Editing Tooth enamel (section)

=== Tooth whitening ===

The discoloration of teeth over time can result from exposure to substances such as [[tobacco]], [[coffee]], and [[tea]].<ref>American Dental Hygienists' Association</ref> The staining occurs in the interprismatic region internally on the enamel, which causes the tooth to appear darker or more yellow overall. In a perfect state, enamel is colorless, but it does reflect underlying tooth structure with its stains since light reflection properties of the tooth are low.

Tooth whitening or [[tooth bleaching]] procedures attempt to lighten a tooth's color in either of two ways: by chemical or mechanical action. Working chemically, a bleaching agent is used to carry out an [[oxidation reaction]] in the enamel and dentin.<ref>Summitt ''et al.'', p. 402</ref> The agents most commonly used to intrinsically change the color of teeth are [[hydrogen peroxide]] and [[carbamide peroxide]]. Oxygen radicals from the peroxide in the whitening agents contact the stains in the interprismatic spaces within the enamel layer. When this occurs, stains will be bleached and the teeth now appear lighter in color. Teeth not only appear whiter but also reflect light in increased amounts, which makes the teeth appear brighter as well. Studies show that whitening does not produce any ultrastructural or microhardness changes in the dental tissues.<ref name=":0" />

Studies show that patients who have whitened their teeth take better care of them.<ref>Fehrenbach, Popowics, p. 175</ref> However, a tooth whitening product with an overall low pH can put enamel at risk for decay or destruction by demineralization. Consequently, care should be taken and risk evaluated when choosing a product which is very acidic.<ref>Summitt ''et al.'', p. 404</ref> Tooth whiteners in toothpastes work through a mechanical action. They have mild abrasives which aid in the removal of stains on enamel. Although this can be an effective method, it does not alter the intrinsic color of teeth. Microabrasion techniques employ both methods. An acid is used first to weaken the outer 22–27 micrometers of enamel in order to weaken it enough for the subsequent abrasive force.<ref>Summitt ''et al.'', p. 420</ref> This allows for removal of superficial stains in the enamel. If the discoloration is deeper or in the dentin, this method of tooth whitening will not be successful.