Initially the dentist takes two impressions of the dental arches of the patient. Thanks to these impressions the dental technician will be able to produce two transparent masks, that will fit perfectly on the dental arches of the patient. The peculiarity of these masks is the presence, on the outer surface, of tanks that will contain the whitening gel. At this point the dentist will show the patient how to put the gel on the masks and how to wear them. The patient will have to wear these masks for 4 to 8 hours, every day for about two weeks. The length of the daily application and of the treatment depends on the concentration of product used (carbamide peroxide 10% to 16%) and on the severity of the discoloration.