Studies show that a whitening product containing 10% Carbamide Peroxide placed in bleaching trays that are worn overnight, or at least 2-4 hours per day for 2-6 weeks is the safest option.
Carbamide Peroxide is made up of 3.5% Hydrogen Peroxide (Water and Oxygen) and 6.5% Urea (Ammonia and Carbon Dioxide). Urea is produced naturally in the body by the liver, eyes and brain. The liver produces 648mg/ day. In comparison, two bleaching trays containing Carbamide Peroxide dental bleach worn overnight produces 3.5mg of Urea. Further to this, the saliva in your mouth decomposes 29mg in just one minute.
The F.D.A. (Food and Drug Administration) considers Carbamide Peroxide safe for lifetime use.
Urea is shown to have no detrimental effect on teeth; it has less of an effect than cola, orange juice and white wine. Carbamide Peroxide has actually been shown to decrease the acidity levels in the mouth. The more acidic the mouth is, the greater the chance there is for decay to occur.