What occurs during the bleaching procedure depends on the type of procedure. These procedures include:

• In-office bleaching. This may take from 30 to 90 minutes to perform and may require several appointments. However, it can be accomplished in a single one-hour appointment for certain patients. A protective gel or rubber dam is placed over the gums to protect them from the bleaching agent, which is then applied to the teeth. In some cases, light, heat or a laser may be used on the bleaching agent to speed up the bleaching process.
  
  
• At-home, dentist-supervised bleaching. The first application may be done at the dental office. The dentist can demonstrate the proper use of the product and the patient can ask questions. The mouthpiece is filled with the bleaching agent and is then worn in the patient’s mouth. The mouthpiece may be worn for about 30 minutes to a few hours each day, or it may be worn overnight.
  
  At-home treatment may take up to several weeks. More severe stains take longer to bleach than lighter stains. In general, wearing the mouthpiece overnight requires less treatment time. The patient will need to return to the dentist’s office regularly to monitor progress and check for any signs of problems, such as gum irritation.
  
  
• Non-vital whitening. A process to whiten teeth that have undergone root canal treatment. This whitening occurs from the inside out. The material used to fill the tooth’s root canal (called gutta percha) is removed and a whitening agent is put in its place. This agent remains inside the tooth for several days before it is removed and the gutta percha is replaced.