This is the reason why those wanting immediate effects will go for the supervised services of the dentist. Design differences for the mouthpiece trays. 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 excessive use and abuse of the teeth whitening paste may damage the person's enamel. So here's the thing, use the product in moderation, or as recommended by the manufacturer. And to get into the safer track, when shopping for this kind of toothpaste you may want to get the paste that carries the seal of approval of the American Dental Association. Home Whitening Kits Or In-Office Teeth Whitening Typically, teeth whitening procedures start with a dentist. After an In-office examination, the dentist would either do the procedure in his clinic then recommend a home kit for the patients to conduct the treatments or follow up procedures at home. There is however cases when home kits are better used. What it contains are silica for example and some aluminum and calcium that will be enough to remove stains but not really to counter the natural discoloration of the teeth as it ages nor does it contain substances that react with the mineral structure to whiten a dark colored teeth. Second, most tooth bleaching agents such as gurgles and gels contain peroxide. Many stains when allowed for a long period of time could get into the dentin forming stains that could show through the enamel. Other factors which could easily get through the enamel to the dentin are cracks in the teeth suffered through a trauma to the tooth, grinding, aging and other accidents. Blood leeching inside the tooth will also tend to stay there and form a stain. Previously, intrinsic stains are believed to be resistant to treatments although today most of it could be removed with close supervision from qualified professionals. Intrinsic stains are caused by the natural process of aging, trauma to the tooth, exposure to drugs containing tetracycline and flourosis.