Under the dentin is the pulp, the core of the tooth composed of soft tissues, blood vessels, and the tooth's nerve. These nerves and blood vessels supply the tooth with nutrients during its formation. When the nerve of a tooth dies from external decay, or decay caused by an abscess, the nerve and pulp have to be removed. Although the nerve and blood vessels brought the tooth vital nutrients during its development, once it's fully formed it no longer needs them for nutrients.