Over time teeth become stained due to a variety of reasons—coffee, tea, red wine, and tobacco are the biggest villains. They contain chromogens—intensely pigmented molecules that can attach to your tooth’s enamel and cause surface stains, also called extrinsic stains. Surface stains can be removed with whitening toothpaste that has mild silica abrasives or cleansers to gently scrub the enamel exterior of the tooth.
Under the hard enamel is a softer, more porous area called dentin that can soak up tougher, deeper, intrinsic stains. Dentin also gets darker as we age. These deeper stains need peroxide bleaching agents to remove them.
Common tooth bleaches are hydrogen peroxide and carbamide peroxide. Carbamide peroxide becomes hydrogen peroxide when applied to the teeth and then behaves the same way. Here’s how it works:
Hydrogen peroxide acts as a strong oxidizing bleaching agent that hits and breaks up those chromogens into smaller, less colored, more diffused molecules. It’s that simple. This is the quickest way to whiten a deep, intrinsic stain. Teeth can be bleached both in a dentist’s office and at home using safe levels of hydrogen or carbamide peroxide.
The bleaching agent used by your dentist’s office is at a higher concentration and used for a shorter time than products for home use but both are safe and effective for whitening teeth. Your dentist will form fit a tray for you to apply the solution. Over-the-counter bleaches come with preformed trays that are not custom fit. Another method is whitening strips which use hydrogen peroxide but without trays.
Some people who use teeth whitening products experience tooth sensitivity that’s caused by the peroxide getting through the dentin to the nerve. In most cases the sensitivity is temporary and you can delay treatment, then try again. However, overuse can damage the tooth enamel or irritate gums so be sure to follow the directions.
Teeth whitening works for most adults at any age but it will not work on caps, veneers, crowns, or white fillings. Tooth darkening may also be caused by dental disease, some antibiotics, or injury to a tooth. In these cases, tooth whiteners will not work well or at all so you should talk to your dentist before you start whitening.