Please explain if it is possible to undo gum receding (gum disease)?

Maybe: Grafting is possible on a case by case basis so see your dentist and get a referral to a specialist for an opinion.

Can be treated: Recession on the gingiva is common and can have numerous causes. It often leads to sensitive teeth due to root exposure. However, there are times that the recession can pull back too far and it needs to be treated. The dentist nor periodontist can perform a type of graft surgery to raise or reposition the receding tissue and help anchor the tooth. Be careful brushing the recession.