Its possible, and I can see the reason - there are certain things that you can't learn from experience and would be hard pressed to discover from random CE ("you don't know what you don't know")..
However, once you are out in practice (and making money/paying loans/bills), it can be hard to get back.
This, by the way, definitely does NOT apply to residencies. You are actually better off practicing as a general dentist for a few years before jumping into a specialty, if anything so you can understand what your referrals are seeing out there..