There are Two Major Methods of Bleaching:
The first occupies applying a high concentration of oxidizing agent for a short period of time, which is also called office bleach. This provides fast results but risks chemical burns to the soft tissues. For that reason, most in-office bleaching procedures use a light-cured protective layer that is thoroughfully painted on the gums and papilla (the tips of the gums between the teeth). The bleaching agent is either carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide or hydrogen peroxide itself. The bleaching gel normally contains up to 35% hydrogen peroxide equivalent.
The other method includes using a thin mouthguard or narrow piece to hold a low concentration of oxidizing agent near the teeth for as long as several hours a day for a period of 5 to 14 days. It is known as take-home or over-the-counter bleaching. This method works slower but has smaller quantity of hazards to the soft tissues. The bleaching agent is usually less than 10% hydrogen peroxide equivalent.
A classic course of bleaching can create remarkable improvements in the cosmetic appearance of most stained teeth; though, some stains do not react to bleaching. Tetracycline staining may need extended bleaching, as it takes longer for the bleach to attain the dentine layer. White-spot decalcifications may also be highlighted and become more visible.
In recent times, there have been made some actions to speed up the bleaching process by the use of light. Studies have shown changeable results as to the effectiveness of light-activated bleaching.
Side Effects of Tooth Bleaching
Chemical burns (if a high-concentration oxidizing agent contacts unprotected tissues, which may bleach or discolor mucous membranes), sensitive teeth, and overbleaching (known in the profession as "fridge-door teeth"). Rebound, or teeth losing the bleached effect and darkening, is also an issue, with some studies showing the recover effect over 30 days. The latest study by Kugel has shown that as much as 4 shades of lightness can be lost over 30 days with light-activated/office bleaching.