I had root canal done on tooth# 31 in Nov. Pain persisted so I went to another endodontist (a board certified). He said one of the canals was not filled all the way. He retreated the tooth in 4/09, went back 3 times, until he completed it in 07/09. He was also unable to fill the same canal. Now there is very small tooth left. I still continue to have pain on the tooth when biting down, even if I remove the temporary. It seems I wasted money for retreatment. What could be causing the pain? If I knew this was going to happen, I could have just had the tooth pulled and an implant placed.