Please read all that you can find on root canals. They are TOXIC! It is dead. Your body is fighting a dead tooth. It is a 24/7 drip of toxins. Since you put your health problems right after the root canal, it would make sense to get rid of it!!! Don't hesitate to do this. Your immune system is being challenged daily. Don't wait until it is too late. A compromised immune system is not a good thing.
Mine have been black for several years and I have just now found an oral surgeon do take these 4 teeth out that are black on front and back. I've got to get blood pressure down first but then teeth will be out and I hope to feel better. Until I read these messages, I did not know this was a sign of infection.
I had the same thing happen to my first root canal. It turned black....then it broke off. My quack dentist failed to tell me that a tooth that has had a root canal is a dead tooth and will turn black and brittle. I had to have the thing redone, two times ..... what a mess. I have two metal posts in that tooth and have had two crowns made to date. This has been going on since the 1970's. It is a front top incisor . I wish I had never had the root canal in the first place. I also have two more, also both top incisors. root canals are just places for infections to set up in the jaw bone. They are always failures. The only ones that profit from root canals are the dentists that collect thousands of dollars from unsuspecting patients. The only thing I go to a dentist for now is extractions. I hate them, they are liars and I would never undergo any more entensive dental work, no matter what. End of rant.
Good luck and I wish I had something good to tell you.
Update: I went to my dentist today because of pain in the gums underneath the root canal. I asked him about the black color at the gum. He said it was a metal plate underneath the crown. He offered not explanation for the pain and suggested a toothpaste for sensitivity. Ugh! He said the x-rays were fine and I had no infection. At this point I don't know what to think. I might try a biological dentist for a second opinion. Hopefully, I can get some help soon.
I had a RC with a cap that had silver underneath it. The discoloration around the gum is a "petina" that occurs from the acidic condition in your mouth and the silver.
I also had a gold crown at the same time. The acid in your mouth with two different metals will create a battery which will interfer with the electrical pulses your brain transmits to other parts of your body.
Find a holistic dentist and get rid of that tooth.