What Teeth Whitening Can and Cannot Do

Professional whitening works, and it works considerably better than whitening toothpaste, which mostly polishes surface stains and cannot change the colour of the tooth itself.

What it treats well is staining built up from tea, coffee, tobacco and time. What it does not treat is discolouration from inside the tooth — a tooth darkened after an injury or a root canal will not respond the same way, and may need a veneer or an internal treatment instead.

It also does nothing to crowns, veneers, bridges or fillings. Those keep their original shade, so if you whiten the teeth around them the mismatch becomes more obvious, not less. That is worth planning for before starting.

Sensitivity during and shortly after whitening is common and usually settles within a few days. Having it done professionally means the strength is controlled and your gums are protected, which is the main safety difference from a shop-bought kit.

How many shades you gain depends on where you start. Anyone promising a specific result before looking at your teeth is guessing.