The art and science of tooth whitening.

Although tooth whitening is one of the most popular dental procedures, it is also one of the least understood. We are still unclear as to its mechanism of action. There is little data as to the effects of both concentration and dose on outcome. The techniques for measuring color change have been brought into question. The cause(s) of sensitivity and the effects of long-term exposure to hydrogen peroxide are not clear. The issue of rebound in color has not been well examined, and issues related to maintenance of the whitening effect are also poorly understood. The immediate placement of composite resin on bleached teeth has been controversial. According to a study evaluating the shear bond strength of composite restorations placed on bleached and nonbleached teeth, there was no statistically significant difference when the composites were placed at 24 hours, 48 hours, four days, or six days. A different study, which evaluated the effects of take-home bleaching systems on enamel surfaces, suggests that a period of four days must elapse before bonding to a tooth bleached with a peroxide material, while no delay is necessary for a non-peroxide-based bleaching system. Most recently, there has been a push to find ways to accelerate and improve the delivery of the whitening process. These include the application of a number of different light sources believed to accelerate the breakdown of peroxide and thus speed up the whitening process. However, the research in this area has been controversial, with publications having quite different conclusions as to the efficacy of light-activated bleaching. Finally, the issues of adverse events and possible side effects were reviewed. The toxicological side effects of tooth bleaching systems seem to be minimal. However, tooth sensitivity can be quite significant. Although its causes are poorly understood, tooth sensitivity is most often seen as the result of tooth dehydration. So while patient demand for tooth whitening is at an all-time high, and dentists have more options for treatment, it's important that dentists evaluate which of these options is most ideal for their patients, factoring in the patients' cost and time issues, as well as sensitivity to the procedure.