Tooth whitening in Gdansk Poland: lightens the colour of a tooth. Whitening of teeth can be achieved by physical removal of the stain, or a chemical reaction. The chemical degradation of the chromogens within or on the tooth is termed as bleaching. The advantage of using a Tooth whitening tray is that it is more effective than laser. It has an efficiency on 16% and laser only 6-9%. Another advantage is you can use the tooth whitening tray(after impression) several times afterwards(years after). You only need to buy a little gel. And it is much less expensive than laser whitening..