Tooth decay. Coloured Scanning Electron Micrograph (SEM) of a hole (a cavity) in a tooth caused by tooth decay. The cavity is seen as a depression (at centre) encrusted with a brown-flaky substance known as plaque. The tooth surface is white. Plaque is a mixture of food particles and the naturally-occurring bacteria that inhabit the mouth. Bacteria feed on the sugars in the food, producing acid as a waste product. This acid corrodes the enamel covering each tooth, eventually causing a hole to develop to the tooth's sensitive interior. Cavities are prevented by good dental hygiene. Tooth decay is treated using fillings Magnification: x150 at 6x6cm size.