Periodontist

 This is perio(gum) disease in which gums resides and root visibility occurs.
This is a serious problem which u have to show to periodontist .

This is normal thing that generally occurs when u don't brush your teeth properly.
This can be cured in one appointment by any dentist .

 This is perio gum disease which can cure by flap surgery.
In flap surgery dentist give small incision to gums, remove it temporarily to see the root bone and other things.
He removed the calculus debris and infected parts either cyst or gums .
After that he placed required materials like bone graft or soft tissue in between flap and tooth .
After he sutured the gums and give coe pack (a type of dressing ).
Dentist give instructions and medicines  and call back him about 7-10 days for removal of sutures.

This is same case as above.