It sometimes happens that a tooth that has been endodontically treated fails to heal or is causes pain despite the therapy: this may occur after months or even years. When it does, the tooth can often be saved by a second endodontic treatment: re-treatment.

Why does a tooth need to be re-treated? Endodontic treatment is needed when the pulp, what the patient usually calls the "nerve", has been irreparably damaged. Although the pulp has been removed and replaced with a filling material, the tooth must be treated again, usually for one of the following reasons:

• Canals not properly cleaned and filled. For the endodontic treatment (devitalization) to be successful, the root canals must be completely cleaned and filled. Sometimes, canals are so narrow, calcified or curved that even the smallest instrument used to clean them cannot reach right to the end. Or a canal might be so small that it is hard to detect. Other canals are only partially filled.
• Root trauma. A recent trauma may have caused the root to fracture and an infection or cyst may have developed at the apex (tip) of the root.
• New caries. A new caries may destroy the tooth crown and expose the filling material within the canal to bacteria and saliva, producing a new infection of the root canals. A fracture or hair-line crack in a filling, or the detachment of a crown or post, even if only partial, may cause the same damage.

Who should do the re-treatment? All dentists have adequate training to enable them to do re-treatment. However, many cases are truly complex, and require the work of specialists in the sector. They spend most of their professional life doing root canals (the dental profession that deals exclusively with treating and sealing root canals with orthograde methods, endodontic treatment and re-treatment, or surgery) and are, therefore, the most expert in this sector.

What happens during re-treatment? The tooth must be reopened, the canals cleaned again and re-filled. Should that not be possible (curved canals, crown posts in the canals, etc.) it may be necessary to make an incision through the gum to expose the root apex, so as to be able to seal it (apicoectomy and retrograde filling).

Is this painful for the patient? Before, during and after treatment the tooth may hurt: In these cases, intra-operative anaesthetic and the appropriate pain-killers generally remove the pain. In any case, this is not a problem that compromises the good result of the therapy.

If the first treatment failed, how can the patient be sure that the re-treatment will be successful? Obviously, there can be no 100% guarantee. Retreatment is often the only alternative to extraction. The dentist will give the patient all the information about alternative therapy, so that he can take an informed decision.

What are the alternatives to retreatment? The alternative is usually extraction. The loss of a tooth may mean that the neighbouring teeth move over, which compromises occlusion and chewing.

The tooth may be replaced by a bridge anchored to the adjacent teeth, if they are present, or retained by an implant into the bone. All of these alternatives are long, costly and artificial.

At present, nothing is better or lasts longer than a natural tooth.

In some cases, re-treatment and apical surgery are impossible, and if the condition of the tooth permits it, an intentional re-implant of the tooth may be possible. The tooth is extracted, the problem that caused the trouble is brought under control, the root is treated, and lastly, the tooth is replaced in its socket.

How expensive is re-treatment? In general, it costs more than the normal treatment of a tooth (devitalization). This is due to the increased difficulty and the longer time needed to achieve a good result.