According to the FDA, the term “bleaching” is permitted to be used only when the teeth can be whitened beyond their natural color. This applies strictly to products that contain bleach — typically hydrogen peroxide or carbamide peroxide.
The term “whitening” on the other hand, refers to restoring a tooth’s surface color by removing dirt and debris. So technically speaking, any product that is used to clean the teeth (like a toothpaste) is considered a whitener. Of course, the term whitening sounds better than bleaching, so it is more frequently used — even when describing products that contain bleach.
The bleach preference for in-office whitening, where time is limited, is powerful and fast-acting hydrogen peroxide. When used in bleaching teeth, hydrogen peroxide concentrations range from approximately nine percent to 40 percent.
By contrast, the bleach of preference for at-home teeth whitening is slower acting carbamide peroxide, which breaks down into hydrogen peroxide. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15 percent solution of carbamide peroxide is the rough equivalent of a five percent solution of hydrogen peroxide.
Pacific dental group remind you that whitening toothpastes may remove minor stains. They do not actually change the overall color of your teeth. If your tooth has darkened after a root canal, bleaching the enamel won’t help. Your dentist can apply a bleaching material to the inside of the tooth, or you may consider a crown or veneer. However, bleaching will not lighten some stains, such as tetracycline stains. In this case, your dentist may recommend covering the discolored areas. This also may be useful when the tooth is chipped or badly damaged.
Source from Colgate.