Types of bleaching:

  • mechanical decolourisation and
  • chemical degradation of chromogens (dyes)

What substances are used:

  • Hydrogen and urea peroxides

Types of dyes:

  • Large organic dyes
  • Dyes with metal particles

Bleaching mechanism:

Hydrogen peroxide breaks the chemical bonds between dye molecules. As a result, the dye molecules remain lighter.

Dyes with metallic components are very difficult to fade, so in these cases mechanical masking of the paint with restorations (seals, veneers, crowns) is recommended.