Scales from the skin of a shark. These sharply pointed placoid scales are also known as dermal teeth or denticles. They give the shark`s skin the feel of sandpaper. The tip of each scale is made of dentine overlayed with dental enamel. The lower part of each scale, which anchors it into the skin, is made of bone. The scales disrupt turbulence over the skin, considerably reducing the drag on the shark as it swims. This design has been investigated by engineers for use on the surfaces of aircraft and boats