Tooth plaque. Coloured scanning electron micrograph (SEM) of dental plaque (green) seen on the surface of a fractured human tooth. The sub- surface enamel structure (red and blue) occupies the lower right half of the image. Plaque is the main cause of tooth decay. It consists of saliva, bacteria and food debris. The bacteria feed on the sugars in food, producing acid as a waste product. This acid corrodes the enamel coating of each tooth, resulting in tooth decay (dental caries). Magnification: x700 at 6x7cm size. x1200 at 4x5"~LANDSCAPE"