3. How is hydrogen peroxide used to whiten teeth?
Tooth whiteners can be applied to teeth using custom made mouthguards
Teeth contain organic molecules in their enamel and the dentin. These molecules reflect light and are responsible for their coloration. The more complex these molecules, the more light they reflect and the more teeth appear stained or discoloured.
Tooth colour can be improved by a number of methods and approaches including whitening toothpastes, professional cleaning by scaling and polishing to remove stain and tartar, internal bleaching of non-vital teeth, external bleaching of vital teeth, microabrasion of enamel with abrasives and acid, and placement of tooth-coloured restorations.
Hydrogen peroxide has a whitening effect because it can pass easily into the tooth and break down complex molecules. Less complex molecules that reflect less light lead to a reduction or elimination of the discoloration of both the enamel and the dentin.
Depending on the concentration of peroxide they contain, tooth whiteners and oral hygene products are either freely sold over the counter for home use, dispensed by dentists for home use, or exclusively applied by dentists in their offices. In the European Union, the free sale of oral hygiene products to consumers is only authorised if they contain no more than 0.1% hydrogen peroxide whereas in the USA, whitening products with considerably higher concentrations are sold. In-office bleaching generally uses relatively high levels of whitening agents, for example 25–35% hydrogen peroxide containing products, for rapid treatments.
Several different techniques are used for bleaching teeth at home. The whitening product may be placed in a mouthguard (or tray) that fits over the teeth, applied through adhesive hydrogen peroxide-containing strips that stick to the surface of the teeth, or “painted” on the teeth in the form of a gel.
The length of treatment depends on the level of discoloration and on the whitening product used. It ranges from short interventions in the dental office to applications at home lasting minutes/hours per day and repeated over a number of days. Single dark teeth can also be bleached successfully. Heavy tobacco stains may need as much as three months of treatment. Whitened teeth generally do not darken after treatment or darken only slightly, and when they do, retreating the teeth can easily be done. More...