These are clear gels that contain a good concentration of peroxide- that main ingredient that facilitates teeth whitening. These gels are often applied to the surface of the teeth with the use of a small brush. Most of the gels that are available in the market will call for you to apply these gels at least twice a day and this should go on for the next 2 weeks. When using hydrogen peroxide for example, the concentration of the mix that is recommended at the back of the bottle should be adhered strictly if not less than what is recommended just to test it out. 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. Intrinsic stains are caused by the natural process of aging, trauma to the tooth, exposure to drugs containing tetracycline and flourosis. Other factor that stains the teeth is grinding. Grinding often attributed to stress accelerates micro cracking of the tooth enamel that will hold tiny debris to be accumulated. You get to the nearest supermarket and buy your weeks' supply of teeth whitening toothpaste and the desensitizing toothpaste. And what you do after is to religiously brush your teeth as recommended by the manufacturer of the product. The other way is the simplest. You get the services of the professional that offers professional teeth whitening services. Since teeth whitening and bleaching are among the simplest cosmetic procedures and provided you do not have cracks crowns porcelain veneers, special teeth and gum conditions, home kits are advisable provided you start with a low mixture of bleaching agents and water. Peroxides that are sold over the counter have indications and recommendations for the mixture which you could use. These rods while very tightly packed have microscopic gaps in between them. The density of the crystalline rods differs from individual to individual and explains the reason why some tooth enamel are tougher than another person's enamel. Nonetheless, all most all of us are born with bright shiny teeth.