Prior to the 1990's essentially the only teeth whitening option that was available to people was "in-office" teeth bleaching treatments performed by the person's dentist. The term "in-office" used here simply means that the actual bleaching process was performed by the dentist while the patient was in their dental chair.
When an in-office bleaching treatment is performed a potent peroxide bleaching agent is applied to the dental patient's teeth. This whitener is then left on for some minutes before being washed off. The effects of in-office bleaching are immediate. It can, however, require several appointments before the desired level of whitening has been achieved.
At-home tray-based teeth bleaching, the process we discuss on the pages of this topic, is a more recent phenomenon. It became popular in the 1990's and is now the most common dentist dispensed method by which teeth are whitened (although there still can be a need for in-office bleaching with some patients). Another name for the tray-based method of teeth bleaching is "nightguard bleaching."
