Up and up whitening strips before and after

Whitening strips can lighten some surface and internal stains, but results vary with enamel, dentine, fillings, and correct use.

A strip holds a peroxide-based gel against the front surfaces of the teeth. The peroxide moves through enamel and breaks down some stain molecules, while toothpaste cannot alter the colour of dental restorations.

Follow the product directions, keep gel off the gums, and do not extend the contact time. Reduce use or stop if sharp sensitivity or gum irritation develops, and treat decay or leaking fillings before whitening.

Arrange an examination for pain, visible cavities, cracked enamel, gum sores, or a single dark tooth. A dentist can distinguish external stain from decay, trauma-related colour change, or a restoration that will not bleach.

Ask whether the discolouration is in enamel or dentine, whether any restorations will mismatch after whitening, and which concentration and wear schedule fit your teeth and gums.