Can my root canal from 5 years ago start hurting and being sensitive to sweet things?

It's possible that the root canal is failing, but another possibility is that the sensitivity you are experiencing is coming from an adjacent tooth. I would recommend returning to your dentist to have the area evaluated. Good luck and I hope this helps. Click save on the save button below my name, so that you may ask me more questions in the future.

It is possible that you can experience pain from a tooth that had root canal treatment.  A canal could have been missed, or the root canal can be failing.  Without doing a proper exam and seeing a few x-rays it will be difficult to tell.  You may also be experiencing referred pain from another tooth.  You need to go see your doctor and have it looked at.

Hello there, 

Firstly, your dentist should make sure that the the pain is not due to an adjacent tooth. Scheduling an appointment with an endodontist is your best bet as it is very possible that a tooth that had a root canal can develop a problem years down the line. 

Hope this helps!