RCT is required when the nerve, connective tissue and blood vessels (called the pulp) inside the tooth become infected through decay or injury. The aim of the treatment is to preserve the tooth by removing all traces of the infected tissue and then sealing it from the tip of the root to the crown of the tooth to prevent further ingress of bacteria from causing infection or an abscess.
If the infection described above is allowed to progress unchecked it could spread to the jawbone (osteomyelitis) or even cause blood poisoning (septicaemia). The alternative to RCT would be to extract the tooth to prevent these consequences.
A local anaesthetic is used and therefore you will feel no pain during the procedure. There may be slight discomfort following the root filling for about 24hrs but many people report no symptoms. Usually any discomfort is controllable using proprietary painkillers such as paracetamol or ibuprofen.
A temporary dressing may be placed after stage 2 in severely infected teeth and the tooth allowed to settle. If this is the case the tooth will be sealed at the next appointment.
RCT is a skilled and time-consuming process. Most planned RCTs are completed in a single visit but if difficult may require further visits. Emergency root fillings would normally require two visits. The procedure can take up to 2 hours in total.
*Source: British Dental Health Foundation