Hydrogen peroxide (H2O2) is the active whitening molecule. It reaches stains inside the tooth and breaks them down.
Carbamide peroxide is a delivery format: it breaks down into about one-third hydrogen peroxide plus urea over 20-30 minutes. That slower release makes it a natural fit for trays and LED kits, where the gel needs to stay active for a longer session.
As a rule of thumb, 10% carbamide peroxide is roughly equivalent to 3.5% hydrogen peroxide.
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