Bleaching teeth

Bleaching teeth

The term "bleaching" describes the removal of extrinsic (external) or intrinsic (stemming from within) discolorations, due either to natural changes or illnesses, or whitening of the shade of one or all natural teeth for cosmetic/aesthetic reasons. This involves the use of chemical bleaches, mainly peroxides, which release oxygen radicals to act as strong oxidants and oxidise the colorant molecules to reduce their visibility.

Almost all bleaches are for use by dental professionals only and just a few ("whitening strips" or "bleaching toothpastes") are available over-the-counter. As bleaching is hardly considered medically indicated, patients must bear the costs themselves. Professional scaling and polishing is usually carried out in advance to remove discoloration deposited on the surface.

Prior to bleaching, the tooth shade is usually determined with a shade guide, documented and the desired degree of whitening defined. For more natural aesthetics, the brightness level should be orientated on the iris of the eye and not deviate noticeably from this. Excessive bleaching is referred to as "over bleaching". The bleach effect may fade after weeks, months or years – bleaching may be repeated. To date there are virtually no known undesirable side-effects to bleaching. Due to the increased proneness to discoloration resulting from demineralisation, no discolouring foodstuffs should be consumed during and immediately following bleaching (prior to remineralisation). Temporary hypersensitivity and intensification of existing "white spots" (hypomineralised regions, decalcified zones) may also occur.

Tooth-coloured restorations (fillings, crowns) do not become whiter by bleaching and must be shade-matched in advance of or following placement (remade) using the special bleach shades provided (such as for some composite filling materials). Fluoridation or remineralisation is usually carried out following bleaching.

External bleaching (vital teeth)

Bleaching is carried out with bleaching gels which usually contain between 10% and 40% carbamide peroxide. It decomposes in an aqueous environment to create one-third hydrogen peroxide, in addition ammonia forms and neutralises the pH value. For so-called "home bleaching" the patient is provided with less concentrated bleach. Customised bleaching trays, vacuum-formed onto the model after blocking out the areas for bleaching (reservoir for bleach), are usually more suitable than prefabricated medication carriers. They are used daily for applying bleaching gel to the required tooth surfaces, e.g. for 1 hour. The tooth shade changes slowly over a period of days and weeks.

"In-office bleaching" is carried out in the dental practice using highly concentrated bleach during one or several appointments lasting up to one hour – the gingiva is coated with protective gel. If the patient remains sitting in the dental chair throughout the entire appointment, this is referred to as "chairside bleaching". "Power bleaching" is claimed to provide for particularly fast and intense whitening using additional activation with energy-rich light.

Internal bleaching (devitalised teeth)

The tooth is opened and the coronal aspect of the root canal filling reduced and sealed with, e.g. glass ionomer cement. The remaining chamber is usually filled with a mixture of low concentration hydrogen peroxide (3%, high concentrations may lead to root resorption) and (sodium)perborate (releases oxygen slowly) before being sealed with an impervious temporary filling. The patient can leave the practice in this state and the bleach remains in place for several days ("walking-bleach method"). Internal bleaching sometimes has to be repeated several times in order to be adequately effective.