I'm not a dentist or dental assistant but I've had a gazillion dental appts with all kinds of stuff being done to my teeth, so I peeked in.
I'll leave the for sure answer to the experts, but my guess is that they'll have to extract what's left and then will suggest/offer putting an implant in it's place.
I have one in my lower jaw from a back tooth that suddenly cracked one day and broke in a similar fashion (really close to the gum line). I've had mine almost 10 years now and had no problems with it. It was expensive (to me, anyway) but I had the whole thing done at a dental surgeon's office (instead of him doing part of it and the regular dentist doing part of it) and he gave me a discount because of that. He also let me pay it out over the process. It's a long process, too. They'll tell you how long it will be from start to finish (setting the post, adding the cap thing, etc.) and I'd say be sure and add a month or two to that estimate because they want to make sure everything is healed completely before moving to the next step. It worked out good for me because it gave me time to save up money before the next step.
Good luck!
