I had a root canal a few years ago and then a kind of plastic temporary crown was placed. The temp crown remained there for 5-6 years. Meanwhile I was told that the worst can happen is the temporary crown to brake. One day I decided to change it. The temp crown was still perfectly fine. I went to have it removed and replaced last year, and the dentist found that the tooth underneath had gone completely black. He said this is nothing to worry about, but I am very worried. Attached please find a pictures of the tooth with the temporary crown, then the tooth underneath after temp crown removed and x-ray image with the new crown placed after. My new crown covers my tooth well, but I worry about the black tooth underneath. Is this normal or it could be dangerous? Is it possible the black tooth to affect the gums and bone. It is one thing for the tooth to get darker, but in this case it is absolutely black. My main concern is whether it could become malignant? Should I keep this tooth? I am even ready to remove it. Please advise.