is mostly detective work. A dentist looks at the pattern: is every tooth dull, or is one tooth a different shade from its neighbors? Are the marks symmetrical bands across several teeth, which points to something that happened during development, or a single dark tooth, which points to injury or infection? Is there a history of a fall, a root canal, or a childhood spent in an area with naturally high fluoride in the water? An X-ray settles questions about the pulp and any hidden decay. Only then does the whitening conversation start.

Why are my teeth yellow even though I brush well?

This is the most common version of the question, and the reassuring answer is that yellowing is often not a hygiene failure at all. It is frequently the dentin talking.

Enamel is the hardest substance in the body, but it does not regenerate. Every year of chewing, grinding and exposure to acidic foods and drinks wears it slightly thinner and more translucent. Beneath it, dentin does the opposite: it keeps laying down new layers throughout life, becoming thicker and a deeper yellow. A thinner window over a darker interior produces a tooth that looks yellower with each decade, no matter how diligently it is brushed. Genetics sets the starting point; some people simply inherit thicker or more opaque enamel than others.

Acid accelerates the process. Frequent citrus, fizzy drinks, wine, or stomach acid reaching the mouth through reflux softens the enamel surface, and brushing immediately afterward scrubs away softened mineral. People who grind or clench at night flatten and thin the biting edges, which often show the first yellow translucency.

There is one hopeful note tucked inside this. Yellowing that comes from dentin is usually the type that peroxide whitening handles best, because the gel is designed to diffuse through enamel and act on the pigmented molecules in the dentin below. Mayo Clinic’s guidance on whitening makes the same broad point: yellowish teeth tend to respond to bleaching, brownish teeth respond less well, and grayish teeth may not respond at all.

What whitening cannot do is put enamel back. If yellowing is driven by erosion, the first conversation is about protecting what remains: managing reflux with a physician, rinsing with water after acidic drinks, waiting a while before brushing, and considering a night guard if grinding is suspected. Those steps are decisions for the dental team, but they matter more than any shade change.

How coffee, tea, wine and tobacco stain the surface

Picture enamel under a microscope: not a smooth sheet but a landscape of tiny ridges and pores, coated in a protein film called the pellicle. That film is sticky, and that stickiness is the whole story of surface stain.

Many dark foods and drinks contain chromogens, which are pigment molecules intensely colored on their own. Tea, coffee and red wine also contain tannins, plant compounds that help pigments bind to the pellicle and to each other. Acidity finishes the job by softening the enamel surface so the pigment settles deeper into its texture. Red wine manages all three at once, which is why it stains so efficiently. Dark berries, tomato-based sauces, balsamic vinegar, soy sauce and heavily colored spices such as turmeric behave similarly.

Tobacco stains through a different route. Tar is dark and sticky by nature, and nicotine, although colorless, turns yellow-brown when it meets oxygen. Both settle into plaque and into any rough or exposed area of the tooth, and the stain from smoking or chewing tends to be more stubborn and darker at the gumline.

Some antiseptic mouth rinses, notably those containing chlorhexidine, can leave a brown surface stain with prolonged use. That is a known, cosmetic effect of an effective medicine; anyone who has been prescribed such a rinse should raise the staining with the prescriber rather than simply stopping it.

Plaque and hardened tartar act like a sponge for all of these pigments, which is why a professional scale and polish is usually the first step, not an afterthought. A surprising share of what people call yellow teeth is removable film, and no gel is needed for that part. What stays after cleaning is the true extrinsic stain that has worked into the enamel, and that is what peroxide is designed to address.

Discoloration from inside: injury, a dying nerve, decay and old fillings

A single tooth that has drifted away from the color of its neighbors is telling a different story from general dulling, and it deserves its own examination.

