Carbamide Peroxide is the ingredient of choice for professional dental whitening. It is widely used by dentists and is manufactured in strengths ranging from 10% to 22% and sometimes a powerful 35% for difficult stains. The reason Carbamide Peroxide Gel is so widely used is that it maintains it’s shelf-life for up to 3 years. Other peroxides, such as Hydrogen Peroxide, begin losing their efficacy immediately after manufacture and lose their potency after only a few months, rendering them completely ineffective.