 Recent studies indicate that substances commonly used to clean the root canal space incompletely sterilize the canal.A properly restored tooth following root canal therapy yields long-term success rates near 97%.In a large-scale study of over 1.6 million patients who had root canal therapy, 97% had retained their teeth 8 years following the procedure, with most untoward events, such as re-treatment, apical surgery or extraction, occurring during the first 3 years after the initial endodontic treatment.