Trauma is the classic cause. A knock hard enough to bruise the pulp can cause bleeding inside the tooth. Blood breaks down, and iron-containing pigments from it seep into the dentin, which is porous. The tooth turns pink at first and then gray or brown over months. Sometimes the pulp survives; sometimes it dies without any pain, a state dentists call pulp necrosis. A tooth with a dead pulp darkens because the tissue inside decomposes and stains the dentin from within. It can also harbor infection silently, which is why one dark tooth is a reason for an X-ray rather than a whitening kit.

Decay is a different color again. Early cavities appear as chalky white spots where mineral has leached out; established decay is brown or black. Whitening does not treat decay and can irritate the exposed nerve inside a cavity. The fix is a filling, and the shade improves when the decayed tissue is removed.

Old dental work contributes more than people expect. Silver-colored metal fillings can corrode and shine gray through thin enamel, and can leave a dark shadow after they are replaced. Tooth-colored composite fillings absorb stain over time, so a tooth that looks patchy may have an aging filling rather than a discolored tooth.

Teeth that have had root canal treatment often darken because the pulp is gone and remnants remain in the chamber. For these teeth, dentists have a dedicated option called internal bleaching, in which whitening material is placed inside the tooth rather than on its surface. Whether that, an external approach or a veneer is appropriate depends on the tooth’s condition, and it is a decision for the treating dentist after examination and imaging.

Medicines, fluoride and childhood: is tetracycline stained teeth whitening realistic?

Some of the most stubborn discoloration was written into the tooth before it ever appeared in the mouth. Enamel and dentin form over several years in early childhood, and anything that disturbs that process leaves a permanent record.

Antibiotics of the tetracycline class are the best known example. During tooth formation these medicines bind to calcium and are incorporated into the developing dentin, where they leave yellow, gray or brown bands that darken further with exposure to light. MedlinePlus notes this occurs when the medicine is taken during the second half of pregnancy or by children younger than about eight, the window in which permanent teeth are still forming. Adult teeth that have already formed are not stained this way, so an adult prescribed a medicine in this class today is not putting their own teeth at risk; any concern about use in pregnancy or childhood belongs with the prescribing clinician, never with a decision to stop treatment.

Fluorosis works similarly. The NIH Office of Dietary Supplements describes it as a change in enamel caused by taking in more fluoride than needed while teeth are developing. Mild fluorosis appears as faint white streaks or flecks; the uncommon severe form produces brown staining and pitting. It is a cosmetic change, not a disease of the tooth.

Childhood illness, high fevers and some inherited conditions can also leave enamel thin, pitted or discolored, a group of changes dentists call enamel hypoplasia.

Does whitening help? Evidence and clinical experience agree that tetracycline banding is among the slowest and least predictable responders; supervised courses tend to be longer and results uneven, and the darker gray bands near the gum often persist. Fluorosis is a special case: because it involves white patches, ordinary bleaching can make the contrast more obvious before the surrounding enamel catches up. Dentists frequently consider alternatives such as microabrasion, which gently polishes away a microscopic surface layer, resin infiltration to mask white spots, or veneers. The right sequence depends on the pattern in front of them.

How teeth whitening actually works on a stain

Strip away the marketing and whitening is one reaction: peroxide meets pigment.

Professional whitening gels contain hydrogen peroxide, or carbamide peroxide, which breaks down into hydrogen peroxide once it is on the tooth. Peroxide is a small, unstable molecule. It slips through the porous enamel into the outer dentin and releases reactive oxygen along the way. Those oxygen molecules attack the long, ring-shaped pigment compounds that give stains their color, snapping them into smaller fragments that reflect light differently and look paler. The stain is not scrubbed off; it is chemically bleached in place, which is why the tooth’s own structure is left intact when the gel is used as directed.

The same mechanism explains the limits. Peroxide works on organic pigments, meaning carbon-based molecules from food, tobacco, blood breakdown or aging dentin. It has little effect on metal-based discoloration, such as the gray shadow of an old amalgam filling. It cannot penetrate porcelain or composite, which have no pores to enter. And it cannot add enamel where enamel has worn away.

