Whitening: what works and what wastes your money

Whitening is the treatment people ask about most and understand least. The short version: peroxide works, abrasives do not, and nothing lightens porcelain.

What actually whitens

Carbamide or hydrogen peroxide, held against the tooth long enough to get through the enamel. That is the whole mechanism. Custom trays do it over ten to fourteen nights; in-chair systems do it faster and with more sensitivity. Everything else is stain removal.

Whitening toothpaste

It polishes surface stain off, which is worth something if you drink a lot of coffee, but it does not change the shade underneath. Used twice daily it is fine. Used as a scrub with a hard brush it wears enamel, and worn enamel looks yellower, not whiter.

Charcoal

Abrasive, and the grit ends up in your gum margins. We have seen enough sanded-down front teeth from charcoal powders to say plainly: do not.

Crowns, veneers and fillings stay put

Porcelain and composite do not lighten. If you have a crown on a front tooth, whiten first, then match the new crown to the new shade. Doing it the other way round means paying twice.

Sensitivity is normal and temporary

About half of people get cold twinges in the first week. A fluoride gel in the trays for a night, or skipping a night, sorts it. It stops when you stop and it does not mean damage.

Clean teeth first

Whitening plaque is a waste of gel. A cleaning before you start also tells us whether the color is stain, an old filling or a dead nerve, and only one of those responds to peroxide.

Trays and gel are $299 here and the trays are yours to keep. Two top-up nights a year is usually all it takes afterwards.