I noticed this a month ago, I never flossed in my life and never went to the dentist once, until 2 months ago. Anyway, I got this black line and I read it is serious so I started flossing everyday, but can someone tell me how serious it is,please I am actually scared. Like I know you are going to be like , duh, you never had good dental health. And I know, but now I want to change that but I don't really know if this can be cured. I am visiting my dentist in 1 week btw.