Most people pick a whitening method by price, and a box of strips from the chemist looks like an easy first try. The gel in that box is the same peroxide a dentist uses, at a lower strength. Strength is one difference. The other is how well the gel is kept off your gums, and whether anyone has looked at your teeth first.
Your own mouth matters more than the product. Old fillings and receding gums decide whether bleaching is safe for you and whether the result will look even.
In-chair whitening at the dentist
This is the fast option. Most clinics finish it in one appointment of about an hour. The dentist paints a protective barrier over your gums, then applies hydrogen peroxide gel, often in the 25–40% range, in several short rounds.
Some practices add a blue curing light. Ask what it is for. The peroxide does the lightening, and plenty of dentists skip the light altogether.
Don’t judge the shade on the day. Enamel dries out in the chair, so teeth look whiter walking out than they will a few days later once they rehydrate. In-chair whitening also brings the sharpest sensitivity of any method in the first 24 to 48 hours, and the highest bill. A lot of dentists send you home with trays as well so you can hold the result.
Take-home trays from your dentist
Trays reach a similar shade, just more slowly: one to two weeks of wear instead of one visit. Your dentist takes a scan or impression and has trays made to fit your teeth. At home you fill them with a milder gel, commonly 10% carbamide peroxide, which breaks down into roughly 3.5% hydrogen peroxide. You wear them for a couple of hours a day, or overnight.
The fit is the point. A snug tray holds the gel on the enamel and away from the gums, which is most of the reason sensitivity tends to be lower than after an in-chair session.
You do have to wear them. Skip several nights and progress stalls. The trays last, though, and a few nights of top-up every so often holds the shade without another full course. Whatever method you use, results commonly last from several months to a few years, and coffee drinkers sit at the shorter end.
Pharmacy and supermarket strips
Australian rules cap whitening products sold straight to the public at 6% hydrogen peroxide, or 18% carbamide peroxide. Anything stronger has to be supplied through a dentist.
For mild yellowing on healthy teeth that are already an even colour, strips can be enough. They are thin plastic films coated in gel, and every box assumes the same tooth shape. Crowded or rotated teeth throw that off. The film misses the edges and the gaps between teeth, which leaves patchy results, and gel pressed against the gums often makes them sore. Expect a slower, smaller change than with a dentist’s products.
What worries dentists more is a tooth that has gone dark on its own. One grey front tooth usually means the nerve inside has been damaged, often by an old knock. No strip will fix it. That tooth needs an exam before anything else.
Sensitivity and how to reduce it
Sensitivity is the most common side effect of every method, and it usually passes. Peroxide travels through the enamel into the dentine underneath and irritates the nerve. Cold drinks or cold air can then bring on sharp twinges. Stronger gel and longer contact both raise the odds.
A potassium nitrate toothpaste helps many people if you start it a couple of weeks before treatment and keep it up during. With trays, try shorter sessions or a night off in between. After an in-chair visit, the dentist can apply a desensitising agent.
Used as directed, peroxide whitening is safe for enamel. Trouble tends to come from overuse, like leaving strips on far longer than the packet says. Gum soreness from stray gel normally clears within a few days of stopping.
When to wait, or expect an uneven result
Pregnancy and breastfeeding are the clearest reasons to hold off. Safety data are thin, and most dentists will tell you to wait. Younger teenagers are another group, since their larger nerve chambers make sensitivity more likely.
Untreated cavities and receding gums need fixing first. Bleaching over either can hurt.
Then there are people who can whiten safely but won’t get the before-and-after photo. Peroxide works best on yellow staining. Grey or brown discolouration from tetracycline antibiotics or fluorosis lightens slowly and unevenly. And the gel does nothing to crowns, veneers, bonding or tooth-coloured fillings. If you have any of those on your front teeth, they will stay the shade they are now while everything around them gets lighter.
Get a dental check before any whitening
The Australian Dental Association advises seeing a dentist before whitening, home kits included. The exam answers two things: whether bleaching is safe for your mouth, and whether the finished shade will look even.
Restorations are where people get caught out. A patient with a visible crown or an old bonded edge may need it replaced after whitening so it matches the new shade. A dentist can plan that order before any gel goes on.
At Gorgeous Smiles, a dental clinic on Exhibition Street in Melbourne’s CBD, whitening sits alongside veneers, and cosmetic work there starts with a consultation to check oral health. That is the point where decay or gum recession should be picked up, before bleaching makes either of them painful.
Book a scale and clean too. Plaque and tartar block the gel, and teeth whitened without a clean can come out patchy.
When you sit down with the dentist, ask whether anything needs treating first and which of your fillings or crowns will show afterwards. Ask what gel strength they plan to use and how they will protect your gums. It is also worth asking whether your type of discolouration responds to peroxide at all. If the answers are vague, ask again before you agree to a package.
Choosing between the three
Strips are a fair first try for mild yellowing on healthy teeth with no front fillings. Trays cost more but let you control the pace, and the finish is usually more even. In-chair whitening is for when you want it done this week. Anyone with visible crowns or veneers, or teeth that are already sensitive, should start with the exam.
This is general information. A dentist who has examined you can tell you what suits your teeth.
