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Failing Root Canal Treatment

An overview of Failing Root Canal Treatment

Failing or root canal (endodontic treatment) of a tooth with a prefabricated post and core.

Development of a re-infection at the root tip (apex) of a previously treated molar tooth is illustrated. Sometimes the problem does not produce pain or other symptoms, and a lesion is noted only on a routine follow-up X-ray image of the tooth.

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.

How does the dentist diagnose a Failing Root Canal Treatment?

Note: ToothIQ.com contains general information. Only a dentist can properly diagnose your specific condition.

Generally, teeth which require endodontic re-treatment will have an area of chronic (long standing) infection at the root tip, which is visible on an X-ray image of the tooth as an obvious dark lesion. The lesion will generally lack a white (corticated) margin, which makes it appear diffuse and “active”. Presence of a white margin around the lesion suggests there has been healing of the original lesion, and in the absence of other signs and symptoms, is not necessarily an indication for endodontic re-treatment—although close follow-up is certainly appropriate.

A tooth with a failing root canal may be accompanied by symptoms, such as swelling, drainage and pain to biting. Frequently the tooth restoration (crown, filling, etc.) may be found to be broken or leaking.

If a root canal filling has been exposed to the mouth more than a day or two due to loss or failure of the crown or filling on the tooth, your dentist may recommend endodontic re-treatment prior to placing a final restoration on the tooth (even in the absence of signs or symptoms). This is because evidence has shown that exposure of root canal fillings to the oral environment for much longer than that has produced a significant number of secondary root canal infections. It is undesirable for all parties involved when the dentist has to drill through a brand new crown to re-treat the root canals.

How is a Failing Root Canal Treatment treated?

Your dentist or endodontist may recommend surgically removing the apex of the tooth’s root instead of, or in addition to re-treating it. This procedure is known as an apicoectomy. The resulting hollow root tip may or may not require a special type of filling known as a retrograde filling (or simply, retrofit).

More commonly, the dentist or endodontist will recommend re-doing the root canal (endodontic treatment) conventionally—through a hole made in the crown of the tooth. In some cases, the tooth may not be feasible to save, and your dentist may recommend removing it (extraction). There are also cases in which infection around the roots of the tooth do not originate inside the tooth root. These cases are generally treated by surgical periodontal procedures.

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Author: Thomas J. Greany, D.D.S. / Editor: Ken Lambrecht

This page was last updated on March 2, 2018.

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