Teeth Whitening

How whitening works

The active ingredient in whitening gels is either hydrogen peroxide or carbamide peroxide, which chemically breaks down the pigmented molecules inside enamel and dentine. Enamel is neither abraded nor removed — the change takes place within the tooth structure itself.

Whitening doesn't work equally well on every kind of discolouration. It's effective against staining from tea, coffee and smoking, and against age-related yellowing. For tetracycline staining, fluorosis, and single dark teeth following trauma, results are limited or a different approach is needed.

Examination comes first

Before whitening begins, any decay is treated, calculus removed and gum health assessed. There are two reasons for this: gel can pass through an open cavity and reach the nerve, and scaling alone can already reveal the true underlying shade of the teeth. For some patients, whitening turns out to be unnecessary once cleaning is done — saying so is part of the treatment too.

Existing fillings and crowns won't whiten. If restorations sit on the front teeth, a colour mismatch will show up after whitening, and they may need replacing. This is always discussed before starting.

Methods

In-clinic whitening

A high-concentration gel is applied once the gums are protected with a barrier. Each session lasts 45 to 60 minutes, and one or two sessions are usually enough.

Take-home whitening

A lower-concentration gel goes into custom-fitted clear trays, worn for a few hours a day or overnight, over 7 to 14 days. It's slower but more controlled, with less sensitivity involved.

The two methods can also be combined.

Sensitivity

Cold sensitivity during whitening and for 24 to 48 hours afterwards is common and temporary. Gels containing potassium nitrate or fluoride can ease it. If sensitivity is pronounced, treatment is paused — there's no need to push through it.

How long results last

The outcome isn't permanent. Staining foods and drinks (coffee, tea, red wine, tobacco) and time will gradually bring the shade back toward its starting point. A top-up every one to two years may be needed, and keeping your take-home trays makes that easier.

Whitening is not carried out during pregnancy or breastfeeding, in anyone under 18, or in those with a peroxide allergy.

This page is general information and does not replace a dental examination. Whether the treatment suits you, and the method and duration, are decided only after an intraoral examination and radiographic assessment.