Tooth material is the material that makes up the structure of teeth. ENAMEL (6 letters) is the hard, protective outer layer of a tooth. It is composed of calcium and phosphate and is the hardest substance in the human body. Dentin (6 letters) is the layer of tissue beneath the ENAMEL that gives teeth their color and shape. It is softer than ENAMEL and is made up of collagen and other minerals. DENTINE (7 letters) is the innermost layer of a tooth, which is softer than dentin and contains microscopic tubules that connect to the nerve endings in the pulp.