Pulpitis refers to the inflammation of the dental pulp within the tooth. The pulp contains the blood vessels the nerves and connective tissue inside a tooth and provides the tooth's blood and nutrients. Pulpitis is mainly caused by bacteria infection which itself is a secondary development of caries (tooth decay). It manifests itself in the form of a toothache.

There are two forms of pulpitis: acute or chronic. Acute pulpitis is usually found in the teeth of children and adolescents and is generally marked by more noticeable pain to the affected teeth than in chronic pulpitis. Symptoms of acute pulpitis include: a constant throbbing pain in the affected tooth that is often made worse by reclining or lying down; acute sensitivity in the affected tooth that becomes painful when confronted with hold or cold stimuli; a sharp stabbing pain in the affected tooth; changes in the affected tooth's colour; or swelling of the gum or face in the area of the affected tooth. Acute pulpitis itself takes two different forms: purulent acute pulpitis in which the pulp is completely inflamed; and gangrenous acute pulpitis in which the pulp begins to die in a less painful manner that can lead into the formation of an abscess (a pocket of pus that forms at the tip of the tooth root).

Pulpitis can also be classified as reversible or irreversible. Reversible pulpitis is caused by caries encroaching on the pulp and manifests itself as mild inflammation of the pulp. It does not have to be treated as it will heal on its own over time. Irreversible pulpitis is caused the progression of reversible pulpitis and manifests itself as severe inflammation of the pulp. The available treatment for irreversible pulpitis is either endodontic (root canal) treatment or tooth extraction.