Retreatment of a Root Canal

About 2 years ago, while I was in college and I was on Christmas break 2008, I had a root canal procedure in the molar identified as #15. After the procedure, my dentist measured the tooth for the crown and then placed a temporary crown over the shaved tooth. I was supposed to receive the permanent crown, in a month when I return home on another break but the permanent one fell out. The dentist had to shave the tooth down more & also replace two orange rubbery fillings that came out. Two months later, I went back to my dentist to have the permanent crown fitted. When the dentist attempted to put the crown on, it didn\'t fit properly. Two months later (it\'s now summer time, I\'ve graduated from college, and now I am home), I go to the dentist to have the new permanent crown placed. The process is finally completed. Fast Forward to now, 1 &1/2 years later. M In the past three weeks, I experienced a massive amount of pain in the molar where the canal was performed. It started as a a constant throbbing pain all over the head and even in my chest. I had a fever the first day this occurred. Some days the pain goes away but still hurts when pressured is applied. Some days I experience the throbbing pain again. I can\'t eat on those days or even speak. I take advil but it doesn\'t always work. A few nights I have been unable to sleep. It seem laying down only makes the pain worse. I went to another Dentist at NYU School of Dentistry. The students and the professor say an infection is in the canal. I went back to my Dentist so that he too could take an x-ray. The infection was there when he first performed the root canal. But other x-rays show the infection remained even after the root canal was performed. I’m pretty sure it was supposed to be removed during the procedure. I am also pretty sure he was aware it remained but did nothing about it because he wanted me to continue to come so that he could make money off my insurance. When I returned to him yesterday to get xrays, he gave me a prescription for antibiotics & removed my crown so that it will relieve the pressure (“your infection presses down on the tooth as your bottom teeth force the teeth up.”) The crown is damamged and cannot be placed back on. I now have no insurance. I have two deep cavities that must be filled. NYU will charge me $700 to retreat the canal. I have no clue how much the new crown will cost. The fillings at NYU may cost $120 each. (Also, one of the cavities was already filled by my dentist in 2009 and fell out during Summer 2010). I don’t trust my dentist. Also we will probably charge way more. I asked him several times for an estimate concerning the fillings and he consistently attempted to beat around the bush. He also said he may need to perform a root canal on the tooth where the filling came out. NYU said the the cavity is deep but a root canal is not necessary. I have decided to have both fillings done. Now that I have antibiotics, I am considering just having the tooth measured for a new crown without having the root canal procedure redone. What should I do?