I went to have my teeth cleaned at my regular dentist office. While i was
there I was told I needed a cavity filled on a back bottom molar.  At this
point there was no pain and I did not know I had a cavity but the filling
would be a minor inexpensive procedure so I made the appointment to have it
filled.  Once it was filled the dentist told me i could chew on that side as
soon as the numbness went away.  That night after the numbness was gone, I
tried to eat supper and when i bit down on that tooth i had sharp shooting
pains that were very intense.  It only lasted a few minutes and went away.  I
tried chewing on that side again the next day and the same thing happened.  I
called my dentist and told him.  He said that it was a very deep cavity, that
in fact, the tooth almost needed a root canal and that i may need to have a
crown put over it.  My question and concern is that the tooth was not hurting
at all before and now i can not chew on that side at all.  Will a crown help
this sharp shooting pain?  is this a bad cavity or could it be a fractured
root or cracked tooth?  I have read that if the tooth is cracked that a crown
will not help?  I would like to know a little more before I spend even more
money on a crown, that if I had known I was going to have to get I would have
left the tooth alone.