Q: I had a root canal treated tooth but my dentist says it has got re-infected. How is that possible?

A root canal treatment involves simply removing the infected part of the tooth – the nerve and blood vessels inside the roots, the walls filed and shaped clean and smooth and finally filling an inert, bio-compatible resinous substance called gutta-percha to seal the canals permanently. Sometimes a crown is placed for reinforcement and everybody wins.

[Can my teeth be the cause of my headaches?]

Fast-forward to maybe 15 years later and another dentist takes an X-ray and says that the root canal treated tooth has got infected and needs re-treatment or, worse yet, an extraction. So how can a root canal-treated tooth get re-infected when everything is closed?

The reasons are multiple:

Firstly and most commonly – missed nerve tissue. Sometimes the nerve and dead tissue was not completely or thoroughly removed. It could be because the canals were not instrumented and filed down wide enough or long enough, or the solvent liquids haven’t been left in long enough. If canals are not prepared to an adequate size, the disinfectant solutions cannot reach all the areas of the nerve tissue and bacteria can live n in these areas and slowly reinfect. Sometimes an entire canal is missed because it did not get spotted during the initial checkup. Remember that the opening of the nerve canals can be as thin as 50 microns. It happens a lot less now because of better lighting, the use of magnification and microscopes and 3D CBCT scanning.

Second, cement or filling breakdown. All cements have a life. Over a period, they breakdown and dissolve and can allow a passage for bacteria to re-enter the root canal system and cause a re-infection.

Third, separated or broken instruments in the canal. Unfortunately, this happens in the best hands also occasionally. The newer generation of files which are used to clean the canals are a lot more flexible than the older generation but are also more prone to breakage. Not every broken file will cause a problem though. Frequently they can be bypassed or removed, and all is good. But occasionally both these options wont work and a tooth might need to be removed as a last resort.

Tanveer Ahmed is an implantologist, dental surgeon and medical director at New Ivory Dental and Implant Clinic. Got a problem? Our fantastic panel of renowned experts is available to answer all your questions related to fashion, well-being, nutrition, finance and hypnotherapy. Email your queries to friday@gulfnews.com.