Delivery matters less than people think, and more than advertising suggests. Dentist-applied whitening in the chair uses a stronger gel with the gums protected, sometimes with a light whose added benefit remains debated. Dentist-made custom trays hold a gentler gel against the teeth at home over a series of days. Over-the-counter strips and rinses use lower concentrations. Whitening toothpastes mostly rely on mild abrasives that polish surface film, with only a small chemical effect.

The NHS is explicit that whitening is a form of dentistry that should be carried out by a dental professional, and that gum irritation and tooth sensitivity are the commonly reported side effects. Cleveland Clinic lists the same two. Both are usually short-lived, a point the timeline section below returns to.

Which cause of tooth discoloration responds to whitening? A comparison

The table below is a map, not a verdict. Real mouths hold several causes at once, and only an examination can weigh them. But it shows why two people using identical gel can get very different results.

Cause	Where the color sits	Typical look	Usual response to peroxide whitening	What dentists often consider instead or first
Coffee, tea, wine, dark foods	Surface film and outer enamel	Even yellow-brown dulling	Generally good, after cleaning	Professional scale and polish
Tobacco	Surface, worse at gumline	Yellow-brown to dark brown	Often good, may need repeat	Cleaning; quitting support
Age-related yellowing	Dentin beneath thinning enamel	Uniform yellow	Generally responds	Protecting remaining enamel
Injury or dead pulp	Inside one tooth	Single gray or brown tooth	Poor from outside	X-ray; root treatment; internal bleaching
Tetracycline-class antibiotics in childhood	Dentin, in bands	Gray, yellow or brown stripes	Slow, uneven, unpredictable	Longer supervised courses; veneers
Fluorosis	Enamel	White flecks, sometimes brown pits	May increase contrast at first	Microabrasion; resin infiltration
Decay	Enamel and dentin	White spot to brown-black	Not appropriate	Filling
Crowns, veneers, fillings	Restorative material	Mismatch with neighbors	None	Polish, replace, or whiten before new work

Two patterns jump out. First, the further inside the tooth the color sits, the less predictable whitening becomes; peroxide reaches outer dentin readily, banded deep dentin slowly and a dead pulp chamber not at all from the surface. Second, anything that is not natural tooth tissue simply does not bleach. Mayo Clinic’s summary is the one to remember: yellow shades respond best, brown less, gray perhaps not at all. Where a row says ‘consider instead’, that is a conversation to have with the dental team, not a shopping list.

Who whitening is usually for, and who is usually asked to wait

Whitening is elective, so the question is rarely whether someone is allowed to have it but whether it is likely to help and whether the mouth is ready.

The typical candidate is an adult with natural teeth, healthy gums, no untreated decay and a stain type that sits in the enamel or outer dentin. Someone whose main complaint is coffee dulling or age-related yellowing, and who has had a recent examination and cleaning, fits that description well. Realistic expectations belong on the list too: natural teeth are not paper white, and a shade that looks natural against the whites of the eyes is the usual aim.

Several groups are commonly asked to wait or to take a different route.

• Anyone with untreated cavities, cracked teeth or worn areas where dentin is exposed, because gel reaching those areas causes pain and can inflame the nerve.
• People with active gum disease or receding gums, since inflamed tissue and exposed root surfaces react badly to peroxide.
• Under-18s. The NHS states that whitening is not recommended for people under 18, partly because young pulp chambers are larger and more sensitive.
• People who are pregnant or breastfeeding, for whom safety data are lacking and clinicians usually defer elective treatment.
• Anyone with a single dark tooth or a suspected dead nerve, who needs imaging before any cosmetic step.
• People planning new crowns, veneers or fillings on front teeth, because whitening first and matching the new work afterward avoids a mismatch.
• Those with a known reaction to peroxide products, or with fluorosis or tetracycline banding, where a different plan may serve better.

None of these is a permanent no. A filled cavity, treated gums or a completed root canal often turns a wait into a yes. The judgment sits with the treating dentist, who can see the whole picture.

