Tooth whitening involves putting a chemical (Hydrogen Peroxide) onto the teeth which has the effect of making them appear whiter. Research shows that hydrogen peroxide at 3.6 per cent gives the best combination of whitening with the least amount of sensitivity (teeth feeling like ice is being applied to them). An EU Directive regulating the use of hydrogen peroxide in tooth whitening came into effect on 31 October 2012. The Directive states that only dentists can carry out tooth whitening using over 0.1 per cent hydrogen peroxide.The new limit for the concentration of hydrogen peroxide that can be applied to the teeth (and only by dentists) is 6 per cent hydrogen peroxide. If teeth are treated with hydrogen peroxide of a strength higher than 6 per cent, it can result in gum burn.
The use of lights (sometimes called lasers) has little effect and only serves to dehydrate teeth so that the whitening effect is temporary. Bleaching trays worn at night for 2 weeks using 10 per cent carbamide peroxide (this releases 3.6 per cent hydrogen peroxide) is the gold standard treatment and is backed by many years of research. It is not recommended that tooth whitening can not be carried out on under 18s or in pregnancy, or in heavy smokers or heavy drinkers.