Dog teeth are made up of four tissue types: pulp, dentin, enamel, and cementum. First, the pulp is the innermost portion of the tooth. It consists of connective tissue, blood vessels, and nerves that nourish the tooth itself. The pulp is made up of two parts, namely the pulp chamber and the root canal. Blood vessels and nerves enter the tooth through the root and the pulp chamber. Next, dentin surrounds the pulp. This is a hard, yellow substance that makes up most of the tooth. Enamel covers this dentin to form the outermost layer of the tooth's crown. The enamel allows the teeth to withstand the pressure of chewing and protects them from bacteria. Lastly, a layer of cementum covers the outside of the tooth's root beneath the gum line. This cementum holds the tooth in place.