Does whitening work on veneers, crowns and fillings?

The short answer is no, and the longer answer is why that creates a planning problem worth knowing about before treatment, not after.

Porcelain veneers, ceramic crowns and tooth-colored composite fillings are manufactured materials. Their color is set at the factory or in the dental laboratory, and they lack the microscopic pores through which peroxide travels. Gel sits on them and does nothing. Metal-based fillings are equally unmoved.

The trap is what happens to the natural teeth around them. Whiten a smile that contains one crown on a front tooth and the neighbors brighten while the crown stays put, so a restoration that once blended perfectly suddenly stands out as too dark. People sometimes assume the crown has stained when in fact everything else has changed around it.

The standard sequence, therefore, is whitening first and new restorations afterward. Dentists generally allow the whitened shade to settle before choosing a matching color, because freshly bleached teeth are slightly dehydrated and look brighter than they will a short while later; the treating dentist will advise how long that interval should be in a given case. Existing restorations that no longer match may be polished, replaced or, in some cases, left alone if they sit out of sight.

Composite fillings deserve a separate note. Unlike porcelain, composite is slightly porous and does pick up stain over years, especially at its edges. A patchy-looking front tooth is sometimes a discolored filling on a perfectly healthy tooth, and a polish or a fresh margin solves what whitening cannot.

There is one more twist. Whitening gel can temporarily soften the bond at the edge of some restorations, which is one reason dentists prefer to schedule any new bonding after whitening has finished. All of this argues for a single conversation covering the whole smile, with the dental team deciding the order of work.

What the days and weeks after whitening usually look like

Whitening has a shape over time, and knowing it prevents both panic and disappointment.

In the first hours, teeth often look their brightest. Part of that is genuine bleaching and part is dehydration, since peroxide gel draws a little moisture out of enamel. As the tooth rehydrates over the following days, the shade settles to its real result, a step down from the first glimpse in the chair. Dentists sometimes call this rebound; it is expected, not a failure.

Sensitivity is the most common companion. Peroxide passing through dentin can irritate the nerve, producing sharp, short zings to cold air or water. The NHS and Cleveland Clinic both describe this as a usual, temporary side effect. It typically eases once treatment stops, and dentists may suggest spacing sessions, using a toothpaste designed for sensitive teeth, or pausing altogether if it is troublesome. Any decision to change the schedule belongs with the dentist who set it.

Gums that touched gel may blanch white or feel sore for a short time; a well-fitted tray and careful application are the usual prevention. Pain that persists, a tooth that becomes tender to bite on, or a gum that ulcerates are not normal and belong in the section on when to call.

Dentists commonly advise avoiding deeply colored food and drink for a short window afterward, on the reasoning that freshly bleached enamel is more porous until it remineralizes. The exact advice varies and is best taken from the person who did the treatment.

How long results last depends almost entirely on the original cause. The NHS puts the range at a few months to up to three years, shorter for people who smoke or drink a lot of tea, coffee or red wine. Age-related yellowing tends to creep back slowly; surface stain returns at the pace of the habit that made it. Touch-up courses are something to plan with the dental team rather than improvise.

What people often get wrong about tooth discoloration

A handful of myths do most of the damage, and each one collapses against the anatomy described earlier.

Whitening toothpaste bleaches teeth. It does not, at least not meaningfully. Most whitening pastes rely on mild abrasives that polish away surface film; the chemical component, if present, is small. They can keep a whitened smile from dulling and remove fresh coffee stain. They cannot change dentin color, and used aggressively they wear enamel.

Lemon juice, baking soda, charcoal or oil pulling will whiten safely. Acidic lemon dissolves enamel mineral outright. Charcoal and heavy baking soda are abrasive, and any brightening comes from scrubbing away the very enamel that protects the yellow dentin, which ultimately makes teeth look yellower. Mayo Clinic’s guidance is direct: there is no good evidence that these home methods whiten teeth, and some can harm them. Oil pulling has no convincing evidence for whitening at all.

