Using my waterpik last night when a crown on my back right molar popped
off.  I've "only" had this crown for about 3 years.  I think the bite
might not have been adjusted properly, because every now and then I
tend to wake up with that side aching a bit - as if I'd been clenching
down on it at night.  And I wonder if that is irritating the root and
causing my sensitivity to cold.

I'm seeing what I guess is the cement used for the crown that is still
on top of the tooth.  It's gray and looks similar to an amalgum (sp?)
filling - I'm hoping it's a filling and not decay.  Anyway, I'm
planning on going to the dentist Monday or Tuesday (as soon as I can
get in) and seeing if they can fix it.

My question is - if there is still cement on the tooth, will they have
to remove that before reapplying the crown?  I'm concerned about the
sensitivity and how that would feel getting that tooth drilled again.
Not really wanting to get a root canal unless it's absolutely
necessary.  I'm sure many of you dentists have had patients in my
situation, and just wondered what your opinions might be on how this
crown should be reapplied, how the tooth will be prepared beforehand,
is it "normal" for a properly applied crown to only last 3 years, and
whether or not you'd recommend a root canal?