WHAT CAUSES A TOOTH TO NEED A ROOT CANAL TREATMENT? The pulp is made up of soft tissue that includes nerves and blood vessels. The pulp will begin to die if it’s infected by bacteria. Bacteria can then multiply and spread, leading to infection that requires either root canal (to save the tooth) or extraction (to remove the tooth leaving). The bacteria and the substrates ultimately pass out through the end of the root canal through the apex which may lead to pain and tenderness to bite on the offending tooth.