My molar (4/7) had a root canal done a few years ago, and now a big piece of it broke, probably 1/4 or 1/3 of the tooth (basically, the "inside wall").

I went to the dentist and he smoothed it out, until it can be taken out. He said that the whole tooth has to go (as broken part reached under the gum line) and an implant be placed. The problem is that implants are extremely expensive. They said it would cost at least $4000 if I'm lucky and it's a "simple one".

So I've been wondering if I can't simply keep the part that is left, for as long as possible. It would be better than having nothing there, considering that an implant, at least for now, is out of the question (no money).

Does anyone knows the problems I can face if I keep it as it is?

Thanks.