Root canal treatment is necessary if the pulp (pulp - a component of the tooth, a small tangle of blood vessels, nerves and lymphatic vessels inside the tooth) that it contains is affected by inflammation or infection. Microorganisms that cause inflammation or infection result from neglected tooth decay, cracking of the tooth, or decay of the tooth itself. Sometimes the cracks appear inconspicuous, but their size is sufficient to allow microorganisms to enter the pulp. Untreated pulp can lead to toothache and lead to abscess.