Whitening ruins enamel. Peroxide whitening carried out by a dental professional does not strip enamel; sensitivity is real but temporary. The genuine risks come from unsupervised use of strong products, overuse, and gel on unhealthy teeth or gums.

Whiter means healthier. Natural enamel has a warm tone, and a tooth can be unnaturally white and riddled with decay, or slightly yellow and perfectly sound. Color is a cosmetic measure, not a health one.

Everyone gets the same result. The whole point of this article is that they do not. A person with surface stain and a person with tetracycline banding using the same tray will end up in very different places.

One dark tooth just needs a stronger gel. It usually needs an X-ray. A lone gray tooth is the pattern of internal bleeding or a dead nerve, and treating it as a stain risks missing an infection.

Questions to ask your care team before whitening

The most useful appointment is the one where the patient arrives with questions about cause rather than shade. A dentist who is asked ‘what is making my teeth this color?’ will give a more honest forecast than one asked ‘how white can you get them?’

These questions tend to open the right conversation.

• Which type of discoloration do I have, extrinsic, intrinsic or a mixture, and how did you decide?
• Is any of my discoloration a sign of a problem that needs treating first, such as decay, a dead nerve or gum disease?
• Do I have any crowns, veneers or fillings on visible teeth that will not change color, and should they be redone afterward?
• Based on the cause, how much change do you realistically expect, and which teeth are least likely to respond?
• Would a professional cleaning alone get me part of the way there?
• Which approach do you recommend for me, in the chair or custom trays at home, and why?
• What side effects should I expect, how long do they usually last, and what should make me stop and call you?
• Is there anything in my medical history, including pregnancy, sensitive teeth or gum recession, that means I should wait?
• If whitening is unlikely to help my type of stain, what alternatives are there and what are their trade-offs?
• How long might the result last given my habits, and how would you plan any touch-ups?

Bring a list of medicines and any history of childhood illness or dental injury, and mention any antiseptic rinse in regular use. Bring, if possible, an old photograph; a dentist can learn a lot from how a smile has changed. Write the answers down. The value of this conversation is that it turns whitening from a hopeful purchase into a plan whose likely outcome is understood before it begins, with every decision resting where it should, with the treating team.

When to call your doctor or dentist about discolored teeth

Most discoloration is cosmetic and unhurried. A few patterns are not, and they justify a prompt call rather than a search for a brighter gel.

Contact a dentist promptly if you notice any of the following.

• A single tooth turning gray, brown or pink, especially after a fall, a blow or a sports injury, even one years ago. This is the signature of internal bleeding or a dying nerve, and an infection can develop without pain.
• Discoloration accompanied by toothache, swelling of the gum or face, a pimple-like bump on the gum, a persistent bad taste, or a tooth that feels loose or high when biting. These point to infection that needs treatment.
• A brown or black area that catches a fingernail or has a soft, sticky feel, which suggests decay rather than stain.
• White or brown spots on a child’s teeth, which may be early decay, fluorosis or an enamel defect and should be assessed while options are widest.
• After whitening: sharp pain that does not settle within a few days of stopping, a tooth that becomes tender to pressure, gums that are white, blistered or ulcerated, or any swelling of the lips or mouth suggesting a reaction to the gel.
• Any sudden color change across many teeth without an obvious dietary cause.

Seek urgent care the same day for facial swelling that is spreading, difficulty swallowing or opening the mouth, or fever alongside a painful tooth; these can signal a dental infection moving beyond the tooth.

If you suspect a medicine or a prescribed mouth rinse is behind new staining, tell the prescriber and the dentist. Do not stop or alter the medicine on your own; the staining is usually manageable and the reason the medicine was prescribed is not. Every next step, from an X-ray to a filling to a whitening plan, is a decision for the clinicians who have examined you.

Frequently asked questions

What is the most common cause of tooth discoloration in adults?

