The toothbrush is an instrument consisting of a small brush on a handle used to clean teeth through tooth brushing. Toothpaste, often containing fluoride, is commonly added to a toothbrush. Toothbrushes are offered with varying textures of bristles, and come in many different sizes and forms. Most dentists recommend using a toothbrush labelled "soft", since firmer bristled toothbrushes can damage tooth enamel and irritate gums as indicated by the American Dental Association. Toothbrushes are often made from synthetic fibers, although natural toothbrushes are also known in many parts of the world.