Hydrogen peroxide has been used for many years to lighten the color of teeth.  Originally, it was applied by dentists in their offices.  Patients may also apply bleaching gels to their teeth at home.  Although tooth bleaching compounds can be purchased by patients in pharmacies or grocery stores, more effective bleaching techniques may be obtained only from dentists.  It is preferable for dentists or dental staff to supervise this type of bleach.  If bleaching is not supervised, crowns and fillings present in your mouth may not match natural tooth structure after bleaching.  Bleaching teeth with peroxide in custom-fitted trays outside the dental office is the most popular and effective method to achieve this lightening of tooth color.