Not sure what it is, but I had a root canal done a few years ago, it was the most painful thing I have experience. The first Dentist gave me an anaesthetic, did not work at all, I think she gave me three injections, I could feel everything, gave me another injection, no help at all and what make it worse that I have some spasm problem and could not sit still or keep calm. She sent me to a specialist, the same happened, the anaesthetics did not do anything, I could feel all the grinding and scratching. Went to another Dentist, he got the job done, I think the only reason why he got it right was that most of the nerves were removed by the previous guys. Now I have to go again, have a big whole in another tooth, and it a hell lot of pain sometimes. Currently using Sensodyne and Listerine which helps. I am looking for alternative ways of anaesthetics, posssible full anaesthetics in a hospital.... But good luck to you,