In adults, the most common causes are surface staining from coffee, tea, red wine and tobacco combined with age-related thinning of enamel over darkening dentin. MedlinePlus lists these alongside poor plaque control, medicines, dental materials, trauma and genetics. Most people have more than one cause at once, which is why a dentist’s examination, rather than the stain’s color alone, decides whether whitening is likely to help.

Why are my teeth yellow when I brush twice a day?

Yellowing that survives good brushing usually comes from inside the tooth, not from its surface. Enamel wears thinner and more translucent with age while the dentin beneath grows thicker and deeper yellow, so more yellow shows through. Acid erosion from reflux or acidic drinks and night-time grinding speed this up. Brushing removes plaque and fresh surface stain but cannot change dentin color or replace lost enamel.

What is the difference between extrinsic vs intrinsic tooth stains?

Extrinsic stains sit on the outer surface of enamel and come from outside sources such as coffee, tea, wine, tobacco or some antiseptic rinses; they respond to cleaning and usually to whitening. Intrinsic stains live within the enamel or dentin, from injury, a dead nerve, aging dentin, fluorosis or childhood antibiotic exposure. Intrinsic color is deeper, so whitening works more slowly and less predictably on it.

Does teeth whitening work on gray teeth?

Gray teeth are the least predictable responders. Mayo Clinic notes that yellowish teeth tend to bleach well, brownish teeth less well and grayish teeth may not respond at all. Gray usually signals deep dentin staining, such as tetracycline banding, or a dead pulp in a single tooth. A dentist may consider longer supervised courses, internal bleaching after root treatment, or veneers, depending on the cause found on examination and X-ray.

Is tetracycline stained teeth whitening possible, or do I need veneers?

Whitening can lighten tetracycline banding, but slowly and unevenly, and the darker gray bands near the gum often persist. Because the pigment is bound into dentin during tooth formation, dentists typically expect longer supervised courses and modest change. Veneers or bonding are commonly discussed alternatives when the banding is dark or the person wants a uniform result. The right route depends on the pattern and depth, judged by the treating dentist.

Does whitening work on veneers, crowns or fillings?

No. Porcelain, ceramic and composite are manufactured materials without the pores peroxide needs to enter, so their color does not change. The natural teeth around them do brighten, which can leave an existing crown or filling looking darker than before. Dentists usually recommend whitening first and matching any new restorations afterward, once the whitened shade has settled, and may polish or replace older work that no longer blends.

Can whitening make fluorosis spots look worse?

It can, at least at first. Fluorosis appears as white flecks or streaks in enamel, and bleaching the surrounding tooth can briefly increase the contrast before the shades even out. For this reason dentists often consider other approaches for fluorosis, such as microabrasion, which polishes away a microscopic surface layer, or resin infiltration to mask the white patches, sometimes in combination with whitening. The choice depends on the severity seen on examination.

How long do teeth whitening results last?

The NHS estimates that whitening results last from a few months to up to three years, varying widely from person to person. Results fade faster in people who smoke or regularly drink tea, coffee or red wine, because the same surface staining simply builds up again. Age-related yellowing returns more slowly. Any touch-up plan should be agreed with the dentist who carried out the treatment rather than improvised.

Is teeth whitening sensitivity permanent?

Sensitivity after whitening is common and usually temporary. Peroxide passing through dentin can irritate the nerve, causing short, sharp reactions to cold that typically ease once treatment stops; the NHS and Cleveland Clinic both describe it as a usual side effect. Pain that persists beyond a few days, a tooth that becomes tender to bite on, or gums that blister or ulcerate are not expected and should be reported to the dentist promptly.

Should I whiten a tooth that turned dark after an injury?

Not before a dentist has examined it and taken an X-ray. A single tooth that darkens after a knock usually reflects bleeding inside the tooth or a nerve that has died, and a dead nerve can harbor infection without pain. Surface whitening does little for this pattern. If the tooth needs root treatment, a dentist may later offer internal bleaching, where whitening material is placed inside the tooth, or discuss a veneer.

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.