I have had 2 root canals.The first was when I was a teenager. I was a clumsy kid, and i tripped and hit my front tooth on a doorknob. It chipped, then turned black. My mother kept telling me to brush my teeth, and when she realized (this was pretty quick) that it was not something on my tooth, I went to the dentists. (For the record, I hate dentists) He examined it and said the impact killed the tooth, so he did a root canal and bleached the tooth. Just before my senior prom, I had the chip fixed. (That was no big deal, since I couldn't feel the tooth anyway.) To this day, when I brush my teeth, you can see the color difference between my two front teeth.
The second was in the Navy. Somehow, I broke one of my molars, but there was enough left that they didn't advise pulling it (Although it was broken fairly close to the gum line.) The tooth was dead, so they did a root canal and made a crown out of dental silver. Shortly after leaving active duty, the silver crown broke. It was never a good option, but the Navy doesn't like to spend money on gold crowns unless absolutely necessary. Also, I would have had to be fitted with a temporary crown, then make several visits back to Dental, and building the crown from dental silver meant one visit. (That way I could spend more time on duty.)
Anyhoo, when I got out, i went to a civilian dentist. After the usual putting down of Military Medicine (very common among doctors and dentists who never put on a uniform) I was fitted for a permanent crown. The dentist says "We have this new cement that should hold it well, since there's only a nub of tooth left." The "new and improved" cement lasted about six months, and the crown fell out. I went back, and he had another type of new cement that was supposed to be the strongest available. Within two months, I was back to have the crown re-cemented on. This hot-shot civilian dentist said "Well, I'll use normal cement, but I don't expect it to hold. If the crown comes off again, we'll have to do surgery to get out the tooth stub."
That was more than 25 years ago, and the crown is still firmly in place!