Teeth whitening is accomplished by applying peroxide chemicals to the teeth (hydrogen peroxide or carbamide peroxide) within a glycerine-like gel. These agents can be applied directly to the teeth, carried by a piece of tape (Crest White Strips), or contained by a mouth tray. The formula for how much whitening occurs is simple: the concentration (strength) of the peroxide x length of time applied = amount of whitening. A weaker peroxide applied for a very long time will whiten teeth just as much as a stronger product applied for a short amount of time. But beware, the primary side effect of whitening is teeth hypersensitivity, and the stronger the peroxide concentration, the more hypersensitivity occurs. Many current whitening products have desensitizing agents added to lessen that side effect. We recommend at-home whitening with a dental office supplied (vs. over the counter) product in a mouth tray. A tube of whitening product may take 4 to 6 weeks of use until empty and the treatment is completed. This provides a good balance of product strength and length of application time to maximize results and minimize hypersensitivity. This approach is also far less expensive than one appointment, in office whitening treatments offered as a spa-like service.