Whitening lightens natural tooth substance. It has no effect on ceramic, composite or metal, and it works far less predictably on grey discolouration, on staining from trauma, and on developmental discolouration laid down while the teeth were forming.
This is the most common disappointment in cosmetic dentistry, and it is entirely avoidable if it is explained beforehand. Knowing which category your discolouration falls into is what makes the expectation realistic.
The two kinds of discolouration
Extrinsic: staining on the surface
Picked up from coffee, tea, red wine, dark sauces, and tobacco, and accumulating on the outer surface and in tiny irregularities in the enamel. This is the kind whitening handles best, and some of it comes off with professional cleaning alone — which is worth doing first, since it sometimes turns out to be most of the problem. See our professional cleaning page.
Intrinsic: colour within the tooth
Within the dentine underneath the enamel. Some intrinsic discolouration responds well to whitening; some barely responds at all. This is where expectations need setting.
What whitening does not touch at all
Crowns, veneers, fillings and bridges. None of them change colour. If you have white fillings or crowns on your front teeth and you whiten, your natural teeth lighten and the restorations stay exactly as they were — and the mismatch is usually more noticeable than the original shade. This is why any restorations at the front need identifying before whitening, and why they are replaced after whitening, matched to the new shade.
Metal-containing restorations, and any grey shadow they cast through a thin tooth.
What responds poorly
Grey teeth
Yellow and brown discolouration generally lightens well. Grey is considerably more resistant, and a grey tooth often improves only modestly.
A single dark tooth after trauma
A tooth that darkened years after a knock has usually lost its nerve, and the discolouration comes from inside. External whitening does little. What can work is internal bleaching, carried out from inside the tooth after root canal treatment, which is a different procedure entirely.
Tetracycline staining
Antibiotics of the tetracycline group taken while teeth were forming can produce banded grey or brown discolouration throughout the tooth. It is among the most resistant of all. Extended whitening over months sometimes improves it; often veneers are the realistic route.
Fluorosis
Excess fluoride during tooth development produces white flecks or patches, and in more severe cases brown mottling. Whitening lightens the surrounding tooth, which can make white patches more obvious rather than less, because it is the contrast that is visible. Other approaches — microabrasion, resin infiltration, or bonding — are often better suited.
Developmental enamel defects
Teeth that formed with abnormal enamel are unpredictable and need assessing individually.
When teeth look darker but are not stained
Two situations are commonly mistaken for staining.
Thinning enamel. Enamel is translucent; the dentine beneath it is yellow. As enamel thins with age, wear, grinding or acid erosion, more of that yellow shows through. The tooth is not stained — it is thinner. Whitening the dentine underneath helps only to a degree, and continuing to use abrasive or acidic products makes it worse.
Exposed root surface. Where gum has receded, the root is exposed, and root surface is naturally darker than crown enamel and does not whiten in the same way. It is also sensitive, which complicates whitening — see gum recession.
What to do when whitening is not the answer
- Professional cleaning first — sometimes that is the whole answer.
- Internal bleaching for a single dark root-treated tooth.
- Composite bonding, which covers discolouration with far less tooth removal than veneers and is reversible.
- Microabrasion or resin infiltration for certain white or brown surface defects.
- Veneers, which cover discolouration reliably but involve permanent tooth reduction.
Which applies depends on what is causing the colour, which is why an examination comes before any of it. Our smile design page explains how a case is planned when more than one tooth is involved.
How to work out which type you have
A rough guide before you spend anything. It will not replace an examination, but it will tell you what conversation to have.
Does it come off with cleaning? If your teeth look noticeably better after a professional clean, a good part of the problem was surface stain. Have that done first — sometimes it is most of the answer.
Is the colour yellow or grey? Yellow and brown respond well to whitening. Grey is considerably more resistant and often improves only modestly.
Is it one tooth or all of them? A single darker tooth, particularly a front one, is usually internal — commonly a tooth that lost its nerve after an old knock. External whitening will not change it; internal bleaching after root canal treatment might.
Is it uniform or patchy? Bands, flecks or patches suggest something that happened while the teeth were forming, and those behave differently — whitening the surrounding tooth can make patches stand out more.
Are the teeth translucent at the edges and yellower overall than they used to be? That is thinning enamel showing the dentine beneath, not staining. Whitening helps only partly, and abrasive or acidic products make it worse.
Do you have white fillings, crowns or veneers at the front? They will not change colour at all, and they need identifying before you start.
The sequence that avoids the mismatch problem
The most common and most avoidable disappointment is whitening successfully and being left with visibly darker restorations. The fix is sequence, and it is simple:
- Have the mouth examined and any decay or gum problem treated.
- Have a professional clean, so you are judging the real starting shade.
- Whiten, and record the shade before and after.
- Wait around two weeks for the shade to stabilise.
- Then replace any front restorations that no longer match, and match anything new to the settled shade.
Doing steps four and five in the other order means paying twice. If you already have several white fillings or crowns at the front, factor their replacement into the cost of whitening before deciding — sometimes that changes the decision entirely, and it is better to know beforehand.
Setting an expectation you can hold the result against
Ask two things before treatment: what is realistically achievable for your teeth specifically, and a recorded starting shade. Without a baseline, people genuinely forget how their teeth looked and conclude nothing happened, when the change was gradual and real.
Frequently asked questions
Why did one of my teeth stay dark after whitening?
Most likely it is a restoration, or the discolouration is internal — commonly a tooth that lost its nerve after an old injury.
Can my white fillings be whitened?
No. They can be replaced to match the new shade once whitening is complete and the colour has settled.
My white spots got worse after whitening. Why?
Whitening can temporarily accentuate white patches. They often become less obvious as the surrounding tooth settles over the following weeks; if they do not, other treatments address them.
Is there anything that whitens a crown?
No. A crown that no longer matches has to be remade.
How do I know which type I have before paying for whitening?
An examination. It takes one appointment and it is the difference between a realistic plan and a disappointment.
Find out what is actually causing the colour
The cause determines the treatment, and guessing wastes money. See our teeth whitening page and professional versus at-home whitening.
To arrange a consultation at our clinic on Abbas El-Akkad in Nasr City, call +20 101 969 7597 or message us on WhatsApp.
