According to the FDA, whitening restores natural tooth color and bleaching whitens beyond the natural color. There are many methods to whiten teeth, such as brushing, bleaching strips, bleaching pen, bleaching gel, laser bleaching, and natural bleaching. Traditionally, at-home whiteners use overnight trays containing a carbamide peroxide gel which reacts with water to form hydrogen peroxide. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15 percent solution of carbamide peroxide is the rough equivalent of a five percent solution of hydrogen peroxide. Over the counter kits whiten with small strips that go over the front teeth. The peroxide oxidizing agent penetrates the porosities in the rod-like crystal structure of enamel and bleaches stain deposits in the dentin. Power bleaching uses light energy to accelerate the process of bleaching in a dental office. The effects of bleaching can last for several months, but may vary depending on the lifestyle of the patient. Factors that decrease whitening include ingestion of ligth colored liquids like coffee, tea and red wine.
According to the American Dental Association, different whitening include: 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. Commercial whitening products intended for home use include gels, chewing gums, rinses, toothpastes, among others.
The ADA recommends to have one’s teeth checked by a dentist before undergoing any whitening method. The dentist should 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.
There are two main methods of gel bleaching—one performed with high-concentration gel, and another with low-concentration agents. High-concentration bleaching can be accomplished either in the dental office or at home. Home bleaching uses high-concentration carbamide peroxide, which is readily available online or in dental stores. This is much more cost-effective than the in-office procedure. Whitening is performed by applying a high concentration of oxidizing agent to the teeth with thin plastic trays for a short period of time, which produces quick results. The application trays ideally should be well-fitted to retain the bleaching gel, ensuring even and full tooth exposure to the gel. Trays will typically stay on the teeth for about 15–20 minutes. Trays are then removed and the procedure is repeated up to two more times. Most in-office bleaching procedures use a light-cured protective layer that is carefully painted on the gums and papilla (the tips of the gums between the teeth) to reduce the risk of chemical burns to the soft tissues. The bleaching agent is either carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide, or hydrogen peroxide itself. The bleaching gel typically contains between 10% and 44% carbamide peroxide, which is roughly equivalent to a 3% to 16% hydrogen peroxide concentration.
Bleaching is not recommended if teeth have decay or infected gums. It is also least effective when the original tooth color is grayish and may require custom bleaching trays. Bleaching is most effective with yellow discolored teeth.