Walk into any chemist and you can spend anything from a few pounds to a few dozen on whiter teeth, and every box on the shelf says whitening on the front. What the boxes never mention is that the law has already decided, before you open the packet, how much any of them is allowed to change.
What do whitening strips actually do?
Think about a white mug you have been drinking tea from all year. There is a brown ring inside it, and a good scrub takes that ring off in a minute, and underneath, the mug is exactly the white it always was. Scrub for an hour and the china still will not go a different colour, because the colour of the china was never what the tea put there.
Teeth are the same, and honestly, that mug is the whole of this article in one picture. There is stain sitting on the outside of the enamel from tea, coffee, red wine, tobacco and years of ordinary living, and then there is the colour of the enamel itself underneath, which is yours, and which drifts darker and yellower as you get older. Lifting the stain and changing the colour are two completely different jobs, and knowing which one you are buying saves you an awful lot of money and disappointment.
Strips do the first job, and they do it reasonably well. A strip is a thin flexible film with a low-strength peroxide gel on one side, and you press it onto your front teeth and leave it there for the half hour or so the box asks for. Holding gel still against a tooth is genuinely the right idea, because peroxide works by contact time, so a strip beats most of the other things in the aisle simply by staying put.
Then there is the strength, which is where the law comes in. Anything sold over a counter in the UK and across the EU is capped at 0.1% hydrogen peroxide, counting whatever the other ingredients release, while a dentist may use up to 6%. That is sixty times the strength, and it is the reason the aisle and the surgery produce such different results. At 0.1% there is enough to loosen surface stain and very little left over for anything deeper. On healthy teeth with a bit of coffee dulling the front of them, that can be a real and visible improvement, and for the tens of pounds a box costs, that is a fair trade.
Now, your teeth sit on a curve and a strip is a flat rectangle, so it presses nicely against the front four and loses contact where the arch turns the corner. That is where the patchy look comes from: the bit the gel touched shifted a little, and the bit it never reached stayed where it was.
Does whitening toothpaste whiten anything?
It cleans beautifully and it changes the colour of nothing, and both halves of that sentence are worth having.
Whitening pastes work with mild abrasives and low-strength agents that polish stain off the surface, so you are back at the mug ring again. Over a couple of months of twice-daily brushing you might see a shade of difference, and all of it is on the outside. Charcoal pastes are the same idea wearing a more dramatic outfit; the black powder is an abrasive, doing what abrasives do. Some pastes also carry a pigment that sits on the enamel and makes yellow read as white to the eye for a while, which is a clever bit of optics and washes off like anything else on the surface.
None of that is a criticism, because there is one job whitening toothpaste is excellent at, and it is the job most people are not buying it for. Once you have a lighter shade, a whitening paste is the thing that keeps the daily tea and coffee from settling back onto it. As a holder of a result it is superb. As a producer of one it was never in the running.
One small kindness to yourself while we are here: since the abrasive is the working part, pressing harder and reaching for a stiffer brush is not the upgrade it feels like. Enamel does not grow back, and you would be polishing at the one layer you want to keep.
What about whitening pens and those LED kits?
A pen is gel in a brush, and you paint a film of it straight onto a wet tooth. You can guess how that goes. It is a bit like putting hand cream on halfway through the washing up: saliva, tongue and lips have taken most of it off in no time, and peroxide needs to sit undisturbed for a long stretch to do anything at all. A pen makes a nice pre-night-out ritual and it will lift a little surface film. What it will not do is change your shade.
The LED kits are more interesting, because the light looks like the technology while the gel is doing whatever actually gets done. Colour change happens when peroxide breaks apart and gets into the enamel, and a blue light does not carry any colour-changing power of its own. It can nudge a reaction along. The catch is arithmetic: nudge a 0.1% gel and you have nudged a 0.1% gel. There is simply not much there for the light to speed up. The kit is held to the same 0.1% a strip is, and what the glow adds is a better unboxing.
The other half of those kits is the mouthpiece, and it is one shape for every mouth in Britain. A tray that was not made for your teeth cannot hold gel precisely on your teeth, so it spreads wherever the gaps are, including onto your gums. Which brings us neatly to the thing that actually separates the surgery version from all of this.
Why is the dentist’s gel different?
Three things, and the strength is only the first of them.
The strength is the headline, though. Gel at up to sixty times what a shop is allowed to sell you passes into the enamel and breaks up the coloured molecules sitting inside it, so the tooth itself becomes lighter. Not the film on the front of the tooth. The tooth. That is the event people picture when they imagine going several shades lighter. In the UK only a dentist, or a hygienist or therapist working on a dentist’s prescription, may legally use gel at those strengths, and not on anyone under eighteen unless there is a medical reason.
Then the trays, which matter more than they sound like they do. Yours are made from a scan of your own teeth, so they are thin, they fit the curve where a flat strip gives up, and they keep the gel on the enamel and off the gums. A made-to-measure glove against a one-size mitten, essentially, except the glove is the difference between an even result and a stripe.
And third, somebody has looked. A worn patch, a tired edge on an old filling, gums that are grumbling: those are the things that decide whether whitening is a good idea this month or a better idea after something small is sorted first. Whitening is done on healthy teeth and healthy gums, which is exactly why the check-up comes first here and why it is not treated as optional. Teeth whitening at Designer Smiles is £400 all in, and that one figure covers the scan, the custom trays and the gel, with nothing added afterwards for the fitting or the shade check.
If money is tight, what is worth buying first?
Here is the honest order, including the parts that send you somewhere other than our diary.
Start with a clean, because a surprising amount of what people see in the mirror as yellow is stain sitting on the surface, and stain comes off. A hygiene visit is £70, and for heavier tea, coffee or tobacco staining, airflow stain removal is £105. If that turns out to be all your teeth needed, you are done for the price of a clean, which is the cheapest good outcome on this page. It is also why a clean is worth having before whitening: the gel starts from the enamel instead of working through a layer of last year’s coffee.
If the stain was mild and you still fancy a nudge, buy the strips. They are the best value thing in the aisle for what they do, and there is no sense paying a dentist for a job a box from the chemist handles.
And if what you actually want is a shade change, save up for the real thing rather than working through the shelf. Three boxes of strips are not one course of whitening; they are three boxes of strips, and 0.1% stays 0.1% however many times you buy it. Whitening here is £200 on the current offer, half the usual £400, with the trays and gel included, and if you are new to the practice the examination beforehand starts from £27.90. Keep the trays afterwards, too, because a top-up later goes in the trays you already have and brings the colour back without starting again.
Is there a wrong time to whiten?
There is, and it catches people out because it is about order rather than danger.
Crowns, veneers, white fillings and composite bonding keep whatever colour they were made in. They are matched, beautifully, to the shade your teeth are on the day the work is done, and they hold it while everything around them moves. So if there is new work coming on your front teeth, whiten first and match second. Do it the other way round and the brand new tooth becomes the darkest thing in your smile, which is a heartbreaking way to spend money.
The other one is simpler. If a tooth has decay, or your gums are sore or bleeding when you brush, whitening waits until those are sorted, because the gel would aggravate both. That is a short conversation at a check-up, and then the whitening follows when your mouth is ready for it.
None of this is an argument against the aisle, by the way. Strips, pastes and pens are decent at the job the law lets them do, and if that is the job you need doing, buy them and enjoy them. It is only worth knowing which job you are paying for, because then nothing on the shelf can disappoint you.
