This is one of the more interesting innovations in dentistry because we can now create a brighter smile without doing invasive procedures like crowns or veneers. Your teeth function in a fairly difficult environment: severe temperature changes, bacterial attack from the plaque and lots of strongly discolouring food substances which can leave their marks after many years of service. These yellowing food stains are called chromagens and if you drink tea, coffee, red wine and especially smoke, there are ample opportunities for these chomagens to be absorbed by the enamel.
These stains can now be removed by using oxidising gels like carbamide peroxide. This penetrates the enamel and oxidises the stains.
There are two different procedures possible for tooth whitening:
a.) Power bleaching: done during a prolonged session in the surgery with high concentration gels, activated even further by putting a light source very close to it. Due to the intensity of the chemicals and the dehydration of the teeth, the colour will move quicker than with the second method, although it should not be used in isolation. To get a longer lasting result you will still need to do home bleaching afterwards.
b.) Home bleaching uses milder concentration of the same carbamide peroxide and is used in an accurately fitting night guard. Think of what rugby player use to protect their teeth but then in a wafer thin variety. It is custom made to fit comfortably so you will notice little of it when you are wearing it. Before going to bed you will put tiny quantities of the gel into the night guard on the surfaces that will be in contact with the teeth. Put the night guard in and go to sleep. The advantage of night time bleaching is the fact that saliva flows are reduced and the gel does not get diluted as quickly as during day time bleaching.