Patrick,

I am only guessing, but maybe your dentist wants to give some time to
see whether or not a root canal is necessary before the permanent crown
is placed.

It is my understanding (now), that anytime a tooth requires a crown,
this generally means there is not much tooth structure left.  With
little tooth structure left, the nerve is more vulnerable to death. If
the nerve dies, then root canal therapy is necessary.

I am saying this only because I needed RCT several weeks after a
permanent crown was placed. During the RC procedure the crown
shattered, so it had to be replaced.  It was an all porcelain crown
(front tooth), so it was expensive!

That is just my guess... expressed in layman's terms.... take at risk!

(I did not see any professional replies, so I thought I might chime
in).  

Best,
Sue (patient)