Bleaching refers to the process of lightening the stains or colours inside enamel or dentine by using chemical agents.


To whiten teeth and regain the normal colour of the teeth.


  • Vital tooth.

    Photograph of front teeth with vital pulp in light brown colour before bleaching.Before bleaching
    Photograph of front teeth with vital pulp in milky white colour after bleaching.After bleaching
  • Non-vital tooth treated by root canal therapy.

    Photograph of teeth after pulp treatment showing discolouration before bleaching.Before bleaching
    Photograph of teeth after pulp treatment showing the restoration to normal colour after bleaching.After bleaching


Bleaching agents are used to oxidize the colour pigments in the discoloured teeth in order to whiten these teeth.


Bleaching agents contain chemicals such as Carbamide Peroxide, Hydrogen Peroxide, etc.

Procedures for bleaching

Bleaching vital tooth

Dentist will use different bleaching methods according to various oral conditions:

  • Take impressions of teeth to make a set of models. Construct a custom whitening tray from the dental laboratory. The patient should fill the tray with the bleaching solution and wear it over the teeth overnight. In addition, the patient should wear the tray every night according to the dentist's instructions and return to the dentist for follow-up appointments according to schedule.

    Photograph showing a custom made whitening tray ready to be worn by a patient for bleaching the teeth.
  • In the dental clinic, the dentist can use a strong light to catalyse the more concentrated bleaching agents to whiten teeth in a shorter time.

    Photograph showing front teeth before bleaching. They look light brown.Before bleaching
    Photograph showing front teeth after bleaching. They look milky while.After bleaching

Treatment duration: 3 to 6 months.

Bleaching of non-vital tooth treated by root canal therapy

  • Endodontic treatment (Root canal therapy) of the tooth must be completed first.
  • Place a cotton pellet soaked with whitening agent inside the pulp chamber and then fill up tooth opening.
  • Visit dentist periodically to check the progress of bleaching, and change the cotton pellet with whitening agent accordingly. When whitening effect is achieved, remove the cotton pellet, clean the pulp chamber and filled up the tooth cavity.

    Photograph of a longitudinal section of a pulp-treated tooth after bleaching.

Duration: The treatment ends when the stains or colours are lightened, which takes approximately 1 - 3 months.

Points to note before using bleaching agents

  • Not all stains or discoloration could be lightened. Some teeth may not achieve maximum whitening effect even after the treatment.
  • Be careful when using bleaching agents and consult your dentist for proper usage of bleaching agents. Improper use of bleaching agents will hurt the gums and the tooth supporting tissues, leading to increase sensitivity of teeth.
  • Harmful to health if bleaching agent is ingested accidentally.

Points to note after bleaching

  • Visit your dentist for check-up as advised.
  • Bleaching can only keep the teeth white for a period of time. Repeated bleaching treatment is needed to keep the teeth white.