There are only a few honest sentences in the whole of tooth whitening, and here is the first: the only ingredient proven to lighten the colour of a tooth is peroxide. Hydrogen peroxide, or carbamide peroxide which breaks down into it. Everything on the shelf that works, works because of peroxide. Everything that contains none is doing something else – usually polishing – however dazzling the packaging.
Why that matters: stains versus shade
Teeth look darker for two different reasons. Surface stains – tea, coffee, red wine – sit on the outside, and a good hygiene visit or a mildly abrasive toothpaste removes them. The underlying shade lives inside the tooth, and no amount of scrubbing reaches it. Peroxide does: it passes gently into the tooth and breaks up the darker pigments from within. That is whitening. Everything else is cleaning – worthwhile, but different.
What UK law actually says
This part is refreshingly clear, and worth knowing before you buy anything:
- Shop products may contain no more than 0.1% hydrogen peroxide. That is roughly sixty times weaker than what a dentist can legally prescribe – enough for the label, rarely enough for the mirror.
- Products up to 6% hydrogen peroxide are legal only through a dentist, after an examination, with the first application supervised. This is the strength that genuinely changes shade.
- Anything above 6% is not legal for cosmetic whitening in the UK – whatever an online listing implies.
- Whitening is for adults. Under-18s can only be treated where there is a clinical reason.
- Only registered dental professionals may carry out whitening. A beautician offering it – however lovely the salon – is acting outside the law, with no obligation to check your teeth first.
None of this is gatekeeping for its own sake. Peroxide at working strength is safe on healthy, examined teeth – and a poor idea on decay, leaky fillings or inflamed gums, which is precisely what the examination is for.
About charcoal, and other black powders
Charcoal toothpaste is a marketing triumph and a dental shrug. It contains no peroxide, so it cannot change the shade of a tooth. What it can do is scrub – some charcoal products are abrasive enough to wear enamel with enthusiastic use, and enamel does not grow back. Thinner enamel shows more of the yellower layer beneath, which is how a “whitening” powder can leave teeth looking slightly darker over time. If you enjoy the ritual, a gentle one used occasionally will do no harm. Just know you are buying a polish, not a whitener.
“Laser”, “LED” and other bright lights
You will also meet whitening sold with a light show – a blue lamp, a “laser boost”, a countdown timer. The honest summary: the lamp looks impressive, but the evidence says the peroxide does the work, and studies comparing gel-with-light against gel-alone find little lasting difference. In-chair whitening is still a perfectly good option – it is faster, and it is done under our supervision – but you are paying for concentrated gel applied carefully, not for the glow. Any practice that implies the light itself whitens teeth is, at best, simplifying.
What realistic results look like
Done properly, whitening lightens most people’s teeth by a few shades over two to three weeks – a natural, believable brightness, not a bathroom-tile glare. Two caveats we always give before anyone pays:
- Crowns, veneers and fillings do not whiten. If they’re visible when you smile, we plan around that from the start – sometimes that changes the order we do things in.
- Mild sensitivity during treatment is common and temporary. We adjust the routine, and it settles when the course ends.
Results also last longer than the marketing fears would have you believe. The shade you reach settles and holds for a year or two for most people, drifting back slowly with tea, coffee and time rather than vanishing overnight. Keeping your trays means keeping the result cheap: a short top-up once a year is usually all it takes, and you do it at home in front of the television.
At Pearl Lane, home whitening with custom-made trays is £350, an in-chair boost with a home kit to maintain it is £495, and once you own trays a top-up syringe is £25 – an annual top-up usually holds the shade. Those are the same figures as our published price list, because of course they are. And at your first appointment we show you a realistic expected result before you commit – if we think whitening won’t give you what you’re hoping for, we will say so and save you the money.
– Dr Priya Nair, dentist