1 teeth whitening treatment. Benefits: Teeth whitening helps to restore a smile tainted by discoloration. In-office teeth whitening produces the fastest results and is the safest form of teeth whitening. How it works: Significant color change in a short period of time is the major benefit of in-office whitening. This protocol involves the carefully controlled use of a relatively high-concentration peroxide gel, applied to the teeth by the dentist or trained technician after the gums have been protected with a paint-on rubber dam. Generally, the peroxide remains on the teeth for several 15 to 20-minute intervals that add up to an hour at most. Those with particularly stubborn staining may be advised to return for one or more additional bleaching sessions.