40 year old root canal developed a vertical root fracture
(Uncasville, CT, USA)
I had a root canal done back in 1977. Unfortunately, it developed a fistula (about 40 years later). The endodontist didn't see a crack on the x-ray, but after the tooth was opened she found a cotton ball and temporary filling that was never replaced, and to our dismay there was a crack underneath. The only positive thing about this story is that the root canal bought me 40 years, and now dental implants are commonly done and very successful, so I am hoping to replace the failed tooth with an implant. Back in the 70's, I probably would have had to get a bridge.