The most common way it is currently done is with the aid of a whitening gel, which is then placed and fits over the tooth or teeth for a period of time by a mould or mouth guard which fits into the mouth. The whitening gel contains two substances called hydrogen/carbamide peroxide which breaks down when oxygen enters the enamel of the tooth or teeth. The result hopefully of this process is that the tooth enamel comes lighter and whiter than before and can lighten the teeth white by one or two shades if treatment is effective. Other whitening treatments include bonding, dental crowns and veneers and bridging.
The treatment period of tooth whitening varies depending on how much the patient want his or her teeth/tooth to be whiten by. The degree of whiteness will also vary from patient to patient depending on the structure of the tooth or teeth; as well as the number of times the treatment has been done previously on the same teeth or tooth.