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Teeth whitening

author icon By Dr. George Ghidrai

Teeth whitening or teeth bleaching is the most common procedure in cosmetic dentistry. According to an accepted definition, whitening restores natural tooth color and bleaching whitens beyond the natural color (although the two words are most of the time interchangeable).

While many whitening options are now available, including over the counter products, dentist-supervised treatments remain the recommended procedures for lightening discolored teeth.

teeth whitening before and after teeth whitening before and after teeth whitening before and after

teeth whitening before and after

Causes of tooth discoloration

Normally, deciduous teeth are whiter than the adult teeth. As a person ages, the adult teeth often become darker due to changes in the mineral structure of the tooth.

In addition, teeth can become stained by bacterial pigments, food-goods or various vegetables ; certain antibacterial medications (like tetracycline) can cause teeth stains or a reduction in the brilliance of the enamel while ingesting colored liquids like coffee, tea, and red wine may also discolor teeth.

Tobacco can cause stains, while certain enamel defects (such as enamel hypoplasia or fluorosis) may lead to yellow discolored teeth.

teeth stains

teeth stains

yellow discolored teeth

yellow discolored teeth

Teeth whitening indications and medical examination

It is a general recommendation that a patient should have the teeth checked by a dentist before undergoing any whitening method.

The dentist will examine the patient thoroughly : take a health and dental history (including allergies and sensitivities), observe hard and soft tissues, placement and conditions of restorations, and sometimes x-rays to determine the nature and depth of possible irregularities.

A shade guide is used to measure tooth color. The shades determine the effectiveness of the whitening procedure, which may vary from two to seven shades.

vita ceramic shade guide vita ceramic shade guide vita ceramic shade guide

shade guide

Tabs of similar hue are clustered into letter groups :

  • A : red-yellow
  • B : yellow
  • C : grey
  • D : red-yellow-grey

The numbers design the chroma : the smaller the number the lighter the chroma.

Teeth whitening is less effective when the original tooth color is grayish ; it is most effective with yellow discolored teeth. Bleaching is not recommended if teeth have decay or infected gums.

Whitener does not work where bonding has been used and neither is it effective on tooth-colored fillings, dental crowns or bridges. Dentures can be whitened using denture cleaners.

Generally, the effects of bleaching can last for several months, but may vary depending on the lifestyle of the patient.


Many whitening methods are available including in-office bleaching, which is applied by a professional dentist ; at-home bleaching, which is used at home by the patient ; over-the-counter, which is applied by patients ; and options called non-dental, which are offered at mall kiosks, spas, salons etc.

  1. In-office whitening

    1. Light-accelerated bleaching

      In-office bleaching are applied by a professional at the dental office. More common, a bleaching gel is light-cured on the surface of teeth after the soft-tissues are carefully painted with a protective layer.

      in office teeth whitening procedure step 1

      a bleaching gel is applied on the surface of teeth after the soft-tissues are painted with a protective layer

      in office teeth whitening procedure step 2

      the bleaching gel is light-cured


      • soft tissues are isolated (for protection) with a resin-based, light-curable barrier (with green in the left image)
      • the professional whitening gel is applied on the surface of teeth (with orange in the left image)
      • the whitening gel is exposed to a light source (halogen light or a dental laser) for 6 to 15 minutes

    2. Internal bleaching

      Internal bleaching procedures are performed on devitalized teeth that have undergone endodontic therapy. Usually, these teeth are discolored due to internal staining of the tooth structure by blood and other fluids that leaked in.

      Unlike external bleaching, which brightens teeth from the outside in, internal bleaching brightens teeth from the inside out.

      internal teeth bleaching internal teeth bleaching internal teeth bleaching

      internal bleaching


      • after the root canal therapy, a hole to the pulp chamber is drilled (1,2 image above)
      • a bleaching agent (such as a peroxide gel) is placed into the pulp chamber so it can work directly inside the tooth on the dentin layer (3,4 image above)
      • the whitening agent is sealed within the tooth over a period of some days and replaced as needed

  2. At-home whitening

    Commercial whitening products intended for home use include gels, chewing gums, rinses, toothpastes and others. Bleaching gels are the most efficient and most commonly used.

    1. Bleaching gels

      Whitening is performed by applying the bleaching gel to the teeth with thin plastic trays for a period that depends on the concentration of the gel:

      • High-concentration gels need several short time applications (15-20 minutes two or three times)
      • Low-concentration gels need several hours for a period of 5 to 14 days

      at home teeth whitening procedure step 1

      the whitening gel is placed inside a plastic tray

      at home teeth whitening procedure step 2

      the plastic tray is positioned over the teeth

    2. Other at-home methods

      Other at-home whitening methods include chewing gums, rinses, toothpastes, various over-the-counter products or some non-dental options.

      Apples, celery and carrots support and help whitening teeth, as they act like natural stain removers by increasing saliva production (the mouth's self-cleaning agent) and scrub the teeth clean.


The side effects that occur most often are a temporary increase in tooth sensitivity and mild irritation of the soft tissues of the mouth, particularly the gums. Normally, these conditions are temporary and disappear within 1 to 3 days of stopping the bleaching treatment.

It is important that patients consult with the dentist before using a tooth whitening system as certain conditions may (temporary) preclude a bleaching treatment (for example, sensitive teeth and gums, receding gums and/or defective restorations).

Tooth whitening does not usually change the color of fillings and other restorative materials. It does not affect porcelain, other ceramics, or dental gold.

Prolonged exposure to bleaching agents may damage tooth enamel. Bleaching is not recommended in children under the age of 16 or in pregnant or lactating women.

Last review and update: August 2021

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