I had a root canal and internal bleaching on a front tooth. After carefully revisiting the Endodontist to get the color right, the permenant filling was placed by my dentist. About 2 months later, the tooth suddenly began to look significantly whiter than the others. It's almost blue. I was convinced my blue listerine was affecting the color so I switched to the original yellow. Any ideas on how to fix this? Could the listerine do anything?