Our mouths are breeding grounds for hundreds of types of bacteria. Plaque that forms on our teeth and in our mouths contain this bacteria which also live on our gums, tongue, and other soft tissues. When we eat food, the bacteria that is in our mouth eat the food too – specifically, sugar – and produce acid. This acid begins to break down the tooth surface, and will eventually cause a hole in the tooth, referred to as dental caries, or dental decay.