Re: one tooth receding gum line?
Jeannette is right. They only way to get gum back is to have a tissue graft. There has to be sufficient bone to keep it there, though. If your gumline is receding you may have bone loss in that area. Tissue grafts may or may not work based on bone amount.
A thorough cleaning from your dentist may stop the gum from receding any further.
I urge you to get to your dentist to have it checked.
Hope this helps.
Best to you,