1.if root canaled tooth nerve is dead, how do i tell if, it reoccurs? 2.if root canaled tooth still feel something, was it unsuccessful, then what..?

RCT: If your tooth has a dead nerve, but rct was not completed, you have to see your dentist to have that work completed. Otherwise the problem is not solved, and the tooth will at some point cause pain and\or swelling. If you still have pain or discomfort, you will have to check back with your own dentist to determine the cause and the appropriate treatment necessary.

Lots of questions...: ... Different answers. The nerve in a tooth that has had root canal therapy has been removed.. It is not 'dead'.. It's just not there. Root canal therapy is not 100% successful. Sometimes the tooth needs to be retreated, sometimes a small surgery is indicated to clean out inflammation/infection. Your dentist and/or endodontist can evaluate the tooth for any treatment.

RCT good or not: If you feel cold temperature it is definitely not done correctly, pain to heat and not cold may be an infection a visible abscess or an insufficient treatment can result in spontaneous pain, pain to bite or contact or swelling. If it is a new tx than there is a healing curve, but make sure the bite is ok. See your dentist or an endodontist if your answer doesn't resolve your questions.