Tooth enamel is the most highly mineralized and hardest substance of the body. Enamel is one of the three major parts of the human tooth, the others being dentin and cementum. It is the normally visible dental tissue of a tooth, and must be supported by underlying dentin. Minerals compose 96% of enamel, with water and organic material composing the rest. Since enamel is semi-translucent, the color of dentin and any restorative dental material underneath the enamel highly affects the outer appearance of the tooth. The color of enamel is a light yellow to grayish white. It varies in thickness over the surface of the tooth. Often, enamel is thickest at the cusp, up to 2.5 mm, and the thickness tapers down to a miniscule amount at its border, which is seen clinically as the cementoenamel junction.

Read the rest of this article: http://en.wikipedia.org/wiki/Tooth_enamel

_______________________________ Today's selected anniversaries:

642: Penda of Mercia defeated and killed Oswald of Northumbria in the Battle of Maserfield, becoming the most powerful of the Anglo-Saxon rulers of the time. (http://en.wikipedia.org/wiki/Penda_of_Mercia)

1100: Henry I was crowned King of England in Westminster Abbey. (http://en.wikipedia.org/wiki/Henry_I_of_England)

1858: Cyrus West Field and colleagues completed the first transatlantic telegraph cable. (http://en.wikipedia.org/wiki/transatlantic_telegraph_cable)

1861: The U.S. government issued its first income tax: 3% of all incomes over 800 dollars (later rescinded in 1872). (http://en.wikipedia.org/wiki/income_tax)

1995: Operation Storm: Croatian forces recovered the town of Knin from the Republic of Serbian Krajina. (http://en.wikipedia.org/wiki/Knin)

_____________________ Wikiquote of the day:

"Live as if you were to die tomorrow. Learn as if you were to live forever." -- Mohandas Gandhi (http://en.wikiquote.org/wiki/Mohandas_Gandhi)