The enamel is the outermost layer of your teeth. Like a hard shell, its primary purpose is to protect the rest of the tooth. The enamel is mostly made of calcium and phosphate, like your bones, but is stronger because of the specific proteins and crystallites that form it. The enamel is also partly responsible for your teeth`s white appearance, and when itdecays, your teeth may start to appear yellow. Decaying enamel could also be to blame for any pain you feel.