16 years ago I had a root canal done to a canine tooth and also one done to premolar tooth. For both of them I had put on a permanent filling. The canine survived for 15 years but changed the color to yellow-black ( I put a crown on it because of the color) while the other one broke of in 2 years. So I was wondering whats the difference between front and back teeth’s and why they last different after the nerve was removed?