Home whitening is the most popular cosmetic dental treatment in the UK, and the most misunderstood. The difference between a kit prescribed by a dentist and one bought online is not marketing — it is the concentration of the active ingredient, the fit of the tray and who is supervising the result.
How whitening actually works
Whitening gels contain hydrogen peroxide or carbamide peroxide, which break down into oxygen molecules that pass through enamel and break up the pigment molecules trapped inside the tooth. It is a chemical process inside the tooth structure, not a cleaning or polishing of the surface.
That is why staining from coffee, tea, red wine and smoking responds well, while grey or intrinsic discolouration — from tetracycline, fluorosis or trauma — responds less predictably.
Dentist-prescribed versus shop-bought
In the UK, whitening products sold directly to the public are limited to very low concentrations of hydrogen peroxide (0.1%). Dentists can prescribe higher concentrations, up to 6% hydrogen peroxide, for adults, with a proper assessment first. Tooth whitening is not permitted for anyone under 18 except where a dentist considers it necessary for health reasons.
The second difference is the tray. A custom tray made from a scan of your teeth keeps the gel against the tooth surface and away from the gums. A one-size kit leaks, irritates gums and produces uneven results.
What a prescribed course involves
- Examination to confirm your teeth and gums are healthy and that the discolouration is likely to respond
- Scan or impression for custom trays
- A trial of the trays and instruction on how much gel to use
- A course of daily or overnight wear, typically two to four weeks
- A review to assess the result and discuss any top-up
What results are realistic?
Most patients see a noticeable change, but no responsible clinician promises a specific number of shades. Results depend on the type of staining, the starting shade, how consistently the trays are worn and whether the discolouration is on the surface or inside the tooth.
What whitening will not do: change the colour of crowns, veneers, composite bonding or fillings. If you have visible restorations on front teeth, they will stay their original shade while the surrounding enamel lightens — which is why sequencing matters.
Sensitivity: common, not dangerous
Most people experience some sensitivity during treatment, usually a short sharp sensation to cold. It typically settles after the course. Using a desensitising toothpaste before and during treatment, reducing wear time, and not overfilling the trays all help. If sensitivity is severe, stop and speak to your dentist rather than pushing through.
Order of treatment matters
If you are planning both whitening and bonding or veneers, whiten first. Composite and ceramic are matched to the shade at the time they are made, and they cannot be lightened afterwards. Whitening after bonding leaves you with bright teeth and a mismatched restoration. Our page on composite bonding explains how shade matching works.
What it costs
At ēm dental, a custom home whitening course starts from £350, and the Enlighten system from £750. Both include the trays and the gel; the current list is on our treatment price list.
Be wary of very cheap “whitening” offers. If a treatment is not supervised by a registered dental professional, it is both less effective and, in the UK, often unlawful.
Looking after the result
- Repeat the course or use a top-up kit when staining returns, usually after a year or more
- Attend hygiene appointments — surface stain is removed professionally and is not the same as whitening
- Rinse after coffee, tea and red wine, and use a straw where practical
- Do not whiten during pregnancy or while breastfeeding without medical advice
Is it right for you?
If your teeth and gums are healthy and your concern is the shade rather than the shape, whitening is usually the least invasive option available. If you have existing restorations on visible teeth, or the discolouration is internal, a different plan may serve you better. You can book a consultation at our W2 clinic.
Frequently asked questions
Does whitening damage enamel?
Supervised whitening with appropriate concentrations does not remove enamel. Overuse, inappropriate products and unsupervised high-strength gels can cause problems, which is why a dental assessment comes first.
How long do results last?
Typically months to a couple of years, depending on your diet, smoking and oral hygiene. Top-ups are normal and expected.
Can I whiten with crowns or veneers?
The restorations will not change colour. If they are visible when you smile, the shade has to be planned around them — sometimes by replacing them.
Is whitening safe for sensitive teeth?
Usually yes, with a lower concentration and a slower course. Your dentist can adjust the protocol, and treating any exposed roots or decay first is essential.
Can I use shop-bought kits instead?
You can, but the legal concentration limit is very low, the trays are not fitted, and results are correspondingly limited. They are not equivalent to a prescribed course.
This article is general information about dental treatment and is not a substitute for clinical advice. For advice about your own teeth, book a consultation at our W2 clinic.