as a healthy pulp would. Treatments include root canal or tooth extraction. In endodontic therapy, removal of the inflamed pulp relieves the pain. The empty root canal system is then obturated with gutta-percha (rubber material that acts as a pressure/pain reliever). Pulp necrosis Pulp necrosis is when the pulp has died/dying. Causes include untreated caries, trauma or bacterial infection. It is often subsequent to chronic pulpitis. Teeth with pulp necrosis undergo a root canal or extraction to prevent further spread of the infection, which may lead to an abscess. Symptoms Necrosis may be symptomatic or asymptomatic. Symptomatic necrosis involves lingering pain response to hot and cold stimuli, spontaneous pain that may cause a patient to awaken during sleep, difficulty eating and senstivity to percussion. Asymptomatic necrosis is non-responsive to thermal stimuli or electric pulp tests, leaving the patient unaware of the pathology. Diagnosis Asymptomatic necrosis is may go unnoticed by the patient and so a diagnosis may not be attempted. Diagnosis may involve X-rays and sensitivity testing with. hot or cold stimuli (using warm gutta-percha or ethyl chloride), or an electric pulp tester. Tooth vitality (blood supply) may be assessed using doppler flowmetry. Sequelae of a necrotic pulp include acute apical periodontitis, dental abscess, or radicular cyst and tooth discolouration. Prognosis and treatment Untreated necrotic pulp may result in further complications, such as infection, fever, swelling, abscesses and bone loss. Two treatment options are available for pulpal necrosis. Pulp response to caries Pulpal response to caries can be divided into two stages – pre- and post-infection. In caries-affected human teeth, odontoblast-like cells appear at the dentine-pulp interface along with specialized pulp immune cells to combat caries. Once they identify specific bacterial components, these cells activate innate and adaptive immunity. In uninfected pulp, leukocytes can sample and respond to the environment, involving macrophages, dendritic cells (DCs), T cells and B cells. This sampling process is part of the normal immune response, as it triggers leukocytes from the circulatory system to adhere to endothelial cells lining blood vessels and then migrates to the site of infection for defence. Macrophages can phagocytose bacteria and activate T cells, triggering the adaptive immune response that occurs in association with DCs. In the pulp, DCs secrete a range of cytokines that influence immune responses, and are key regulators of the infection defence. A comparatively small number of B cells are present in healthy pulp tissue, and