I've had more dental work than I care to admit. I also ignored taking care of my teeth for many years when I was younger. Now I'm also paying the price-- and it's high!
I have a bridge in the front of my mouth. It's five teeth wide and is secured to the outermost real teeth. No problems yet, after about three years, but I've been good about flossing above the bridge too.
As far as root canals go, I've had several.
There is always a chance that you'll need to get a root canal a second or third time for the same tooth. The root has so many little branches that it's imppossible to get them all the intitial time, so any one of them can become re-infected. That's happened to me twice. The final time for one tooth resulted in such a bad infection, that I lost the tooth and have a slightly visible hole in my gum. It was pretty damn painful. The dentist shot me 18 times with novacaine and it still hurt like hell. (My mom is an aenesthisist (sp?) and has strictly advised me never to have a dentist put me under; they simply don't have enough training.) Luckily you only notice a small hole in my gum if you know it's there, but I'd rather have my gum back!