Failing Root Canal Treatment
Sometimes teeth which have had a root canal treatment become re-infected, and require retreatment. The most common cause of failing root canal is a broken or leaking restoration, recurrent caries, or crowns which are poorly adapted to the tooth. Less than 10% of endodontically treated teeth are lost to failure of the root canal treatment itself. Among endodontically treated teeth which require removal, most (approximately 60%) are lost to failure of the restoration (crown, etc.). About 30% are lost to periodontal disease.
It can be difficult to tell whether an asymptomatic lesion observed on an X-ray, is from the original infection, or whether it represents a failing root canal treatment—particularly if historical images are not available for comparison. Often, the original lesion will develop a clearly visible outline (a cortication, or solidification of the spherical bony wall around it) as it heals, forming what is known as an apical scar. If such a feature can be observed radiographically, and doesn’t appear to change over time, it may not be necessary to retreat the tooth.
Endodontic re-treatment involves the same steps as initial endodontic treatment, with the added complexity of removing the existing root canal filling material and any structural posts or other materials which have been placed in the tooth to reinforce its strength.