What are the reasons why tooth whitening gel expires?

There are three reasons that whitening gel, as well as many other products expire. 1-The active ingredients are unstable and slowly change so as to be spoiled or lose their potency so as to be unusable. This is the reason for the whitening gel, which usually contains peroxides which gradually lose their strength. read more

The trays themselves don’t do any of the bleaching work--it’s the whitening gel, usually around a 22% carbamide peroxide mixture, that seeps into your porous enamel and interacts with the discolored molecules in your teeth. The gel’s oxygen molecules break down the discolored bonds and spread throughout the inside of the tooth (Haywood, 2004). read more