Inside the tooth, under the white enamel and a hard layer called the dentin, is a soft tissue called the pulp. The pulp contains blood vessels, nerves and connective tissue, and helps to grow the root of your tooth during development. In a fully developed tooth, the tooth can survive without the pulp because the tooth continues to be nourished by the tissues surrounding it.
In short, RCT removes infeced pulp tissue and bacteria inside a tooth's pulp canals. It is performed by a general dentist or an endodontist.