Root canal treatment is a dental procedure that relieves pain caused by an infected tooth or an abscess. During the endodontic process, the inflamed pulp is removed. The inner surfaces of the teeth are then cleaned and disinfected and sealed with a filling. Root canal treatment is necessary when oral bacteria invade the pulp of the tooth. This usually happens when tooth decay is left untreated for a long time. It can also happen if your tooth is cracked or damaged due to trauma.