Let me begin by apologizing to everybody but "bob" for the rant that is to
follow.

The problem may not be that nobody wanted to answer your question.  In
looking over your dental question, you are asking more of a legal or
business practice question.  It is obvious that your original dentist does
not meet your needs, and possibly the second one does.  The hard thing about
compelling the dentist to refund your money is that you paid.  It sounds
like your dentist is trying to work out any lingering problems that you paid
him to do.  If you want to choose an alternate procedure that is your
choice, and as a consequence, will have to pay for the new procedure.  If
you don't like the dentist, get a new one.  I hate to be the one to give you
the bad news, but the answers to your problem are so obvious that people
most likely didn't respond because they can't understand your thought
process.

Your problems wasn't a dental problem, it was a business problem.  You paid
for a service, and didn't like the fact that after the original service they
had to fix it once, and want to fix it a second time.

Had you stated your problem, then asked a question such as "I had CEREC
performed on a tooth, and it had to be fixed 2 times, are there any problems
with having it removed and getting a traditional crown?"  I would imagine
that you would have had a good response.  But since you want business/legal
advice nobody is going to go for that.