Teeth generally become more darkly pigmented with age and exposure to such materials as tea and coffee, and it has long been a goal of dentistry to provide a means to safely and effectively reverse this darkening process. Historically there are two approaches to the problem. The first involves removing pigmentation that has adhered onto the surface of the teeth. This is commonly achieved through the use of abrasives, sometimes augmented with solvents. While rapidly effective, these techniques have the disadvantage of only being able to remove extrinsic stains, leaving all internal pigmentation unchanged. Thus the whitening effect is extremely limited.
A more recent innovation involves a method of using oxidizing agents to penetrate into the tooth structure and bleach out the undesired pigmentation. The active agents are usually either weak solutions of hydrogen peroxide or carbamide peroxide, which is more stable than hydrogen peroxide.
While effective on both extrinsic and intrinsic discolorations, one major problem encountered with this second approach is the enormous amount of treatment time needed to gain adequate penetration of the tooth structure by the whitening agent. At present, the method of application of the whitening agent utilizes either custom or stock trays that are shaped to hold the bleaching agent against the teeth to be whitened. These trays are then filled with the peroxide, and worn for long periods of time, sometimes even overnight. After a series of lengthy treatments, the teeth will usually begin to show the desired whitening effect. The length of these treatments can be discouraging and increases the cost. It is therefore desirable to find a method to more rapidly whiten the teeth.