Molar tooth surface. Coloured scanning electron micrograph (SEM) of the upper surface of a molar tooth. The molars are broad ridged teeth found at the back of the jaws of mammals. The ridges allow them to be used to chew and grind food to help break down tough parts. This tooth has four main cusps (points). The tooth is partly covered in a mixture of bacteria, saliva and carbohydrates known as dental plaque (beige). Plaque is a cause of tooth decay (caries) and leads to the formation of a hard deposit called tartar (calculus). A cavity has begun to form in the tooth (lower right). Magnification: x8 when printed at 10cm wide.