Do Teeth Whitening Strips Work, and Are They Safe?

A whitening strip is a flexible plastic film coated with a peroxide gel, usually hydrogen peroxide or carbamide peroxide. You press it onto the front of the teeth and leave it for the time on the pack. The peroxide passes into the enamel and breaks down the pigment molecules inside, which is real bleaching, not polishing.

That is what separates strips from whitening toothpaste. A paste is on the tooth for two minutes and mostly removes surface stain. A strip keeps gel against the tooth for long enough to change its colour. The short overview of strips on the home whitening page puts them in context with the other home options.

Expect a modest lightening, not a film-star shade. Strips tend to work best on mild to moderate yellowing in healthy, fairly straight teeth. Grey, brown or banded staining responds much less, and no strip can promise a particular shade.

The pack will give a schedule, often daily use for a couple of weeks, and the change builds up over those days. It is not permanent. The result fades gradually, and it fades faster if you drink tea or coffee through the day, smoke, or chew paan. Some people repeat a course after a few months, but doing it too often raises the risk of sensitivity and gum irritation, so keep to the label.

Peroxide reaches the nerve through the enamel, so sharp twinges to cold and air are common during a course and usually settle within a day or two of stopping. If the teeth become properly painful, stop and have them checked, because the sensitivity may be coming from a crack, decay or an exposed root.

A strip is flat and the gum edge is not, so gel can seep onto the gum. That can cause stinging, redness and a white patch of tissue that fades. The page on white gums after whitening explains why that happens and what to do. Trim the strip so it does not overlap the gum, and wipe away any gel that squeezes out.

Used as directed on healthy teeth, strips are generally regarded as safe. Using them for longer than the label says, or several times a day, is where harm starts. The wider safety picture is on the page about whether teeth whitening is safe.

Strips are cut to fit a smooth, gently curved row. On crowded, rotated or overlapping teeth the film does not touch every surface, so the bleached areas and the untouched areas end up as different shades. The gaps between teeth and the back of the teeth are missed too. The strip also covers only the front six to eight teeth, so the rest of the smile can look darker by comparison.

Crowns, veneers, fillings and bonding do not whiten at all. If you have restorations on the front teeth, whitening the natural teeth around them can leave a visible mismatch, and fixing that means replacing the restoration. Ask before you start, not after.

See a dentist before using strips if you have any of these: a cavity or a broken filling, bleeding or swollen gums, exposed roots or already sensitive teeth, visible front restorations, or staining that is grey, brown or present since childhood. Peroxide reaching an open cavity or a diseased gum is painful and can make the problem worse.

Strips are not advised under 18 because the nerve of a young tooth is larger and closer to the surface. Most dentists also defer whitening during pregnancy and breastfeeding as a precaution, since there is not enough research to be sure. A scaling alone sometimes removes enough stain that no whitening is needed.

Brush gently and dry the front of the teeth first, apply the strip firmly with no overlap on the gums, and leave it for no longer than the pack says. Do not eat or drink while wearing it. Avoid tea, coffee, red wine and tobacco for the first couple of days, and stop if you get lasting pain or sore gums.

Dentist-made trays hold gel evenly against every tooth and keep it off the gums, so they suit crowded teeth and give a more even result. In-chair whitening protects the gums with a barrier and is described in the professional whitening procedure. Call the clinic to ask which whitening options are available, and see the smile design service for the wider plan.