unfinished root canal?!

i had a root canal started two years ago in september. my dentist said he had to wait to hear from my insurance company before he could finish them. i had called the receptionist a week later and she said they havent heard anything that they would call and set up an appointment as soon as they heard something. i have two root canals that are still not finished after two years. the one on the top left side of my bouth had lost the packing and putty and then fell out. the one on the bottom left hada also lost its putty but its still in contact. there is a lot of pain. i had been to the hospital with an abscess in my mouth where the upper one was started. now the lower is starting to swell. i called my dentist to see what was going on and he said my insuranced denied the claim. so i called my insurance company and they said they never recieved a claim. now im sitting here with $800.00 in unpaid hospital bills for my tooth and at a loss what to do.. can i sue them? give them a lesson and maybe theyd do better at there job.