According to the American Dental Association (ADA) and the nine dentists we spoke to, either hydrogen peroxide or carbamide peroxide is what you should look for in whitening products.

Carbamide peroxide 6.5%; otic soln. 5–10 drops in ear canal. Keep drops in ear several minutes. Use twice daily for up to 4 days. May irrigate with warm water.

They act by removing plaque and both internal and external stains on the tooth by release of certain chemicals like carbamide ...