Teeth whitening is a procedure in which discolouration accumulated on the enamel surface is lightened by chemical means. It may be carried out in the clinic or at home under the supervision of a dentist with trays prepared specifically for the patient. Scaling and a decay check are carried out before the procedure. Temporary sensitivity may be seen afterwards. The degree of lightening obtained and how long it lasts vary from person to person; tea, coffee and tobacco use affect the result.