Dental enamel is the hardest mineral in the human body. It consists mainly of minerals. However, minerals are acid-soluble. So if the dental enamel is exposed to acids for a long time it dissolves. The first sign of a cavity is the appearance of white spots on the dental enamel. If further minerals are removed from the enamel it breaks down and a hole or cavity forms. But food and drinks are not the only sources of acid in the mouth. The main causes of tooth decay or caries are sugar and food remains, as bacteria which live in the mouth convert sugar and sugar components from the diet into acids. These bacteria settle on the surface of the teeth and form a sticky coating called plaque. So brushing the teeth twice a day is not only important to remove food remains but also to remove this plaque at regular intervals so as to stop the bacteria from growing and producing acid. Floss is necessary to remove the plaque that is in between the teeth where the toothbrush cannot get.