Can anyone tell me what is this? I pulled this from my repaired tooth whose filling crumbled. I started to feel it with my tongue, and couldn't get it out with anything other than pincers, because it was stuck in my gum. Didn't hurt at all, I already pulled a similar string out once. At first I thought it might be a dead tooth root or a root canal filling, but I've searched around and it doesn't look like it, so I'm not sure. It's relatively long and rigid.
Thank you for the advice.