Teeth Whitening (Oral Care)

Whitening splits into two mechanisms that share one word on the box. Polishing lifts stain that has settled on the surface from coffee, tea, red wine and tobacco. Bleaching changes the color of the tooth itself, and only peroxide does that.

Hydrogen peroxide breaks into fragments small enough to pass through enamel into the dentin beneath and split the colored molecules trapped there. Carbamide peroxide is a slower carrier that releases roughly a third of its weight as hydrogen peroxide, so 10 percent carbamide behaves like about 3.5 percent hydrogen. Contact time counts as much as concentration. That is why a tray worn for hours at low strength can match a short session at a high one. Lamps and lights add heat and theater, and the evidence that they add whitening is thin.

Strips carry gel on a flexible film and hold it against the front teeth for 30 minutes a day over one to two weeks. Custom trays made from an impression by a dentist hold gel against every surface and stop at the gum edge, which is why they whiten evenly. Boil and bite trays leak. Pens paint on gel that saliva removes within minutes. Whitening toothpaste and whitening rinses belong in the polishing group, since neither one holds peroxide against a tooth long enough to matter.

Restorations do not bleach. Crowns, veneers and tooth colored fillings keep their original shade. A front filling matched to your teeth today will stand out once the teeth around it lighten. That is the most common regret after a first course. Gray banding from tetracycline and white mottling from fluorosis respond poorly or unevenly. Rules differ by country: the European Union caps consumer products at 0.1 percent hydrogen peroxide and routes anything from 0.1 to 6 percent through a dentist, while the United States sets no equivalent limit over the counter, so check your own market before comparing numbers on a box.

Sensitivity is the usual price, sharp and triggered by cold, and it normally fades within a few days of stopping. Sore gums mean gel is sitting on tissue, which a trimmed tray or less gel fixes. Have a dentist look first if you have decay, a cracked filling or gum disease, because peroxide reaching a nerve through a hole is painful and achieves nothing. Refrigerate gel if the packet says so, respect the printed date since peroxide weakens on the shelf, and keep deeply staining drinks away for a day or two after each session while the surface is more porous.