Sorry you put out so much money. I had a permanently crowned tooth become infected as well. No RC in it, but there was decay under the crown. I don't understand how this happened either. It did lead to me loosing that tooth, because when it was found, it was into the middle of the tooth.
Dentists charge alot of money, and sometimes these MEGA places just don't care enough to tell you the truth, or treat you correctly.
Get that dentist that is well educated. It took me alot of time to find one.
All myh best to you. ginnie