If the crown is well made, usually not.

Well made fixed prosthetics don't 'shift'.
--

W_B
Take out the G'RBAGE
wubbabubbazG@RBAGEyahoo.com

I'm pretty sure they remove the decay from the tooth before applying
the crown. In this case, the tooth would be "sealed" and if the decay
removed, there would be nothing in there that would decay (unless a new
cavity was created).

I'm guessing that's why sometimes dentists don't know if you need a
filling or a root canal - because once they start removing the decay it
may then expose the pulp.

Keep in mind, I'm not a dentist.

There is always a slight chance for decay under a crown.  No matter how
sealed the margins are, it is possible for  bacteria to get under the crown.
However, if the crown fits properly, the likelihood of this becoming a
clinical problem is VERY rare.  If the bite of the crown/bridge is balanced
for your occlusion, and you don't have any changes in your opposing teeth,
the likelihood of anything shifting also is very rare.  I would not worry
about this as long as your dentist does a "proper job" on your dental
treatment.  Nothing lasts forever -- no one gets out of this world alive.

IF the patient has un-controlled decay rates due to oral hygiene, sugar/acid
dietary habits, health problems and/or genetics, then the tooth can still
decay at the margin where the crown ends and the tooth material begins.