Yes, whitening strips work on surface stains for most people with healthy, natural teeth. A thin, flexible strip holds whitening gel against the front of your teeth, where it lifts staining from coffee, tea, red wine and smoking. How much whiter you get depends on your starting shade, the type of staining and finishing the full course.
Strips are not the same as whitening at the dentist, and they will not suit everyone. In Denmark, the Danish Environmental Protection Agency (Miljøstyrelsen) says the best advice is to see a dentist if you want whiter teeth, and to contact your dentist before you start if you whiten at home. This guide explains what strips can and cannot do, so you can decide.
How do teeth whitening strips work?
Each strip is coated on one side with whitening gel. You press it onto clean, dry teeth and fold the edge behind them, so the gel stays in close contact with the tooth surface for the treatment time. The gel helps break down stain build-up across the surface, so teeth look gradually brighter as the course goes on.
The strip itself does two jobs: it keeps the gel where it is needed, and it keeps it off your gums as far as possible. That is why fit matters. Strips that sit flat and stay put give a more even result than strips that slip.
In SmilePro strips sold in Denmark and the EU, the whitening ingredient is PAP (phthalimidoperoxycaproic acid). The full ingredient list, including hydroxyapatite and potassium citrate, is on the teeth whitening strips page.
How long do whitening strips take to work?
Many people notice a visible difference after the first few applications. SmilePro strips whiten teeth by up to 5 shades. The course is one 30-minute treatment a day for 7 days; after that, the other 7 treatments in the pack are top-ups, one every 2 weeks (or once a week if you drink a lot of coffee, tea or red wine), to help stop stains setting in again. At once every 2 weeks that is about three months of top-ups from one pack. Stopping the course halfway usually means a smaller change. After each treatment, wait 1 hour before eating or drinking anything except water.
Check your shade in daylight before your first strip and again at the end, so you can see the difference for yourself. A photo taken in the same spot and light each time works well.
What results can you expect?
Strips work best on surface staining from coffee, tea, red wine and smoking, which the Danish Dental Association (Tandlægeforeningen) names among the biggest causes of discoloured teeth. Tandlægeforeningen also notes that it is hard to predict how well bleaching will work, and that teeth which look discoloured because of large old fillings, plaque or their position in the mouth will not be helped. Fillings, crowns and veneers will not go whiter than their original colour.
Results also depend on where you start. Teeth change colour naturally with age, and long-standing staining takes longer to lift than recent staining. If you have visible dental work at the front of your mouth, ask your dentist before whitening, because natural teeth can lighten while crowns and veneers stay the same shade.
Who should not use whitening strips?
SmilePro strips are not for anyone under 18, or anyone pregnant or breastfeeding, and Danish rules do not allow tooth bleaching on anyone under 18. Do not use them if you have gum disease, an oral infection or recent dental surgery, or amalgam fillings without consulting a dentist first. If you have sensitive teeth or unhealthy gums, see a dentist first. If you wear braces, wait until they are off, as the result can be uneven.
Do not use strips for more than 14 consecutive days without a dentist's supervision, stop and see a dentist if your gums or mouth become irritated (redness, swelling or soreness), and do not swallow the gel. Avoid direct contact of the whitening gel with your gums, and avoid contact with your eyes.
How to get the best results from whitening strips
Brush with water and pat your teeth dry, press the gel side on firmly and fold the edge behind your teeth, then leave the strips on for the full 30 minutes. Peel them off and wipe or rinse away any leftover gel. Follow the instructions for the whole course and never leave strips on longer than directed.
A few habits help the result last:
- Cut back on coffee, tea, red wine and smoking during and after the course. Tandlægeforeningen notes that teeth pick up new colour more easily in the first days after bleaching.
- Brush twice a day. A whitening toothpaste helps lift everyday surface stains between treatments.
- Keep up regular dental check-ups.
Strips or an LED whitening kit?
Choose strips for simplicity and travel, and an LED kit for a bigger change in shorter sessions. Both are used once a day for a 7-day course. SmilePro strips take 30 minutes, need no light and whiten up to 5 shades. The SmilePro Advanced Kit takes 10 minutes a day with a blue and red LED light and whitens up to 8 shades in 7 days.
| SmilePro Whitening Strips | SmilePro Advanced Kit | |
|---|---|---|
| Time per treatment | 30 minutes | 10 minutes |
| Course | One treatment a day for 7 days, plus 7 top-ups in the pack (one every 2 weeks) | One treatment a day for 7 days |
| Light | None | Blue and red LED |
| Result | Up to 5 shades whiter | Up to 8 shades in 7 days |
| Price | See the Strips price | See the Kit price |
| Best for | Travel and top-ups | Your first course |
Many people use both: the kit for the first course, then strips or refill pens to keep their shade. If you move between the kit and strips, wait 2 weeks between finishing a course with one and starting a course with the other.
Are whitening strips safe?
Whitening strips that meet EU rules are generally safe for adults with healthy teeth and gums when used exactly as directed. Some people notice temporary sensitivity or gum irritation; Tandlægeforeningen says the twinges usually stop after a couple of days. SmilePro strips are enamel safe and formulated to help prevent sensitivity in healthy teeth.
Miljøstyrelsen found in 2021 that many whitening products for home use did not comply with the law, so buy from a seller that lists every ingredient. If your teeth are already sensitive, speak to a dentist before you start. More detail in our guide, Is teeth whitening safe in Denmark?
Shop SmilePro teeth whitening strips, 14 treatments (a 7-day course plus 7 top-ups), or the LED teeth whitening kit, with a 30-day money-back guarantee.
Sources
This guide is general information, not dental advice. If you have any concerns about your teeth or gums, speak to a dentist.
- Miljøstyrelsen (Danish Environmental Protection Agency), Tandblegning, read 7 October 2026.
- Tandlægeforeningen (Danish Dental Association), Blegning af tænder, read 7 October 2026.
- SmilePro, Terms and Conditions, section 4, "Product Use and Cautions" (who should not use SmilePro products).
- SmilePro product information: Teeth Whitening Strips and Advanced Teeth Whitening Kit.
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