The dentist will do a filling if the patient doesn't want a root canal. Often that just ends up in a root canal, as the tooth gets painful. I have had two, one resulting from a broken tooth in a car accident and one from my canals calcifying in on my tooth and causing great pain. Since the root canals, no pain, it's been years now. My husband has had three, same thing, no pain, no problems. So out of 5 together we haven't lost any teeth from it up to now. I would root canal it and try to keep the tooth. Usually pain results after a root canal because the dentist was not thorough when doing it and left a piece in there that later becomes irritated and inflamed. I wouldn't trade my dentist for anyone else though, he's great and VERY thorough, and guarnatees his work. It all depends on what you want to deal with or your partircular problem. I would advise against the filling though, it probably will hurt and be very sensitive after that it done, if it's that deep.