He would more likely do the RCT through the crown. If the crown is permanently cemented the dentist would have to cut it off. Obviously the crown then would have to be remade. If the RCT was done through the crown a filling could be placed to salvage the crown.
the problem is that,as you say, you were in pain since the day the root canal was finished. If this is true, the crown should not have been done at all. The proper way to handle it is to wait until the tooth is asymptomatic before placing a crown. Was your dentist aware that the tooth still bothered you? If so, the crown should not have been done. IF things were handled this way, you would not have to deal with removing and redoing a crown. either way, if it were my practice, I'd do the crown over at no charge.
the best way is to have the crown removed (drilled off) and redone after the root canal retreatment. I would not recommend trying to "tap" off the crown. the tooth underneath can get damaged (not to mention the crown itself being damaged) and it is difficult to make it seat properly when it is recemented after the retreatment of your root canal. most commonly, root canals are done right through the crown, and then the "hole" is filled in afterwards. but now you have a brand new crown that has a hole in it that's been repaired. If your dentist has a heart, he'd offer to remove the crown and then redo it when your root canal retreatment (which should be done by a good root canal specialist) is done. I'd get at least 2 opinions from root canal specialists before proceeding with all this work. There could be many reasons beside the root canal for your discomfor.
Thanks Mike for your comments
If My Doctor want's to redo again is he going to bill again?(1000 dollars was already billed for rootcanal + crown)
I think he is responsible for the way he treated and he shouldn't bill further.
Please advice.