The White Board

Carbamide Peroxide & Hydrogen Peroxide...
What's the Difference?

By Jeff MacDonald
Laboratory Manager/Lead Chemist
Discus Dental, LLC

The two most common peroxides used in teeth whiteners on the market today are hydrogen peroxide and carbamide peroxide. While they are very closely related, they are different enough that it is worth spending time to discuss the similarities and the differences.

Hydrogen peroxide is just that, the chemical with the formula of H2O2. It is usually created as a water solution (H2O2 dissolved in water). During use, it breaks down into one or more radicals that are the actual chemical "bits" that chemically whiten the teeth. It is usually the "hydroxyl radical" that does the work, but there can be others.

Carbamide peroxide is hydrogen peroxide dissolved in urea crystals. For "palatability" issues, the name carbamide peroxide is used instead of the more proper name, urea peroxide. The fact that it is hydrogen peroxide, just dissolved in something, tells us 2 things:

  1. It is less powerful, weight by weight, than "pure" hydrogen peroxide and because the chemistry is predictable, you can "convert" the concentration of carbamide peroxide into "equivalents" of hydrogen peroxide, and vice versa. It turns out (per the USP) that 1% hydrogen peroxide is equivalent to 2.765% carbamide peroxide:

    1% H2O2 = 2.765% carbamide peroxide

    or

    % carbamide peroxide = % H2O2 x 2.765

    and the reverse:

    1% carbamide peroxide = 0.361% H2O2

    or

    % H2O2 = % carbamide peroxide /2.765

  2. Because carbamide still has H2O2 as the active ingredient (but it's dissolved) it has to undergo one more step before it can whiten, and it will act more slowly.

Activated hydrogen peroxide is unstable and is active for usually only 30-60 minutes. By adding urea, it is more stable and releases about 50% of its active ingredient in the first two hours. The rest is released over the next 4 to 6 hours.

In general, hydrogen peroxide products are used for short daytime use and carbamide peroxide is used for longer overnight periods.


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