Patient-friendly definition from the DentistsDirectory.org dental glossary.
The dental pulp is the soft connective tissue that occupies the hollow interior of the tooth — the pulp chamber in the crown and the root canals extending down each root. Unlike the hard enamel and dentin that form the exterior shell of the tooth, the pulp is a living tissue containing blood vessels that supply nutrients, sensory nerve fibres that detect temperature, pressure, and pain, and immune cells that respond to bacterial invasion.
The dental pulp's primary functions are sensory and nutritive. The nerve fibres within the pulp are responsible for the sensations associated with teeth — both the helpful sensitivity that alerts you when a tooth is damaged or attacked by bacteria, and the painful sensitivity of exposed dentin and tooth infections. During tooth development in childhood, the pulp also plays a role in dentin formation; once a tooth is fully developed, the pulp's role shifts to maintenance and sensory function. A tooth can function normally without its pulp after root canal treatment — it loses sensation and some internal nutritive support, but the surrounding tissues continue to nourish its exterior surfaces.
The pulp can become irreversibly damaged through deep decay reaching the pulp chamber, a crack or fracture exposing the pulp to bacteria, trauma, or repeated dental procedures on the same tooth. Pulpitis (pulp inflammation) progresses from reversible (where the pulp can recover after the stimulus is removed) to irreversible (where the pulp is dying and cannot recover). Irreversible pulpitis typically causes spontaneous, lingering pain and requires root canal treatment — complete removal of the pulp tissue, cleaning and shaping of the canals, and filling them with an inert material to prevent reinfection.