A little over a year ago I had cracked a back molar. (there was no sign of grinding either, the Dr. (dentist A) said that I had a hard bite.) The dentist decided to do a root canal and put on a crown. The crown lasted about a year and a couple of months until it too cracked. When I went back to get it replaced, dentist A was no longer there. Dentist B said that she could replace the crown (from porceline to lava) and then recommend a bite guard (of which I objected to due to the $300 price tag). Dentist B went ahead and preped the tooth and put on a temp. crown. When I went back to have the lava crown put on, it was sitting too high. After 30-45 minutes of filing it down and fitting it to my tooth the lava crown finally cracked! So they had to take another impression and send off for a new lava crown. She then put on the temp crown again and 5 days later I am experiencing throbing and pain when I bite down. It will change from time to time. For instance when I lie down the pain will subside for awhile, then it will return. I had mentioned pain to her while she was prepping the tooth the first time and she said that I should not be feeling any pain at all because the nerve is suppose to be dead. Is that true. She also said it may be the tooth text to it, but the pain is not coming from that tooth. It also hurts on the gum above the tooth where the root canal was done. Can you give me any suggestions as to what is causing the pain??