Question:

I had root canals done on my two front upper teeth 35 years ago, and apart from replacing the crowns a couple of times (current pair is about 8 years old), have had no problems until recently. About a month ago, the gum around one of the central teeth and its lateral neighbour became infected. The inflammation and pain subsided within a week and by the time I got a dentist appt a week ago, I had no ill effects from it. At that appt, my dentist said that an xray showed a lesion at the root of the tooth and I was referred to a specialist for an apioectomy (sp?). A phone conversation with the specialist`s assistant indicated that I would lose the crown as well, as they would first try to redo the root canal and then do the apioectomy if that failed to clear out the infection. My questions are: (1) Wouldn`t it make more sense to treat the root first, where the lesion is, and spare the crown if possible? (2) How does the root canal actually become infected (the person I talked to on the phone said that it was likely not completely cleaned out when the root canal was originally done, but that was 35 years ago!)? thanks!

Answer:

Root canals can become reinfected (even after 35 years) when there is leakage around the restoration (usually a crown) that is covering the teeth. Eventually all crowns will start to leak. With the leakage comes bacteria, and once bacteria get back into a root canal they can cause problems. This leakage could be due to recurrent dental decay, a poor fitting crown, or the eventual washing out of the cement that helps hold the crown on the tooth.

Your assumption is correct in that it is highly doubtful that the root canal had not been cleaned out 35 years ago. If that were true, you would have had problems a lot sooner. The reason retreatment of the root canal is necessary instead of having the root-end surgery is because of the afore-mentioned recontamination of the root canal. The surgery simply removes the cyst, and the endodontist can put a filling in the end of the root. However, this does not deal with the bacteria that reside in the root. Even a root-end filling will start to leak in time. Therefore the recommended therapy is to redo the root canal and clean the contaminated canal and reseal it and then see if the apical surgery is necessary.

For more information:

Go to the Root Canals health topic.