Teeth whitening, is a common procedure in general dentistry.  Oxidizing agents such as hydrogen peroxide or carbamide peroxide are used to lighten the shade of the tooth. According to the American Dentist Association there are different options to whiten one's teeth that include: in-office bleaching, which is applied by a professional dentist; at-home bleaching, which is to be used at home by the patient.  High-concentration bleaching can be accomplished either in the dental office, or at home. Performing the procedure at home is accomplished using high-concentration carbamide peroxide. Whitening is performed by applying a high concentration of oxidizing agent to the teeth with thin plastic trays for a short period of time, which produces quick results. The ADA recommends to have one's teeth checked by a dentist before undergoing any whitening method. The dentist should examine the patient thoroughly: take a health and dental history, observe hard and soft tissues, placement and conditions of restorations, and sometimes x-rays to determine the nature and depth of possible irregularities.