Re: White outline between teeth and gums
It looks like the start of calculus (hardened plaque). You probably should get to the dentist for a professional cleaning. Plaque can build up along the gumline and harden. When it does that, brushing won't remove it. That's why we all should have our teeth cleaned by a dental professional regularly.
You can't remove this by yourself. You need to make that appt.
My best to you,