Teeth whitening: what it can and cannot change

The most common disappointment with whitening is not that it failed. It is that it was never the right treatment for the discolouration in question.

Whitening lightens the natural tooth structure. That is the whole of what it does — and understanding it explains almost every case where the result falls short of what someone hoped for.

Two different kinds of discolouration

Extrinsic staining sits on the outside of the enamel. Coffee, tea, cardamom, red foods, and tobacco all deposit pigment on the surface over time, and it accumulates fastest on rough areas and around the gumline.

This kind is often not a whitening problem at all. A scale and polish removes surface deposit and the stain that has bound to it. Patients are frequently surprised at the shade change from a cleaning alone, and it costs less than whitening.

Intrinsic discolouration is in the tooth itself. Enamel thins with age and the yellower dentine beneath shows through more. Some medications taken during tooth development, notably tetracycline, leave banding. A tooth that has had trauma or root canal treatment can darken on its own.

Whitening works on intrinsic discolouration. It is the only one of the two it genuinely addresses.

What whitening will not lighten

Nothing artificial in your mouth changes colour. This is the single most important thing to know before booking.

• Composite fillings
• Crowns, veneers, and bridges
• Dentures

If you have a white filling in a front tooth, whitening the teeth around it will make that filling stand out more, not less, because it stays exactly the shade it was. That is not a complication — it is predictable, and it is why we check what restorations you have before agreeing to treat. Sometimes the honest plan is to whiten first and replace the filling afterwards to match the new shade.

Teeth with grey banding from tetracycline respond poorly and unevenly. Where the discolouration is deep, veneers are the treatment that actually addresses it, and we will say so rather than sell a course of whitening that cannot reach it.

Sensitivity

Temporary sensitivity is common, not a sign something went wrong. The whitening agent passes through enamel into the dentine, and the nerve responds. It typically settles within a day or two.

It is more likely, and more intense, if you already have exposed root surfaces from gum recession, untreated decay, or cracked enamel. All three are reasons to have the mouth examined before whitening rather than after — treating an active problem comes first.

Before you book

A short examination establishes three things: which kind of discolouration you have, whether there is active decay or gum inflammation that needs treating first, and which of your existing restorations will not change colour.

Ten minutes spent on that is what separates a result you are pleased with from one that surprises you.

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General information, not a treatment plan. Whitening is not recommended during pregnancy or breastfeeding, and some causes of a single darkened tooth need investigating rather than whitening.