In the long on-going saga (see previous thread: Yet another crown
question) I've just lost another one. Actually it's still there, just
wedged in between adjacent teeth and pointing towards and rubbing
against my cheek. I suppose I could use a pair of Craftsman needle
nose pliers ... <g>.

Well, while pondering this further punishment in life it occurred to
me:

When I grind my food my lower jaw works to make circles and to move up
and down. Why then are molars not flat? Surely as the bottom teeth
move (say) left to right the raised parts will encounter the downward
pointing tooth placing lots of lateral strain (even a blow) on the
upward pointing nub and even the upper tooth? Worse, if any of the
teeth are uneven in their contact points (say: the first molar is
slightly higher that the second) then one or other will take a real
beating. Hmmm, it's amazing that any of them survive.

Presuming that the answer is that you (the dental people) make lots of
effort to see that there aren't too many impacts, could it be that the
reason I'm getting so many crowns coming out is that my dentist hasn't
done enough in this regard? Agreed the bonds are weak and the teeth
are fragile but that's even more of a reason to make sure that the
teeth can't impact each other.

One other question on the same line. When I grind (lightly) my teeth I
can hear (or feel, I'm not sure) a noise like a finger rubbing across
a smooth but not slippery surface such as glass. I presume it's caused
by the continuous breaking of the tension between the finger and the
glass. What's this noise called?