I have black lines under my gums

[hught]

I've been desperately trying to get rid of gum disease and it's working semi-ok (although it's taken a while to get to this point), however now I've found that I can move my gum line to reveal a mm underneath and it is thick black lines that won't come off.
What is this?! And what do I do?!

You ask your hygienist
she will have a good idea of what it is and how to get it off
it could be a line of calculus/ tartar. It could be stain
it could be staining inside the tooth itself which will need a cosmetic approach or might be just the natural colour of the tooth
but definitely ask your hygienist

How is the rest of your health? I only ask because there may be something else going on - issues with teeth can be related to other parts of the body

Probably subgingival calculus. When calculus is above the gum it tends to be a yellowish creamy colour but under the gum it will be black

I had this on back tooth, was sure it had gone rotten but dentist cleaned it all of