I had a dental implant done for a missing tooth on the lower left side, third tooth in from the back. At the time, my gum was not as severely recessed. Now my gum is extremely receding and quickly. The dentist who performed the implant said my implant isn't rejecting, but I got a second opinion and the other dentist said it's possible that is what is occurring. Is a bone graft possible to help my gum stop caving in? The implant itself seems ok but the gum is very painful.