"I cannot find where it says that. All I can find is where it says that an infection is indicated if the root of the tooth turns black."
At the bottom of the tooth is where she said it was black.
I would think that is where an infection would first show up unless you had other indications (unexplained health problems) etc..
I'm not a dentist, but if I had a RC that was black, that would indicate to me that something was wrong with the tooth and I would have it removed. Healthy teeth don't turn black. Well actually if you've read any of my posts on RC's, you would know I wouldn't wait until it was black.