Can orthodontists help with receding gums?

Sometimes. If the receding gums are caused by mal- positioned teeth. However most of the time these problems require a periodontist!
Cause? If problem caused by teeth being positioned beyond good bone support, orthodontist can reposition teeth ideally. This will not restore what's been lost, but will make your gums easier to care for. Important that you ask your dentist for referral to both orthodontist and periodontist (gum specialist) for initial evaluation. They can then work with your dentist to optimize your dental health.