Root The root is the part of the tooth that extends into the bone and holds the tooth in place. It makes up approximately two-thirds of the tooth. Enamel The enamel is the outermost layer of a tooth. As the hardest tissue in your body, it helps to protect teeth from bacteria. It also provides strength so your teeth can withstand pressure from chewing. Dentin Dentin is a layer of mineralized tissue just below the enamel. It extends from the crown down through the neck and root. It protects teeth from heat and cold.