My dentist gave me some research about the correlation between root canals and all kinds of diseases, including MS. He said extract it scrape away the dead bone. The bone will regrow after the dead bone is removed. He seemed pretty sure that getting the root canals out (and thus the toxic infection) would improve my overall health condition.
I got that root canal exactly 4 years before I lost my vision.
I also just found out yesterday that Copaxone causes tooth decay. I am still convinced it is the safest DMT so I won't switch anyway. It did make me feel less guilty somehow though to know that the tooth problems come from the medicine and are not somehow my fault.