The Chairside Instructor 29 Root Canal (Endodontic) Therapy Decay, Cavities and Restorations Healthy tooth and root A metal rod (post) may be placed in the root canal to help retain the core (filling) material, which supports the restoration (crown). The crown of the tooth is then restored. If bone is lost due to infection at the root tip, this will heal over several months after the root canal is cleaned and sealed. Tooth decay can cause an abscess (infection). The decay is removed and an opening is made through the crown of the tooth into the pulp chamber. The pulp is removed, and the root canals are cleaned, shaped, and disinfected. The root canals and pulp chamber are filled. Steps of Root Canal Therapy