The mouthpiece trays that are available for supervised whitening sessions are considered as more reliable as compared to the ones that are available over the counter. The basis for this is simple. At least with the dentist-supervised procedures, the dentist can visit the person's home and can customize the site of the mouthpiece tray. The shade of your teeth will also be measured thru the Vitapan shade guide to arrive at a correct shade that your teeth should have. The teeth are not expected to shade lighter than its natural cast. Following that, a retractor will be placed inside the mouth to expose the teeth in the zone visible when you smile. Because of this, the market is being flooded with different brands every time and because it is one of those procedures that are fast and effective without the pain (mostly), it is so very easy to ride the bandwagon; yet, side effects could happen even adversely if unbeknown to the customer, the products are not used as indicated. The polishing action is important as this will remove the plaque and dirt found at the surface of the teeth. The mouth will then be isolated with the use of the gauze. This is a necessary step so that the teeth will be dry for the rest of the procedure. There will be times when the retractors will be used as well, and this is important so that your lips and tongue will not get in contact with the whitening agents incorporated in the solution. While studies have shown (Kugel et al) that the effect of peroxides at decreasing the tooth enamel is very insignificant, it nonetheless tends to make the teeth more sensitive for some time and when the proportion of the mix is on the strong side, the mix could result to painful gums and cause irritation to the surrounding tissues inside the mouth. Consider the list below, and be guided accordingly. These procedures are not best for those below 16 years of age. The procedures in teeth whitening may compromise the pulp chamber and the nerve of the tooth. And at that stage, the pulp is still enlarged and when done for people of this age then this may only irritate that area.